Biochemistry Exam 5

What is an allosteric inhibitor of gluconeogenesis?

AMP

What is an allosteric inhibitor of phosphofructokinase?

ATP

For the first five steps of glycolysis, the appropriate sequence of enzymes is: A phosphofructokinase-1 (PFK-1). B. hexokinase / glucokinase. C. fructose bisphosphate aldolase. D. Phosphoglucoisomerase. E. triose phosphate isomerase (TPI).

B, D, A, C, E

What phosphoryl donor is used in the reaction of converting oxaloacetate to phosphoenolpyruvate?

GTP

Glucokinase has a Km value of 10.0 mM, whereas hexokinase has a Km value of 0.1 mM. This means that glucokinase acts on glucose only at _____________ glucose concentrations.

HIGH

What is a reason that glucose is a common metabolic fuel used by living organisms?

In its stable ring structure, glucose is unlikely to nonezymatically glycosylate proteins.

What is the function of glucokinase?

It supplies glucose 6-phosphate for glycogen synthesis and formation of fatty acids.

In lactase-deficient individuals, gut bacteria ferment lactose to lactic acid, also generating______ and ______?

Methane Hydrogen

If glucose was labeled with 14C at carbon #6, what carbon of pyruvate would have the 14C?

Methyl Carbon

What MUST be regenerated for glycolysis to proceed?

NAD+

The step that commits glucose to glycolysis is catalyzed by: ..... (write the abbreviated enzyme only)

PFK phosphofructokinase

Phosphofructokinase-1 is NOT used when fructose is metabolized to pyruvate in the liver.

True

What intermediate is needed for the conversion of galactose into glucose by reacting with galactose 1-phosphate?

UDP-glucose

Transformation of glucose into lactate in the presence of oxygen in tumors is called aerobic glycolysis or

Warburg Effect

What ion does alcohol dehydrogenase contain in its active site?

Zn2+

What are the allosteric inhibitors of pyruvate kinase?

alanine and ATP

What enzymes catalyze virtually irreversible reactions of glycolysis? Select all that apply. a. phosphoglycerate kinase b. phosphofructokinase c. aldolase d. hexokinase e. pyruvate kinase

b, d, e

What molecule, which is an intermediate in the citric acid cycle, inhibits phosphofructokinase in the liver?

citrate

What reaction does glyceraldehyde 3-phosphate dehydrogenase catalyze?

conversion of glyceraldehyde 3-phosphate into 1,3-bisphosphoglycerate

The purpose of phosphorylating glucose in the cytosol is to:

destabilize glucose.

What is the name of an ATP-generating process in which organic compounds act both as the donor and as the acceptor of electrons?

fermentation

What is the result of the reaction sequence of glycolysis, where glucose undergoes a phosphorylation, an isomerization, and a second phosphorylation?

formation of fructose 1,6-bisphosphate

In the second half of the glycolytic pathway, ____ ATP molecules are produced and with the offset of ____ ATPs consumed in the first half, the net yield is ____ ATPs per glucose.

four; two; two

Overconsumption of which monosaccharide may lead to obesity, fatty liver, and insulin insensitivity?

fructose

What is the allosteric stimulator of pyruvate kinase?

fructose 1,6-bisphosphate

What molecule activates pyruvate kinase by feed-forward stimulation?

fructose 1,6-bisphosphate

Expression of what molecules is stimulated by glucagon?

fructose 1,6-bisphosphate and phosphoenolpyruvate carboxykinase

What molecule inhibits fructose 1,6-bisphosphatase?

fructose 2,6-bisphosphate

Cataracts, a clouding of the lens, form because galactose is converted into

galactitol

What stimulates protein kinase A, which leads to inactivation of liver pyruvate kinase?

glucagon

The concentration of which molecule increases when phosphofructokinase is inactive?

glucose 6-phosphate

What molecule inhibits hexokinase activity?

glucose 6-phosphate

What are the main noncarbohydrate precursors of gluconeogenesis?

glycerol, amino acids, lactate

Dihydroxyacetone phosphate is:

isomerized to glyceraldehyde-3-phosphate by triose phosphate isomerase (TPI)

What organ is the site of gluconeogenesis?

kidneys

What class of enzymes catalyzes the reaction of transferring a phosphoryl group from ATP to acceptor?

kinases

Two primary raw materials for gluconeogenesis in the human liver are:

lactate and alanine.

What organ controls the level of glucose in blood?

liver

What organ is the main site of fructose metabolism?

liver

Choose the cell compartment where free glucose forms during gluconeogenesis.

lumen of endoplasmic reticulum

In what form does oxaloacetate leave the mitochondrion?

malate

Substrate-level phosphorylation occurs in glycolysis in the reaction catalyzed by ____ and belongs to ____ class of enzymes.

phosphoglycerate kinase; transferase

What reaction is catalyzed by aldolase?

reversible cleavage of F-1,6-BP to DHAP and GAP

How many high-energy phosphate bonds are expended in gluconeogenesis?

six

Glycolysis is the metabolic pathway during which _____ of glucose.

two molecules of pyruvate and two molecules of ATP are formed from one molecule

α-D-Glucose + ATP → ____ + ____ + H+

α-D-glucose-6-phosphate; ADP