Proteins and Enzymes | OCR A-Level Biology B (Advancing Biology) (H422)
Proteins and Enzymes
- 99 questions
- 6 subtopics
- Biology content, examined on all three papers
- Component 01, Component 02 and Component 03
Proteins and Enzymes is examined in all three written papers — the specification states that Components 01, 02 and 03 can each assess content from any of the five modules, so nothing is confined to one paper.
It covers amino acids, peptide bonds and chromatography, globular protein structure: enzymes and haemoglobin, enzyme action and the rate of reaction, blood clotting and first aid, enzymes and inhibitors in medicine and blood donation and stored blood products.
Sample questions from Proteins and Enzymes
Answer each one closed book first, then open the answer.
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Amino acids, peptide bonds and chromatography
Describe how a chromatogram of an amino acid mixture is prepared and run.
Show the answer
A pencil origin line is drawn near one end of the paper, a small concentrated spot of the mixture is applied and dried, and the paper is suspended in a covered tank with the solvent just below the origin line so that the solvent rises by capillary action until it nears the top, when the solvent front is marked. -
Amino acids, peptide bonds and chromatography
Give the equation used to calculate an Rf value.
Show the answer
Rf equals the distance moved by the solute divided by the distance moved by the solvent. -
Globular protein structure: enzymes and haemoglobin
What is meant by quaternary structure?
Show the answer
It is the arrangement of two or more separate polypeptide chains, together with any prosthetic group, into a single functional protein molecule. -
Globular protein structure: enzymes and haemoglobin
Give three features that make a protein globular rather than fibrous.
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The chain folds into a compact roughly spherical shape, its amino acid sequence is irregular rather than repeating, and its hydrophilic R groups lie on the outside so the molecule is soluble in water. -
Enzyme action and the rate of reaction
What is the effect of increasing temperature on the rate of an enzyme-catalysed reaction, and why?
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Rate rises at first because enzyme and substrate molecules gain kinetic energy and collide more often with sufficient energy, but above the optimum the hydrogen and ionic bonds holding the tertiary structure break, the active site changes shape and the rate falls sharply as the enzyme denatures. -
Enzyme action and the rate of reaction
How does a non-competitive inhibitor work?
Show the answer
It binds to a site elsewhere on the enzyme, which changes the tertiary structure and so distorts the active site; the substrate can no longer fit, and adding more substrate does not overcome the effect. -
Blood clotting and first aid
What reaction does thrombin catalyse?
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Thrombin catalyses the conversion of the soluble plasma protein fibrinogen into insoluble fibrin. -
Blood clotting and first aid
Why is a bleeding limb raised above the level of the heart?
Show the answer
Raising it lowers the blood pressure in the vessels of the wound, so blood is lost more slowly and a clot forms more easily.
The 6 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Amino acids, peptide bonds and chromatography | Recall questions on the structure of amino acids and their R groups, peptide bond formation, running a paper chromatogram of amino acids, developing it with ninhydrin safely, calculating and using Rf values, and two-way chromatography. | 18 |
| Globular protein structure: enzymes and haemoglobin | Recall questions on primary, secondary, tertiary and quaternary protein structure, the bonds including disulfide bridges that hold it, haemoglobin and its haem prosthetic group, the features and solubility of globular proteins, and denaturation. | 15 |
| Enzyme action and the rate of reaction | Recall questions on enzyme specificity and the induced fit model, activation energy, the effects of temperature, Q₁₀, pH, substrate and enzyme concentration, competitive and non-competitive inhibitors, and measuring initial rates of catalase activity with a gas syringe. | 18 |
| Blood clotting and first aid | Recall questions on platelets and calcium ions at a wound, the enzyme cascade that produces an insoluble mesh, why its precursors circulate inactive, and first aid for heavy bleeding. | 16 |
| Enzymes and inhibitors in medicine | Recall questions on why tissue damage raises blood enzyme levels, what a raised amylase suggests, how streptokinase clears a clot, aspirin and warfarin as anticoagulants, and monitoring during treatment. | 14 |
| Blood donation and stored blood products | Recall questions on ABO antigens and antibodies, agglutination after a mismatched transfusion, universal donors and recipients, the rhesus factor in pregnancy, donor criteria, screening and deferral, and leuco-depleted blood, packed red cells, platelets, clotting factor concentrates and stored plasma. | 18 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR A-Level Biology B (Advancing Biology) Active Recall Guide
Every topic, not just this one. 2,895 questions with their answers.