This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Metabolism”.
1. Catabolic pathways result in _______________ of the molecules.
Explanation: Catabolism refers to the disassembly of complex molecules to form simpler products. Catabolism hence serves two roles: providing raw materials for synthesis of products and making chemical energy available for survival of a cell.
2. Energy released by catabolic pathways is stored in how many forms?
Explanation: Energy released by catabolic pathways is stored primarily in two forms: high energy phosphates like adenosine triphosphate and high energy electrons (NADPH).
3. Anabolic pathways are energy-requiring.
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.
4. How many molecules of ATP are formed per molecule of oxidation of glucose?
Explanation: The free energy released by complete oxidation of glucose is ΔG⁰’ = -686 kcal/mol; which is very large. The free energy required to convert ADP to ATP is relatively small ΔG⁰’ = +7.3 kcal/mol. Upto 36 molecules of ATP can be formed per molecule of glucose.
5. The TCA cycle occurs in which region of a prokaryotic cell?
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.
6. Glycolysis begins with which of the following reactions?
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.
7. NAD is a _________
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.
8. NAD⁺ can be derived from which vitamin?
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.
9. In fermentation, which of the following is regenerated?
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.
10. In case of repeated contraction, muscle cells regenerate NAD⁺ by converting pyruvate to _____________
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.
11. Yeast cells convert pyruvate to lactate.
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.
12. A cell’s reservoir of NADPH represents its _______________
a) oxidation state
b) oxidation power
c) tensile strength
d) reducing power
Explanation: A cell’s reservoir of NADPH is a measure of its reducing power and the usable energy. NADPH is a compound similar to NADH but with an additional phosphate group.
13. How many mechanisms exist for altering the shape of an enzyme, playing a role in regulating glucose oxidation?
Explanation: For regulating glucose oxidation, there are two mechanisms that are responsible for altering the shape of an enzyme’s active site namely covalent modification and allosteric modification.
14. Protein kinases are responsible for transferring which group?
Explanation: Protein kinases are a class of enzymes that transfer phosphate group to other proteins (covalent modification). These are hence vital in hormone action, cell division and gene expression.
15. How many types of protein kinases are there?
Explanation: There are two types of protein kinases: one adds phosphate group to tyrosine residues in a protein and the other adds phosphate group to serine or threonine residues.
Sanfoundry Global Education & Learning Series – Cell Biology.
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