Topic 1: Biological Molecules Flashcards
(96 cards)
1
Q
What is a monomer?
A
The smaller units from which larger molecules are made.
2
Q
What is a polymer?
A
Molecules made from a large number of monomers joined together.
3
Q
What does a condensation reaction do?
A
Joins 2 molecules together with a formation of a chemical bond and involves the removal of a water molecule.
4
Q
What does a hydrolysis reaction do?
A
Breaks a chemical bond between 2 molecules and involves addition of a water molecule.
5
Q
What are monosaccharides?
A
The monomers from which larger carbohydrates are made
6
Q
What are some examples of monosaccharides?
A
Glucose,fructose and galactose.
7
Q
What is an isomer?
A
2 molecules with the same molecular formula but with the atoms connected in a different way.
8
Q
What is a disaccharide?
A
A disaccharide is formed when 2 monosaccharides are joined together by a condensation reacion.
9
Q
What type of bond is formed when 2 monosaccharides join?
A
A glycosidic bond
10
Q
What are some examples of disaccharides?
A
Maltose
Sucrose
Lactose
11
Q
Which 2 monosaccharides make up Maltose.
A
Alpha glucose + Alpha glucose
12
Q
Which 2 monosaccharides make up Sucrose?
A
Glucose + Fructose
13
Q
Which 2 monosaccharides make up lactose?
A
Glucose + Galactose
14
Q
What are polysaccharides?
A
Formed when more than 2 monosaccharides are joined together.
15
Q
How are glycogen and starch formed?
A
The condensation of alpha glucose molecules.
16
Q
How is cellulose formed?
A
The condensation of beta glucose molecules.
17
Q
What is the test for reducing sugars?
A
Add benedicts solution to a sample and heat in a water bath. If the solution turns brick red then reducing suagrs are present.
18
Q
What is the test for non reducing sugars?
A
Add benedicts solution to a sample and heat in a water bath. If the colour does not change from blue to brick red then reducing sugars are not present. Get a new sample and add dilute hydrochloric acid it willl hydrolyse the di and ploy saccharides into monossacchrides. place test tube in a water bath. Neutralise by adding sodium hydrogencarbonate. Then carry out the benedicts test again. If a non reducing sugar is present then colour will change from blue to brick red.
19
Q
What is the test for starch?
A
Add Iodine dissolved in potassium iodide solution to the sample. If starch iss present the sample changes from browny-orange to blue black.
20
Q
What is the structure of a triglyceride?
A
One molecule of glycerol and 3 fatty acids.
21
Q
What are the properties of the fatty acid tails?
A
Hydrophobic meaning lipids are insoluable in water. Fatty acids can be saturated (no double bonds) or unsaturated (have double bonds) which causes the chain to kink.
22
Q
What type of bond forms in the condensation of glycerol and and a fatty acid?
A
Ester bond
23
Q
Where are phospholipids found?
A
In cell membranes.
24
Q
What is the structure of a phospholipid?
A
Same as triglyceride expect one of the fatty acid molecules is replaced by a phosphate group. The phosphate group is hydrophillic and the fatty acid tails are hydrophobic.
25
How does the structure of triglycerides relate to their properties?
Triglycerides are mainly used as a storage molecule for energy, this is helped by the fatty acid tails storing lots of chemical energy, lots of energy is released when they are broken down.
They are also insoluable in water therefore don't affect the water potential of the cell.
26
How does the structure of phospholipids relate to their properties?
Phospholipids make up the bilayer of a cell membrane, which controls what enters and leaves the cell. The heads are hydrophillic and tails are hydrophobic so they form a double layer with their heads facing out towards the water. The centre of the bilayer is hydrophobic so water soliubale substances cant easily pass through acting as a barrier to those substances.
27
What is the emulsion test for lipids?
Shake the sample with ethanol, add some distilled water, if lipids are present then a white emulsion will form.
28
What are the monomers from which proteins are made up of called?
Amino acids
29
What is a dipeptide?
Formed through the condensation of 2 amino acids.
30
What is a polypeptide?
Formed through the condensation of many amino acids.
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What is the name of the bond formed between amino acids?
peptide bond
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What is the primary structure of a protein?
The unique sequence of amino acids in the polypeptide chain.
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What is the secondary structure of a protein?
Coiling or pleating of the polypeptide chain, hydrogen bonds form between the amino acids, forms either an alpha helix or a beta pleated sheet.
34
What is the tertiary structure of a protein?
The protein is folded further to form a unique 3D shape, more bonds form between different parts of the polypeptide chain including hydrogen bonds and ionic bonds. Disulfide bridges also form. The 3D shape is determined by where the bonds form which is determined by the amino acid sequence.
35
What is the quaternary structure of a protein?
Proetins which are made of more than 1 polypeptide chain, each chain has its own tertiary structure they all interact with non covalent bonds to form a stable protein complex. Examples include haemoglobin and insulin.
36
What are enzymes?
Biological catalysts which speed up the rate of chemical reactions in the body by lowering the activiation energy needed to start the reaction. The active site is specific due to it's tertiary structure.
37
What is the lock and key model?
Early scientists came up with this theory that said an enzymes active site is complementary to a substrate molecule so acts as a lock for the key and forms an enzyme substrate complex.
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What is the induced fit model?
New evidence shows that when the substrate binds to the active site, the shape of the active site is slightly altered to accomodate the substrate. This helps explain why enzymes are so specific and only bond to one particular substrate.
39
How to enzyme's properties relate to their tertiary structure?
Each different enzyme has a different tertiary structure and therefore active site. If the substrate doesn't match the active site then an enzyme substrate complex won't be formed and a reaction will not be catalysed. If tertiary structure is altered then this will change the shape of the active site so enzyme substrate complex can't form,
40
How does temperature affect the rate of enzyme activity?
More heat means more kinetic energy so molecules move faster, increases the frequency of collisons between substrates and active sites, energy of collisions also increases meaning each one is more likely to be successful. But if temperature exceeds the optimum, the reaction can stop, as bonds are broken in the enzyme causing the active site to change shape, the enzyme has become denatured and can no longer form an enzyme substrate complex.
41
How does PH affect the rate of enzyme activity?
Too high or too low a PH, the H+ and OH- ions can disrupt the ionic bonds and hydrogen bonds that hold together the enzymes tertiary structure. The active site changes shape and the enzyme denatures so fewer enzyme substrate complexes form.
42
How does substrate concentration affect the rate of enzyme activity?
Higher the substrate concentration the faster the reaction as increases the frequency of collisions between the enzyme and substrate so more active sites will be occupied. This is only true though up to a saturation point, all the active sites are full so adding more substrate makes no difference.
43
How does enzyme concentration affect the rate of enzyme activity?
More enzyme molecules there are in a solution, the more likely a substrate molecule is to collide with one and form an enzyme substrate complex. But if the amount of substrate is limited there comes a point where there is more than enough enzyme molecules do deal with all the substrate so adding more enzyme will then have no further effect.
44
What is a competitive inhibitor?
Have the same shape to that of substrate molecules. They compete with the substrate to bind to the active site but no reaction occurs, they block the active site so no substrate can fit in. Increasing the concentration of substrate increases rate of reaction as it will out compete the inhibitor knocking it out the active site.
45
What is a non competitive inhibitor?
Bind to the enzyme at an alternative place to the active site, Causes the active site to change shape so subtrate molecules can no longer bind to it. Inhibitor is not the same shape as the active site so increasing the substrate concentration will have no difference on the rate.
46
What is the function of DNA?
Used to store your genetic infomation
47
What is a DNA nucleotide made up of?
- A pentose dexyribose sugar
- A phosphate group
- A nitrogenous base
48
What are the names of the 4 nitrogenous bases?
-Adenine
-Thymine
-Cytosine
-Guanine
49
What is name of the bond formed in the condensation of 2 nucleotides?
Phosphodiester bond
50
What are the complementary base pairings in DNA
- Adenine and Thymine
- Guanine and Cytosine
51
Describe the structure of DNA?
- Double helix
- Double stranded
- ploynucleotide strands
- Hydrogen bonds between bases
- Very long
52
What is the function of RNA?
Transfers genetic infomation from the DNA to the ribosomes. Ribosomes are formed from RNA and proteins.
53
What is an RNA nucleotide made up of?
- Pentose ribose sugar
- Phosphate group
- A nitrogenous base
54
What are the complementary base pairings in RNA?
- Adenine and Uracil
- Guanine and Cytosine
55
How does the structure of RNA differ to DNA?
- Rna has a ribose sugar, DNA has deoxyribose
- DNA is longer than RNA
- RNA is single stranded, DNA is double stranded and twisted into a double helix held together by hydrogen bonds
- RNa has bases A,U,C and G and DNA has bases A,T,C and G
56
What did Watson and Crick discover?
That DNA was a double helix structure.
57
Why did scientists doubt that DNA carried the genetic code?
As it had a relatively simple chemical composition, some argued it must be carried by proteins.
58
What does semi conservative DNA replication ensure?
That there is genetic continuity between generations of cells.
59
How does semi conservative DNA replication occur?
1. DNA helicase breaks the hydrogen bonds between bases on the 2 polynucleotide DNA strands. This makes the helix unwind to form 2 single strands.
2. Each original strand acts as a template for a new strand. Complementary base pairing means that free floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand.
3. DNA polymerase joins the nucleotides of the new strands together in condensation reactions, hydrogen bonds then form between the bases of the original and new strands.
60
How did Meselson and Stahl provide evidence for semi conservative dna replication?
1. 2 samples of bacteria were grown for many generations one in a nutrient broth containing light nitrogen and one in a broth containing heavy nitrogen. As the bacteria reproduced they took up the nitrogen from the broth to help make nucleotides for new DNA. The nitrogen gradually became part of the bacteria's DNA.
2. A sample of DNA was taken from each batch of bacteria and spun in a centrifuge. The DNA from the heavy nitrogen bacteria settled lower in the centrifuge tube than the DNA from the light nitrogen bacteria.
3. Then the bacteria grown in the heavy nitrogen broth were taken out and put in broth containing only light nitrogen. The bacteria were left for 1 round of DNA replication and then another DNA sample was taken out and spun.
4. If replication was conservative the original heavy DNA would settle at the bottom and the new light DNA would settle at the top.
5. If replication was semi conservative, the bacterial DNA molecule would contain one strand of the old DNA containing heavy nitrogen and one strand of new DNA containing light nitrogen. So the DNA would settle between where the light nitrogen and heavy nitrogen settled.
6. The DNA settled in the middle showing that DNA molecules contained a mix of heavy and light nitrogen.
61
What is ATP?
Stands for adenosine triphosphate, it is a nucleotide derivative made of the base adenine, a ribose sugar and 3 phosphate groups. It is an immediate source of energy for biological processes.
62
What happens in the hydrolysis of ATP?
When energy is needed by a cell, ATP is broken down into ADP (adenosine diphosphate) and Pi (inorganic phosphate) A phosphate bond is broken and energy is released. The reaction is catalysed by ATP hydrolase. This releases energy which can be used to drive energy requiring processes in the cell. ATP hydrolysis can be coupled to other energy requiring reactions - this means that the energy released can be used directly to make the coupled reaction happen and not be lost as heat.
63
What happens to the inorganic phosphate released during hydrolysis?
Can be added to another compound- phosphorylation which often makes the compound more reactive.
64
What happens in the synthesis of ATP?
ATP can be resynthesized in a condensation reaction between ADP and Pi. Happens during photosynthesis and respiration. Catalysed by the enzyme ATP synthase.
65
Why is water considered a dipolar molecule?
The oxygen atom has a slight negative charge and the hydrogen atoms have a slight positive charge. It has an unevenly distributed charge.
66
Why do hydrogen bonds form between water molecules?
Negative and positve charges attract to each other, the negative charge on one water molecule is attracted to the positive charge on another this results in hydrogen bonds forming between oxygen and hydrogen molecules on neibouring molecules.
67
What is a metabolite?
A substance involved in a metabolic reaction.
68
What reactions is water a metabolite in?
Condensation, hydrolysis and photosynthesis.
69
Why is water a good solvent?
Due to water's dipolar nature, the positive end is attracted to a negative ion and the negative end is attracted to a positive ion, so the ions gets completelyh surrounded by water molecules so they dissolve.
70
How does water being a good solvent benefit living organisms?
They can take up useful substances like mineral ions dissolved in water and they can be transported round their body.
71
Why does water have a high latent heat of vaporisation?
It takes a lot of energy to break the hydrogen bonds between water molecules so lots of energy is used up when water evaporates.
72
Why does water having a high latent heat of vaporisation benefit living organisms?
Water provides a significant cooling effect. e.g when we sweat large amounts of heat energy from the skin is transferred to the water to evaporate it therefore remving the heat and cooling us down.
73
Why does water has a high specific heat capacity?
When water is heated a lot of heat energy is used to break the hydrogen bonds between water molecules so there is less heat energy to actually increase the water temperature.
74
Why does water having a high specific heat capacity benefit living organisms?
Water doesn't experience rapid temperature changes making water a good habitat as temperature underwater is more likely to be more stable than on land.
75
What is cohesion?
The attraction between molecules of the same type.
76
Why are water molecules very cohesive?
Water molecules are very cohesive due to their polar nature.
77
How does cohesion benefit living organisms?
Helps water to flow e.g when water moves up the xylem in the transpiration stream as a continuous column of water
78
What does strong cohesion also mean?
Water has a high surface tension when it comes into contact with air. This is the reason why animals like pond skaters can walk on water.
79
What is an inorganic ion?
An ion that does not contain carbon. They occur in solution in the cytoplasm of cells and in the body fluids of organisms.
80
What does each ions specific role depend on and what does it determine?
It's properties. whether it is found in low or high concentrations.
81
What is the role of iron ions in haemoglobin?
Haemoglobin is made up of 4 different polypeptide chains each with an iron ion (Fe2+) in the centre. This ion is what binds to the oxygen in haemoglobin. When oxygen is bound, the Fe2+ ion becomes an Fe3+ ion until oxygen is released.
82
What is the role of hydrogen ions?
PH is calculated based on the concentration of H+ ions in the environment. The more H+ present the lower the PH. Enzyme controlled reactions are all affected by PH.
83
What is the role of sodium ions?
Involved in the co transport of glucose and amino acids in absorbtion.
84
What is the role of phosphate ions?
When a phosphate ion (|PO43-) is attached to another molecules it becomes a phosphate group, DNA, RNA and ATP all contain phosphate groups. Phosphate groups allow nucleotides to join forming phosphodiester bonds to form a polynucleotide. Bonds between phosphate groups store the energy in ATP.
85
What are the bonds between monomers in starch?
1.4 and 1,6 glycosidic bonds.
86
What is the function of starch?
Storage of glucose in plants.
87
How does the structure of starch relate to it's function?
Amylopectin is branched so larger surface area for hydrolysis by enzymes to turn it back into glucose. Helix shape makes it compact so can fit a lot of glucose into a small space, also resistant to digestion.
Insoluable so wont affect water potential.
88
What are the bonds between monomers in glycogen?
1,4 and 1,6 glycosidic bonds.
89
What is the function of glycogen?
Storage of glucose in animals.
90
How does the structure of glycogen relate to it's function?
Branched so increases surface area for rapid hydrolysis. Insolubale so no osmotic effect.
91
What are the bonds between monomers in cellulose?
1,4 glycosidic bonds.
92
What is function of cellulose?
Strengthens the cell wall.
93
What is the structure of cellulose?
Straight long chains
unbranched
chains held in parallel by hydrogen bonds forming microfibrils.
94
How the the structure of cellulose relate to it's function?
Hydrogen bonds provide collective strength so resists outward pressure, stops cells bursting making it turgid.
Insoluable so more osmotic effect.
95
What is the structure of starch?
Made of 2 polymers:
- Amylose- unbranched helix
- Amylopectin- branched molecule.
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