1. What type of bond is formed in the condensation reaction between two amino acids ?
Answer
Peptide bond.
2. What type of bond allows for alpha-helices and beta-pleated sheets to form within the secondary structure of a polypeptide ?
Answer
Hydrogen bonds.
3. Which bonds help to contribute to a protein's tertiary structure ?
Answer
Hydrogen, disulfide bridges, and ionic bonds.
4. Use a labelled diagram to show the general structure of an amino acid.
Answer
5. The figure below shows the effect of substrate concentration on the rate of reaction of a particular enzyme. Name two variables that should have been kept constant during this investigation.
Answer
Enzyme concentration and pH.
6. The graph obtained at 18°C is different from the graph obtained at 25°C. Explain why the two graphs are different between A and B.
Answer
An increase in temperature raises the kinetic energy, which results in more enzyme–substrate complexes being formed due to more frequent collisions. At 25°C, the temperature is closer to the optimum, allowing the reaction to proceed more efficiently.
7. Explain why the two graphs are the same between B and C.
Answer
Enzyme concentration is the limiting factor. The enzymes are working at their maximum rate, with all active sites in use.
8. Describe the result you would expect if the investigation was repeated at 18°C with a non-competitive inhibitor.
Answer
The line follows the same shape as the existing line, remaining below the 18°C line all the way along.
9. The figure below shows some of the steps involved in developing an erection. Erectile dysfunction occurs when the blood flow to the penis is insufficient for a man to maintain an erection. Sildenafil is a drug used to treat erectile dysfunction. Sildenafil is similar in shape to cGMP. Explain how sidenafil is effective in treating erectile dysfunction.
Answer
Sildenafil is a competitive inhibitor. It fits into the active site of the enzyme phosphodiesterase and prevents cGMP from being broken down or converted to GMP.
10. Suggest why sildenafil does not cause erections unless a man is sexually aroused.
Answer
Nitric oxide is needed to activate the enzyme. Nitric oxide is only produced when aroused, and cGMP is also only produced when aroused.