A-level Past Paper 2 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
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
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
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
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
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
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
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
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
10
Q
Give reasons why blood lactate concentration remains constant between 5 and 15 minutes. (3)
A
- sufficient oxygen supply
- for aerobic respiration
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
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
13
Q
Give reasons for variation in the lung volumes of healthy individuals. (2)
A
- different gender
- different age
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
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
16
Q
Describe how glucose moves into cells by facilitated diffusion. (2)
A
- carrier protein
- from high to low conc.
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
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
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
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
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
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
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
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
25
Describe the role of the dendrites in a neurone. (3)
- form connections w/ other neurones
- involved in summation
- initiate an action potential in the axon
26
Explain why tranexamic acid will result in reduced blood loss during surgery. (3)
- fibrin forms mesh that traps r.b.cs
- tranexamic acid stops breakdown of fibrin
- allowing clots to remain in place
27
Decide why tranexamic acid prevents plasmin breaking down fibrin. (3)
- tranexamic acid has very similar structure to lysine
- tranexamic acid acts as a competitive inhibitor
- stopping plasmin bindnig to fibrin
28
Describe what happens to lysosomes once their contents have been digested. (2)
- lysosomes fuse with cell surface membranes
- contents of lysosome released from cell
29
Explain how a single base mutation can lead to an altered primary structure. (3)
- change in base results in change in triplet code
- changes mRNA codons
- resulting in different A.A sequence
30
Explain why the use of CRISPR-Cas9 technology can be described as personalised medicine. (2)
- individuals have different mutations
- the RNA molecule will be specific to each individual
31
Explain how the phospholipids are arranged in two layers in a cell surface membrane. (3)
- hydrophilic regions orientated towards water
- hydrophobic regions orientated away from water
- water-based solution either side of the cell membrane
32
Describe how PET scans can be used to investigate brain structure. (2)
- PET scans detects production of gamma rays
- provides 3D image
33
Explain why different mutations in the CFTR gene can lead to differences in the severity of symptoms of CF. (2)
- different mutations have different effects on the protein produced
- varying the thickness of the mucus
34
Explain the role of the brain in reducing the student's heart rate after exercise. (2)
- chemoreceptors detect change in pH
- cardiovascular control centre sends impulses to the heart
35
Describe how the brain reduces the activity of the sweat glands after exercise. (2)
- thermoreceptors detect decrease in temperature
- thermoregulatory centre sends fewer impulses to sweat glands
36
Explain why too much exercise could be harmful to the human body. (3)
- joint damage
- suppression of immune system
- leading to an increased risk of infection
37
Compare and contrast the structures of an actin filament and collagen. (3)
both:
- have secondary structure
- only actin has a tertiary structure
- collagen has 3 chains, actin only has 1
38
Explain how genetically identical cells in zone 3 can differentiate to give rise to different tissues. (3)
- presence of different stimuli
- different genes activated
- different proteins made
39
Deduce what happens to the lactate in these cells. (2)
- lactate is converted to pyruvate
- pyruvate is converted to glucose
40
Explain why the liver is an organ and not a tissue. (2)
- made up of many tissues
- carrying out several functions
41
Explain why some ATP is broken down during glycolysis. (2)
- ATP supplies energy to break down glucose
- to produce 3-carbon compounds
42
Explain what happens at the synapse to cause a decrease in saliva production when stimulated. (4)
- 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
Describe the role of enzymes involved in the synthesis of personalised proteins in GMOs. (3)
- DNA helicase unzips DNA
- RNA polymerase involved in making mRNA
- enzymes join A.As together
43
Describe the role of sodium ions in the functioning of a mammalian rod cell. (3)
- 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
Describe how the structure of phospholipase allows it to hydrolyse phospholipids. (4)
- enzyme structure determined by amino acid sequence
- tertiary structure provides an active site
- active site complimentary to phospholipid
- to break ester bond
45
Give two functions of the Golgi apparatus. (2)
- modifies proteins
- forms vesicles
46
Explain how the structure of a muscle fibre is related to its specialised function. (3)
- many mitochondrion to supply ATP
- presence of myofibrils
- myofibrils allow contraction of muscles
47
Explain why the frequency of this allele may change from one generation to the next. (3)
- allele may undergo mutation
- due to natural selection
- because people with the condition may not have children
48
Explain the need for reduced NAD to be oxidised in a mitochondrion. (2)
- to allow ATP synthesis
- to regenerate NAD
49
Describe how meiosis leads to genetic variation in the gametes produced. (2)
- independent assortment of chromosomes
- crossing over between chromatids
50
Explain how vesicles are involved in the successful fertilisation of an egg cell by only one sperm. (2)
- cortical granules fuse with egg cell surface membrane
- releasing contents that harden zona pellucida
51
Explain why some genes show linkage and others show sex-linkage. (3)
- there are more genes than chromosomes
- linkage relates to genes located on same chromosome
- sex-linkage relates to genes on the sex chromosome
52
Describe the structure of an unbranched polysaccharide. (2)
- polysaccharides made up of many monosaccharide components
- only 1-4 glycosidic bonds present
53
Describe how an enzyme could break down the polysaccharide component of mucopolysaccharides. (2)
- hydrolysis
- of glycosidic bonds
54
Determine why animal A does not need a circulation system but animal B does. (4)
- 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
Explain why a mammal born with a hole between the two ventricles will have these symptoms. (3)
- 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
Explain why high blood pressure can increase the risk of developing CVD. (3)
- high b.p causes damage to endothelium of arteries
- causing inflammatory response
- plaque develops and narrows lumen of artery
57
Describe two structural differences between fast twitch and slow twitch muscle fibres. (2)
- FT has few mitochondria , ST has many
- FT has few capillaries, ST has many
58
Explain the importance of the membrane not being permeable to H+ ions. (4)
- to stop H+ diffusing out
- so H+ can move down concentration gradient
- by chemiosmosis
- to synthesise ATP
59
Describe how the tertiary structure of myosin is related to its function. (3)
- folded into specific shape with globular head
- that can bind to actin
- myosin has site that can bind with ATP
60
Describe how atrioventricular valves work during one cardiac cycle. (2)
- valves open when atria contract
- ventricles close when ventricles contract
61
Explain how the difference between the structure of a pulmonary artery and vein is related to the function of the pulmonary vein. (2)
- larger lumen
^ as blood pressure lower
62
Describe why a region of the brain may appear lighter in an image obtained by a fMRI scan. (3)
- due to more activity
- an increase in blood flow to this region
- fMRI signals not absorbed by oxygenated blood
63
Describe why a combined PET and CT scan may be better at detecting cancer than just the scans on their own. (3)
- using both provides information on function and structure
- PET scan shows areas that are more active
- CT scan gives location
64
Describe the interaction of the muscles in the eye that led to the dilation of the pupil. (3)
- antagonistic of muscles
- in the iris
- radial muscles contract, circular muscles relax
65
Explain how a bone marrow stem cell can give rise to red blood cells. (4)
- by differentiation
- due to certain stimuli
- causing some genes to be activated
- mRNA produced from activated genes
66
Describe how the neurotransmitter crosses this synapse. (2)
- vesicles fuse with presynaptic membrane, releasing acetylcholine
- which crosses synapse by diffusion
67
Explain why alcohol affects the concentration of betalain in these cells. (3)
- decreases betalain conc.
- due to betalain diffusing out
- bcs alcohol increases membrane permeability
68
Explain one way in which cartilage at the ends of bones in the knee joint reduce wear and tear. (2)
- cushioning
- to absorb shocks
69
Describe how lactose is formed from two monosaccharides. (2)
- glucose & galactose
- joined by glycosidic bond
