Lesson 5 - Yeast Biochemistry SAQ
This lesson enables you to test yourself on the material covered in the Yeast Biochemistry lesson, and determine the level to which you have met the learning outcomes.
Suggested Response - Q2
*Answer both parts of this question:
a) Draw an equation showing how a coenzyme takes part in a reaction in which compound A is reduced to compound B and indicate how the coenzyme might be re-oxidised in a subsequent biochemical reaction.
b) ATP is the principal molecule used by cells to conserve energy. How many molecules of ATP are formed per molecule of glucose consumed via fermentation and respiration, respectively?
Response:
a) Specific enzymes catalyse these reactions, and they use coenzymes, which can be reversibly oxidised and reduced. The most common of these coenzymes are NAD and NADP.
The equation would be:
AH + NAD(P) = B + NAD(P)H
A similar balancing reaction will regenerate oxidised NAD(P):
C + NAD(P)H = DH + NAD(P)
b) Glycolysis (EMP pathway) converts glucose into pyruvate. During this conversion, two molecules of ATP are used, and four molecules of ATP are produced, so the net gain is two molecules.
In respiration, the electron transport chain is active, and the process of oxidative phosphorylation generatea ATP. In this reaction, typically 36 molecules of ATP are formed for each molecule of glucose consumed. In this case, the total yield is 36 molecules from oxidative phosphorylation plus two molecules from glycolysis, so 38 molecules in total.