Ch 3

T/F: Amino acids are synthesized from intermediates in glycolysis and in the citric acid cycle

T

T/F: Ammonia is incorporated into organic molecules primarily during the synthesis of the amino acids glutamate and glutamine

T

T/F: In photosynthesis, energy from sunlight is used to drive the synthesis of ATP and NADPH

T

T/F: Many bacteria and plants can synthesize all 20 amino acids found in proteins

T

T/F: Nucleic acid synthesis occurs by polymerization of nucleotide monophosphates into DNA or RNA

T

T/F: Polymerization of amino acids to form proteins requires additional energy in the form of ATP and GTP

T

Fatty acids are broken down in a stepwise process, ___ carbons at a time. a. 2 b. 4 c. 6 d. 8

a

Glycolysis yields a net gain of ___ ATP molecules per molecule of glucose. a. 2 b. 4 c. 32 d. 38

a

In eukaryotic cells, glycolysis takes place in the a. cytosol b. nucleus c. mitochondria d. endoplasmic reticulum

a

The trypsin substrate binding site contains an aspartate residue, which is able to form an ionic bond with which amino acids in its polypeptide substrates? a. lysine or arginine b. flutamate or glutamine c. leucine or phenylalanine d. serine or threonine

a

What are the energetic consequences of coupling a reaction with a + delta G to one with a larger - delta G? a. an delta G that is favorable overall and drives the reaction with a + delta G in the forward direction b. an outcome in which both reactions are energetically unfavorable overall c. an outcome in which the overall delta G is + d. an outcome in which the overall delta G is unfavorable

a

A reaction in which the substrate glucose binds to the enzyme hexokinase and the configuration of both molecules changes is an example of a. a lock-and-key mechanism b. an induced fit mechanism c. competitive inhibition d. allosteric inhibition

b

For humans, ___ essential amino acids must be provided by the diet. a. 0 b. 9 c. 18 d. 20

b

How many carbons does the acetate group of acetyl CoA have? a. 1 b. 2 c. 3 d. 4

b

In glycolysis, the key control enzyme that is inhibited by excess ATP is a. hexokinase b. phosphofructokinase c. alcohol dehydrogenase d. all of the above

b

The hydrolysis of ATP to ADP and phosphate allows glucose-6-phosphate to be synthesized from glucose and phosphate because the a. heat produced from ATP hydrolysis drives glucose-6-phosphate synthesis b. enzymatic coupling of these two reactions allows the energy of ATP hydrolysis to drive the synthesis of glucose-6-phosphate c. energy of glucose phosphorylation drives ATP splitting d. all of the above

b

The lock-and-key and induced-fit models are two alternative models that can explain how enzyme and substrates interact. These two models can be distinguished from one another according to changes in a. reaction solution viscosity as substrates and enzymes bind b. substrate and enzyme shape as binding occurs c. reaction solution temperature as a result of the endothermic cooling that occurs during substrate binding d. reaction solution color during enzyme-substrate binding

b

Which of the following is a key molecule in the electron transport chain in mitochondria? a. citrate b. cytochrome c c. pyruvate d. tetrahydrofolate

b

Which statement below best describes the usual relationship of the inhibitor molecule to the allosteric enzyme in feedback inhibition of enzyme activity? a. the inhibitor is the substrate of the enzyme b. the inhibitor is the product of the enzyme-catalyzed reaction c. the inhibitor is the final product of the metabolic pathway d. the inhibitor is a metabolically unrelated signal molecule

b

As compared on a per gram basis to carbohydrates, fatty acids produce approximately ___ energy through the oxidation process. a. the same b. 50 percent more c. 2.5 times more d. 10 times more

c

Coenzymes are a. additional enzymes in a pathway b. proteins that form dimeric enzymes c. small molecules that work with an enzyme to enhance reaction rate d. small molecules that allosterically regulate enzymes

c

In eukaryotic cells, the citric acid cycle occurs in the a. cytosol b. nucleus c. mitochondria d. chloroplasts

c

The delta G for hydrolysis of ATP to ADP and P(i) is ___ kcal/mole. a. greater than +7.3 b. +7.3 c. -7.3 d. -0.5

c

What is the change in free energy (delta G) for the hydrolysis of ATP to ADP and P in the cell? a. -12 kcal/mol b. -1.2 kcal/mol c. -7.3 kcal/mol d. -kcal/mol

c

Why are chymotrypsin, trypsin, elastase, and thrombin all grouped together as members of the serine protease family? a. because of the presence of a serine residue, each has similar charge and shape properties in their substrate insertion pockets b. because of the presence of a serine residue, each can form a heptahedral complex with its substrate c. because of the presence of a serine residue, each can form a tetrahedral transition state with its substrate d. because of the presence of a serine residue, each can be modified by cell wall biosynthetic degradative enzyme, chitinase

c

Because of the central role that one amino acid plays in the mechanism by which proteins are cleaved by the enzymes trypsin and chymotrypsin, these enzymes are called ___ proteases. a. histidine b. lysine c. arginine d. serine

d

Enzymes act by a. lowering the overall free energy change of the reaction b. decreasing the distance reactants must diffuse to find each other c. increasing the activation energy d. decreasing the activation energy

d

In humans, how many amino acids must be taken up in the diet? a. 0 b. 20 c. 19 d. 9

d

In the synthesis of glycogen, glucose-1-phosphate reacts with a nucleotide triphosphate to form ___ -glucose a. ADP b. GDP c. CDP d. UDP

d

Like other catalysts, enzymes a. increase the rate of reactions without being consumed in reactions b. shift the chemical equilibrium from more reactants to more products c. do not alter the chemical equilibrium between reactants and products d. both a and c

d

The end products of anaerobic metabolism of glucose may be any of the following except a. acetaldehyde b. ethanol c. lactate d. methanol

d

The free-energy change of a reaction is determined by the a. intrinsic properties of the reactants and products b. concentrations of the reactants and products c. temperature of the reactants and products d. all of the above

d

Under aerobic conditions, the end product of glycolysis is a. ethanol b. lactate c. phosphoenolpyruvate d. pyruvate

d

Under anaerobic conditions, the end product of glycolysis is a. ethanol b. lactate c. pyruvate d. ethanol or lactate

d