AQA A LEVEL RESPIRATION EXAM QUESTIONS FULLY SOLVED & UPDATED.

Suggest the advantages of the change in blood flow in blood vessels during exercise. [3 marks] - answer--more blood flow to muscles during exercise -supplying more glucose and oxygen/ removing carbon dioxide/ lactic acid/ heat -for high rate of respiration/ to meet increased demand for energy Explain how microorganisms contributed to the increase in temperature during processing of organic waste. [2 marks] - answer-respiration produces heat explain the advantage of showing the data using standard deviations rather than ranges. [2 marks] - answer-SD is spread of data around the mean SD reduces the effect of anomalies SD can be used to determine if difference in results is significant. not significant/ due to chance/ not due to chance aerobic respiration produces more ATP per molecule of glucose than aerobic respiration. Explain why. [2 marks] - answer-oxygen is terminal electron acceptor/ oxygen combines with electrons and protons aerobic respiration oxidative phosphorylation anaerobic respiration only glycolysis occurs ...After a number of days, this injection of antigen resulted in the myelin sheaths in the mice being damaged. some cell bodies of neurones were also damaged. Suggest how the injection of the antigen resulted in the myelin sheaths being damaged. [3 marks] - answer-antigen stimulated immune response antibodies produced/ B/T cells divide antibodies attach myelin sheath Suggest why having a large number of mitochondria with this unusual ultrastructure could lead to neurone dying. [3 marks] - answer-fewer Cristae so less oxidative phosphorylation so not enough ATP produced to keep neurones alive ...For the first 10 minutes, the tap attached to the tube A was left open and the syringe from tube B was removed. Suggest three reasons why the apparatus was left for 10 minutes. [3 marks] - answer-1. equilibrium reached 2. allow for pressure change in apparatus 3. allow respiration rate of seeds to stabilise // suggest and explain why the chosen temperature was 20C for this experiment. 2 marks - answer-optimum temperature for normal growth of seeds optimum temperature for enzymes involved in respiration during the experiment, the coloured liquid in the tubing moved towards tube B. explain what caused this. [3 marks] - answer-oxygen taken up/ used by seeds CO2 given out is absorbed by KOH so pressure in B decreases ...Mitochondrial disease often causes muscle weakness. use your knowledge of respiration and muscle contraction to suggest explanations for this effect of MD. [3 mark] - answer-reduction in ATP production by aerobic respiration less force generated because fewer actin and myosin interactions in muscle fatigue caused by lactate from anaerobic respiration suggest how the change in the anticodon of a tRNA leads to MD [3 marks] - answer-change to tRNA leads to wrong amino acid being incorporated into protein tertiary structure of protein changed protein required for oxidative phosphorylation/ the Krebs cycle, so less/ no ATP made if someone has MD, the concentration of lactate in their blood after exercise is usually much higher than normal. suggest why. [3 marks] - answer-mitochondria/ aerobic respiration not producing much ATP With MD increased use of ATP supplied by increase in anaerobic respiration more lactate produced and leaves muscles by diffusion describe how acetyl coenzyme A is formed in the link reaction. [2 marks] - answer-pyruvate is oxidised and decarboxylated addition of coenzyme A ...Oxalocatate is the first substrate to bind with enzyme citrate synthase. This induces a change in the enzyme, which enables the acetylcoenzyme A to bind. Explain how oxalocetate enables the acetylcoenzyme A to then bind to the enzyme. [2 marks] - answer-Changes in shape of active site active site now complementary Describe the part played by the inner membrane of a mitochondrion in producing ATP. [3 marks] - answer-electrons transferred down electron transport chain provide energy to take protons into space between membranes protons pass back, through ATPase Energy used to combine ADP and phosphate to produce ATP Why was the solution in which the mitochondria were suspended isotonic? [1 mark] - answer-prevent damage to mitochondria caused by differences in water potential Explain why the scientist did not use glucose as the respiratory substrate [2 marks] - answer-Glucose broken down during glycolysis in cytoplasm glucose cannot cross mitochondrial membrane Explain why the oxygen concentration would change during this investigation. [1 marks] - answer-terminal acceptor in electron transport chain and used to make water In which part of the mitochondria does the Krebs cycle take place? - answer-matrix Name two substances for which there would be net movement into the mitochondrion. [2 marks] - answer-1) ADP 2) pyruvate 3) P/ Inorganic phosphate 4) reduced NAD 5) Oxygen The mitochondria in muscles contain many cristae. Explain the advantage of this. [2 marks] - answer-large surface area for electron transport chain/ oxidative phosphorylation provide ATP for contradiction In the link reaction pyruvate is converted to a substance with molecules effectively containing only two carbons atoms. Describe what happens in this process. [2 marks] - answer-pyruvate is decarboxylated/ carbon atom is removed/ CO2 formed then it is oxidised so reduced NAD formed/ and a molecule of Coenzyme A is added to form acetylcoezyme A The Krebs cycle, which takes place in the matrix, releases hydrogen ions. These hydrogen ions provide a source of energy for the synthesis of ATP, using coenzymes and carrier proteins in the inner membrane of the mitochondrion. Describe the roles of the coenzymes carrier proteins in the synthesis of ATP. [3 marks] - answer-NAD/ FAD reduced H+ ions transferred from coenzyme to coenzyme energy made available as electrons passed on energy used to synthesis ATP from ADP and phosphate protons flown back into inter membrane space When glucose is repaired what happens to the energy which is not incorporated into ATP? [1 mark] - answer-it is released as heat At the end of a sprint race. a runner continues to breathe rapidly for some time. Explain the advantage of this. [2 marks] - answer-lactate been produced oxygen used to break down lactate and convert it back to pyruvate/ glucose When one mole of glucose is repaired anaerobically, only 2 moles of ATP are produced. Explain why less energy is released in anaerobic respiration. [1 mark] - answer-mark scheme answer: Glucose only partly broken down/ only broken down to lactate not in the mark scheme only uses glycolysis no oxygen for oxidative phosphorylation which produces most of the ATP On islands in the Caribbean, there are almost 150 species of lizards belonging to the genus Anolis. Scientists believe that these species evolved from two species found on mainland USA. Explain how the Caribbean species could have evolved. [6 marks] - answer-- geographical isolation -separate gene pools between populations -variation due to mutation -different environments/ selection pressures/ different abiotic/ biotic conditions -selected organisms survive and reproduce -leads to change in allele frequency anoles sagrei is a species of lizard that is found on some of the smallest Caribbean islands. describe how you could use the mark-release-recapture method to estimate the number of Anolis sager on one of these islands. [4 marks] - answer-capture/ collect sample method of marking does not harm lizard leave sufficient time for lizards to randomly distribute before collecting a second sample population = number in first sample x number in second sample divided by number of marked lizards in second sample Large areas of tropical forest are still found on some Caribbean islands. The concentration of carbon dioxide in the air of these forests changes over a period of 24 hours and at different heights above ground. use your knowledge of photosynthesis and respiration to describe and explain how the concentration of carbon dioxide in the air changes. -Over a period 24 hours -At different heights above ground. [5 marks] - answer-high concentration of carbon dioxide linked with respiration/ in darkness no photosynthesis in dark/ photosynthesis only in light in light use more ecabron dioxide than produced/ are of photosynthesis greater than rate of respiration decrease in carbon dioxide concentration with height at ground level less photosynthesis/ more respiration In muscles, pyruvate is converted to lactate during anaerobic respiration. Explain why connecting pyruvate to lactate allows the continued production of ATP during anaerobic respiration. [2 marks] - answer-regenerates NAD/ oxidises reduced NAD NAD used in glycolysis In muscles, some of the lactate is converted back to pyruvate when they are well supplied with oxygen. Suggest one advantage of this. [1 mark] - answer-pyruvate used in aerobic respiration/ lactate is toxic Explain why oxygen is needed for the production of ATP on the cristae of the mitochondrion. (3) - answer-oxygen is terminal electron acceptor acerbic respiration oxidative phosphorylation (produces most of the ATP) anaerobic respiration only glycolysis occurs what is a transcription factor? [2 marks] - answer-protein that moves from cytoplasm to DNA and binds to specific gene blocks premRNA CREB is a protein synthesised in the cytoplasm of neurones. transport CREB from the cytoplasm into the matrix of a mitochondrion requires two carrier proteins. use your knowledge of the structure of a mitochondrion to explain why transport of CREB requires two carrier proteins. [2 marks] - answer-mitochondria contains two membranes so for each membrane a different carrier protein needed CREB lead to the formulation a protein that removes electrons and protons from reduced NAD in the mitochondrion. Huntington's disease (HD) causes the death of neurones. people with HD produce a substance called Huntington. Some scientists have suggested that binding of Huntington to CREB may lead to the death of neurones. Suggest how binding of Huntington to CREB may lead to the death of neurones. [3 marks] - answer-binding to CREB prevents transcription/ mRNA formation binding of Huntington prevents production/ translation of protein that removes electrons/protons from NAD Fewer electrons to electron transport chain/ slows oxidative phosphorylation fewer protons fro proton gradient not enough ATP produced to keep cell alive Explain how a sport drink could provide an energy boost when running. [3 marks] - answer--drink contains carbohydrates/ sugars so raises blood glucose concentration contains slat so glucose more rapidly absorbed increase glucose to muscles for respiration more/ faster respiration so more energy please ATP is useful in many biological processes. Explain why. (4) - answer--phosphorylates/ makes compounds more reactive -releases small amount of energy so little is wasted as heat -broken in one step/ immediate source of energy -can be easily remade/ reformed Describe how ATP is made in mitochondria [6 marks] - answer-ATP produced in Krebs cycle Krebs cycle and link reaction produce reduced coenzymes/ reduced NAD and reduced FAD electrons released from reduced coenzyme electrons pass along carries/ through electron transport chain energy released energy provided for protons to diffuse into inter membrane space and back through ATP synthase ADP/ ADP + Pi Plants produce ATP in their chloroplasts during photosynthesis. They also produce ATP during respiration. Explain why it is important for plants to produce ATP during respiration in addition to during photosynthesis. [5 marks] - answer-in the dark no ATP production in photosynthesis some tissues unable to photosynthesise/ produce ATP ATP cannot be moved for cell to cell/ stored plant uses more ATP than produced in photosynthesis atp for active transport Heat stress is a condition that often occurs in plants to high temperatures for a prolonged period of time. Heat stress is a major factor in limiting the rate of photosynthesis. Heat stress decreases the light-dependent reaction of photosynthesis. Explain why this leads to a decrease in the light-dependent reaction. [2 marks] - answer-Less ATP Less reduced NADP A decrease in the activity of the enzyme rubisco would limit the rate of photosynthesis. Explain why. [2 mark] - answer-Less carbon dioxide (reacts) with RuBP so less GP Where precisely is rubisco found in a cell? - answer-stroma (of chloroplast) Describe how alterations to tumour suppressor genes can lead to the development of tumours. [3 marks] - answer-increased methylation (of tumour suppressor genes) mutation (in tumour suppressor genes) tumour suppressor genes are not transcribed/ expressed OR Amino acid sequence/ primary structure altered (results in) rapid/ uncontrollable cell division Explain why a log scale is used to record the number of cells [1 mark] - answer-large range/ difference/ increase in numbers Many yeast cells die during the death phase. Suggest one reason why. [1 mark] - answer-decrease/no glucose OR increase in ethanol The scientists concluded that the results shown in Figure 5 were due to succession taking place. Use Figure 5 to explain why the scientists reached this conclusion. [4 mark] (A Level Paper 2 June 2018) - answer-Beach grass is the pioneer species pioneers change the (abiotic) environment/ factors so less hostile for named species OR So more suitable for named species Conifer/ hardwood trees represent climax community Furosemide is sometimes used to treat high blood pressure. Suggest how furosemide would cause a decrease in blood pressure.[1 mark] - answer-lower volume of blood Furosemide inhibits the absorption of sodium and chloride ions from the filtrate produced in the nephrons. Explain how furosemide causes an increase in the volume of urine produced. [3 marks] - answer-Water potential of filtrate/ tubule decrease less water (reabsorbed) by osmosis (from filtrate/ tubule) collecting duct (is where osmosis occurs) In genetic crosses, the observed phenotypic ratios obtained in the offspring are often not the same as the expected ratios. [2 marks] - answer-Small sample size fertilisation of gametes is random linked genes epistasis lethal genotypes Use the information provided to explain why the number of offspring with different phenotypes are not as expected Phenotype of offspring / number of offspring Tall plants and normal leaves - 1860 Tall plants and mottled leaves - 68 Dwarf plants and normal leaves - 57 Dwarf plants and mottled leaves - 580 - answer-Genes are linked produces fewer tall, mottled and dwarf, normal offspring crossing over has occurred Dopamine is a neurotransmitter released in some synapses in the brain. The transmission of dopamine is similar to that of acetylcholine. Dopamine stimulates the production of nerve impulses in postsynaptic neurones. Describe how. Do not include in your answer the events leading to the release of dopamine and the events following production of nerve impulses at postsynaptic neurones. [3 marks] - answer-dopamine diffuses across synapse attaches to receptors on postsynaptic membrane stimulates entry of sodium ions and depolarisation Dopamine has a role in numerous processes in the brain including pain relief. The release of dopamine can be stimulated by chemicals called endorphins produced in the brain. Endorphins attach to opioid receptors on presynaptic neurones that release dopamine. Morphine is a drug that has similar structure to endorphins and can provide pain relief. Explain how. [2 marks] - answer-Morphine attaches to opioid receptors (more) dopamine released (to provide pain relief) GABA is a neurotransmitter released in some inhibitory synapses in the brain. GABA causes negatively charged chloride ions to enter postsynaptic neurones. Explain how this inhibits postsynaptic neurones. [3 marks] - answer-(Inside of postsynaptic) neurone becomes more negative/ hyperpolarisation/ inhibitory postsynaptic potential; more sodium ions required (to reach threshold) OR Not enough sodium ions enter (to reach threshold) for depolarisation/action potential What is meant by genome? [1 mark] - answer-All the DNA in a cell Explain why the antibody binds to the transcription factor. [2 mark] - answer-antibody has a specific/ tertiary structure/ shape complementary shape/ structure Describe the roles of two named types of enzymes used to insert DNA fragments into plasmids. [2 marks] - answer-Restriction endonuclease/ enzymes to cut plasmid/ vector ligase joins gene/ DNA to plasmid/ vector The soybean cells were screened for the presence of the P34 protein. This process involved the use of gel electrophoresis to operate proteins extracted from soybean cells. Suggest two features of the structure of different proteins that enable them to be operated by gel electrophoresis. [2 marks] - answer-1. mass/ number of amino acids/ polypeptides 2. charge 3. R groups (differ) One hypothesis for Lactase Persistence (LP) in humans suggests that the selective pressure was related to some human populations farming cattle as a source of milk. Describe how farming cattle as a source of milk could have led to an increase in LP. [4 marks] - answer-LP due to mutation OR allele due to mutation milk provides named nutrient; individuals with LP more likely to survive and reproduce OR individuals with advantageous allele more likely to survive and reproduce; Directional selection; frequency of allele increases )in offspring/ next generation Use the information provided to explain why the number of people showing lP would rapidly increase once selection for this condition had been established. [2 marks] - answer-dominant allele; (always) expressed/ shown (when present in phenotype/ offspring) OR Expressed when only one (dominant allele) present; Lactase persistence is caused by a mutation in DNA. This mutation does not occur in the gene coding for lactase. Suggest and explain how this mutation causes LP. [2 marks] - answer-Mutation in promoter (DNA/ gene) for transcription factor OR Mutation in promoter (region/ DNA) for the gene OR Mutation in gene for transcription factor; Lactase gene continues to be transcribed/ active 'Complete chromatopsia is a form of complete colour blindness. It is caused by having only rods and no functional cone cells. People with complete chromatopsia have difficulty in seeing detail...' People with complete chromatopsia have difficulty in seeing detail. Explain why. [3 marks] - answer-Only rods; Several rods connected to single neurone Rods single set of impulses to brain Red-colour blindness affects more men than women. Explain why. [2 marks] - answer-Gene/ allele i son the X chromosome Females require two alleles/ females can be heterozygous/ carriers and males require one allele; People with red-green colour blindness are unable to distinguish between red and green, and also between other colours. Explain why. [3 marks] - answer-green sensitive pigment/ cones non-functional OR Cones that detect green light non-functional; three different types of pigment/ cone; other/ different colours due to stimulation of more than one cone/ pigment Current research into the treatment of red-green blindness involves the use of induced pluripotent stem cells. Suggest how iPS cells could correct red-green colourblindness. [2 marks] - answer-iPS cells divide iPS cells develop/ differentiate into green sensitive cones The use of iPS cells could have advantages over the use of gene therapy to correct red-green colour blindness. Using the information from the passage, suggest and explain reasons why. [3 marks] - answer-(Use of iPS cells) long-term; (Use of iPS cells) less chance of rejection/ immune response; (Use of iPS cells) single treatment; Harm/ side effects from using viruses (in gene therapy) Describe how calcium ions are involved in synaptic transmission. [2 marks] - answer-(Nerve impulses causes) Ca2+ to eneter presynaptic neurone/membrane ca2+ entry causes fusion of vesicles with presynaptic membrane/ causes exocytosis When a neurone transmits a series of impulses, its rate of oxygen consumption increases. Explain why. [2 marks] - answer-(more) respiration (more) energy supplied/ more ATP supplied for active transport of ions/ 'sodium-potassium pump' Dopamine is released at synapses in parts of the brain where pleasure is perceived. Use information from Figures 1 and 2, and explain how the use of cocaine can result in feelings of pleasure. [3 marks] - answer-cocaine blocks transport of dopamine out of synaptic cleft dopamine concentration rises continues to stimulate/ bind to receptors causes continued firing of impulses