Deck 12: Chemical Logic of Metabolism

Question 1

In stage ____ metabolism,a catabolic pathway might produce ________ while the opposing anabolic pathway might produce _________.

A)2;monosaccharides;polysaccharides
B)3;CO₂;glucose
C)2;acetyl CoA;lipids
D)1;amino acids;proteins
E)3;NH₃;nucleotides

Answer 1

D

Question 2

Based on the following reaction,what is the respiratory quotient for stearic acid?
C₁₈H₃₆O₂ + 26 O₂ $\to$ 18 CO₂ + 18 H₂O

A)1.44
B)0.69
C)1.39
D)0.72
E)none of the above

Answer 2

0.69

Question 3

Which of the following pairs of pathways,if active at the same time,would be considered a futile cycle?

A)gluconeogenesis and citric acid cycle
B)fatty acid $\beta$ -oxidation and glycolysis
C)fatty acid synthesis and glycolysis
D)fatty acid synthesis and citric acid cycle
E)glycolysis and gluconeogenesis

Answer 3

glycolysis and gluconeogenesis

Question 4

Which of the following functional groups is a commonly seen nucleophile in biochemical reactions?

A)aldehyde
B)deprotonated alcohol
C)amide
D)carbocation
E)iodide ion

Question 5

Which of the following eukaryotic organisms is both autotrophic and heterotrophic?

A)yeast
B)humans
C)Venus fly trap
D)redwood trees
E)mushrooms

Question 6

Which of the following functional groups is commonly the electrophile in nucleophilic acyl substitutions?

A)ester
B)hydroxide ion
C)amine
D)thiol
E)carboxylate

Question 7

Which of the following would be considered a biosynthetic pathway?

A)glycolysis
B)glycogen synthesis
C)fatty acid $\beta$ -oxidation
D)citric acid cycle
E)electron transport

Question 8

The concentration of which of the following ions can make a significant change in the $\Delta$ G for reactions that involve ATP?

A)Mg²⁺
B)Na⁺
C)Cl^-
D)K⁺
E)Ca²⁺

Question 9

Which of the following statements regarding the general concepts of metabolism is true?

A)once glucose is converted to pyruvate,there is no way to convert pyruvate back to glucose
B)when triacylglycerols are used as fuel,only the fatty acids can be metabolized,the glycerol is a waste product
C)amino acids serve as substrates for many pathways including glycolysis and the citric acid cycle
D)the citric acid cycle is generally considered an anabolic pathway while gluconeogenesis is generally considered a catabolic pathway
E)none of the above

Question 10

Which of the following types of reactions best describes the reaction shown below?

A)nucleophilic substitution
B)nucleophilic addition
C)nucleophilic acyl substitution
D)elimination
E)carbonyl condensation

Question 11

Which of the following represents a correct compartmentation of a biochemical process with its cellular location?

A)fatty acid oxidation: endoplasmic reticulum
B)RNA synthesis: Golgi complex
C)citric acid cycle: mitochondria
D)gluconeogenesis: lysosome
E)none of the above

Question 12

Of the following,which would have the most reduced state of carbon,and therefore,would yield the largest amount of energy per gram?

A)glucose
B)glycogen
C)alanine
D)stearic acid
E)all of the above would have identical energy yields

Question 13

Which of the following accurately describes the adenylate energy charge?

A)numerator: 2 [ATP] + [ADP];denominator: [ATP] + [ADP] + [AMP]
B)numerator: [ATP] + [ADP];denominator: [ATP] + 0.5 [ADP] + 0.25 [AMP]
C)numerator: [ATP] + 0.5 [ADP];denominator: 2 [ATP] + [ADP] + 0.5 [AMP]
D)numerator: [ATP] + 0.5 [ADP];denominator: [ATP] + [ADP] + [AMP]
E)none of the above

Question 14

The formation of a hemiacetal when glucose undergoes cyclization represents what type of reaction?

A)nucleophilic substitution
B)nucleophilic addition
C)carbonyl condensation
D)elimination
E)oxidation

Question 15

During the oxidation of glucose within a typical animal cell,reduced electron carrier such as NADH are produced.What is the terminal electron acceptor of the electrons carried by NADH?

A)NAD⁺
B)FAD
C)O₂
D)H₂O
E)none of the above

Question 16

The glycolytic reaction
fructose-6-phosphate + ATP $\to$ fructose-1,6-bisphosphate + ADP

Has an ATP-coupling coefficient of _____ while the gluconeogenic reaction

Fructose-1,6-bisphosphate + H₂O $\to$ fructose-6-phosphate + P_i

Has an ATP-coupling coefficient of _____.

A)1;0
B)-1;0
C)1;-1
D)-1;1
E)none of the above

Question 17

________ is commonly used as an oxidizing agent in catabolic pathways while ________ is commonly used as a reducing agent in anabolic pathways.

A)NAD⁺;NADH
B)NAD⁺;FADH₂
C)NADP⁺;NADH
D)FAD;FADH₂
E)NAD⁺;NADPH

Question 18

Which of the following types of reactions best describes the formation of a peptide bond?

A)nucleophilic substitution
B)nucleophilic addition
C)nucleophilic acyl substitution
D)elimination
E)carbonyl condensation

Question 19

What is the oxidant in the following reaction?

A)ethanol
B)NAD⁺
C)acetaldehyde
D)NADH
E)H⁺

Question 20

The phosphorylation of creatine (Cr)by ATP forming creatine phosphate (Cr-P)is rather endergonic ( $\Delta$ G°´ = + 12.6 kJ/mol).Which of the following explains how this reaction proceeds in a typical muscle cell?

A)in the cytosol,[ATP] is high and [Cr] is high allowing the reaction to proceed
B)in the mitochondria,[ATP] is high and [Cr-P] is low allowing the reaction to proceed
C)Cr-P is rapidly transported across the cellular membrane allowing for high levels of Cr-P in the cytosol
D)in the mitochondria,[ADP] is high allowing phosphorylation of Cr to occur
E)none of the above

Question 21

Pyruvic acid has the formula C₃H₄O₃.Write the reaction for its complete combustion.What is its respiratory quotient? Does this mean that it is more oxidized or less oxidized than glucose?

Question 22

Complete oxidation of glucose by burning in a calorimeter gives a $\Delta$ G°´ of -2870 kJ/mol.If we assume this to be the maximum energy that can be extracted from glucose,what is the percent of energy that is captured in a cell given that about 32 ATP can be made from a single molecule of glucose? $\Delta$ G°´ for ATP hydrolysis is -30.5 kJ/mol while $\Delta$ G for ATP hydrolysis in a cell is about -51 kJ/mol.

Question 23

Show the reduction of pyruvate by NADH.Since NADH reduces molecules by a hydride reduction,what type of reaction is pyruvate undergoing?

Question 24

Many enzyme-catalyzed reactions that transfer a phosphate from one molecule to another utilize a histidine residue in the active site of the enzyme.The histidine participates in covalent catalysis by performing a nucleophilic attack on a phosphate,forming an intermediate phosphohistidine (the phosphate covalently attached to the histidine residue).Using ATP as the phosphate donor,show the reaction to form the phosphohistidine intermediate-you do not have to show arrow pushing.