Biochemistry - Problem Drill 16: Carbohydrate Metabolism

Transcription

1 Biochemistry - Problem Drill 16: Carbohydrate Metabolism No. 1 of 10 Instructions: (1) Read the problem statement and answer choices carefully (2) Work the problems on paper as 1. Fill in the diagram below substrate and pathway with respect to carbohydrate metabolism in biological organisms. Use the starting and ending components as a clue. (A) Glucose, glycogen (B) Glucose, glycolysis (C) Pyruvate, lactose (D) Glycolysis, glucose (E) None of the above No, this is not a correct response. B. Correct! Yes, this is the correct response. No, this is not a correct response. No, this is not a correct response. E. Incorrect! No, one of the answers listed is correct. The correct answer is (B).

2 No. 2 of Which of the following is glucose not the starting material for? (A) Glycogen synthesis (B) Starch synthesis (C) Fructose synthesis (D) Lactose synthesis (E) Sucrose synthesis No, glucose is the starting material for the synthesis of this molecule. The question is asking for which it is NOT the starting material for. B. Incorrect No, glucose is the starting material for the synthesis of this molecule. The question is asking for which it is NOT the starting material for. C. Correct! Yes, glucose is not the starting material for fructose synthesis. No, glucose is the starting material for the synthesis of this molecule. The question is asking for which it is NOT the starting material for. E. Incorrect! No, glucose is the starting material for the synthesis of this molecule. The question is asking for which it is NOT the starting material for. Glucose is the starting material for the synthesis of: glycogen, starch, lactose and sucrose. The correct answer is (C).

3 No. 3 of When glucose enters the pentose phosphate pathway it has two fates or routes. Look at the diagram below and select which answers best completes it. (A) Oxidative, Fermentation (B) Anaerobic, Aerobic (C) Degenerative, Generative (D) Oxidative phase, Non-Oxidative Phase (E) All of the above No, consider when glucose enters the pentose phosphate pathway what two things can happen? No, consider when glucose enters the pentose phosphate pathway what two things can happen? No, consider when glucose enters the pentose phosphate pathway what two things can happen? D. Correct! Yes, the two phases that glucose can enter once in the pentose phosphate pathway are: oxidative and non-oxidative phases. E. Incorrect! No, one of the answers provided is correct. The correct answer is (D).

4 No. 4 of Where in the living biological organism does the Pentose Phosphate Pathway occur? (A) Cytosol (B) Mitochondria (C) Cell Membrane (D) Nucleus (E) Endoplasmic Reticulum A. Correct! Yes, the Pentose Phosphate Pathway occurs in the cytosol. E. Incorrect! The Pentose Phosphate Pathway occurs in the cytosol of biological organisms. The correct answer is (A).

5 No. 5 of is an enzyme that connects the pentose phosphate pathway to glycolysis. (A) Acetalase (B) Transcarbamolase (C) Methalase (D) Gluconase (E) Transketolase E. Correct! Yes transketolase is an enzyme that connects the pentose phosphate pathway to glycolysis. Transketolase is an enzyme that connects the pentose phosphate pathway to glycolysis. It sends excess sugar phosphates into the main carbohydrate metabolic pathways. The correct answer is (E).

6 No. 6 of The glyoxylate cycle allows the net synthesis of glucose from and is an example of gluconeogenesis. (A) Fructose (B) Glucose-6-phosphates (C) Citrate (D) Succinate (E) Acetyl-CoA E. Correct! Yes, the glyoxylate metabolic cycle is a pathway that allows the net synthesis of glucose from acetyl-coa. The glyoxylate cycle is a metabolic pathway typical of plants, some microbes, and yeast and recently shown to be present in vertebrates and insects. It allows organisms to use fats for the synthesis of carbohydrates. The correct answer is (E).

7 No. 7 of Gluconeogenesis is the formation of glucose from non-sugar substrates with the exception of. (A) Pyruvate (B) Lactate (C) Glycerol (D) Glucogenic amino acids (E) None of the above It is partially correct. This is non-sugar substrate, but there are more listed. It is partially correct. This is non-sugar substrate, but there are more listed. It is partially correct. This is non-sugar substrate, but there are more listed. It is partially correct. This is non-sugar substrate, but there are more listed. E. Correct! There is no exception above. All four substrates mentioned are non-sugar compounds to form glucose. Logically, this is the only correct answer for what is being asked. Gluconeogenesis is the formation of glucose from non-sugar substrates like pyruvate, lactate, glycerol and glucogenic amino acids. This happens mostly in the liver during times of fasting or intense exercise. The correct answer is (E).

8 No. 8 of Which of the following statements is correct with respect to glycolysis and gluconeogenesis? (A) Glycolysis and gluconeogenesis are reciprocally regulated. (B) Phosphofructokinase-1 is a regulatory enzyme for both. (C) Fructose-1, 6-bisphosphates is a regulatory enzyme for both. (D) Activators of one pathway inhibit the other. (E) All of the statements are correct. No. This is a correct statement however it is not the best response to the question. No. This is a correct statement however it is not the best response to the question. No. This is a correct statement however it is not the best response to the question. No. This is a correct statement however it is not the best response to the question. E. Correct! Yes, this is the best answer to the question. All of the statements are accurate with respect to glycolysis and gluconeogenesis pathways. A. Glycolysis and gluconeogenesis are reciprocally regulated. B. Phosphofructokinase-1 is a regulatory enzyme for both. C. Fructose-1, 6-bisphosphates is a regulatory enzyme for both. D. Activators of one pathway inhibit the other. The correct answer is (E).

9 No. 9 of Which of the following statements is incorrect with respect to glycogen synthesis? (A) Glycogen synthesis is endergonic. (B) Glycogen is synthesized from multimers. (C) Glycogen synthase lengthens the glycogen chain. (D) Glycogenin is necessary to start glycogen synthesis. (E) UTP is the energy source for glycogen synthesis. No, this is a correct statement. B. Correct! No, glycogen is synthesized from monomers of glucose 1-phosphate by glycogen synthase. No, this is a correct statement. No, this is a correct statement. E. Incorrect! No, this is a correct statement. Glycogen is synthesized from monomers of glucose 1-phosphate by the enzyme glycogen synthase. The correct answer is (B).

10 No. 10 of Fill in the blank. Starch is a high molecular weight polymer made up of monomeric units. (A) Fructose (B) Hexose (C) Heptose (D) Beta-galactose (E) Glucose No, this molecule is not the basis of starch formation. No, this molecule is not the basis of starch formation. No, this molecule is not the basis of starch formation. No, this molecule is not the basis of starch formation. E. Correct Yes, starch is a high molecular weight polymer made up of glucose monomeric units linked by alpha 1 to 4 linkages. When in doubt go with glucose with respect to metabolic pathways. Glucose is used as a precursor in many different pathways. Starch is a high molecular weight polymer made up of glucose monomeric units linked by alpha 1 to 4 linkages. The correct answer is (E).