Under aerobic conditions, pyruvate formed in glycolysis enters the mitochondrion and is involved in the link reaction. Enzymes are essential for the Krebs cycle to operate. Their activity can be altered by hydrogen peroxide, which is made in some of the reactions inside the mitochondrion. An investigation was done to find out how two different concentrations of hydrogen peroxide affected an enzyme of the Krebs cycle. The enzyme’s activity was recorded over 10 minutes after exposure to the two hydrogen peroxide concentrations. The findings are shown in Fig. 9.1.
(a)[2]
Name the two coenzymes that take part in the link reaction.
(b)[3]
Describe the effect shown in Fig. 9.1 of hydrogen peroxide concentration on the activity of the Krebs cycle enzyme.
(c)[4]
Reduced NAD and reduced FAD are made during the Krebs cycle. They transfer hydrogen to the inner mitochondrial membrane where oxidative phosphorylation takes place. The first two stages of oxidative phosphorylation are: 1. Hydrogen atoms separate into protons and electrons. 2. Electrons pass along the electron transport chain, releasing energy. Outline the steps that occur to complete oxidative phosphorylation.
(d)[3]
Fig. 9.2 shows the oxygen consumption of a person during fast-running exercise.
Suggest why the oxygen consumption takes time to return to normal after exercise.
Worked solution & mark scheme
This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: “NAD” …