Question

1. What effect does an absence of oxygen (O2) have on the electron transport chain? What would happen if, in this anaerobic environment, you artificially decreased the pH of the intermembrane space of the mitochondrion? Explain.

2. Would you expect high levels of ATP to inhibit or activate glycolysis? Explain your answer.

3. A glucose-fed yeast cell is moved from an aerobic environment to an anaerobic one. How would its rate of glucose consumption change if ATP were to be generated in the yeast at the same rate as before? Explain.

4. Imagine you are a pharmacological researcher who wants to design a drug that inhibits a particular enzyme. Upon reading the scientific literature, you find that the enzyme's active site is similar to that of several other unrelated enzymes. Would a competitive or noncompetitive inhibitor be a better drug? Explain.

Answer 1

In the absence of oxygen, NAD+ will not be regenerated in tthe electron transport chain (ETC). The ETC can't run because there is no oxygen to act as the final electron acceptor. This means that the ETC will not be accepting electrons from NADH as its source of power, so NAD+ will not be regenerated.

Low pH increases the concentration of base causing mitochondria to pump out H+ to the inter membrane space leading to ATP production. The intermembrane space having the lowest pH in the mitochondria, due to the high H+ concentration. The high external acid concentration causes an increase in H+ in the inter membrane space leading to increased ATP production by ATP synthetase.

Phosphofructokinase (PFK) is the most important control element in the glycolytic pathway. PFK is able to regulate glycolysis through allosteric inhibition. A high ratio of ATP to ADP will inhibit PFK and glycolysis.

The glucose concentration has been shown to affect the rate of yeast fermentation and carbon dioxide production. A moderate concentration of glucose it will cause fermentation rates to increase and with it an increase production of carbon dioxide.

In competitive inhibition an inhibitor that resembles the normal substrate binds to the enzyme, usually at the active site, and prevents the substrate from binding. The active site is a region on an enzyme which a particular protein or substrate can bind to.