Exam 3 - Biochem

In steps 5-8 of the citric acid cycle, the high-energy molecules ______, _______, and _________ are produced, and ________ is regenerated to begin another turn of the cycle…

a) GDP, FADH2, NADH/H⁺, oxaloacetate

b) GTP, FADH₂, NADH/H⁺, oxaloacetate

c) ATP, FADH₂, NADH/H⁺, citrate

d) ADP, FAD, NAD⁺, oxaloacetate

e) GDP, FADH₂, NADH/H⁺, isocitrate

b) GTP, FADH₂, NADH/H⁺, oxaloacetate

Which of the following is not true of the citric acid cycle?

a) all enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase, which is bound to the inner mitochondrial membrane.

b) in the presence of malonate, one would expect succinate to accumulate

c) oxaloacetate is used as a substrate but is not consumed into the cycle.

d) succinate dehydrogenase channels electrons directly into the electron transport chain

e) the condensing enzyme is subject to allosteric regulation by ATP and NADH

a) all enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase, which is bound to the inner mitochondrial membrane.

The two main purposes of the citric acid cycle are:

a) synthesis of citrate and gluconeogenesis

b) degradation of acetyl-CoA to produce energy and to supply precursors for anabolism.

c) degradation of pyruvate to produce energy and to supply precursors for anabolism

d) degradation of glucose to produce energy and to supply precursors for anabolism.

e) degradation of pyruvate to produce energy and to synthesize oxaloacetate for gluconeogenesis.

b) degradation of acetyl-CoA to produce energy and to supply precursors for anabolism.

The relative concentrations of ATP and ADP control the cellular rates of:

a) glycolysis

b) oxidative phosphorylation

c) pyruvate oxidation

d) the citric acid cycle

e) all of the above

e) all of the above

Which of the following answers complete the sentence correctly?

a) succinate dehydrogenase is an iron-sulfur protein like actonitase

b) contains FAD and NAD+ cofactors like pyruvate dehydrogenase

c) is an integral membrane protein unlike the other enzymes of the citric acid cycle

d) carries out an oxidative decarboxylation like isocitratee dehydrogenase

e) is inhibited by mevalonate

a) succinate dehydrogenase is an iron-sulfur protein like actonitase

A reaction which involves a substrate-level phosphorylation is:

a) isocitrate →a-ketoglutarate

b) citrate →isocitrate

c) succinyl-CoA →succinate

d) succinate → fumarate

e) fumarate →malate

c) succinyl-CoA →succinate

Citrate synthase and the NAD⁺ specific isocitrate dehydrogenase are two key regulatory enzymes of the citric acid cycle. These enzymes are inhibited by:

a) acetyl-CoA and fructose-6-phosphate

b) AMP and/or NAD⁺

c) AMP and/or NADH

d) ATP and/or NAD⁺

e) ATP and/or NADH

e) ATP and/or NADH

A water-soluble component of the electron transport chain that can diffuse freely in the intermembrane space and can carry electrons is ________________.

a) ubiquinone

b) 2,3-BPG

c) cytochrome c

d) cytochrome oxidase

e) heme

c) cytochrome c

Which of the following statements about oxidative phosphorylation is correct?

a) Electron transfer in mitochondria is accompanied by an asymmetric accumulation of protons on one side of the inner mitochondrial membrane

b) It predicts that oxidative phosphorylation can occur even in the absence of an intact inner mitochondrial membrane

c) The effect of uncoupling reagents is a consequence of their ability to carry electrons through membranes

d) The membrane ATP synthase has no significant role in the chemiosmotic theory.

e) All of the above are correct.

a) Electron transfer in mitochondria is accompanied by an asymmetric accumulation of protons on one side of the inner mitochondrial membrane

Cholestrol is transported in the blood in the form of:

a) free cholestrol

b) oligosaccharide

c) LDL

d) leukotrienes

e) none of the above

c) LDL

Which of the following is not a characteristic of fatty acids?

a) even number of carbons

b) trans double bonds

c) 10-20 carbons

d) unbranced

e) synthesized by the human body

b) trans double bonds

Saturated triacyglycerols are usually ________ because ___________.

a) liquids; they have relatively short fatty acid chains

b) liquids; their rigid fatty acid chains do not fit together closely

c) liquids; they contain impurities from their natural sources

d) solids; they have relatively long fatty acid chains

e) solids; their flexible fatty acid chains allow the molecules to fit together closely

e) solids; their flexible fatty acid chains allow the molecules to fit together closely

Which reaction can be used to convert oils into fats?

a) hydrogenation

b) hydrolysis

c) esterification

d) saponification

e) dehydration

a) hydrogenation

The saponification reaction used to form soaps can be more specifically described as:

a) acid catalyzed hydrolysis

b) base catalyzed hydrolysis

c) hydrogenation

d) dehydrogenation

e) dehydration

b) base catalyzed hydrolysis

The hydrocarbon end of a soap molecules is:

a) hydrophilic and attracted to grease

b) hydrophobic and attracted to grease

c) hydrophilic and attracted to water

d) hydrophobic and attracted to water

e) neither hydrophobic nor hydrophilic

b) hydrophobic and attracted to grease

Triacyglycerols obtained from the diet are transported through the lymph system and bloodstream by which of the following lipoproteins?

a) LDL

b) HDL

c) VLDL

d) chylomicrons

d) chylomicrons

Biomolecules can be classified as lipids on the basis of:

a) a common structure consisting of long hydrocarbon chains.

b) the presence of many hydroxyl groups and at least one carbonyl group

c) the presence of at least one amine group and one carboxylic acid group on each molecule.

d) the physical properties of odor, color, and melting point within certain guidelines.

e) the physical property of solubility in nonpolar organic solvents.

e) the physical property of solubility in nonpolar organic solvents.

The biochemical roles of lipids are:

a) short-term energy storage, transport of molecules, and structural support

b) storage of excess energy, component of cell membranes, and chemical messengers

c) catalysis, protection against outside invaders, motion

d) component of cell membranes, catalysis, and structural support.

e) neurotransmitters, hormones, transport of molecules

b) storage of excess energy, component of cell membranes, and chemical messengers

Which of the following is not a consequence of partial hydrogenation of vegetable oils?

a) longer shelf life

b) lower melting temperature

c) reduction of some cis double bonds to single bonds

d) conversion of some cis double bonds to trans double bonds

e) increased risk of cardiovascular disease upon consumption by humans

b) lower melting temperature

Which of the following statements apply(applies) to the β-oxidation of fatty acids? (more than one)

1) the process takes place in the cytosol of mammalian cells

2) carbon atoms are removed from the acyl chain one at a time

3) before oxidation, fatty acids must be converted to their CoA derivatives.

4) NADP+ is the electron acceptor.

5) The products of β-oxidation can directly enter the citric acidcycle for further oxidation

3) before oxidation, fatty acids must be converted to their CoA derivatives.

5) The products of β-oxidation can directly enter the citric acidcycle for further oxidation

The complete metabolism of one molecule of myristic acid, a fatty acid with 14 atoms of carbon, would require __________ turns of the β-oxidation cycle.

a) 6

b) 7

c) 12

d) 14

e) 16

a) 6

Transport of fatty acids from the cytoplasm to the mitochondrial matrix requires:

a) ATP, carnitine, and coenzyme A

b) ATP, carnitine, and pyruvate dehydrogenase

c) ATP, coenzyme A, and hexokinase

d) ATP coenzyme A, and pyruvate dehydrogenase.

e) carnitine, coenzyme A, and hexokinase

a) ATP, carnitine, and coenzyme A

An essential amino acid is one that:

a) is required for the synthesis of all proteins

b) must be obtained in the diet because the human body cannot synthesize it

c) can safely be omitted from the diet because the human body can produce it in unlimited amounts

d) must be provided in the diet for individuals with specific hereditary enzyme deficiencies

e) has a relatively simple carbon skeleton

b) must be obtained in the diet because the human body cannot synthesize it

The first step in amino acid catabolism is _______.

a) transamination

b) decarboxylation

c) oxidation

e) esterification

e) tautomerization

a) transamination

When the amine group of glutamate is replaced with carbonyl group, the process is called:

a) hydrolysis

b) oxidative deamination

c) reductive deamination

d) oxidative decarboxylation

e) phosphorylation

b) oxidative deamination

The common features of catabolism of all amino acids include

a) removal of the amine group and conversion of the carbon skeleton to intermediates which can enter the citric acid cycle

b) hydrolysis of peptide linkages and production of CO₂ as waste

c) hydrolysis of peptide linkages and production of urea as waste

d) diversion of the carbon skeletons into gluconeogenesis

e) diversion of the carbon skeletons into ketogenesis

a) removal of the amine group and conversion of the carbon skeleton to intermediates which can enter the citric acid cycle

All of the carbon backbones from amino acids end up as intermediates in the ________.

a) citric acid cycle

b) urea cycle

c) β-oxidation sequence

d) both a and c

e) none of the above

a) citric acid cycle

The source of nitrogen for the synthesis of nonessential amino acids is:

a) glutamate

b) acetate

c) pyruvate

d) oxaloacetate

e) urea

a) glutamate

The enzyme that removes an amine group from an amino acid and moves it to a a-ketoglutarate is classified as a:

a) ligase

b) phosphatase

c) transaminase

d) dehydrogenase

e) kinase

c) transaminase

The conversion of nitrogen derivates to urea takes place in the:

a) blood

b) kidneys

c) liver

d) brain

e) intestines

c) liver

Amino acids that can be synthesized in the body are called _________ amino acids.

a) essential

b) glycogenic

c) ketogenic

d) nonessential

d) nonessential