Biology Exam Questions AS Level Flashcards
(134 cards)
1
Q
Describe how the complementary strand of HIV DNA is made. (3)
A
1) Complementary nucleotides
2) Join by DNA polymerase
3) Forming phosphodiester bonds.
2
Q
Contrast the structures of DNA and mRNA molecules to give six differences.
A
1) DNA is double stranded, mRNA is single stranded.
2) DNA is long, mRNA is short.
3) DNA nucleotides have thymine, mRNA nucleotides have uracil.
4) DNA nucleotides have deoxyribose, mRNA nucleotides have ribose.
5) DNA has hydrogen bonding, mRNA has no hydrogen bonding.
6) DNA has introns, mRNA doesn’t.
3
Q
Describe the difference between the structure of a triglyceride molecule and the structure of a phospholipid molecule.
A
1) In a phospholipid, a fatty acid is replaced by a phosphate group.
4
Q
Describe how you would test for the presence of a lipid in a sample of food. (3)
A
1) Add ethanol and shake.
2) Add water and shake.
3) White emulsion means positive test.
5
Q
Describe how a saturated fatty acid is different from an unsaturated fatty acid.
A
1) Saturate fatty acids have single bonds between the carbons.
6
Q
Why can’t a fat substitute be digested in the gut by lipase? (2)
A
1) The fat substitute is not complementary.
2) So it is unable to bind to lipase.
7
Q
Describe how ATP is resynthesised in cells. (3)
A
1) ADP and Pi
2) Join by ATP synthase
3) During respiration
8
Q
Give two ways in which the hydrolysis of ATP is used in cells.
A
1) To provide energy for other reactions.
2) To add phosphate to other substances and make them more reactive.
9
Q
Describe the induced-fit model of enzyme action. (2)
A
1) Active site is not complementary to substrate.
2) Shape of active site changes as substrate binds.
10
Q
Describe how giving this vaccine leads to production of antibody against HPV. (5)
A
1) Vaccine contains antigen from HPV.
2) Antigens are displayed on antigen presenting cells
3) Specific Helper T Cells stimulate specific B cells.
4) B cell divides by mitosis to give plasma cells.
5) Plasma cell produces antibody.
11
Q
There is genetic diversity within HPV. Give three ways doctors could use base sequences to compare different types of HPV.
A
1) Compare base sequences of DNA.
2) Look for mutations.
3) Compare mRNA.
12
Q
Describe the function of DNA helicase and DNA polymerase.
A
1) DNA helicase - breaking hydrogen bonds between strands.
2) DNA polymerase - joins adjacent nucleotides.
13
Q
Contrast the structures of ATP and a nucleotide found in DNA to give three differences.
A
1) ATP has ribose, DNA nucleotide has deoxyribose.
2) ATP has 3 phosphate groups, DNA nucleotide has 1 phosphate group.
3) ATP base is always adenine, DNA nucleotide base can be different.
14
Q
Explain the advantages of lipid droplet and micelle formation. (3)
A
1) Droplets increase surface are for lipase action.
2) So faster hydrolysis of lipids.
3) Micelles carry fatty acids and glycerol to intestinal epithelial cell.
15
Q
How is the golgi apparatus involved in the absorption of lipids? (3)
A
1) Modifies triglycerides.
2) Combines triglycerides with proteins.
3) Forms vesicles.
16
Q
Explain the role of the heart in the formation of tissue fluid.
A
1) Contraction of ventricles produces hydrostatic pressure.
2) This forces water and some dissolved substances out of blood capillaries.
17
Q
Lymphoedema is a swelling in the legs which may be caused by a blockage in the lymphatic system.
Suggest how a blockage in the lymphatic system could cause lymphoedema.
A
1) Excess tissue fluid builds up.
18
Q
Explain how the chromosome number is halved during meiosis. (2)
A
1) Homologous chromosomes
2) One of each pair goes to opposite poles.
19
Q
Describe the process of crossing over and explain how it increases genetic diversity. (4)
A
1) Homologous pairs of chromosomes form a bivalent.
2) Chiasmata form.
3) Alleles are exchanged.
4) Producing new combinations of alleles.
20
Q
A
21
Q
Give five properties of water that are important in biology.
A
1) Is a metabolite
2) Is a solvent
3) Has a high specific heat capacity.
4) Has a large latent heat of vaporisation.
5) Has cohesion.
22
Q
Define species.
A
1) A group of organisms that are able to produce fertile offspring.
23
Q
Define species richness.
A
1) The number of different species in a community.
24
Q
Name the blood vessels that carry blood to the heart muscle.
A
1) Coronary arteries.
25
What is a monomer?
1) A smaller repeating unit that makes up polymers.
26
Give three features of DNA and explain how each one is important in the semi-conservative replication of DNA.
1) Two strands so they can both act as a template.
2) Weak hydrogen bonds so two strands can easily separate.
3) Complementary base pairing allows accurate replication.
27
Name the main biological molecule in a cell wall and in a cell surface membrane.
1) Cell surface membrane - phospholipids.
2) Cell wall - Glycoprotein.
28
What is the proteome of a cell?
The number of different proteins that a cell is able to produce.
29
Give four structural differences between a molecule of messenger RNA (mRNA) and a molecule of transfer RNA (tRNA).
1) mRNA has no amino acid attachment site, tRNA has an amino acid attachment site.
2) mRNA doesn't have hydrogen bonds, tRNA has hydrogen bonds.
3) mRNA has more nucleotides than tRNA.
4) mRNA has codons, tRNA has anticodons.
30
Describe how translation leads to the production of a polypeptide. (5)
1) mRNA associates with a ribosome.
2) tRNA brings a specific amino acid.
3) Anticodon on tRNA binds to complementary codons on mRNA.
4) Ribosome moves along to next codon.
5) Amino acids are joined by peptide bonds by condensation reactions to form a polypeptide.
31
State and explain the property of water that can help to buffer changes in temperature. (2)
1) Water has a high specific heat capacity.
2) Can gain or lose a lot of heat without changing temperature.
32
Describe the pathway taken by an oxygen molecule from an alveolus to the blood.
1) Across alveolar epithelium.
2) Across the epithelium of the capillary.
33
Explain how one feature of an alveolus allows efficient gas exchange to occur. (2)
1) Alveolar epithelium is one cell thick.
2) Reduces the diffusion distance.
34
Give three ways in which the DNA in a chloroplast is different from DNA in the nucleus.
DNA in chloroplasts:
1) Circular not linear.
2) Shorter
3) Not associated with histones
4) Fewer genes
5) No introns
35
Not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide.
Give two reasons why. (2)
1) DNA code is degenerate.
2) Mutations occur in introns.
36
What is a monoclonal antibody?
1)Antibodies with the same tertiary structure.
37
Give one example of using monoclonal antibodies in a medical treatment.
1)Binds drugs to specific cells.
38
Describe the role of antibodies in producing a positive result in an ELISA test. (4)
1) First antibody is complementary in shape to antigen.
2) Second antibody with enzyme attached is added.
3) Second antibody attaches to antigen.
4) Colour changes.
39
Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill. (3)
1) Water and blood flow in opposite directions.
2) Maintains a diffusion gradient of oxygen.
3) Diffusion along the length of the gill.
40
Explain how the active site of an enzyme causes a high rate of reaction. (3)
1) Lowers activation energy.
2) Induced fit causes active site of enzyme to change shape.
3) So E-S complex causes bonds to break.
41
Describe a biochemical test to confirm the presence of protein in a solution. (2)
1) Add biuret reagent.
2) Positive result is purple.
42
Describe 3 ways in which all dipeptides are similar and one way in which they might differ.
Similarities
1) Amine group at one end.
2) Carboxyl group at one end.
3) Two R groups.
Difference:
1) Different R groups.
43
Describe a biochemical test to show that raffinose solution contains a non-reducing
sugar. (3)
1) Heat with acid and neutralise.
2) Heat with Benedict's solution.
3) Red precipitate colour.
44
Explain the arrangement of phospholipids in a cell-surface membrane. (3)
1) It is a bilayer.
2) Hydrophobic tails are repelled from water.
3) Hydrophilic heads are attracted to water.
45
Describe how an ester bond is formed in a phospholipid molecule. (2)
1) Condensation reaction.
2) Between glycerol and fatty acid.
46
State and explain the property of water that helps to prevent temperature increase in a
cell. (2)
1) High Specific Heat Capacity
2) Buffers changes in temperature.
47
Describe how a phagocyte destroys a pathogen present in the blood. (4)
1) Phagocyte engulfs pathogen.
2) Forms a phagosome.
3) Fuses with lysosome.
4) Enzymes hydrolyse the pathogen.
48
Give three types of cell, other than pathogens, that can stimulate an immune response.
1) Cells infected by virus
2) Cancer cells.
3) Cells from transplants.
49
What is the role of the disulfide bridge in forming the quaternary structure of an antibody?
Joins two different polypeptides.
50
Outline the role of organelles in the production, transport and release of proteins from
eukaryotic cells. (4)
1) DNA in nucleus is a code for protein.
2) Ribosomes produce proteins
3) Mitochondria produce ATP for protein synthesis.
4) Vesicles transport proteins.
51
Suggest why a nucleus is not visible in a TEM.
1) Nucleus is not stained.
52
Give two advantage of viewing a biological specimen using a transmission electron
microscope compared with using a scanning electron microscope.
1) Higher resolution.
2) Can view internal structures.
53
Describe and explain the mechanism that causes lungs to fill with air. (3)
1) Diaphragm contracts and EIM muscles contract.
2) Volume in lungs increase, pressure decreases.
3) Air moves down a pressure gradient.
54
Describe how mRNA is produced from an exposed template strand of DNA. (3)
1) Free RNA nucleotides form complementary base pairs.
2) Phosphodiester bonds form.
3) By action of RNA polymerase.
55
Define the term exon.
1)Base sequence coding for a polypeptide.
56
Describe binary fission in bacteria. (3)
1) Replication of circular DNA.
2) Replication of plasmids.
3) Division of cytoplasm to produce daughter cells.
57
Describe how HIV is replicated. (5)
1) Attachment proteins attach to receptors on helper T cells.
2) RNA enters cell.
3) Reverse transcriptase converts RNA into DNA.
4) Viral protein produced
5) Virus particles assembled and released from cell.
58
Name the fixed position occupied by a gene on a DNA molecule.
1) Locus
59
Describe how a gene is a code for the production of a polypeptide. (3)
1) Because base sequence
2) In triplets
3) Determine primary structure of polypeptide.
60
Describe how the structure of glycogen is related to its function. (4)
1) Coiled so it is compact.
2) Branched so more ends for faster hydrolysis.
3) Polymer of glucose so easily hydrolysed.
4) Insoluble so doesn't affect water potential.
61
Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs. (3)
1) Renal vein
2) Vena cava to right atrium
3) Right ventricle to pulmonary artery.
62
Explain how water from tissue fluid is returned to the circulatory system. (4)
1) Plasma proteins remain
2) Creates water potential gradient
3) Water moves to blood by osmosis.
4) Returns to blood by lymphatic system.
63
Describe the mechanism for the absorption of amino acids in the ileum. (4)
1) Facilitated diffusion of amino acid.
2) Co transport
3) Sodium ions actively transported from cell to blood.
4) Creating sodium ion concentration gradient.
64
Give the two types of molecule from which a ribosome is made.
1) Protein
2) RNA
65
Name two structures found in all bacteria that are not found in plant cells.
1) Circular DNA
2) Murein cell wall
66
Name two features of HIV particles that are not found in bacteria.
1) Capsid
2) Reverse Transcriptase
67
Describe how monomers join to form the primary structure of a protein. (3)
1) Condensation reaction between amino acids.
2) Forming peptide bonds.
3) Creating a specific sequence of amino acids.
68
Describe one similarity and one difference between the induced-fit model of enzyme action and the lock and key model of enzyme action.
Similarity:
1) Enzyme-substrate complex formed.
Difference:
1) Active site changes shape in induced fit but doesn't in lock and key.
69
Explain a property of iron ions that enables these ions to carry out their role in red blood cells. (2)
1) They're polar
2) So they bind with oxygen to form oxyhaemoglobin
70
What is a tumour?
Abnormal cells
71
Define universal, non-overlapping and degenerate.
Universal - The same triplet always codes for the same amino acid.
Non-overlapping - Each base is only part of one triplet.
Degenerate - More than one triplet of bases code for each amino acid.
72
Explain why phospholipids can form a bilayer but triglycerides cannot. (3)
1) Phospholipids are both hydrophobic and hydrophillic.
2) Triglycerides are only hydrophillic.
3) Hydrophilic head attracts water.
73
State 3 roles of a helper T cell.
1) Stimulates cytotoxic T cells
2) Stimulates B cells
3) Stimulates phagocytes.
74
Describe how gas exchange occurs in single-celled organisms and explain why this method cannot be used by large, multicellular organisms. (3)
1) Diffusion across cell surface membrane.
2) Larger organisms have a smaller sa:v ratio.
3) Diffusion pathway would be too long.
75
Describe how you could use cell fractionation to isolate chloroplasts from leaf tissue. (3)
1) Break open cells and remove debris.
2) Solution is cold/isotonic/buffered.
3) Second pellet is a chloroplast.
76
Name two ways in which meiosis produces genetic variation.
1) Crossing Over
2) Independent Segregation
77
Other than hunting, suggest three reasons why populations might show very low levels
of genetic diversity.
1) Inbreeding
2) Founder Effect
3) Genetic Bottleneck
78
The hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary. Explain why.
1)Loss of water
79
High blood pressure leads to an accumulation of tissue fluid. Explain how. (3)
1) High blood pressure = High hydrostatic pressure.
2) Increases outward pressure from arterial end of capillary.
3) So more tissue fluid formed.
80
The water potential of the blood plasma is more negative at the venule end of the
capillary than at the arteriole end of the capillary. Explain why. (3)
1) Water has left the capillary.
2) Proteins in the blood are too large to leave the capillary
3) Giving higher concentration of blood proteins.
81
E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains
a constant shape. Explain why. (3)
1) Cell unable to change shape.
2) Because e.coli has a cell wall.
3) Which is made of murein.
82
Suggest one advantage of programmed cell death.
1) Prevents replication of virus.
83
Suggest and explain why the combined actions of endopeptidases and exopeptidases are more efficient than exopeptidases on their own. (3)
1) Endopeptidases hydrolyse internal peptide bonds.
2) Exopeptidases hydrolyse the bonds on the ends.
3) More ends increases surface area.
84
Suggest and explain four xerophytic features the leaves of a plant might have.
1) Hairs which trap water vapour.
2) Thick waxy layer to increase diffusion distance.
3) Needles to reduce surface are to volume ratio.
4) Curled leaves to trap water vapour.
85
Suggest how widening of blood vessels can reduce ventricular blood pressure. (3)
1) Larger lumen
2) Reduces blood pressure.
3) Less friction in blood vessels.
86
Describe how the structures of starch and cellulose molecules are related to their functions. (3 for starch) (4 for cellulose)
Starch:
1) Helical so compact.
2) Branched so glucose is easily released for respiration.
3) Large so can't leave cell.
Cellulose:
1) Long/straight unbranched chains of beta glucose.
2) Joined by hydrogen bonds.
3) To form fibrils.
4) This provides strength to the cell.
87
Describe three differences between the structure of a cellulose molecule and a glycogen molecule.
1) Cellulose is made up of beta glucose, glycogen is made up of alpha glucose.
2) Cellulose has straight chains, glycogen is branched.
3) Cellulose has only 1,4 glycosidic bonds, Glycogen has 1,4 and 1,6 glycosidic bonds.
88
Describe and explain two features of starch that make it a good storage molecule.
1) Insoluble so doesn't affect water potential.
2) Large so can't cross cell membrane.
3) Polymer of alpha glucose so provides glucose for respiration.
4) Branched so compact.
89
Describe how mRNA is produced in a plant cell. (5)
1) DNA helicase breaks hydrogen bonds between complementary bases.
2) One strand acts as a template.
3) Free RNA nucleotides align by complementary base pairing.
4) RNA polymerase joins adjacent nucleotides forming phosphodiester bonds.
5) Pre-mRNA is formed which is spliced to form mRNA.
90
Two proteins have the same number and type of amino acids but different tertiary box
structures.
Explain why. (2)
1) Different sequence of amino acids.
2) Forms ionic, hydrogen and disulfide bonds in different places.
91
The secondary structure of a polypeptide is produced by bonds between amino acids.
Describe how. (3)
1) Hydrogen bonds.
2) Between NH and C=O
3) Forming beta pleated sheets and alpha helices.
92
Explain why oxygen uptake is a measure of metabolic rate in organisms. (1)
1) Oxygen used in respiration which provides ATP.
93
Give two similarities in the movement of substances by diffusion and by osmosis.
1) Movement down a gradient.
2) Passive
94
Explain why the student used only the first 5 mm from the tip of an onion root. (1)
1) Where mitosis occurs.
95
Explain why the student pressed down firmly on the cover slip. (1)
1) Spread out cells so light passes through.
96
What is digestion? (2)
1) Hydrolysis of
2) Large insoluble substances to make smaller soluble substances.
97
Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells. (3 each)
Comparisons:
1) Identical nucleotide structure.
2) Nucleotides joined by phosphodiester bond.
3) DNA in chloroplast similar to DNA in prokaryotes.
Contrast:
1) Eukaryotic DNA is longer.
2) Eukaryotic DNA contains introns.
3) Eukaryotic DNA is linear, prokaryotic DNA is circular.
98
Describe the role of enzymes in the digestion of proteins in a mammal. (4)
1) Hydrolysis of peptide bonds.
2) Endopeptidases act in the middle of the polypeptide.
3) Exopeptidases act at the end of the polypeptide.
4) Dipeptidases act between two amino acids.
99
Describe and explain the effect of increasing carbon dioxide concentration on the
dissociation of oxyhaemoglobin. (2)
1) More oxygen dissociating.
2) By increasing acidity.
100
Use your knowledge of semi-conservative replication of DNA to suggest:
1. the role of the single-stranded DNA fragments.
2. the role of the DNA nucleotides. (2 in 1) (1 in 2)
1) Template. Determines the order of nucleotides.
2) Forms complementary DNA strand.
101
Describe and explain the role of antibodies in stimulating phagocytosis. (2)
1) Binds to antigen.
2) Antibodies cause agglutination
102
Give six differences between mitosis and meiosis.
1) One division in mitosis, two divisions in meiosis.
2) Daughter cells are genetically identical in mitosis, daughter cells are genetically different in meiosis.
3) Two cells produced in mitosis, four cells produced in meiosis.
4) Separation of homologous chromosomes only occurs in meiosis.
5) Crossing over only occurs in meiosis.
6) Independent segregation only occurs in meiosis.
103
The genetic diversity of species is measured by comparing
differences in the base sequence of DNA or differences in the base sequence of mRNA. Give two other ways in which genetic diversity between species is measured.
1) Comparing features.
2) Comparing primary structure of protein.
104
Describe the roles of iron ions, sodium ions, and phosphate ions in cells. (1 in iron) (2 in sodium) (2 in phosphate)
Iron Ions:
1) Haemoglobin binds with oxygen.
Sodium Ions:
1) Co transport of glucose into cells.
2) Because sodium moved out by active transport.
Phosphate ions:
1) Phosphorylates other compounds making them more reactive.
2) Used to produce ATP.
105
The movement of substances across cell membranes is affected by membrane structure. Describe how. (5)
1) Phospholipid bilayer allows diffusion of non-polar substances.
2) Phospholipid bilayer prevents diffusion of polar substances.
3) Carrier proteins allow for active transport.
4) Number of channel and carrier proteins determine how much movement occurs.
5) Cholesterol affects fluidity.
106
A competitive inhibitor decreases the rate of an enzyme-controlled reaction. Explain how. (3)
1) Inhibitor is similar in shape to substrate.
2) Binds to active site.
3) Prevents E-S complexes from forming.
107
Explain how HIV affects the production of antibodies when AIDS develops in a person (3)
1) Less antibody produced.
2) Because HIV destroys helper T cells.
3) So few B cells activated.
108
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels. (5)
1) Micelles contain bile salts and fatty acids.
2) Brings fatty acids to the lining of the ileum.
3) Fatty acids absorbed by diffusion.
4) Triglycerides reformed in cells.
5) Vesicles leave the cell via exocytosis.
109
Describe how the structure of a protein depends on the amino acids it contains. (5)
1) Primary structure is the sequence of amino acids.
2) Secondary structure formed by hydrogen bonding.
3) Tertiary structure formed by interactions between R groups.
4) Creates active site in enzymes.
5) Quaternary structure contains more than one polypeptide chain.
110
Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveoli. (3)
1) Less carbon dioxide moves out of lungs.
2) So reduced concentration gradient between blood and alveoli.
3) More carbon dioxide stays in blood.
111
Define the term mutagenic agent. (1)
1) A factor that increases the rate of mutations.
112
What term is used to describe this method of naming organisms? (1)
1) Binomial
113
Apart from mutation, explain one other way genetic variation within a species is increased. (2)
1) Random fusion of gametes.
2) Produces new allele combinations.
114
Describe how an ATP molecule is formed from its component molecules. (3)
1) ATP is made up of adenine, ribose and 3 phosphate groups.
2) Condensation reaction.
3) ATP synthase.
115
Explain five properties that make water important for organisms
1) A metabolite in respiration.
2) A solvent so metabolic reactions can occur.
3) HSHC so buffers changes in temperature.
4) LLHOV so provides a cooling effect.
5) Cohesion so produces surface tension supporting small organisms.
116
Describe the process of semi-conservative replication of DNA. (6)
1) DNA helicase breaks hydrogen bonds between the two strands.
2) Both strands act as a template.
3) Free floating DNA nucleotides align due to complementary base pairing.
4) DNA polymerase joins adjacent nucleotides.
5) Forming phosphodiester bonds.
6) Each new DNA molecule consists of one old strand and one new strand.
117
What is a gene? (1)
1) A sequence of DNA bases that codes for a polypeptide.
118
Describe how the production of messenger RNA (mRNA) in a eukaryote cell is different from the production of mRNA in a prokaryote cell. (2)
1) Pre mRNA produced in eukaryote cell.
2) Splicing only occurs in eukaryote cell.
119
Describe the role of ATP in the process of translation in protein synthesis. (2)
1) Provides energy
2) So peptide bonds formed between amino acids.
120
Describe and explain two ways that structures shown in a part of a cell lining the ileum increase the rate of absorption by this cell. (Microvilli and Mitochondria).
1) Microvilli increase surface area for more channel/carrier proteins.
2) Many mitochondria release energy for active transport.
121
Describe how the process of meiosis results in haploid cells.
1) DNA replication
2) Two divisions
3) Separation of homologous chromosomes in first division.
4) Separation of sister chromatids in second division.
5) Produces 4 haploid cells.
122
Describe how the structure of the insect gas exchange system:
* provides cells with sufficient oxygen
* limits water loss.
Explain your answers.
(6)
1) Spiracles, trachea, tracheoles.
2) Spiracles allow diffusion of oxygen.
3) Tracheoles are highly branched so large surface area for exchange.
4) Tracheoles have thin walls so short diffusion distance to cells.
5) Chitin is impermeable so reduces water loss.
6) Spiracles can close to prevent water loss.
123
Describe how humans breathe in and out. (6)
Breathing in:
1) Diaphragm muscles contract and flatten.
2) EIM contract and ribcage is pulled up and out.
3) Volume increases inside the thoracic cavity and pressure decreases.
Breathing out:
1) Diaphragm relaxes and moves up.
2) EIM relax and ribcage is pulled down and in.
3) Volume decreases in the thoracic cavity and pressure increases.
124
Name two biological molecules that can be coded for by a gene.
Do not include a polypeptide or protein in your answer.
1) rRNA
2) tRNA
125
ATP synthase comprises several polypeptides, so is said to have
a __________ structure. It catalyses the synthesis of an ATP molecule by a ___________
reaction; this involves the _________ of a water molecule.
The ATP synthase in Figure 1 is in a mitochondrion so would catalyse reactions
during ____________ .
1) Quaternary
2) Condensation
3) Loss
4) Aerobic Respiration
126
Suggest how the shape of the ATP synthase allows it to catalyse the synthesis of ATP. (2)
1) Active site is complementary to ADP + Pi.
2) E-S complex forms.
127
Suggest how the shape of the ATP synthase allows it to allow the movement of H+ ions. (2)
1) Channel protein.
2) Allows facilitated diffusion of H+.
128
Galacto-oligosaccharides (GOS) are polymers of galactose.
Explain why GOS are described as polysaccharides. (2)
1) Galactose is a monosaccharide.
2) Several monosaccharides join by a condensation reaction.
129
Name the type of blood vessel that controls blood flow to muscles and explain how
these blood vessels change blood flow during exercise. (3)
1) Arteriole
2) Smooth muscle relaxes
3) Vasodilation increases blood flow.
130
Describe the hydrolysis reactions involved in the digestion of triglycerides. (2)
1) Breaking of ester bonds.
2) By addition of water.
131
Describe three functions of bile salts.
1) Emulsify lipids.
2) Increases surface area for lipase activity.
3) Form micelles
132
Describe the behaviour of chromosomes in prophase and metaphase of mitosis. (2)
1) Prophase - chromosomes condense.
2) Metaphase - Chromosomes line up on the equator.
133
Outline the similarities in, and the differences between, the structures of DNA and
RNA molecules. (3 similarities, 3 differences)
Similarities:
1) Polymers of nucleotides.
2) Have phosphodiester bonds
3) Have CGA as bases.
Differences:
1) Deoxyribose in DNA, ribose in RNA.
2) Thymine in DNA, uracil in RNA.
3) Double stranded DNA, single stranded RNA.
134
Outline the similarities in, and the differences between, the structures of chloroplasts
and mitochondria. (3 similarities, 3 differences)
Similarities:
1) Double membrane
2) Both contain circular DNA.
3) Both contain ribosomes.
Differences:
1) Pigments vs no pigments
2) Stroma vs matrix
3) Starch grains vs no starch grains
