A level Biology OCR A Paper 3 high demand exam questions from ExamBuilder with markcheme
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OCR A HIGH DEMAND QUESTIONS
Institution
OCR
In this document you will have the most high demand questions for A-Level Biology Paper 3 OCR A. You have most important topics that come up almost every year with mark schemes at the end. They have been carefully selected for your own benefit. These questions are a good way to prepare yourselves f...
1(a). Amino acids can be converted to other molecules and used in respiration.
Fig. 4.1 shows the formulae of five amino acids that can be used in respiration.
Fig. 4.1
Fig. 4.2 shows an outline of the link reaction and the Krebs cycle.
Fig. 4.2
i. The table below contains information about three amino acids.
Use Fig. 4.1 and Fig. 4.2 and your own knowledge to draw a conclusion about which amino acid is being described.
Write your conclusions and a justification for each conclusion in the table.
Conclusions
Information about
amino acid Name of amino
Justification
acid
Converted to pyruvate ......................................................
with the fewest changes
......................................................
Converted to
......................................................
α-ketoglutaric acid with
the fewest changes
......................................................
, ......................................................
The amino acid with
the highest RQ ......................................................
[4]
ii. Outline the reactions that must occur to convert α-ketoglutaric acid to oxaloacetate in Fig. 4.2.
[2]
(b). A person’s RQ changes when they exercise.
Fig. 4.3 shows how RQ changes with the power a person exerts during exercise. Power, measured in watts (W), increases as the intensity
of physical exercise increases.
Fig. 4.3
What can you conclude about respiration at 0, 50 and 250 W based on the RQ values?
0W
50 W
250 W
[3]
2(a). Fig. 2.1 shows three images, C to E, of animal cells undergoing mitosis.
(b). The eukaryotic cell cycle is regulated by three checkpoints. Mutations can occur in genes that control the cell cycle checkpoints.
Scientists recorded observations of two different tissues.
i. In one tissue, the scientists found a genetic mutation that stopped the metaphase checkpoint from working.
Suggest an abnormality the scientists might observe in the cells of this tissue.
[1]
ii. In the other tissue, the scientists observed cells with chromosomes that had been replicated despite containing damaged DNA.
Suggest which cell cycle checkpoint is no longer working in this tissue and justify your answer.
[1]
(c). Scientists recorded the population growth of bacteria in a closed culture. The scientists added various nutrients to the culture,
including nitrate .
Fig. 2.3 shows the growth curve of the bacterial population.
Fig. 2.3
i. A student looked at Fig. 2.3 and made the following statement:
‘The bacterial growth curve in Fig. 2.3 looks very different from a standard growth curve for bacterial populations.’
Use evidence from Fig. 2.3 to evaluate the student’s statement.
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