Describe the role of a ribosome in the production of a polypeptide. /3 - Correct answer1. mRNA binds to ribosome;
2. Idea of TWO codons/binding sites;
3. tRNA with ANTICODONS binds;
4. (Catalyses) formation of PEPTIDE bond between AMINO ACIDS (held by tRNA
molecules);
5. Moves along (mRNA to t...
AQA A-Level Biology Paper 1
Describe the role of a ribosome in the production of a polypeptide. /3 - Correct answer-
1. mRNA binds to ribosome;
2. Idea of TWO codons/binding sites;
3. tRNA with ANTICODONS binds;
4. (Catalyses) formation of PEPTIDE bond between AMINO ACIDS (held by tRNA
molecules);
5. Moves along (mRNA to the next
codon);
Describe the structure of glycogen. /2 - Correct answer-1. Polysaccharide of α-glucose;
OR
polymer of α-glucose;
2. (Joined by) glycosidic bonds
OR
Branched structure;
NHE3 actively transports one sodium ion into the cell in exchange for one proton
(hydrogen ion) out of the cell.
Use your knowledge of transport across cell membranes to suggest how NHE3
does this. /3 - Correct answer-1. Co-transport;
2. Uses (hydrolysis of) ATP;
3. Sodium ion and proton bind to the protein;
4. Protein changes shape (to move sodium ion
and/or proton across the membrane);
Explain the curves for max protease activity over time at 50C and 60C. /4 - Correct
answer-1. Both denatured (by high temperature);
2. Denaturation faster at 60 °C due to more (kinetic) energy;
3. Breaks hydrogen/ionic bonds (between amino acids/R groups);
4. Change in shape of the active site/active site no longer complementary so fewer
enzyme-substrate complexes formed;
Describe the action of these membrane-bound dipeptidases and explain their
importance. /2 - Correct answer-1. Hydrolyse (peptide bonds) to release amino acids;
2. Amino acids can cross (cell) membrane;
OR
Dipeptides cannot cross (cell) membrane;
OR
Maintain concentration gradient of amino acids for absorption;
Explain why the scientists suggested that patients should be treated with both the
current antibiotic and the new one.
, Use information from Figure 2 (old antibiotic decreases number of bacteria, new one
decreases it more) and your knowledge of evolution of antibiotic resistance in bacteria
in your answer. /3 - Correct answer-1. (From Fig 2) New/old antibiotic does not kill all
bacteria;
OR
(From Fig 2) Some bacteria are resistant to the new/old antibiotic;
2. Resistant bacteria will reproduce to produce (more) resistant bacteria;
3. (Use of both) one antibiotic will kill bacteria resistant to the other antibiotic;
OR
Unlikely that bacteria are resistant to both the new and the old antibiotic;
OR
Use of both antibiotics (likely to) kill all/most bacteria;
When measuring the leakiness of herbicide-treated cell membranes to ions, why did the
scientists gently shake the flasks containing the leaf discs? /1 - Correct answer-
(Shaking) So all surfaces of the leaf discs are exposed (to water)/so all submerged;
OR
To maintain diffusion/concentration gradient (for ions out of leaf discs);
Scientists have found a virus that produces a protein very similar to human
collagen.
Suggest how the immune response to this viral protein can result in the
development of rheumatoid arthritis? /2 - Correct answer-1. The antibody against virus
(antigen) will bind to collagen;
2. This results in the destruction of the (human) cells/collagen;
Explain six ways in which an insect's tracheal system is adapted for efficient gas
exchange. /3 - Correct answer-1. Tracheoles have thin walls so short
diffusion distance to cells;
2. Highly branched/large number of
tracheoles so short diffusion distance to
cells;
3. Highly branched/large number of
tracheoles so large surface area (for gas
exchange);
4. Tracheae provide tubes full of air so fast diffusion (into insect tissues);
5. Fluid in the end of the tracheoles that
moves out (into tissues) during exercise
so faster diffusion through the air to the
gas exchange surface;
OR
Fluid in the end of the tracheoles that
moves out (into tissues) during exercise
so larger surface area (for gas exchange);
6. Body can be moved (by muscles) to move air so maintains diffusion/concentration
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