1. Energy released by catabolic pathways is stored in how many forms?
a) 1
b) 2
c) 3
d) 4
Explanation: Energy released by catabolic pathways is stored primarily in two forms: high energy phosphates like adenosine triphosphate and high energy electrons (NADPH).
2. Anabolic pathways are energy-requiring.
a) True
b) false
Explanation: Anabolic pathways lead to the formation of complex molecules from simpler raw products. These require chemical energy which is supplied by the exergonic catabolic pathways.
3. How many molecules of ATP are formed per molecule of oxidation of glucose?
a) 12
b) 24
c) 36
d) 48
Explanation: In one cycle of glycolysis, 6 ATP is obtained. Each molecule of glucose gives 2 pyruvate which corresponds to 6 ATP. There is also formation of 2 acetyl-CoA molecules which is about 24 ATP. Thus each molecule of Glucose give 36 ATP. ( Note that about 34 ATP molecules are consumed in glycolysis thus the net yield is 2 ATP).
4. The TCA cycle occurs in which region of a prokaryotic cell?
a) cytosol
b) mitochondria
c) ribsomes
d) golgi complex
Explanation: There are two stages in the catabolism of glucose namely glycolysis which occurs in the cytosol and tricarboxylic acid (TCA) cycle which occurs in the cytosol of prokaryotes and mitochondria of eukaryotes.
5. Glycolysis begins with which of the following reactions?
a) reduction
b) oxidation
c) phosphorylation
d) acidification
Explanation: Glycolysis begins with the addition of a sugar molecule to a phosphate group. Phosphorylation activates the sugar molecule to take part in later steps of the process and also reduce the concentration of glucose in the cytoplasm, promoting continued diffusion from blood to the cell.
6. NAD is a _________
a) enzyme
b) cofactor
c) protein
d) nucleoside
Explanation: Nicotinamide adenine dinucleotide is a non-protein cofactor called coenzyme. NAD plays a key role in the metabolism of the cell by donating and accepting electrons.
7. NAD⁺ can be derived from which vitamin?
a) A
b) C
c) Riboflavin
d) Niacin
Explanation: NAD⁺ is the reduced state of the coenzyme NAD. It is derived from the vitamin niacin and is loosely bound to the enzyme dehydrogenase.
8. In fermentation, which of the following is regenerated?
a) Starch
b) Oxygen
c) NAD⁺
d) NADH
Explanation: Cells are able to regenerate NAD⁺ by fermentation. In this process the transfer of electrons take place from NADH to pyruvate or to a compound derived from pyruvate.
9. In case of repeated contraction, muscle cells regenerate NAD⁺ by converting pyruvate to _____________
a) glycogen
b) lactate
c) starch
d) cellulose
Explanation: In case of repeated contraction, the oxygen levels drop down and make it difficult to keep up with the cell’s metabolic demands. Under these conditions, skeletal muscle cells regenerate NAD⁺ by converting pyruvate to lactate
10. Yeast cells convert pyruvate to lactate.
a) true
b) false
Explanation: Unlike the cells of skeletal muscles, which convert pyruvate to lactate in case of low oxygen supply; the yeast cells convert pyruvate to ethanol.