B2 Part B Flashcards
1
Q
What are enzymes and what are they made of?
A
Enzymes are substances that are produced naturally and act as a biological catalysts. They are made up of proteins.
2
Q
Define the term ‘catalyst’
A
A catalyst is a subctance which increases the speed of a reaction without being changed or used up
3
Q
Fill in the gaps:
Enzymes have a unique …….. that locks onto the substance involved in the reaction and usually they will only be able to catalyse ……… reaction.
A
Enzymes have a unique shape that locks onto the substance involved a reaction and usually they will only be able to catalyse one reaction.
4
Q
Which two factors will effect whether enzymes are working at their optimum? Draw the rate of reaction graph for each of these if it helps
A
- Temperature
- pH
5
Q
At what temperature do enzymes in the human body usually work best?
A
37°C
6
Q
If temperature is too high or pH is too high or low, what will happen to enzymes?
A
The bonds holding them together will break, destroying their unique shape and causing them to ‘denature’.
7
Q
What do digestive enzymes do to starch, proteins and fats?
A
Digestive enzymes break down big molecules of starch, proteins and fats into sugars, amino acids, glycerol and fatty acids because they are smaller and can therefore move into the body more easily.
8
Q
What does amylase do and where is it produced?
A
Amylase converts starch into sugars like maltose and dextrin.
It is made in the salivary glands, the pancreas and the small intestine.
9
Q
How does protease aid the digestive system and where is it created?
A
Protease breaks down proteins into amino acids and is made in the stomach (where it is better known as pepsin), the pancreas and the small intestine.
10
Q
What does lipase do to lipids and where in the body is it in effect?
A
Lipase converts lipids into glycerol and fatty acids, it is made in the pancreas and the small intestine.
11
Q
What are the two main purposes of bile?
A
- To neutralise stomach acid
- Emulsify fats (gives a bigger surface area for lipase to work on)
12
Q
List the 9 main parts of the digestive system
A
- Salivary glands
- Gullet (oesophagus)
- Liver
- Stomach
- Gall bladder
- Pancreas
- Large intestine
- Small intestine
- Rectum
13
Q
What is the purpose of the salivary glands?
A
They produce amylase enzyme in the saliva to help break down food.
14
Q
List the three main functions of the stomach
A
- It pummels the food with it’s muscular walls
- Produces the protease enzyme, pepsin
- Produces hydrochloric acid to kill bacteria and create the right pH for the protease enzyme to work
15
Q
What is produced in the liver, stored in the gall bladder and released into the small intestine?
A
Bile
16
Q
What does the pancreas do?
A
Produces protease, amylase and lipase enzymes. It releases these into the small intestine.
17
Q
What happens in the large intestine?
A
Excess water is absorbed from the food
18
Q
List the two functions of the small intestine
A
- To make protease, amylase and lipase enzymes to complete digestion
- To absorb digested food into the blood
19
Q
What is stored in the rectum?
A
Faeces (waste)
20
Q
Define the term ‘respiration’
A
Respiration is the process of releasing energy from glucose (which occurs in every cell)
21
Q
What is aerobic respiration and where (in cells) does it most often occur?
A
Respiration that needs oxygen and is the most efficent way to release energy from glucose, it usually happens in mitochondria.
22
Q
Give the word equation for aerobic respiration
A
Glucose + Oxygen ⇒ carbon dioxide + water + energy
23
Q
List the four main examples of how energy released by aerobic respiration is used in various life forms
A
- To build up larger molecules from smaller ones (eg. proteins from amino acids)
- To allow the muscles of animals to contract and enable movement
- To maintain body temperature in mammals and bird
- To build sugars, nitrates and other nutrients into amino acids and then into proteins in plants
24
Q
Why does excersise increase heart and breathing rate?
A
An increase in muscle activity requires more glucose and oxygen to be supplied, meaning extra CO2 must be removed from the muscle cells and for this to happen blood has to flow at a faster rate.
25
What is glucose sometimes stored as and where in the body? What can happen to this store during excersise?
Some glucose may be stored as glycogen, in each muscle's individual store or the liver. During vigorous excersise stored glycogen can be converted back to glucose to provide more energy.
26
What happens when a person excersises but their body can't supply enough oxygen to their muscles?
Muscles will begin to perform anaerobic respiration (without oxygen) rather than aerobic.
27
Give the word equation for anaerobic respiration
glucose ⇒ energy + lactic acid
28
List three disadvantages of anaerobic respiration
* Lactic acid builds up in muscle, which creates a painful sensation
* It causes muscle fatigue so they stop contracting effectively.
* It releases less energy than aerobic respiration
29
Anaerobic respiration leads to an ................... debt.
Anaerobic respiration leads to an **oxygen debt**
30
Why do you continue breathing hard for a while after you have stopped excersising?
Because the lungs, heart and blood couldn't supply oxygen to muscles fast enough during excerise, a person will breathe hard even after they stop excersising to make up for it. Blood will flow through your muscles to remove lactic acid by oxidising it. While high levels of CO2 and lactic acid are detected in the blood by the brain, the pulse and breathing rate remain high.
31
What type of enzymes are most commonly used in biological detergents and why?
Mainly protein and fat digesting enzymes (proteases and lipases) because they break down animal and plant matter, they're ideal for removing stains like food or blood.
32
Fill in the gaps: Biological detergents are more effective at working at ........ .............. than other types of detergent (eg.......)
Biological detergents are more effective at working at **low temperatures** than other types of detergent (eg. 30°C)
33
List three ways enzymes are used to change foods
1. Proteins in some baby foods are 'pre-digested' by proteases
2. Carbohydrases can turn starch syrup into sugar syrup
3. Glucose syrup can be turned into fructose syrup using isomerase enzyme - fructose is sweeter so less of it is needed, good for sliming foods and drinks.
34
Give four advantages of using enzymes in industry
1. They are specific, so will only catalyse the reaction you want them to
2. They require lower temperatures, which saves energy and money
3. They work for a long time, so after the initial cost of buying them, they can be used continually.
4. They are biodegradable
35
List four disadvantages of using enzymes in industry
1. Some people can develop allergies to them
2. They can be denatured even by a small increase in temperature
3. They are expensive to produce
4. Contamination of the enzyme with other substances can affect the reaction
36
What does DNA stand for?
**d**eoxyribo**n**ucleic **a**cid
37
Where is DNA found?
DNA can be found in the nucleus of animal and plant cells, in long molecules called chromosome.
38
# Fill in the gaps:
A gene is a ........ ... ............ A gene will contain the instructions to make a specific protein. Cells make proteins by stringing ............ ........... together in a particular order. Only 20 ........... ........... are used but they make up thousands of different proteins.
A gene is a **section of DNA**. A gene will contain the instructions to make a specific protein. Cells make proteins by stringing **amino acids** together in a particular order. Only 20 **amino acids** are used but they make up thousands of different proteins.
39
DNA determines what proteins a cell produces, which in turn determines what?
DNA determines what proteins a cell produces, which in turn determines **what type of cell it is.**
40
Describe the process of DNA (or genetic) fingerprinting in 4 steps
1. Isolation - separate the DNA from other tissues
2. Fragmentation - use an enzyme to break the DNA into short lengths
3. Separation - pass an electric current across a layer of gel which has the DNA fragments at one end. The fragments will move different distances across the gel. This is called gel electrophoresis
4. Comparison - match the pattern of fragments on the gel with other samples of DNA (eg. those collectes at a crime scene)
41
Some people want there to be a national genetic database of everyone in the country so DNA found at a crime scene can be checked against the whole population. Give three reasons why someone might oppose this idea
1. It's an invasion of privacy
2. It would be difficult to totally secure the data
3. Scientific problems - false positives can occue is errors are made or if the data is misinterpreted
42
What is mitosis and when does it occur?
When a cell reproduces itself by splitting to form two identical offspring. This happens when plants and animals want to grow or to replace cells that have been damaged.
43
How many copies do humans have of each chromosome?
2 (one from the mother, one from the father)
44
Describe the process of mitosis in 4 steps
1. The DNA is copied and forms X-shaped chromosomes. Each 'arm' of the chromosome is an exact duplicate of the other.
2. The chromosomes line up at the centre of the cell and cell fibres pull them apart, two arms of each chromosome go to opposite sides of the cell.
3. Membranes form around each of the sets of chromosomes so that they become the nuclei of the new cell.
4. Lastly, the cytoplasm divides.
45
What does meiosis produce?
Meiosis produces cells which have half the normal number of chromosomes.
46
What are gametes?
Cells used in sexual reproduction that only have one copy of each chromosome (23 in total). Male and female gametes will fuse together to form the whole 46 chromosomes.
47
Describe meiosis in 5 stages
1. The cell divides, duplicating its DNA so that one arm is an exact copy of the other.
2. In the first division, the chromosome pairs line up in the centre of the cell.
3. The pairs are then pulled apart, so that each new cell only has one copy of each chromosome. Some of the father's and some of the mother's chromosomes go into each new cell.
4. In the second division, the chromosomes line up and their arms are pulled apart.
5. At the end, you get four gametes with only a single set of chromosomes in it.
48
What is so special about embryonic stem cells?
They can become any type of cell by differentiation.
49
In most animal cells, the ability to ................. is lost at an early stage, but lots of ........ cells don't ever lose this ability
In most animal cells, the ability to differentiate is lost at an early stage, but lots of plant cells don't ever lose this ability
50
Name two places where stem cells can be found
* In early human embryos
* In adult bone marrow (although these stem cells aren't so versatile)
51
List a few ways stem cells can be used for medical purposes
* Bone marrow transplants can be used to treat blood diseases (eg. sickle cell anaemia)
* To replace faulty cells - eg. beating heart muscles (heart disease), insulin producing cells (diabetes), nerve cell (spinal chord injuries)
52
How do doctors create cultures of one specific type of cell?
By changing the environment stem cells are grown in and therefore manipulating the differentiation. So far, this has been successful on occasion but lots more research is needed.
53
Why might somebody oppose embryonic stem cell research?
They feel human embryos shouldn't be used for experiments because each one is a potential human life.
54
Give two arguments in favour of stem cell research
* Curing patients who already exist and are suffering is more important than the rights of embryos
* Embryos used in research are the unwanted ones anyway, who would otherwise be destroyed
55
The 23rd pair of chromosomes in every human body cell is labelled either XX or XY - what does this control?
Gender
XY = Male
XX = Female
56
How do the X and Y chromosomes enter sperm/egg cells?
When making sperm, the X and Y chromosomes are drawn apart in the first division in meiosis. There's a 50% chance that each sperm gets either X or Y.
When making eggs, the original cell has two X chromosomes so all eggs have one X.
57
Who was Gregor Mendel and of which area of biology did he provide the foundation?
An **Austrian monk** who trained in mathematics and natural history. On his garden plot at the monastery, he noted how **chracteristics of plants were passed on from one generation to the next.** He lived from 1822 - 1884 and the results of his work published in 1866 became **the foundation of modern genetics**.
58
Which 3 important conclusions did Mendel reach?
1. Characteristics in plants are determined by "hereditary units".
2. Hereditary units are passed on from both parents, one unit from each parent.
3. Hereditary units can be dominant or recessive - if an individual has both a dominant and recessive unit for a characteristic, the dominant will be expressed.
Note: We now know hereditary units to be genes byt in Mendel's time, nobody knew anything about DNA or genes.
59
What are 'alleles'?
Alleles are different versions of the same gene.
60
If an organism has two alleles for a particular gene that are the same, then it's ................ If it's two alleles for a particular genes are different, then it's .......................
If an organism has two alleles for a particular gene that are the same, then it's **homozygous**. If it's two alleles for a particular genes are different, then it's **heterozygous**.
61
If two alleles in an organism are different then only one can determine what characteristic is present, this is called the ................. gene, whereas the other is known as the ...............
How is a dominant gene indicated on a genetic diagram?
If two alleles in an organism are different then only one can determine what characteristic is present, this is called the **dominant** gene, whereas the other is known as the **recessive.**
A dominant gene is recognisable on a gentic diagram because it is symbolised by a capital letter.
62
Draw a genetic diagramin which the mother has a dwarf gene and the fatehr has a tall gene
63
What is cystic fibrosis caused by and why doesn't everyone who carries the gene have the disorder?
A recessive allele, 'f', carried by about 1 person in 25.
Because it's recessive, people with only one copy of the allele won't have the disorder - they're known as carriers. For a child to have cystic fibrosis, both parents must either be carriers or sufferers.
64
What is Cystic Fibrosis?
Cystic Fibrosis is a genetic order of cell membranes, which resultes in the body producing a lot of sticky thick mucus in the air passaged and pancreas.
65
What is Polydactyl?
Polydactyl is a genetic disorder where a baby is born with extra fingers or toes.
66
What is Polydactyl caused by?
The disorder is caused by a dominant allele, 'D', and can therefore be inherited if just one parent carries the disease.
67
How can genetic disorders be identified/prevented in IVF babies?
Before the embryos are implanted into a mothers womb it's possible to remove a cell from each embryo and analyse it's genes. Genetic disorders can be detected in this way and embryos with 'good' alleles can be implanted, and the ones with 'bad' alleles may be destroyed.
68
Why might somebody disagree with embryonic screening? (4)
1. People might want to screen their embryos to pick the most 'desirable' ones
2. The rejected embryos (precious potential human lives) are destroyed
3. It implies people with genetic problems are 'undesirable' and could create prejudice.
4. Screening is expensive
69
List 4 arguments for embryonic screening
1. It will reduce suffering
2. There are laws in place to stop it going so far
3. During IVF most embryos are destroyed anyway
4. Treating disorders costs the government a lot of money
70
What are fossils?
Fossils are the remains of organisms (plants or animals) that are found preserved in rocks.
71
Describe how fossils are created from gradual replacement
1. Things like teeth, shells and bones dont decay easily and therefore last for a long time when they're buried
2. They're eventually replaced by minerals as they decay, forming a rock like substance shaped like the original hard body part
3. Surrounding sediment also turns to rock, but the fossil stays distinct
72
How is a fossil formed from a cast/impression?
When an organism is buried in a soft material like clay, the clay hardens around it and the organism decays, leaving a cast of itself. Similarly, footprints can be pressed into these materials when soft, leaving an impression when it hardens.
73
List 3 examples of where fossil preservation can occur where no decay happens
1. In amber (a clear yellow 'stone' made from fossilised resin) and tar pits there's no oxygen or moisture so decay microbes can't survive and dead organisms may be preserved.
2. In glaciers, it's too cold for decay microbes to work.
3. Peat bogs are too acidic for decay microbes.
74
Give 6 reasons why a species might go extinct
1. If the organisms environment changes quickly eg. destruction of habitat
2. If a new predator kills them all
3. If a new disease takes hold
4. If they can no longer compete with another species for food
5. If a catastrophic event occurs (eg. a volcanic eruption or collision with an asteroid)
6. If a new species develops (speciation)
75
What is speciation and when does it occur?
Speciation is the development of a new species, it occurs when populations of the same species become so different that they can no longer breed together to produce fertile offspring.
76
What is isolation?
Isolation is when popualtions of a species are separated.
77
When does isolation of species occur? Try and explain it in 3 main steps
1. Isolation between two populations of the same species will happen predominantly due to there being a **physical barrier** (eg. floods, earthquakes, mountain ranges) between the two.
2. **Conditions** on eitherside of the barrier will be slightly different and therefore each population will develop different characteristics, due to **natural selection**.
3. Eventually individuals from a popualtion will have changed so much that they **won't be able to breed with the other** and it is then that the two groups will have become separate species.
78
