Chap 14 (part 1): Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

In humans, gluconeogenesis:

can result in the conversion of protein into blood glucose

When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase… Which statement is MOST nearly correct?

ΔG° is +1.7 kJ/mol

There is reciprocal regulation of glycolytic and gluconeogenic reactions interconverting fructose-6-phosphate and fructose-1,6-bisphosphate. Which statement is NOT correct?

The phosphofructokinase-1 reaction is endergonic

Which statement regarding glycolysis is true?

The oxidation reaction in glycolysis produces two high-energy molecules

What role(s) does ATP have with respect to PFK-1?

Substrate and allosteric inhibitor

What is the net yield of ATP produced by the anaerobic fermentation of one molecule of sucrose in myocytes?

Four

Which statement is false concerning glycolysis?

It results in the synthesis of NAD+

Which enzyme acts in the pentose phosphate pathway?

6-phosphogluconate dehydrogenase

The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate do NOT involve:

oxidation of NADH to NAD+

What is the net yield of ATP produced by the anaerobic fermentation of one molecule of galactose to two molecules of lactate in myocytes?

Two

During strenuous exercise… The MOST important reaction involved in the reoxidation of NADH is:

pyruvate → lactate

Which method directly regulates PFK-1?

allosteric activation by AMP

Cellular isozymes of pyruvate kinase are allosterically inhibited by concentrations of:

high; ATP

Which substrate cannot contribute to net gluconeogenesis in mammalian liver?

palmitate

In comparison with the resting state, actively contracting human muscle tissue has a:

higher rate of lactate formation

Which statement about gluconeogenesis in animal cells is true?

The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate is not catalyzed by phosphofructokinase-1, the enzyme involved in glycolysis

Which statement about gluconeogenesis is false?

It consists entirely of the reactions of glycolysis, operating in the reverse direction

The first reaction in glycolysis that results in the formation of an energy-rich compound is catalyzed by:

glyceraldehyde 3-phosphate dehydrogenase

The metabolic function of the pentose phosphate pathway is to:

generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids

The compound [18F]2-fluoro-2-deoxyglucose is a(n):

imaging agent used to detect tumors

Which statement about the pentose phosphate pathway is correct?

It provides precursors for the synthesis of nucleotides

The anaerobic conversion of one molecule of glucose to two molecules of lactate by fermentation is accompanied by a net gain of:

two molecules of ATP

Which amount of ATP and NADH identifies net production when one molecule of DHAP is converted to one molecule of pyruvate?

two molecules of ATP and one molecule of NADH

Which statement does NOT describe a general function of the pentose phosphate pathway?

The pentose phosphate pathway produces reduced molecules whose electrons may be shuttled to the mitochondria for oxidative phosphorylation

The conversion of one molecule of fructose 1,6-bisphosphate to two molecules of pyruvate by the glycolytic pathway results in a net formation of:

two; NADH; four

In the alcoholic fermentation of glucose by yeast, thiamine pyrophosphate is a coenzyme required by:

pyruvate decarboxylase

What is the general name for an enzyme that catalyzes an intramolecular phosphoryl shift?

mutase

An enzyme used in both glycolysis and gluconeogenesis is:

3-phosphoglycerate kinase

Which products of glycolysis serve to store energy?

ATP and NADH

Which reaction does NOT convert gluconeogenic precursors to the next step in gluconeogenesis?

Lactate is converted to alanine using lactate dehydrogenase

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change ΔG°′ of 23.8 kJ/mol. Under what conditions will the free-energy change ΔG be negative?

When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products

Which statement is true for glycolysis?

A dehydration reaction generates a high-energy molecule

Why is an anaerobic fate of pyruvate necessary in skeletal muscle?

It allows for the reoxidation of NADH to NAD⁺, as NAD⁺ is in limited supply during anaerobic conditions

If glucose, radioactively labeled in the C-2 position with ¹⁴C, is used as a substrate in a yeast extract maintained under strictly anaerobic conditions, what is the location of ¹⁴C in the product ethanol?

CH₃—¹⁴CH₂—OH

In humans, the Cori cycle shifts part of the metabolic burden of active muscle to the liver. Which two metabolic pathways are involved in this cycle?

glycolysis and gluconeogenesis

Which statement is NOT true concerning glycolysis in anaerobic muscle?

It is an endergonic process

In a tissue that metabolizes glucose via the pentose phosphate pathway, C-1 of glucose would be expected to end up principally in:

carbon dioxide

Which process is NOT involved in the steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate?

catalysis by an isomerase enzyme

Gluconeogenesis must use "bypass reactions" to circumvent three reactions in the glycolytic pathway that are highly exergonic and essentially irreversible. Reactions carried out by which three of the enzymes listed must be bypassed in the gluconeogenic pathway?

1, 3, 4

The pentose phosphate pathway is multifunctional with metabolic flexibility. Which statement is false with respect to this pathway?

It generates NADH for reductive biosynthesis

If glucose labeled with ¹⁴C at C-2 were metabolized in the liver, the first radioactive pyruvate formed would be labeled in _ carbon(s).

its carbonyl

Glycogen is converted to monosaccharide units by:

glycogen phosphorylase

In an anaerobic muscle preparation, lactate formed from glucose labeled in C-2 would be labeled in:

only the carbon atom carrying the OH