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