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Alevel Bio > A-level Past Paper 2 > Flashcards

A-level Past Paper 2 Flashcards

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Biology 101 flashcards
1
Q

Describe how low serotonin levels in an individual can affect the transmission of impulses in the brain. (2)

A
  • seratonin is a neurotransmitter
  • less seratonin results in fewer depolarisations of post synaptic membrane
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2
Q

Describe how the use of MDMA could affect the transmission of impulses in the brain. (2)

A
  • MDMA increases seratonin concentration
  • more action potentials produced
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3
Q

Explain how the use of MDMA could result in the development of depression. (2)

A
  • use of MDMA results in depletion of seratonin
  • lack of seratonin associated with depression
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4
Q

Describe how the SAN is involved in bringing about a change in heart rate as the level of activity increases. (2)

A
  • more impulses to the SAN
  • leading to more frequent atria contractions
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5
Q

Explain how pressure differences in the heart ensure efficient pumping of the blood into the arteries. (3)

A
  • pressure increases in the ventricles
  • causing atrioventricular valves to close
  • causing semilunar valves to open
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6
Q

Explain why cystic fibrosis affects the rate of oxygen uptake in the lungs. (3)

A
  • CF causes thick mucus
  • which cannot be moved by cilia
  • restricting air flow through bronchi
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7
Q

Describe the reaction that joins two alpha-glucose molecules to form a disaccharide. (2)

A
  • condensation reaction
  • involving OH groups on both molecules
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8
Q

Compare and contrast the structures of trehalose and maltose. (2)

A
  • both contain glycosidic bonds
  • in trehalose, one of the glucose monomers is inverted
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9
Q

Explain the advantage of insects storing both trehalose and glycogen. (4)

A
  • glucose is used in respiration to provide ATP
  • glycogen is a polymer of glucose
  • glycogen is branched so can release glucose rapidly
  • breakdown of trehalose provides a more immediate source of glucose
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10
Q

Give reasons why blood lactate concentration remains constant between 5 and 15 minutes. (3)

A
  • sufficient oxygen supply
  • for aerobic respiration
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11
Q

Describe how the concentration of calcium ions around the myofibrils is controlled. (3)

A
  • calcium ions released from sarcoplasmic reticulum
  • in response to nerve impulse
  • calcium channels open to allow calcium ions to enter the sarcoplasm
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12
Q

Explain the electrical changes in an axon that allows these nerve impulses to be detected. (4)

A
  • potential difference across axon changing
  • sodium channels open
  • followed by potassium channels opening
  • potassium ions move out of the axon
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13
Q

Give reasons for variation in the lung volumes of healthy individuals. (2)

A
  • different gender
  • different age
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14
Q

Give a reason for calculating the surface area for gas exchange to volume ratio in this investigation. (1)

A
  • to allow valid comparison
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15
Q

Explain why individuals with severe emphysema will tire more easily than healthy individuals. (3)

A
  • smaller surface area for gas exchange
  • therefore, reduced oxygen uptake
  • therefore, less oxygen for aerobic respiration, causing fatigue
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16
Q

Describe how glucose moves into cells by facilitated diffusion. (2)

A
  • carrier protein
  • from high to low conc.
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17
Q

Explain how the structure of glycogen allows it to be an energy store. (3)

A
  • polymer of glucose
  • provides glucose for respiration
  • branched for rapid hydrolysis
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18
Q

Explain how transcription factors could activate insulin gene expression in beta cells. (3)

A
  • interactions b/w transcription factors & promoter region
  • RNA polymerase binds to promoter region
  • mRNA produced
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19
Q

Compare and contrast the structures of a saturated and unsaturated fatty acid. (3)

A

both:
- have a carboxylic acid group
- have hydrocarbon chains

  • saturated = straight chain, unsaturated have kinks in their chains
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20
Q

Explain why bacteria are able to multiply in the bloodstream when they enter the body. (3)

A
  • ideal pH available
  • suitable temperature for bacterial enzymes
  • glucose used for respiration
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21
Q

Explain why blood clot formation in capillaries could cause tissues to die. (2)

A
  • lumen of capillaries blocked
  • preventing supply of oxygen to cells
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22
Q

Explain how fMRI can be used to identify the part of the brain responsible for interpreting information from the visual cortex. (3)

A
  • MRI detects blood flow in brain
  • increased brain activity increases blood flow
  • fMRI detects area where less signal is absorbed
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23
Q

Describe how thermoregulatory mechanisms help avoid heat stress. (4)

A
  • thermoreceptors detect temperature increase
  • thermaregulatory centre in hypothalamus is stimulated
  • hypothalamus sends impulses to sweat glands
  • decreased metabolic rate
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24
Q

Explain why it is necessary for the cardiac output of marathon runners to increase during a race. (2)

A
  • to allow aerobic respiration
  • to provide more energy
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25
Q

Describe the role of the dendrites in a neurone. (3)

A
  • form connections w/ other neurones
  • involved in summation
  • initiate an action potential in the axon
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26
Q

Explain why tranexamic acid will result in reduced blood loss during surgery. (3)

A
  • fibrin forms mesh that traps r.b.cs
  • tranexamic acid stops breakdown of fibrin
  • allowing clots to remain in place
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27
Q

Decide why tranexamic acid prevents plasmin breaking down fibrin. (3)

A
  • tranexamic acid has very similar structure to lysine
  • tranexamic acid acts as a competitive inhibitor
  • stopping plasmin bindnig to fibrin
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28
Q

Describe what happens to lysosomes once their contents have been digested. (2)

A
  • lysosomes fuse with cell surface membranes
  • contents of lysosome released from cell
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29
Q

Explain how a single base mutation can lead to an altered primary structure. (3)

A
  • change in base results in change in triplet code
  • changes mRNA codons
  • resulting in different A.A sequence
30
Q

Explain why the use of CRISPR-Cas9 technology can be described as personalised medicine. (2)

A
  • individuals have different mutations
  • the RNA molecule will be specific to each individual
31
Q

Explain how the phospholipids are arranged in two layers in a cell surface membrane. (3)

A
  • hydrophilic regions orientated towards water
  • hydrophobic regions orientated away from water
  • water-based solution either side of the cell membrane
32
Q

Describe how PET scans can be used to investigate brain structure. (2)

A
  • PET scans detects production of gamma rays
  • provides 3D image
33
Q

Explain why different mutations in the CFTR gene can lead to differences in the severity of symptoms of CF. (2)

A
  • different mutations have different effects on the protein produced
  • varying the thickness of the mucus
34
Q

Explain the role of the brain in reducing the student’s heart rate after exercise. (2)

A
  • chemoreceptors detect change in pH
  • cardiovascular control centre sends impulses to the heart
35
Q

Describe how the brain reduces the activity of the sweat glands after exercise. (2)

A
  • thermoreceptors detect decrease in temperature
  • thermoregulatory centre sends fewer impulses to sweat glands
36
Q

Explain why too much exercise could be harmful to the human body. (3)

A
  • joint damage
  • suppression of immune system
  • leading to an increased risk of infection
37
Q

Compare and contrast the structures of an actin filament and collagen. (3)

A

both:
- have secondary structure

  • only actin has a tertiary structure
  • collagen has 3 chains, actin only has 1
38
Q

Explain how genetically identical cells in zone 3 can differentiate to give rise to different tissues. (3)

A
  • presence of different stimuli
  • different genes activated
  • different proteins made
39
Q

Deduce what happens to the lactate in these cells. (2)

A
  • lactate is converted to pyruvate
  • pyruvate is converted to glucose
40
Q

Explain why the liver is an organ and not a tissue. (2)

A
  • made up of many tissues
  • carrying out several functions
41
Q

Explain why some ATP is broken down during glycolysis. (2)

A
  • ATP supplies energy to break down glucose
  • to produce 3-carbon compounds
42
Q

Explain what happens at the synapse to cause a decrease in saliva production when stimulated. (4)

A
  • fewer calcium ions enter pre-synaptic neurone
  • fewer vesicles fuse with pre-synaptic membrane
  • less neurotransmitters bind to receptors on post-synaptic membrane
  • membrane may not be depolarised
43
Q

Describe the role of enzymes involved in the synthesis of personalised proteins in GMOs. (3)

A
  • DNA helicase unzips DNA
  • RNA polymerase involved in making mRNA
  • enzymes join A.As together
43
Q

Describe the role of sodium ions in the functioning of a mammalian rod cell. (3)

A
  • sodium ions pumped out of rod cells
  • in the light, sodium ions do not move back into rod cell
  • in the dark, sodium ions can move back into rod cell
44
Q

Describe how the structure of phospholipase allows it to hydrolyse phospholipids. (4)

A
  • enzyme structure determined by amino acid sequence
  • tertiary structure provides an active site
  • active site complimentary to phospholipid
  • to break ester bond
45
Q

Give two functions of the Golgi apparatus. (2)

A
  • modifies proteins
  • forms vesicles
46
Q

Explain how the structure of a muscle fibre is related to its specialised function. (3)

A
  • many mitochondrion to supply ATP
  • presence of myofibrils
  • myofibrils allow contraction of muscles
47
Q

Explain why the frequency of this allele may change from one generation to the next. (3)

A
  • allele may undergo mutation
  • due to natural selection
  • because people with the condition may not have children
48
Q

Explain the need for reduced NAD to be oxidised in a mitochondrion. (2)

A
  • to allow ATP synthesis
  • to regenerate NAD
49
Q

Describe how meiosis leads to genetic variation in the gametes produced. (2)

A
  • independent assortment of chromosomes
  • crossing over between chromatids
50
Q

Explain how vesicles are involved in the successful fertilisation of an egg cell by only one sperm. (2)

A
  • cortical granules fuse with egg cell surface membrane
  • releasing contents that harden zona pellucida
51
Q

Explain why some genes show linkage and others show sex-linkage. (3)

A
  • there are more genes than chromosomes
  • linkage relates to genes located on same chromosome
  • sex-linkage relates to genes on the sex chromosome
52
Q

Describe the structure of an unbranched polysaccharide. (2)

A
  • polysaccharides made up of many monosaccharide components
  • only 1-4 glycosidic bonds present
53
Q

Describe how an enzyme could break down the polysaccharide component of mucopolysaccharides. (2)

A
  • hydrolysis
  • of glycosidic bonds
54
Q

Determine why animal A does not need a circulation system but animal B does. (4)

A
  • both have same volume
  • animal A has larger s.a
  • and larger s.a to vol ratio
  • so sufficient s.a in animal A for diffusion
55
Q

Explain why a mammal born with a hole between the two ventricles will have these symptoms. (3)

A
  • less oxygen available for aerobic respiration
  • deoxygenated blood mixes with oxygenated blood
  • therefore, reducing the concentration of oxygen in the blood circulating the body
56
Q

Explain why high blood pressure can increase the risk of developing CVD. (3)

A
  • high b.p causes damage to endothelium of arteries
  • causing inflammatory response
  • plaque develops and narrows lumen of artery
57
Q

Describe two structural differences between fast twitch and slow twitch muscle fibres. (2)

A
  • FT has few mitochondria , ST has many
  • FT has few capillaries, ST has many
58
Q

Explain the importance of the membrane not being permeable to H+ ions. (4)

A
  • to stop H+ diffusing out
  • so H+ can move down concentration gradient
  • by chemiosmosis
  • to synthesise ATP
59
Q

Describe how the tertiary structure of myosin is related to its function. (3)

A
  • folded into specific shape with globular head
  • that can bind to actin
  • myosin has site that can bind with ATP
60
Q

Describe how atrioventricular valves work during one cardiac cycle. (2)

A
  • valves open when atria contract
  • ventricles close when ventricles contract
61
Q

Explain how the difference between the structure of a pulmonary artery and vein is related to the function of the pulmonary vein. (2)

A
  • larger lumen

^ as blood pressure lower

62
Q

Describe why a region of the brain may appear lighter in an image obtained by a fMRI scan. (3)

A
  • due to more activity
  • an increase in blood flow to this region
  • fMRI signals not absorbed by oxygenated blood
63
Q

Describe why a combined PET and CT scan may be better at detecting cancer than just the scans on their own. (3)

A
  • using both provides information on function and structure
  • PET scan shows areas that are more active
  • CT scan gives location
64
Q

Describe the interaction of the muscles in the eye that led to the dilation of the pupil. (3)

A
  • antagonistic of muscles
  • in the iris
  • radial muscles contract, circular muscles relax
65
Q

Explain how a bone marrow stem cell can give rise to red blood cells. (4)

A
  • by differentiation
  • due to certain stimuli
  • causing some genes to be activated
  • mRNA produced from activated genes
66
Q

Describe how the neurotransmitter crosses this synapse. (2)

A
  • vesicles fuse with presynaptic membrane, releasing acetylcholine
  • which crosses synapse by diffusion
67
Q

Explain why alcohol affects the concentration of betalain in these cells. (3)

A
  • decreases betalain conc.
  • due to betalain diffusing out
  • bcs alcohol increases membrane permeability
68
Q

Explain one way in which cartilage at the ends of bones in the knee joint reduce wear and tear. (2)

A
  • cushioning
  • to absorb shocks
69
Q

Describe how lactose is formed from two monosaccharides. (2)

A
  • glucose & galactose
  • joined by glycosidic bond

Alevel Bio (8 decks)

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