biological molecules and the whole of cells Flashcards
(151 cards)
1
Q
Cytochrome c is a protein used in the reactions of respiration and is found across species of animals, plants and unicellular organisms
Suggest why the widespread occurrence of cytochrome c is considered to be evidence for evolution?
A
Cytochrome c is a protein used in the reactions of respiration and is found across species of animals, plants and unicellular organisms
Suggest why the widespread occurrence of cytochrome c is considered to be evidence for evolution?
Cytochrome c is present in the cells of a wide variety of organisms, suggesting that they could all have descended from a common ancestor
2
Q
a) . What is a polymer
b) . What is a monomer
A
a). What is a polymer
A large, complex molecule composed of many monomers joined together
b). What is a monomer
A small, basic molecular unit that can form a polymer
3
Q
Give two examples of monomers
A
Give two examples of monomers
Monosaccharides, nucleotides and amino acids
4
Q
Explain what happens in a condensation reaction between two monomers
A
Explain what happens in a condensation reaction between two monomers
A chemical bond is formed between the monomers and a molecule of water is released
5
Q
Describe how you would test a piece of food for the presence of lipid
A
Describe how you would test a piece of food for the presence of lipid
- Dissolve in alcohol, then add water;
- White emulsion shows presence of lipid.
6
Q
Suggest one advantage of the different percentage of cholesterol in red blood cells compared with cells lining the ileum
A
Suggest one advantage of the different percentage of cholesterol in red blood cells compared with cells lining the ileum
Red blood cells free in blood
7
Q
E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why.
A
E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why.
Cell unable to change shape Because cell has a cell wall and the Wall is rigid
8
Q
Explain the difference in the structure of the starch molecule and the cellulose molecule
A
Explain the difference in the structure of the starch molecule and the cellulose molecule
Starch formed from α-glucose but cellulose formed from β-glucose;
9
Q
Starch molecules and cellulose molecules have different functions in plant cells.
Each molecule is adapted for its function.
Explain one way in which starch molecules are adapted for their function in plant cells.
A
Starch molecules and cellulose molecules have different functions in plant cells.
Each molecule is adapted for its function.
Explain one way in which starch molecules are adapted for their function in plant cells.
Insoluble so doesn’t affect water potential
Compact
Large molecule; Cannot leave cell.
10
Q
Explain how cellulose molecules are adapted for their function in plant cell
A
Explain how cellulose molecules are adapted for their function in plant cell
Long and straight chains become linked together by many hydrogen bonds to form fibrils which Provides strength (to cell wall).
11
Q
Messenger RNA (mRNA) is used during translation to form polypeptides. Describe how mRNA is produced in the nucleus
A
Messenger RNA (mRNA) is used during translation to form polypeptides. Describe how mRNA is produced in the nucleus
Helicase; breaks down hydrogen bonds
Only one DNA strand acts as template;
RNA nucleotides attracted to exposed bases; Attraction according to base pairing rule;
RNA polymerase joins (RNA) nucleotides together;
Pre-mRNA spliced to remove introns
12
Q
Describe the structure of proteins.
A
Describe the structure of proteins.
Polymer of amino acids
Joined by peptide bonds;
Formed by condensation;
Primary structure is order of amino acids;
Secondary structure is folding of polypeptide chain due to hydrogen
bonding;
Tertiary structure is 3-D folding due to hydrogen bonding and ionic / disulfide bonds;
Quaternary structure is two or more polypeptide chains
13
Q
Describe how proteins are digested in the human gut
A
Describe how proteins are digested in the human gut
hydrolysis of peptide bonds;
Endopeptidases break polypeptides into smaller peptide chains; Exopeptidases remove terminal amino acids;
Dipeptidases hydrolyse / break down dipeptides into amino acids
14
Q
A student investigated the effect of chewing on the digestion of starch in cooked wheat.
He devised a laboratory model of starch digestion in the human gut.
- Volunteers chewed cooked wheat for a set time. The wheat had been cooked in boiling water.
- This chewed wheat was mixed with water, hydrochloric acid and a protein-digesting enzyme and left at 37 °C for 30 minutes.
- A buffer was then added to bring the pH to 6.0 and pancreatic amylase was added. This mixture was then left at 37 °C for 120 minutes.
- Samples of the mixture were removed at 0, 10, 20, 40, 60 and 120 minutes, and the concentration of reducing sugar in each sample was measured.
- Control experiments were carried out using cooked wheat that had been chopped up in a blender, not chewed.
(a) What reducing sugar, or sugars, would you expect to be produced during chewing? Give a reason for your answer.
(b) In this model of digestion in the human gut, what other enzyme is required for the complete digestion of starch
(c) What was the purpose of step 2, in which samples were mixed with water, hydrochloric acid and pepsin?
(d) in the control experiments, cooked wheat was chopped up to copy the effect of chewing.
Suggest a more appropriate control experiment. Explain your suggestion
A
A student investigated the effect of chewing on the digestion of starch in cooked wheat.
He devised a laboratory model of starch digestion in the human gut.
- Volunteers chewed cooked wheat for a set time. The wheat had been cooked in boiling water.
- This chewed wheat was mixed with water, hydrochloric acid and a protein-digesting enzyme and left at 37 °C for 30 minutes.
- A buffer was then added to bring the pH to 6.0 and pancreatic amylase was added. This mixture was then left at 37 °C for 120 minutes.
- Samples of the mixture were removed at 0, 10, 20, 40, 60 and 120 minutes, and the concentration of reducing sugar in each sample was measured.
- Control experiments were carried out using cooked wheat that had been chopped up in a blender, not chewed.
(a) What reducing sugar, or sugars, would you expect to be produced during chewing? Give a reason for your answer.
- Maltose
- Salivary amylase breaks down starch.
(b) In this model of digestion in the human gut, what other enzyme is required for the complete digestion of starch
Maltase
(c) What was the purpose of step 2, in which samples were mixed with water, hydrochloric acid and pepsin?
Mimics effect of stomach
(d) in the control experiments, cooked wheat was chopped up to copy the effect of chewing.
Suggest a more appropriate control experiment. Explain your suggestion
- Add boiled saliva
- Everything the sameAs the experiment but salivary amylase denatures
15
Q
C is a protein with a carbohydrate attached to it. This carbohydrate is formed by joining monosaccharides together. Name the type of reaction that joins monosaccharides together.
A
Condensation
16
Q
Some cells lining the bronchi of the lungs secrete large amounts of mucus. Mucus contains protein.
Name one organelle that you would expect to find in large numbers in a mucus-secreting cell and describe its role in the production of mucus.
Organelle …
Description of role …
A
Some cells lining the bronchi of the lungs secrete large amounts of mucus. Mucus contains protein.
Name one organelle that you would expect to find in large numbers in a mucus-secreting cell and describe its role in the production of mucus.
Organelle
Golgi (apparatus)
Description of role
- Package / process proteins;
17
Q
Draw the disaccharide that would be formed from a condensation reaction between:
a) . alpha glucose and galactose
b) . alpha glucose and fructose
A
Draw the disaccharide that would be formed from a condensation reaction between:
a) . alpha glucose and galactose
b) . alpha glucose and fructose
18
Q
Draw the structure of the beta glucose
A
Draw the structure of the beta glucose
19
Q
a) What is the name of the bond that forms between two monosaccharides
b) what molecule is released during a condensation reaction between two monosaccharides
A
a) What is the name of the bond that forms between two monosaccharides
Glycosidic
b) what molecule is released during a condensation reaction between two monosaccharides
Water
20
Q
Which monosaccharides make up the disaccharides:
maltose sucrose and lactose
A
Which monosaccharides make up the disaccharides:
maltose sucrose and lactose
a-glucose + fructose —> sucrose
a-glucose + galactose —> lactose
a-glucose + a-glucose —> maltose
21
Q
Describe how to test for reducing sugars and say what a positive and negative result would look like
A
Describe how to test for reducing sugars and say what a positive and negative result would look like
Add Benedicks reagent to a test sample and heat it in a water bath that’s been brought to the boil.
look at the colour of the sample for the result.
a positive result would be a coloured precipitate (green, orange, yellow or brick red, depending on the concentration of the reducing sugar) and a negative result would be blue.
22
Q
Why is starch good for storage
A
Why is starch good for storage
It doesn’t affect water potential so it doesn’t cause water to enter cells by osmosis which would make them swell
23
Q
Explain an advantage of amylopectin that makes it suitable for energy storage
A
Explain an advantage of amylopectin that makes it suitable for energy storage
It has lots of side branches which means the enzymes that break amylopectin down can get to the Glycosidic bonds easily which means that glucose can be released quickly when it is needed
24
Q
Which polysaccharide in starch is the major component of plant cell walls
A
Which polysaccharide in starch is the major component of plant cell walls
Cellulose
25
Describe the structure of the polysaccharide cellulose and explain how it structure makes it suited to its function in cell walls
Describe the structure of the polysaccharide cellulose and explain how it structure makes it suited to its function in cell walls
Celulose is made from long unbranched chains of beta glucose these are joined by hydrogen bonds to form microfibrils
microfibrils are very strong which means they provide support/strength/rigidity in a cell wall
26
Sketch and label a diagram of a microfibril
Sketch and label a diagram of a microfibril
27
Describe the method you would use to test for the presence of starch and see what a positive and negative result would look like
Describe the method you would use to test for the presence of starch and see what a positive and negative result would look like
Use the iodine test – add iodine dissolved in potassium iodide solution into a test sample.
look at the colour of the sample for the result.
a positive result would be dark blue-black and a negative result would be a browny-orange colour
28
Cow’s milk contains the sugar lactose. Many cats are unable to digest cow’s milk because they are lactose intolerant.
Cow’s milk can be made suitable for these cats by treating it with the enzyme lactase to hydrolyse lactose.
This makes the cow’s milk lactose-free.
Beads are coated with lactase and placed in a tube, as shown in the diagram below. Cow’s milk flows over the beads and the lactose is hydrolysed.
(a) Attaching lactase to the beads is a more efficient use of lactase than adding the lactase directly to cow’s milk.
Suggest three reasons why it is more efficient to attach lactase to the beads.
(b) Monosaccharides and disaccharides taste sweet.
The lactose-free milk made after hydrolysis with lactase tastes sweeter than the cow’s milk containing lactose.
Suggest why.
Cow’s milk contains the sugar lactose. Many cats are unable to digest cow’s milk because they are lactose intolerant.
Cow’s milk can be made suitable for these cats by treating it with the enzyme lactase to hydrolyse lactose.
This makes the cow’s milk lactose-free.
Beads are coated with lactase and placed in a tube, as shown in the diagram below. Cow’s milk flows over the beads and the lactose is hydrolysed.
(a) Attaching lactase to the beads is a more efficient use of lactase than adding the lactase directly to cow’s milk.
Suggest three reasons why it is more efficient to attach lactase to the beads.
(Lactase / beads) can be reused
No need to remove from milk
Allows continuous process
The enzyme is more stable
Avoid end-product inhibition.
(b) Monosaccharides and disaccharides taste sweet.
The lactose-free milk made after hydrolysis with lactase tastes sweeter than the cow’s milk containing lactose.
Suggest why.
Lactose hydrolysed to galactose and glucose, So more sugar molecules
So more sugars produced are sweeter than lactose
29
Give two ways in which the structure of starch is similar to cellulose.
Give two ways in which the structure of starch is similar to cellulose.
Are polymers and contain glycosidic bonds
30
Give two ways in which the structure of starch is different from cellulose.
Give two ways in which the structure of starch is different from cellulose.
Starch contains alpha glucose, branched and not straight
31
In plants, mass transport of sugars takes place through columns of sieve cells in the phloem. Other cells, called companion cells, transport sugars into, and out of, the sieve cells.
(i) Using the diagram, suggest and explain one other way in which sieve cells are
adapted for mass transport.
No organelles / very little cytoplasm / cytoplasm at edge / more room / hollow / large vacuole / large space / thick walls
(So) easier flow / (thick / strong walls) resist pressure
In plants, mass transport of sugars takes place through columns of sieve cells in the phloem. Other cells, called companion cells, transport sugars into, and out of, the sieve cells.
(i) Using the diagram, suggest and explain one other way in which sieve cells are
adapted for mass transport.
No organelles / very little cytoplasm / cytoplasm at edge / more room / hollow / large vacuole / large space / thick walls
(So) easier flow / (thick / strong walls) resist pressure
32
Using the diagram, suggest and explain one other way in which companion cells are adapted for the transport of sugars between cells.
Using the diagram, suggest and explain one other way in which companion cells are adapted for the transport of sugars between cells.
Mitochondria release energy / ATP / site of respiration;
For active transport / uptake against concentration gradient.
33
Starch molecules and cellulose molecules have different functions in plant cells. Each molecule is adapted for its function.
Explain one way in which starch molecules are adapted for their function in plant cells.
Starch molecules and cellulose molecules have different functions in plant cells. Each molecule is adapted for its function.
Explain one way in which starch molecules are adapted for their function in plant cells.
Insoluble so doesn’t affect water potential
34
Explain how cellulose molecules are adapted for their function in plant cells.
Explain how cellulose molecules are adapted for their function in plant cells.
Long and straight chains become linked together by many hydrogen bonds to form fibrils that provide strength (to cell wall).
35
A student investigated the effect of chewing on the digestion of starch in cooked wheat.
He devised a laboratory model of starch digestion in the human gut. This is the method he
used.
1. Volunteers chewed cooked wheat for a set time. The wheat had been cooked in boiling water.
2. This chewed wheat was mixed with water, hydrochloric acid and a protein-digesting enzyme and left at 37 °C for 30 minutes.
3. A buffer was then added to bring the pH to 6.0 and pancreatic amylase was added. This mixture was then left at 37 °C for 120 minutes.
4. Samples of the mixture were removed at 0, 10, 20, 40, 60 and 120 minutes, and the concentration of reducing sugar in each sample was measured.
5. Control experiments were carried out using cooked wheat that had been chopped up in a blender, not chewed.
(a) What reducing sugar, or sugars, would you expect to be produced during chewing? Give a reason for your answer
(b) In this model of digestion in the human gut, what other enzyme is required for the complete digestion of starch
(c) What was the purpose of step 2, in which samples were mixed with water, hydrochloric acid and pepsin
(d) in the control experiments, cooked wheat was chopped up to copy the effect of chewing.
Suggest a more appropriate control experiment. Explain your suggestion
A student investigated the effect of chewing on the digestion of starch in cooked wheat.
He devised a laboratory model of starch digestion in the human gut. This is the method he
used.
1. Volunteers chewed cooked wheat for a set time. The wheat had been cooked in boiling water.
2. This chewed wheat was mixed with water, hydrochloric acid and a protein-digesting enzyme and left at 37 °C for 30 minutes.
3. A buffer was then added to bring the pH to 6.0 and pancreatic amylase was added. This mixture was then left at 37 °C for 120 minutes.
4. Samples of the mixture were removed at 0, 10, 20, 40, 60 and 120 minutes, and the concentration of reducing sugar in each sample was measured.
5. Control experiments were carried out using cooked wheat that had been chopped up in a blender, not chewed.
(a) What reducing sugar, or sugars, would you expect to be produced during chewing? Give a reason for your answer
Maltose;
Salivary amylase breaks down starch
(b) In this model of digestion in the human gut, what other enzyme is required for the complete digestion of starch
Maltase
(c) What was the purpose of step 2, in which samples were mixed with water, hydrochloric acid and pepsin?
Mimics effect of stomach
(d) in the control experiments, cooked wheat was chopped up to copy the effect of chewing.
Suggest a more appropriate control experiment. Explain your suggestion
Add boiled saliva;
Everything same as experiment but salivary amylase denatured.
36
In humans, the enzyme maltase breaks down maltose to glucose. This takes place at normal body temperature.
Explain why maltase:
• only breaks down maltose
• allows this reaction to take place at normal body temperature (5)
In humans, the enzyme maltase breaks down maltose to glucose. This takes place at normal body temperature.
Explain why maltase:
• only breaks down maltose
• allows this reaction to take place at normal body temperature (5)
37
Scientists have investigated the effects of competitive and non-competitive inhibitors of the enzyme maltase.
Describe competitive and non-competitive inhibition of an enzyme.
Scientists have investigated the effects of competitive and non-competitive inhibitors of the enzyme maltase.
Describe competitive and non-competitive inhibition of an enzyme.
Tertiary structure of enzyme means active site is complimentary to maltose/substrate
Enzyme is a catalyst which lowers the activation energy required by forming enzyme substrate complex
38
Explain how a sports drink could provide an energy boost when running.
Explain how a sports drink could provide an energy boost when running.
Drink contains carbohydrates / sugars so raises blood glucose concentration quickly;
Contains salt so glucose more rapidly absorbed;
Increases glucose to muscles for respiration;
faster respiration so faster energy release
39
Nutritionists investigated the relationship between eating oily and non-oily fish and the incidence of asthma. They analysed the diets of children with asthma and the diets of children without asthma.
Children with asthma
Children who eat no fish: 28%
Children who ate only oily fish: 16%
Children who ate non-oily fish: 56%
children without asthma
Children who eat no fish: 16%
Children who ate only oily fish: 30%
Children who ate non-oily fish: 54%
(a) What conclusions can you make from the data?
(b) Describe how you could use the emulsion test to show the presence of oil in a sample of fish.
Nutritionists investigated the relationship between eating oily and non-oily fish and the incidence of asthma. They analysed the diets of children with asthma and the diets of children without asthma.
Children with asthma
Children who eat no fish: 28%
Children who ate only oily fish: 16%
Children who ate non-oily fish: 56%
children without asthma
Children who eat no fish: 16%
Children who ate only oily fish: 30%
Children who ate non-oily fish: 54%
What conclusions can you make from the data?
Fewer children with asthma eat fish;
Fewer children with asthma eat oily fish;
only 2% difference in children with or without asthma who eat non-oily fish.
Describe how you could use the emulsion test to show the presence of oil in a sample of fish.
Shake with ethanol
Then add water;
White / milky / cloudy layer indicates oil
40
Describe how you test a piece of food for the presence of lipid
Describe how you test a piece of food for the presence of lipid
Dissolve in alcohol, then add water; White emulsion shows presence of lipid.
41
Newborn babies can be fed with breast milk or with formula milk. Both types of milk contain carbohydrates, lipids and proteins.
* Human breast milk also contains a bile-activated lipase. This enzyme is thought to be inactive in milk but activated by bile in the small intestine of the newborn baby.
* Formula milk does not contain a bile-activated lipase.
Scientists investigated the benefits of breast milk compared with formula milk.
(a)
The scientists used kittens as model organisms in their laboratory investigation.
(a) Other than ethical reasons, suggest two reasons why they chose to use cats as model organisms.
mammals likely to have same physiology / reactions as humans;
Small enough to keep in laboratory / produce enough milk to extract;
(Can use a) large number.
(b) Before starting their experiments, the scientists confirmed that, like human breast milk, cat’s milk also contained bile-activated lipase.
To do this, they added bile to cat’s milk and monitored the pH of the mixture.
Explain why monitoring the pH of the mixture could show whether the cat’s milk contained lipase.
Hydrolysis of lipids produces fatty acids;
Which lower pH of mixture.
Newborn babies can be fed with breast milk or with formula milk. Both types of milk contain carbohydrates, lipids and proteins.
* Human breast milk also contains a bile-activated lipase. This enzyme is thought to be inactive in milk but activated by bile in the small intestine of the newborn baby.
* Formula milk does not contain a bile-activated lipase.
Scientists investigated the benefits of breast milk compared with formula milk.
(a)
The scientists used kittens as model organisms in their laboratory investigation.
Other than ethical reasons, suggest two reasons why they chose to use cats as model organisms.
mammals likely to have same physiology / reactions as humans;
Small enough to keep in laboratory / produce enough milk to extract;
(Can use a) large number.
42
Structure of the phospholipid is different from triglyceride describe the phospholipid
Structure of the phospholipid is different from triglyceride describe the phospholipid
Has a phosphate group instead of one of the fatty acids in the triglyceride
43
What is meant by an unsaturated fatty acid
What is meant by an unsaturated fatty acid
Double bonds present between carbons in a fatty acid
44
Does starch only contain the elements carbon oxygen and hydrogen
Does glycogen only contain the elements carbon oxygen and hydrogen
Does deoxyribose only contain the elements carbon oxygen and hydrogen
Does DNA Helicase only contain the elements carbon oxygen and hydrogen
Is starch made from amino acid monomers
Is glycogen made from amino acid monomers
Is deoxyribose made from amino acid monomers
Is DNA helicase made from amino acid monomers
Is starch found in both animal cells and plant cells
Is glycogen found in both animal cells and plant cells
Is deoxyribose found in both animal cells and plant cells
Is DNA helicase found in both animal cells and plant cells
Does starch only contain the elements carbon oxygen and hydrogen
No
Does glycogen only contain the elements carbon oxygen and hydrogen
Yes
Does deoxyribose only contain the elements carbon oxygen and hydrogen
Yes
Does DNA Helicase only contain the elements carbon oxygen and hydrogen
Yes
Is starch made from amino acid monomers
No
Is glycogen made from amino acid monomers
No
Is deoxyribose made from amino acid monomers
No
Is DNA helicase made from amino acid monomers
Yes
Is starch found in both animal cells and plant cells
No
Is glycogen found in both animal cells and plant cells
No
Is deoxyribose found in both animal cells and plant cells
Yes
Is DNA helicase found in both animal cells and plant cells
Yes
45
Hydrogen bonds are important in cellulose molecules. Explain why.
Hydrogen bonds are important in cellulose molecules. Explain why.
Holds cellulose molecules together
cellulose molecules form microfibrils, providing strength
H bonds are strong in large numbers
46
A starch molecule has a spiral shape. Explain why this shape is important to its function in cells.
A starch molecule has a spiral shape. Explain why this shape is important to its function in cells.
Compact and tightly packed
47
Triglycerides are taken into the body as part of a balanced diet. These triglycerides contain fatty acids including omega-3 fatty acids.
It has been discovered that omega-3 fatty acids are associated with health benefits.
The benefits include faster development of nerve cells and clearer vision.
Omega-3 fatty acids are also associated with protection from heart disease, arthritis and cancer.
Triglycerides in food —> Digestion and release of fatty acids In the small intestine —> fatty acids are transported to tissue by blood —> Fatty acids are taken up by cells —> Used to make plasma membranes, Required for energy, and Converted to other fatty acids
Use the information in the figure to explain two ways in which fatty acids are important in the formation of new cells.
Triglycerides are taken into the body as part of a balanced diet. These triglycerides contain fatty acids including omega-3 fatty acids.
It has been discovered that omega-3 fatty acids are associated with health benefits.
The benefits include faster development of nerve cells and clearer vision.
Omega-3 fatty acids are also associated with protection from heart disease, arthritis and cancer.
Triglycerides in food —> Digestion and release of fatty acids In the small intestine —> fatty acids are transported to tissue by blood —> Fatty acids are taken up by cells —> Used to make plasma membranes, Required for energy, and Converted to other fatty acids
Use the information in the figure to explain two ways in which fatty acids are important in the formation of new cells.
Fatty acids used to make phospholipids; Phospholipids in membranes;
More phospholipids more membranes made;
Fatty acids respired to release energy;
More triglycerides more energy released;
Energy used for cell production
48
Draw the triglyceride that would be formed from condensation reactions between a molecule of glycerol and three molecules of propanoic acid
Draw the triglyceride that would be formed from condensation reactions between a molecule of glycerol and three molecules of propanoic acid
49
Explain how the structure of phospholipids make them able to form the bilayer of cell membranes
Explain how the structure of phospholipids make them able to form the bilayer of cell membranes
Phospholipid heads are hydrophilic and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side this makes the centre of the membrane bilayer hydrophobic, so water-soluble substances can’t easily pass through it
50
What is the primary, Secondary tertiary and Quaternary structure of a protein
What is the primary, Secondary tertiary and Quaternary structure of a protein
Primary structure is the sequence of amino acid in the polypeptide chain
Secondary structure is when hydrogen bonds formed between the amino acid’s which make it coil into an alpha helix or folded into a beater pleated sheet
Tertiary structure is when the chain of amino acid is coiled and folded further hydrogen bonds and ionic bonds form between different parts of the polypeptide chain and disulfied bridges also form whenever two molecules of the amino acid cysteine come close together
Quaternary structure is the way these polypeptide chains are assembled together which is the proteins final 3-D structure
51
The biuret test for proteins And what precipitate presents a positive result
The biuret test for proteins
The test solution needs to be alkaline so first you add a few drops of sodium hydroxide solution then you add some copper sulphate solution
Purple colour indicates protein
52
What organ produces amylase
What organ produces maltase
What organ produces amylase
Pancreas
What organ produces maltase
Small intestine
53
Maltose is hydrolysed by the enzyme maltase.
| Explain why maltase catalyses only this reaction
Maltose is hydrolysed by the enzyme maltase.
Explain why maltase catalyses only this reaction
active site is complementary to substrate/maltose;
(Only) maltose can fit;
To form enzyme substrate complex.
54
Give one function of lysosomes
Give one function of lysosomes
Breakdown toxins
55
Describe and explain how centrifuging the culture allowed the scientists to obtain a cell-free liquid
Describe and explain how centrifuging the culture allowed the scientists to obtain a cell-free liquid.
heavy cells;
move to bottom of tube (when centrifuged); supernatant can be removed.
56
H. pylori cells produce an enzyme that neutralises acid.
| Suggest one advantage to the H. pylori of producing this enzyme.
H. pylori cells produce an enzyme that neutralises acid.
Suggest one advantage to the H. pylori of producing this enzyme.
Break down toxins
57
A principle of homeostasis is the maintenance of a constant internal environment. An increase in the concentration of carbon dioxide would change the internal environment and blood pH.
Explain the importance of maintaining a constant blood pH.
A principle of homeostasis is the maintenance of a constant internal environment. An increase in the concentration of carbon dioxide would change the internal environment and blood pH.
Explain the importance of maintaining a constant blood pH.
enzyme (in blood) affected by change in pH;
eg haemoglobin, carrier protein in plasma membrane
(Resultant) change of charge/shape/tertiary structure;
less oxygen binds with haemoglobin / less transport across membranes / fewer substrates can fit active site / fewer enzyme-substrate complexes.
58
Suggest how the antidote can reduce poisoning by cyanide.
Suggest how the antidote can reduce poisoning by cyanide.
(Antidote reacts with / binds to cyanide) so cyanide cannot bind to enzyme / cytochrome oxidase
59
technician investigated the effect of temperature on the rate of an enzyme-controlled reaction. At each temperature, he started the reaction using the same volume of substrate solution and the same volume of enzyme solution
Give one other factor the technician would have controlled
technician investigated the effect of temperature on the rate of an enzyme-controlled reaction. At each temperature, he started the reaction using the same volume of substrate solution and the same volume of enzyme solution
Give one other factor the technician would have controlled
Concentration of substrate solution
60
Rate of reaction =
Rate of reaction = change in y /change in x
61
Scientists determined that a sample of DNA contained 18% adenine.
What were the percentages of thymine and guanine in this sample of DNA?
Scientists determined that a sample of DNA contained 18% adenine.
What were the percentages of thymine and guanine in this sample of DNA?
```
Thymine 18 (%)
Guanine 32 (%).
```
62
Directions in which each new DNA strand is being produced.
explain why the arrows point in opposite directions
DNA has antiparallel strands
2. (Figure 1 shows) shape of the nucleotides is different
3. Enzymes have active sites with specific shape;
4. Only substrates with complementary shape
Directions in which each new DNA strand is being produced.
explain why the arrows point in opposite directions
DNA has antiparallel strands
2. (Figure 1 shows) shape of the nucleotides is different
3. Enzymes have active sites with specific shape;
4. Only substrates with complementary shape
63
Draw the dipeptides and polypeptide that would be formed from a condensation reaction between:
glycine and valine
Alanine and glycine
Glycine alanine and valine
Draw the dipeptides and polypeptide that would be formed from a condensation reaction between:
glycine and valine
Alanine and glycine
Glycine alanine and valine
64
What term is used to describe an enzyme acts outside cells
What term is used to describe an enzyme acts outside cells
Extra cellular
65
Explain in terms of activation energy Why an enzyme enables reactions to happen at lower temperatures than without an enzyme
Explain in terms of activation energy Why an enzyme enables reactions to happen at lower temperatures than without an enzyme
Activation energy is needed to start a chemical reaction
the activation energy is often provided as heat
with the presence of an enzyme the activation energy required to start a reaction is lowered
therefore not as much Heat is needed so the reaction that can take place will be at a lower temperature than it could do without an enzyme
66
What is the main difference between the lock and key model and the induced fit model
What is the main difference between the lock and key model and the induced fit model
In the lock and key model the active site has a fixed shape that is complimentary to the substrate but in the induced fit model of the active site has to change shape slightly to allow the substrate to bind tightly
67
Methanol is broken down in the body into formaldehyde
The buildup of formaldehyde can cause death the enzyme that hydrolyses
The reaction is alcohol dehydrogenase
Someone had been poisoned with methanol they could be helped by being given ethanol as soon as possible explain why
Methanol is broken down in the body into formaldehyde
The buildup of formaldehyde can cause death the enzyme that hydrolyses
The reaction is alcohol dehydrogenase
Someone had been poisoned with methanol they could be helped by being given ethanol as soon as possible explain why
Ethanol has a similar shape to methanol this means it will act as a competitive inhibitor binding to the active site of alcohol dehydrogenase and blocking methanol molecules this means lower levels of methanol will be hydrolysed so the toxic products formaldehyde won’t build up to fatal levels
68
Explain how non-competitive inhibition prevents enzyme activity
Explain how non-competitive inhibition prevents enzyme activity
A non-competitive inhibitor molecule binds to the enzyme away from the active site its presence alters the shape of the active site meaning that substrate molecules can no longer bind here this prevents enzyme activity
69
Describe the structure of sucrose and explain how it is formed
Describe the structure of sucrose and explain how it is formed
Sucrose is made from a fructose molecule and a glucose molecule which are joined by a Glycosidic bond formed during a condensation reaction
70
Draw two monosaccharides that join together to form sucrose
Draw two monosaccharides that join together to form sucrose
71
Describe a biochemical test you could use to identify the presence of a non-reducing sugar
Describe a biochemical test you could use to identify the presence of a non-reducing sugar
Initially the sample is heated in a water bath that’s been brought to the boil with Benedict Regent to rule out the presence of reducing sugars a new test sample is then heated in a water bath that’s been brought to the boil with dilute hydrochloric acid and then neutralised with sodium hydrocarbonate next the sample is heated with Benedicts regent
the test sample would form a coloured green yellow orange brick red precipitate if a non-reducing sugar was present
72
Glycogen is a polysaccharide describe the structure of glycogen and explain how it structure makes it suited to its function
Glycogen is a polysaccharide describe the structure of glycogen and explain how it structure makes it suited to its function
Glycogen is a long branched chain of alpha glucose
animals use it to store excess glucose
many branches means that the glucose can be released quickly for energy
it is also compact shape so it is easy to store
73
The biuret test can be used to test for the presence of protein in a sample describe how this test would be carried out including what observations would indicate positive and negative results
The biuret test can be used to test for the presence of protein in a sample describe how this test would be carried out including what observations would indicate positive and negative results
Add a few drops of sodium hydroxide solution to the test sample then add some copper sulphate solution if protein is present the solution will turn purple if there is no protein present the solution will stay blue
74
Draw the structure of an amino acid
Draw the structure of an amino acid
75
Describe the process by which pepsin breaks down a protein
Describe the process by which pepsin breaks down protein
The protein binds to pepsin is active site to form an enzyme substrate complex this lowers the activation energy for the breakdown of the protein by putting strain on the peptide bonds making them easier to break
the reaction is catalysed and the products are released
76
Describe the enzymes tertiary structure and how it relates to its properties
Describe the enzymes tertiary structure and how it relates to its properties
The tertiary structure is the 3-D structure of the polypeptide chain formed by hydrogen bonding and ionic bonding between different parts of the chain disulphide bridges can also be formed between cystiene R groups
the tertiary structure determines the shape of the active site of an enzyme
the shape of the active site makes the enzyme specific to its substrate
77
Explain what happens when an enzyme is denatured
Explain what happens when an enzyme is denatured
The shape of the active site has changed so it’s no longer complimentary in shape to the substrate and will not find to it to catalyse the reaction
78
Suggest two variables you would control if you investigating the activity of gastric lipase a different pH values
Suggest two variables you would control if you investigating the activity of gastric lipase a different pH values
Temperature and substrate concentration
79
Scientist analysed a section of double-stranded DNA there were 68 bases in total (34 base pairs) and 22 of the bases were adenine how many of the bases were:
(a) cytosine
(b) thymine
(c) guanine
Scientist analysed a section of double-stranded DNA there were68 bases in total (34 base pairs) and 22 of the bases were adenine how many of the bases were:
(a) cytosine 12
(b) thymine 22
(c) guanine 12
80
What is the function of DNA
What are ribosome is made up of
Name the monomer of DNA and RNA
Describe the structure of the DNA nucleotide
Name the four possible bases in DNA
What type of bond, present in a new poly nucleotide chain, consists of two ester bonds and a phosphate group
What is the function of DNA
It’s stores genetic information
What are ribosome is made up of
RNA and proteins
Describe the structure of the DNA nucleotide
A DNA nucleotide contains a phosphate group, the pentose sugar deoxyribose and a nitrogen-containing organic base
Name the four possible bases in DNA
Adenine thymine cytosine and thymine
What type of bond, present in a new poly nucleotide chain, consists of two ester bonds and a phosphate group
Phosphodiester bonds
81
Describe how a DNA double helix is formed from two polynucleotide strands
Name of the sugar in RNA
Name the four possible bases in RNA
Describe three differences between DNA and RNA
What caused many scientists to doubt that
Describe how a DNA double helix is formed from two polynucleotide strands
Two DNA polynucleotide strands join together by hydrogen bonding between complimentary base pairs – A with T and G with C.
2 hydrogen bonds form between A and T, and three hydrogen bonds formed between C and G. the antiparallel strands then twist round each other to form the DNA double helix
Name of the sugar in RNA
Ribose
Name the four possible bases in RNA
Adenine, thymine, cytosine and uracil
Describe three differences between DNA and RNA
DNA is double-stranded whereas RNA is single standard
The pentose sugar in DNA is deoxyribose but its ribose in RNA
DNA contains the base thymine whereas RNA doesn’t it contains uracil instead
What caused many scientists to doubt that DNA carried the genetic code
DNA has a relatively simple chemical composition
82
DNA is copied by semiconservative replication of DNA what is meant by this
DNA is copied by semiconservative replication of DNA what is meant by this
It is where half of the new strands of DNA are from the original molecule of DNA
83
Name the two enzymes involved in DNA replication
describe the first stage of DNA replication in which two strands of DNA are separated
describe the second stage of DNA replication where the single strands of DNA act as templates
Name the two enzymes involved in DNA replication
DNA helicase and DNA polymerase
describe the first stage of DNA replication in which two strands of DNA are separated
DNA helicase breaks the hydrogen bonds between the bases on the two polynucleotide DNA strands this makes the helix unwind to form two single strands
describe the second stage of DNA replication where the single strands of DNA act as templates
Free-floating DNA nucleotides are attached to their complimentary exposed bases on each original template strand – A with T and C with G
84
In addition to ADP and ATP cells can also contain a molecule called AMP adenosine monophosphate
suggest what the structure of this molecule is
In addition to ADP and ATP cells can also contain a molecule called AMP adenosine monophosphate
suggest what the structure of this molecule is
AMP is made from a molecule of adenine and a molecule of ribose and one phosphate group
85
The movement of calcium irons across a cell membrane can occur via the energy requiring process of active transport
This movement of calcium ions is coupled to the breakdown of ATP. suggest why.
The movement of calcium irons across a cell membrane can occur via the energy requiring process of active transport
This movement of calcium ions is coupled to the breakdown of ATP. suggest why.
The breakdown/hydrolysis of ATP releases energy, so when this reaction is coupled to the process of active transport it provides the energy for this process directly
86
Describe the structure of a molecule of ATP
what is ATP broken down into
by what type of reaction is ATP broken down
what enzyme catalyses the breakdown of ATP
how can inorganic phosphate released by the breakdown of ATP be used
Describe the structure of a molecule of ATP
A molecule of ATP is made from a molecule of adenine, a molecule of ribose and three phosphate groups
what is ATP broken down into
ADP and Pi
by what type of reaction is ATP broken down
Hydrolysis
what enzyme catalyses the breakdown of ATP
ATP hydrolase
how can inorganic phosphate released by the breakdown of ATP be used
It can be used to phosphorylate another compound/added to another compound, which often makes the compound more reactive
87
ATP can be re-formed by the addition of an inorganic phosphate to ADP
what type of reaction is this and give an example of a process during which this reaction takes place
ATP can be re-formed by the addition of an inorganic phosphate to ADP
what type of reaction is this and give an example of a process during which this reaction takes place
Condensation reaction
this reaction takes place in photosynthesis and respiration
88
Name two reactions that water is involved in
why is water classed as a polar molecule
what is a hydrogen bond
what is a metabolite
Name two reactions that water is involved in
Condensation and hydrolysis
why is water classed as a polar molecule
Because it has a slight negative charge on one side and a slight positive charge on the other
what is a hydrogen bond
A weak bond between a slightly positively charged hydrogen atom in one molecule and a slightly negatively charged atom in another molecule
what is a metabolite
A substance involved in a metabolic reaction
89
What makes water useful as a solvent
water has a high latent heat of vaporisation what does this mean
explain why water has a high specific heat capacity
what is cohesion
why is cohesion between water molecules important in plants
What makes water useful as a solvent
Its polarity
water has a high latent heat of vaporisation what does this mean
Lots of heat is used to change it from a liquid to a gas
explain why water has a high specific heat capacity
Because when water is heated, a lot of the heat energy is used to break the hydrogen bonds between water molecules.
this means there is less heat energy available to actually increase the temperature of the water
what is cohesion
The attraction between molecules of the same type, for example two water molecules
why is cohesion between water molecules important in plants
Strong cohesion between water molecules allows water to travel in columns in the xylem tissue inside plants. substances are transported around plants in this way
90
What is an inorganic ion
An ion that doesn’t contain carbon
where do you inorganic ions occur
They are present in solution in the cytoplasm of cells and in the body fluids of organisms
What determines an ions specific role
It’s specific properties
What ions are part of haemoglobin molecules
Iron ions
what is the role of these ions in haemoglobin
They bind to oxygen
name the ion that is linked to pH
Hydrogen ions/H+ ions
which type of ion is involved in moving glucose and amino acids across cell membranes
Sodium ions/Na+
what is the name of this process
Co-transport
What is an inorganic ion
where do you inorganic ions occur
What determines an ions specific role
What ions are part of haemoglobin molecules
what is the role of these ions in haemoglobin
name the ion that is linked to pH
which type of ion is involved in moving glucose and amino acids across cell membranes
what is the name of this process
91
ATP hydrolysis is coupled to the action of DNA Helicases in unwinding a DNA molecule during DNA replication
describe the reaction of ATP hydrolysis
Suggest why ATP hydrolysis is coupled to the action of DNA helicase
name one of the molecule that contains a phosphate ion
ATP hydrolysis is coupled to the action of DNA Helicases in unwinding a DNA molecule during DNA replication
describe the reaction of ATP hydrolysis
During ATP hydrolysis, ATP is broken down into a molecule of ADP and a phosphate group a phosphate bond is broken and this releases energy this reaction is catalysed by ATP hydrolase
Suggest why ATP hydrolysis is coupled to the action of DNA helicase
ATP hydrolysis can be coupled to reactions that require energy so that energy can be supplied directly to the reaction and allow it to take place
DNA Helicase must therefore require energy in order to unwind DNA molecules by breaking hydrogen bonds
92
When humans exercise vigourously they lose water from their bodies in sweat
name the property of water that enables sweating to have a cooling effect on the body during exercise. explain how it has this affect
sweat contains ions such as sodium ions, dissolved in water, describe how sodium ions dissolve in water
give one use of sodium ions in the body
When humans exercise vigourously they lose water from their bodies in sweat
name the property of water that enables sweating to have a cooling effect on the body during exercise. explain how it has this affect
Water has a high latent heat of vaporisation which means it carries away a lot of heat energy when it evaporates from the surface so when sweat evaporates from the body it carries away heat energy which cools the surface in it helps to lower the temperature of the body
sweat contains ions such as sodium ions, dissolved in water, describe how sodium ions dissolve in water
Water is a polar molecule/has a slightly positively charged and in a slightly negative charged and the slightly negative charged end of a water molecule will be attracted towards these positively charged sodium ions
the ions will become totally surrounded by water molecules and this means they are dissolved in water
give one use of sodium ions in the body
A molecule of glucose can be cold transported into the cell alongside sodium ions
93
Name all the parts you could find in the mitochondrion
Name all the parts you could find in the mitochondrion
The matrix the outer membrane and the Cristae
94
Give two functions of the cell surface membrane
Describe the function of the nucleus
Describe the appearance of the Golgi apparatus
Give one function of the lysosome
What is the function of the smooth endoplasmic reticulum
Explain the difference between a tissue and an organ
What is an organ system?
Give two functions of the cell surface membrane
To regulate movement of substances into and out of the cell and to respond to chemicals like hormones
Describe the function of the nucleus
The nucleus controls the cells activities by controlling the transcription of DNA
Describe the appearance of the Golgi apparatus
It is a group of fluid filled membrane-bound flattened sacks
Give one function of the lysosome
To digest invading cells and to break down worn out components of the cell
What is the function of the smooth endoplasmic reticulum
It’s synthesisers and processes lipids
Explain the difference between a tissue and an organ
Are tissues by similar cells are grouped together, whereas an organ is by different tissues are grouped together to perform a particular function
What is an organ system?
And organ systems is where different organs work together to carry out a particular function
95
Suggest why the capsule and the flagellin make prokaryotic cells well adapted to living in the gut
Suggest why the capsule and the flagellin make prokaryotic cells well adapted to living in the gut
The capsule is a layer of slime can help protect the bacterium from attack by the hosts immune system the flagellin allows the bacteria to move through the gut
96
Where is murein used in prokaryotic cells
Name and describe the process by which prokaryotic cells reproduce
What is a capsid
What is the role of viral attachment proteins
Where is murein used in prokaryotic cells
In the cell wall
Name and describe the process by which prokaryotic cells reproduce
Binary fission.
the circular DNA and plasmids replicate, the main DNA loop is only replicated once but the plasmids can be replicated several times the cell gets bigger and the DNA loops move to opposite poles of the cell. The cytoplasm begins to divide and new cell walls begin to form. the cytoplasm divides and two two daughter cells are produced. each daughter cell has one copy of the circular DNA but a variable number of copies of the plasmids
What is a capsid
The protein coat that surrounds the core of genetic material in a virus
What is the role of viral attachment proteins
They allow a virus to attach to specific host cells which have the complimentary receptor proteins
97
Convert:
millimetre to micro meter
micro meter to nanometre
Convert:
millimetre to micro meter x1000
micro meter to nanometre x1000
98
Order of organelles separated in cell fractionation is Nuclei Chloroplasts Mitochondria Lysosomes ER and Ribosomes
Good way of remembering:
Order of organelles separated in cell fractionation is Nuclei Chloroplasts Mitochondria Lysosomes ER and Ribosomes
Naughty Clever Monkeys Like Eating Red Raspberries
99
Suggest what type of microscope you would use in each of the following scenarios and give a reason for each answer.
studying how E. coli bacteria replicate
Studying the 3-D structure of red blood cells
studying virus particles that are 0.1 micro meter in diameter
Suggest what type of microscope you would use in each of the following scenarios and give a reason for each answer.
studying how E. coli bacteria replicate
An optical microscope, as electron microscopes can only be used on dead specimens
Studying the 3-D structure of red blood cells
SEN, as they can give 3-D images
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studying virus particles that are 0.1 micro meter in diameter
Electron microscope (TEM/SEM) as the virus particles are smaller than the maximum resolution of optical microscopes
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100
What is the maximum resolution for an optical microscope and an electron microscope
What type of microscope would you use to study lysosomes
How do you transmission electron microscope’s work
how do you scanning electron microscope’s work
give one advantage and one disadvantage of TEMs
What is the maximum resolution for an optical microscope and an electron microscope
OP- 0.2 micro metres
EM- 0.0002 micro metres
What type of microscope would you use to study lysosomes
EM
How do you transmission electron microscope’s work
TEMs use electromagnets to focus a beam of electrons, which is then transmitted through the specimen. denser parts of the specimen absorb more electrons, which makes them look darker on the image you end up with
how do you scanning electron microscope’s work
SEM’s scan a beam of electrons across the specimen. this knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image
give one advantage and one disadvantage of TEMs
Advantage: gives high resolution images so can be used to look at small objects and the internal structure of organelles
disadvantage: can only be used on thin specimens and can only be used on non-living specimens
101
Give one advantage of SEMs over TEMs
What is the temporary mount microscope slide
What is a microscope artefact
How did the first scientists to use electron microscopes distinguish between artefacts and organelles
Give two ways homogenisation for cell fractionation is done
describe what happens at the filtration step of cell fractionation and explain why it is carried out
Give one advantage of SEMs over TEMs
Can be used on thick specimens, whereas TE and can’t
What is the temporary mount microscope slide
I prepared microscope slide in which the specimen has been suspended in a drop of liquid
What is a microscope artefact
Something that you can see down the microscope that isn’t part of the cell
How did the first scientists to use electron microscopes distinguish between artefacts and organelles
They repeatedly prepared specimens in different ways if an object could be seen with one preparation technique but not another, it was more likely to be an artefact in it than an organelle.
Give two ways homogenisation for cell fractionation is done
By vibrating the cells, or by grinding the cells up in a blender
describe what happens at the filtration step of cell fractionation and explain why it is carried out
The homogenised cell solution is filtered through a gauze to separate any large cell debris or tissue debris, like connective tissue, from the organelles
102
What happens in anaphase
What happens in anaphase
Centromeres have divided, separating each pair of sister chromatids and the spindle fibres have contracted, pulling the chromatids to opposite poles of the spindle by their centromeres
103
What happens in metaphase
What happens in metaphase
Chromosomes line up down the middle of the cell and are attached to spindle fibres
104
The scientist is looking at tissue sample under a microscope she counts 150 cells undergoing mitosis, of those, 12 cells are in prophase. 1 complete cell cycle of the tissue lasts 0.70 days how long do the cells spend in prophase give your answer in hours
The scientist is looking at tissue sample under a microscope she counts 150 cells undergoing mitosis, of those, 12 cells are in prophase. 1 complete cell cycle of the tissue lasts 0.70 days how long do the cells spend in prophase give your answer in hours
(12/150) x 16.8 = 1.3 hours in prophase
105
Methotrexate and vincristine Are drugs to use to treat cancer methotrexate blocks the formation of nucleotides within cells and vincristine prevent the formation of spindle fibres within the nucleus of cells
which stage of the cell cycle is distributed by:
(a) methotrexate
(b) vincristine
Methotrexate and vincristine Are drugs to use to treat cancer methotrexate blocks the formation of nucleotides within cells and vincristine prevent the formation of spindle fibres within the nucleus of cells
which stage of the cell cycle is distributed by:
(a) methotrexate
(b) vincristine
106
What is the cell cycle
why is mitosis needed
what stage of the cell cycle does all the DNA unravel
What is the cell cycle
The process that all body cells from multi cellular organisms used to grow and divide
why is mitosis needed
For growth and for repairing damaged tissues
what stage of the cell cycle does all the DNA unravel
Interphase
107
describe what happens during prophase
describe what happens during telophase
what is cytokinesis
what is cancer
describe what happens during prophase
During prophase the chromosomes condense, getting shorter and fatter.
the Centrioles start moving to opposite ends of the cell, forming the spindle.
the nuclear envelope breaks down and chromosomes lie free in the cytoplasm
describe what happens during telophase
During telophase the chromatids reach the opposite poles on the spindle
they uncoil and become long and thin again there now called chromosomes again
a nuclear envelope forms around each group of chromosomes so there are now two nuclei
the cytoplasm divides and there are now two daughter cells that are genetically identical to the original cell and to each other
what is cytokinesis
Division of the cell cytoplasm
what is cancer
It’s a tumour that invades surrounding tissues
108
Mitotic index =
Mitotic index = number of cells with visible chromosomes/total number of cells observed
109
If you observed 30 cells and four of them had visible chromosomes what is the mitotic index
If you observed 30 cells and four of them had visible chromosomes what is the mitotic index
4/30 = 0.13
110
A student prepared a stained squash slide of cells from a hyacinth root tip, in order to investigate mitosis
Why is it necessary for the student to add a stain in order to investigate mitosis
Name one suitable stain that he could’ve used
Describe how the student should have squashed the tissue on the slide to avoid damaging the chromosomes
would you expect the mitotic index of these root tip cells to be higher or lower than the mitotic index of your cells taken from a mature hyacinth leaf explain your answer
A student prepared a stained squash slide of cells from a hyacinth root tip, in order to investigate mitosis
Why is it necessary for the student to add a stain in order to investigate mitosis
To make the chromosomes easier to see under the microscope
Name one suitable stain that he could’ve used
Toluidine blue O
Describe how the student should have squashed the tissue on the slide to avoid damaging the chromosomes
The student should have put a cover slip on top of the specimen and pushed on firmly making sure that he didn’t smear the coverslip sideways
would you expect the mitotic index of these root tip cells to be higher or lower than the mitotic index of your cells taken from a mature hyacinth leaf explain your answer
The mitotic index for the root tip cells would be higher because they are part of a tissue that is undergoing a lot of growth – unlike the mature leaf
111
Describe how to focus an optical microscope on a specimen
what is an eyepiece graticule
what is the purpose of a stage micro meter
Describe how to focus an optical microscope on a specimen
The slide containing the specimen should first be clipped onto the slide then an objective lens should be selected and the course adjustment knob used to position the objective lens just above the slide finally, while looking down the eyepiece, the fine adjustment knob should be used to adjust the focus until a clear image of the specimen can be seen
what is an eyepiece graticule
And eyepiece graticule is fitted onto the eyepiece it’s like a transparent ruler with the numbers, but no units
what is the purpose of a stage micro meter
A stage micro meter is used to work out the value of the divisions on the eyepiece graticule at a particular magnification
112
A scientist is the studying secretary epithelial cells from the stomach under an optical microscope the microscope has a magnification of x 100 and the resolution of 0.2 micro metres the ribosomes in the epithelial cells are 25 micro metre in diameter will the scientist be able to see them using the light microscope explain your answer
A scientist is the studying secretary epithelial cells from the stomach under an optical microscope the microscope has a magnification of x 100 and the resolution of 0.2 micro metres the ribosomes in the epithelial cells are 25 micro metre in diameter will the scientist be able to see them using the light microscope explain your answer
Know the microscope has a resolution of 0.2 micro metres which means it can’t distinguish between objects that are smaller than 0.2 micro metres such as the ribosomes
113
The scientist sees an image of an epithelial cell that is 4 mm in diameter calculate the actual diameter of the cell
The scientist sees an image of an epithelial cell that is 4 mm in diameter calculate the actual diameter of the cell
Size of real object = size of image/magnification
4÷100 = 0 .04 mm
114
One of the main functions of secretary epithelial cells in the stomach is to produce and secrete digestive enzymes suggest one organelle that is likely to present in large numbers in the epithelial cells to aid this function explain your choice
One of the main functions of secretary epithelial cells in the stomach is to produce and secrete digestive enzymes suggest one organelle that is likely to present in large numbers in the epithelial cells to aid this function explain your choice
Ribosomes as these are the site of protein synthesis
115
The scientist also separated the organelles by cell fractionation in order to study each one individually describe and explain the process of cell fractionation
The scientist also separated the organelles by cell fractionation in order to study each one individually describe and explain the process of cell fractionation
First the cell membranes are broken down by homogenisation to release the organelles into solution
the solution is kept ice cold to prevent enzymes breaking down the organelles
an isotonic solution is used to prevent damage to organelles by osmosis
a buffer solution is added to maintain the pH the homogenised to sell solution is then filtered through a gauze to separate any large-cell debris or tissue debris from the organelles ultracentrifugation is then carried out to separate each organelle from the others the cell fragments are poured into a tube and spun in a centrifuge to separate out the heaviest organelles, which remains in the palate at the bottom of the tube, leaving the others Suspended in the supernatant this process is then repeated at higher and higher speeds to separate out all the organelles
116
Penicillins are a group of antibiotics that are only effective against prokaryotic cells they work by inhibiting cell wall synthesis, leading to sell lysis (bursting) explain why penicillin antibiotics can clear bacterial infections in humans without harming the infected individuals cells
Penicillins are a group of antibiotics that are only effective against prokaryotic cells they work by inhibiting cell wall synthesis, leading to sell lysis (bursting) explain why penicillin antibiotics can clear bacterial infections in humans without harming the infected individuals cells
Bacteria are prokaryotic cells, so the penicillin inhibits the synthesis of the cell walls, eventually leading to cell lysis and death human cells are eukaryotic animal cells and so have no cell wall so penicillin antibiotics leave the cells unaffected
117
Antibiotics can be used to target other features of prokaryotic cells give an example of a feature that could be targeted and explain what it would be appropriate
Antibiotics can be used to target other features of prokaryotic cells give an example of a feature that could be targeted and explain what it would be appropriate
Antibiotic to target the capsule of prokaryotic cells which human cells don’t have.this would leave the prokaryotics more open to attack from the cells of the hosts immune system
118
Suggest a function of each of the following membranes:
(a) The membrane surrounding a chloroplast
(b) the membrane surrounding a bacterial cell
Suggest a function of each of the following membranes:
(a) The membrane surrounding a chloroplast
To keep the enzymes needed for photosynthesis all in one place
(b) the membrane surrounding a bacterial cell
To control what substances enter and leave the cell
119
Chloride ions need to pass through the cell surface membrane to get inside the cell how might they move across the membrane
Chloride ions need to pass through the cell surface membrane to get inside the cell how might they move across the membrane
Using carrier proteins/channel proteins in the membrane
120
The protein content of a typical cell membrane is around 50% in energy releasing organelles such as mitochondria demand rises to around 75% suggest a reason for this difference
The protein content of a typical cell membrane is around 50% in energy releasing organelles such as mitochondria demand rises to around 75% suggest a reason for this difference
Energy releasing organelles require lots of substances such as nutrients enzymes and ATP to travel across the membrane so some of these substances will require help from proteins to get across the membrane so these membranes will have a higher protein content
121
A person removes some raspberries from the freezer and that have frozen solid and leaves them on a plate to defrost when he returns there is a red puddle on the plate around the fruit use your knowledge of cell membranes to explain what has happened
A person removes some raspberries from the freezer and that have frozen solid and leaves them on a plate to defrost when he returns there is a red puddle on the plate around the fruit use your knowledge of cell membranes to explain what has happened
Freezing the raspberries will have caused ice crystals to form and pierce the cell surface membranes, making the membrane highly permeable when they thawed this will have caused the red pigment to leak out of the raspberry cells as they defrosted
122
An experiment was carried out to investigate the effect of increasing methanol concentration on the permeability of beetroot cell membranes
beetroot cubes were soaked in varying concentrations of methanol for a set amount of time then a colorimeter was used to read the absorbance of the liquid once the beetroot cubes had been removed the results of the experiment where are used to produce a graph
give four variables that should have been controlled in this experiment
Give two things that should be done with the colorimeter before its used to measure the absorbance of the liquid samples
An experiment was carried out to investigate the effect of increasing methanol concentration on the permeability of beetroot cell membranes
beetroot cubes were soaked in varying concentrations of methanol for a set amount of time then a colorimeter was used to read the absorbance of the liquid once the beetroot cubes had been removed the results of the experiment where are used to produce a graph
give four variables that should have been controlled in this experiment
The size of the beetroot cubes the beetroot the cubes came from the volume of methanol solution the cubes were soaked in and the temperature of the equipment and surroundings
Give two things that should be done with the colorimeter before its used to measure the absorbance of the liquid samples
It should be turned on and left for five minutes to stabilise and it should be Calibrated to 0 using a cuvette containing distilled water
123
Why is the phospholipid bilayer described as fluid
Describe the movement of proteins within the bilayer
What is the glycoprotein
Explain the meaning of the term is hydrophilic and hydrophobic
Explain why a cell membrane is an affective barrier against water-soluble substances
Why is the phospholipid bilayer described as fluid
Because the phospholipids are constantly moving
Describe the movement of proteins within the bilayer
Some of the proteins are fixed in position, others may move sideways
What is the glycoprotein
A protein with a carbohydrate attached
Explain the meaning of the term is hydrophilic and hydrophobic
Hydrophilic means attracts water hydrophobic means repels water
Explain why a cell membrane is an affective barrier against water-soluble substances
The centre of the phospholipid bilayer is hydrophobic so the membrane doesn’t allow water-soluble substances through it
124
How does the cell-surface membrane controls what enters and leaves the cell
Describe the role of cholesterol in a cell membrane
How does the cell-surface membrane controls what enters and leaves the cell
Some proteins in the membrane allow the passage of large or charged particles that would otherwise find it difficult to cross the membrane
Describe the role of cholesterol in a cell membrane
Cholesterol helps make the membrane less fluid and more stable it maintains shape of animal cells and creates a barrier to polar substances
125
Briefly describe how you could investigate the effect of temperature on the permeability of the cell membranes
Briefly describe how you could investigate the effect of temperature on the permeability of the cell membranes
Cut equal sized beetroot cubes and place each cube in a test tube
add the same volume of water to each test tube 5 cm³ then place each test tube in a water bath set at different temperature (10, 20,30,40,50 degrees Celsius) and leave them for the same length of time
remove the beetroot cubes from each test tube and then use a colorimeter to measure the absorbance of the remaining liquid
this will indicate how much a pigment has been released by each beetroot cube and therefore how permeable the membrane is at each temperature tested
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The photograph shows Ink diffusing through a beaker of water explain what is happening to the ink molecules
The photograph shows Ink diffusing through a beaker of water explain what is happening to the ink molecules
The ink molecules are moving from an area of high concentration to an area of low concentration
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Carbon dioxide as a waste product of respiration and must be removed from cells how will each of the following affect the rate of diffusion of carbon dioxide across a cell surface membrane explain your answer in each case
(a) Increasing the thickness of the cell membrane
(b) Increasing the number of faults in the cell membrane
(c) Reducing the concentration of carbon dioxide outside of the cell
Carbon dioxide as a waste product of respiration and must be removed from cells how will each of the following affect the rate of diffusion of carbon dioxide across a cell surface membrane explain your answer in each case
(a) Increasing the thickness of the cell membrane
The distance the particles have to travel is further so the rate of diffusion will decrease
(b) Increasing the number of faults in the cell membrane
The surface area of the cell will increase so the rate of diffusion will increase
(c) Reducing the concentration of carbon dioxide outside of the cell
The concentration gradient will increase so the rate of diffusion will increase
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Simple diffusion and facilitated diffusion both move particles down the concentration gradient across the cell membrane suggest how you could determine whether a particle is being transported by simple or facilitated diffusion in an experimental setting explain your answer
Simple diffusion and facilitated diffusion both move particles down the concentration gradient across the cell membrane suggest how you could determine whether a particle is being transported by simple or facilitated diffusion in an experimental setting explain your answer
You could increase the concentration gradient of the particle and monitor the rate of diffusion facilitated diffusion requires proteins to transport particles across the cell membrane there are a fixed number of proteins in the membrane once all the proteins are in use increasing the concentration gradient won’t increase the rate of facilitated diffusion any further whereas increasing the concentration gradient will continue to increase the rate of simple diffusion
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Give three factors that affect the rate of simple diffusion
Briefly describe power carrier protein transports molecules across a cell membrane
What is the channel protein
Describe the role of channel proteins in the transport of particles across a cell membrane
Give three factors that affect the rate of simple diffusion
Concentration gradient, surface area, thickness of the exchange surface
Briefly describe power carrier protein transports molecules across a cell membrane
First, a large molecule attaches to a carrier protein in the membrane.then, the protein changes shape.this releases the molecule on the opposite side of the membrane
What is the channel protein
Channel proteins are proteins within the cell membrane that form pores
Describe the role of channel proteins in the transport of particles across a cell membrane
Channel proteins allow charged particles to pass through cell membrane via facilitated diffusion
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Explain how increasing the number of carrier and channel proteins in the membrane would affect the rate of facilitated diffusion
Explain how increasing the number of carrier and channel proteins in the membrane would affect the rate of facilitated diffusion
It would increase the rate of facilitated diffusion as it would allow more particles to be transported across the membrane at the same time
131
Describe the net movement of water molecules in each of the following situations:
Human cheek cells with the water potential of -300 kPa are placed in a salt solution with the water potential of -325 kPa
Apple slices with the water potential of -750 kPa are placed in a beaker of pure water
Orange squash with the water potential of -450 kPa is sealed in a length of visking tubing and suspended in a solution of equal water potential
Describe the net movement of water molecules in each of the following situations:
Human cheek cells with the water potential of -300 kPa are placed in a salt solution with the water potential of -325 kPa
What are molecules will move from the cheek cells into the salt solution
Apple slices with the water potential of -750 kPa are placed in a beaker of pure water
Water molecules will move into the apple slices out of the beaker of water
Orange squash with the water potential of -450 kPa is sealed in a length of visking tubing and suspended in a solution of equal water potential
There will be no net movement of water molecules as the water potential in both solutions is the same so the solutions are isotonic
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Defined three factors that affect the rate of osmosis
Defined three factors that affect the rate of osmosis
The water potential gradient the thickness of the exchange surface and the surface area of the exchange surface (the larger the surface area of the faster the rate of osmosis)
133
Describe an investigation that you could do to find the water potential of potato cells
Describe an investigation that you could do to find the water potential of potato cells
Cut equal size chips from a potato divide the chips into groups of three and measure the mass of each group
make up several different sucrose concentrations place each group of chips into a different sucrose solution and leave all the chips for the same length of time
remove the chips and measure the mass of each group again
record each groups percentage change in mass then make a calibration curve by plotting the percentage change in mass against the concentration of sucrose solution the group was in and read off the concentrationwhere the curve crosses the X axes
look up the water potential for that concentration of solution in for example a textbook to give you the water potential of the potato cells
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The thyroid gland needs iodide ions to make hormones so there is a higher concentration of iodide ions inside the thyroid cells than in the blood plasma the sodium iodide co-transporter is involved in transporting iodide ions into the thyroid gland
the concentration of sodium ions is higher in the blood plasma than in the thyroid gland
Which ion needs to be actively transported by the sodium iodide co-transporter explain your answer
Using your knowledge of transporters, describe and explain how active transport is carried out by the sodium iodide co-transporter
The thyroid gland needs iodide ions to make hormones so there is a higher concentration of iodide ions inside the thyroid cells than in the blood plasma the sodium iodide co-transporter is involved in transporting iodide ions into the thyroid gland
the concentration of sodium ions is higher in the blood plasma than in the thyroid gland
Which ion needs to be actively transported by the sodium iodide co-transporter explain your answer
The iodide ions because it needs to move from an area of low concentration to an area of higher concentration
Using your knowledge of transporters, describe and explain how active transport is carried out by the sodium iodide co-transporter
The co transporter binds to an iodide ion and the sodium ion
the sodium ion moves across the membrane into the thyroid gland down its concentration gradient
this moves Idoide ions across the membrane into the cell against its concentration gradient
135
Describe the chemical reaction that occurs to release energy from ATP
Describe the chemical reaction that occurs to release energy from ATP
Hydrolysis reaction occurs which splits ATP into ADP and inorganic phosphate
136
Describe how the following are used to transport substances across the cell membrane during active transport:
Carrier proteins and co-transporters
Describe how the following are used to transport substances across the cell membrane during active transport:
Carrier proteins and co-transporters
Carrier protein
A molecule attaches to a carrier protein in the membrane
the protein then changes shape and releases the molecule on the opposite side of the membrane
the process requires energy
Co-transporters
Call transporters bind twi molecules at a time the concentration gradient of one of the molecules is used to move the other molecule against its own concentration gradient
137
Why are sodium ions important in the transport of glucose from the Ileum into the blood
Why are sodium ions important in the transport of glucose from the Ileum into the blood
Because sodium ions diffuse from the lumen of the Ileum into the intestinal epithelium cells down the concentration gradient, through a sodium-glucose co-transporter protein
at the same time the co-transporter carries glucose into the epithelium cell against a concentration gradient glucose is then able to diffuse into blood from the epithelial cell
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Will the rate of active transport increase or decrease with an increasing number of carrier proteins
Will the rate of active transport increase or decrease with an increasing number of carrier proteins
Increase
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What are antigens
Why do some antigens generate an immune response
What are antigens
The molecule found on the surface of cells that can generate an immune response when detected by the body
Why do some antigens generate an immune response
The immune system identifies them as foreign
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What is the function of helper T cells
What is the function of helper T cells
When activated by antigens presented by phagocytes helper T cells release chemical signals to activate phagocytes, cytotoxic T cells and B cells
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What is the function of plasma cells
What is the function of plasma cells
Function of plasma cells is to produce antibodies
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What is the difference between a cellular immune response and the humoral immune response
What is the difference between a cellular immune response and the humeral immune response
The cellular immune response involves the T cells and other immune cells they interact with for example phagocytes the humoural response involves B-cells, clonal selection and the production of monoclonal antibody
143
Give three differences other than speed between primary and secondary immune response
Give three differences other than speed between primary and secondary immune response
The Primary response happens the first time a pathogen invades, the secondary response happens the second time a pathogen invades the primary response involves b and T cells the secondary response also involve memory cells there are symptoms with the primary response but not with the secondary response
144
# Define the term active and passive immunity
how do you vaccines give people immunity
what is heard immunity
described two issues surrounding the use of vaccinations
Define the term is active and passive immunity
Active immunity is the type of immunity you get when your immune system makes its own antibodies after being stimulated by an antigen
passive immunity is the type of immunity you get from being given antibodies made by a different organism your immune system doesn’t produce any antibodies of its own
how do you vaccines give people immunity
Vaccines contain antigens that cause your body to produce memory cells against a particular pathogen this makes you immune
what is heard immunity
Heard immunity is when un-vaccinated people are protected because the occurrence of the disease is reduced by the number of people who are vaccinated
described two issues surrounding the use of vaccinations
145
What is antigenic variation and explain why you can become ill with the flu even if you’ve been infected by the influenza virus before
What is antigenic variation and explain why you can become ill with the flu even if you’ve been infected by the influenza virus before
Antigenic variation is when the antigens on the surface of the pathogen change
if the influenza virus undergoes antigenic variation
the memory cells produced from the first infection will not recognise the different antigens
the immune system has to carry out a primary response to the new antigens this takes time to get rid of the infection which is why you get ill again
146
The scientist is using the indirect ELISA to test its patient for an allergy to gluten.
1st she coats a well plate with gluten protein.
she then adds the patient serum samples of three of the Wells.
she then washes the well plate and adds a secondary antibody that has an attached enzyme
the scientist washes the well plate again then adds a substrate solution
(A) Why is the well plate washed out after the secondary antibody is added
(B) The substrate will change colour if it reacts with the enzyme bound to the secondary antibody what would you expect the scientist to observe if the patient is allergic to the gluten protein explain your answer
(C) suggest why the scientist adds patients serum sample to more than one well
(D) Two control wells are used in this test
in one well antibodies specific to the gluten proteins are used instead of patient serum
in the other well a salt solution is used instead of patients serum
suggest what each of these controls are designed to show
state what would you expect the results of the test to be in each case
The scientist is using the indirect ELISA to test its patient for an allergy to gluten.
1st she coats a well plate with gluten protein.
she then adds the patient serum samples of three of the Wells.
she then washes the well plate and adds a secondary antibody that has an attached enzyme
the scientist washes the well plate again then adds a substrate solution
(A) Why is the wallplate washed out after the secondary antibody is added
To remove any unbound secondary antibodies so there won’t be a false positive result if there are no primary antibodies present
(B) The substrate will change colour if it reacts with the enzyme bound to the secondary antibody what would you expect the scientist to observe if the patient is allergic to the gluten protein explain your answer
The substrate will change colour, because there will have been primary antibodies to the gluten protein in the patient serum these will have bound to the gluten protein in the well and then the secondary antibody will have bound to them this means the enzyme that the substrate reacts with will be present in the well
(C) suggest why the scientist adds the patient serum sample to more than one well
To reduce the likelihood of getting a false result
(D) To control wells are used in this test
in one well antibodies specific to the gluten proteins are used instead of patient serum
in the other well a salt solution is used instead of patients serum
suggest what each of these controls are designed to show
state what would you expect the results of the test to be in each case
The control using antibodies shows a positive result it shows that the secondary antibody will bind to the gluten protein so the result will be a colour change the control using salt solution should show a negative result it shows that all unbound secondary antibody is removed by washing the wall plate so the results will be no colour change
147
Describe how HIV replicates
Why can’t antibiotics be used against viruses
Describe how HIV replicates
The viral attachment protein attaches to a receptor molecule on the cell membrane of the host T helper cellThe capsid is then released into the cell where it uncoats and releases RNA into the cell cytoplasm in the cell reversed transcriptase is used to make up complimentary strand of DNA from the viral RNA
double-stranded DNA is made from this which is inserted into the human DNA
enzymes in the cell are used to make viral proteins from the inserted viral DNA
the viral proteins are assembled into new viruses which bud from the cell and go on to infect other cells
Why can’t antibiotics be used against viruses
Antibiotics are used to target bacterial enzymes and ribosomes, which are different to those in humans viruses do not have their own enzymes and ribosomes they use those found in the host so cannot be targeted in this way
148
Describe the process of phagocytosis
Outline the main stages of the immune response after phagocytosis
Describe the process of phagocytosis
When a phagocyte recognises the antigens on the pathogen the cytoplasm of the phagocyte moves around the pathogen engulfing it the pathogen is now contained in a phagocytic vacuole inside the phagocyte a lysosome fuses with the phagocytic vacuole and the lysozymes inside the lysosome break down the pathogen
Outline the main stages of the immune response after phagocytosis
The phagocytes present foreign antigens from engulfed pathogens on their surface
receptor proteins on the surface of helper T cells bind to the antigens activating the T cells activated helper T cells release chemical signals that activate phagocytes cytotoxic T cells and B cells
when B cells which are covered in antibodies meet an antigen with a complimentary shape they bind to itThis along with chemical signals released from helper T cells activates the B cells this is clonal selection
the B cells then divide into plasma cells
the plasma cells then produce antibodies specific to the antigens
149
Describe the structure of an antibody
Describe the structure of an Antibody
An Antibody has variable regions where the antigen binds
Each antigen has a different shaped variable region with a different tertiary structure
they also have a constant region that is the same in all antibodies
An antibody consists of light chains and heavy chains that are joined together by disulphide bridges
150
Describe on ethical issues surrounding the use of monoclonal antibodies
Describe on ethical issues surrounding the use of monoclonal antibodies
Monoclonal antibodyies are made using animal cells and some people disagree with using animals this way
151
The sense strand:
The antisense strand:
We read DNA through the .. because ...
The sense strand: 5’ to 3’
The antisense strand: 3’ to 5’
We read DNA through the sense strand because it’s the template
