CHO Integration

Question 1

Which enzyme is primarily activated by insulin during the well-fed state in carbohydrate metabolism?
a) Hexokinase
b) Glucokinase
c) Phosphofructokinase-1
d) Fructose 1,6-bisphosphatase

Answer 1

b) Glucokinase

Question 2

What is the main difference between hexokinase and glucokinase?
a) Hexokinase has higher Km and higher Vmax
b) Glucokinase is allosterically inhibited by glucose-6-phosphate
c) Hexokinase is present in all tissues, glucokinase mostly in liver
d) Glucokinase is inhibited by fructose-6-phosphate

Answer 2

c) Hexokinase is present in all tissues, glucokinase mostly in liver

Question 3

Which enzyme is inhibited by fructose 2,6-bisphosphate?
a) Phosphofructokinase-1
b) Fructose 1,6-bisphosphatase
c) Pyruvate kinase
d) Glucose 6-phosphatase

Answer 3

b) Fructose 1,6-bisphosphatase

Question 4

Pyruvate kinase is allosterically activated by:
a) ATP
b) Alanine
c) Fructose 1,6-bisphosphate
d) Citrate

Answer 4

c) Fructose 1,6-bisphosphate

Question 5

Which enzyme is induced by glucagon during fasting via genetic regulation?
a) Pyruvate kinase
b) HMG-CoA synthase
c) Hexokinase
d) Acetyl CoA carboxylase

Answer 5

b) HMG-CoA synthase

Question 6

What effect does phosphorylation have on pyruvate kinase during fasting?
a) Activation
b) Inactivation
c) No effect
d) Allosteric inhibition

Answer 6

b) Inactivation

Question 7

During fasting, acetyl CoA carboxylase is:
a) Activated by dephosphorylation
b) Inhibited by phosphorylation
c) Activated by insulin
d) Activated by malonyl CoA

Answer 7

b) Inhibited by phosphorylation

Question 8

What is the role of malonyl CoA in fatty acid metabolism?
a) Activates CPT-1
b) Inhibits CPT-1
c) Activates beta-oxidation
d) Inhibits fatty acid synthesis

Answer 8

b) Inhibits CPT-1

Question 9

Which enzyme catalyzes the conversion of acetyl CoA to malonyl CoA?
a) Fatty acid synthase
b) Acetyl CoA carboxylase
c) HMG-CoA reductase
d) Carnitine palmitoyltransferase I

Answer 9

b) Acetyl CoA carboxylase

Question 10

Which enzyme is competitively inhibited by statins?
a) HMG-CoA reductase
b) Acetyl CoA carboxylase
c) Pyruvate kinase
d) Phosphofructokinase-1

Answer 10

a) HMG-CoA reductase

Question 11

What is the main effect of AMP on phosphofructokinase-1 (PFK-1)?
a) Activation
b) Inhibition
c) No effect
d) Competitive inhibition

Answer 11

a) Activation

Question 12

Which allosteric effector activates glycogen phosphorylase in muscle?
a) ATP
b) Glucose
c) AMP
d) Glucose 6-phosphate

Answer 12

c) AMP

Question 13

Insulin promotes the activation of which lipolytic enzyme in adipose tissue?
a) Hormone-sensitive lipase
b) Lipoprotein lipase
c) Acetyl CoA carboxylase
d) Phosphorylase kinase

Answer 13

b) Lipoprotein lipase

Question 14

How does glucagon affect glycogen synthase?
a) Phosphorylates and inactivates it
b) Dephosphorylates and activates it
c) Binds and activates it directly
d) Has no effect

Answer 14

a) Phosphorylates and inactivates it

Question 15

What is the effect of high ATP levels on beta-oxidation?
a) Stimulates
b) Inhibits
c) No effect
d) Activates CPT-1

Answer 15

b) Inhibits

Question 16

Which enzyme produces NADPH via pyruvate cycling in pancreatic beta cells?
a) Glucose-6-phosphate dehydrogenase
b) Malic enzyme
c) Citrate lyase
d) Acetyl CoA carboxylase

Answer 16

b) Malic enzyme

Question 17

Which enzyme is responsible for the irreversible step in gluconeogenesis converting pyruvate?
a) Pyruvate kinase
b) Pyruvate carboxylase
c) Phosphofructokinase-1
d) Glucose 6-phosphatase

Answer 17

b) Pyruvate carboxylase

Question 18

Malonyl CoA inhibits which enzyme to prevent simultaneous fatty acid synthesis and oxidation?
a) Acetyl CoA carboxylase
b) Carnitine palmitoyltransferase I (CPT-1)
c) Fatty acid synthase
d) Hormone-sensitive lipase

Answer 18

b) Carnitine palmitoyltransferase I (CPT-1)

Question 19

Which enzyme is activated by insulin through dephosphorylation to promote glycolysis?
a) Pyruvate kinase
b) Phosphofructokinase-1
c) Glucose 6-phosphatase
d) Pyruvate carboxylase

Answer 19

a) Pyruvate kinase

Question 20

Which enzyme is activated by insulin through dephosphorylation to promote glycolysis?
a) Pyruvate kinase
b) Phosphofructokinase-1
c) Glucose 6-phosphatase
d) Pyruvate carboxylase

Answer 20

c) Glucose 6-phosphatase

Question 21

What inhibits hexokinase activity?
a) Glucose
b) Glucose-6-phosphate
c) ATP
d) Fructose 6-phosphate

Answer 21

b) Glucose-6-phosphate

Question 22

Which enzyme is activated by acetyl CoA as an allosteric activator?
a) Pyruvate carboxylase
b) Pyruvate kinase
c) Hexokinase
d) Phosphofructokinase-1

Answer 22

a) Pyruvate carboxylase

Question 23

Which enzyme is involved in the first step of ketogenesis?
a) HMG-CoA reductase
b) HMG-CoA synthase
c) Acetyl CoA carboxylase
d) Carnitine palmitoyltransferase I

Answer 23

b) HMG-CoA synthase

Question 24

Which hormone primarily activates phosphoprotein phosphatases in the fed state?
a) Glucagon
b) Insulin
c) Epinephrine
d) Cortisol

Answer 24

b) Insulin

Question 25

What is the effect of fructose-6-phosphate on glucokinase? a) Activates it b) Inhibits it by binding to the active site c) Facilitates its translocation to the nucleus to inhibit activity d) No effect

Answer 25

c) Facilitates its translocation to the nucleus to inhibit activity

Question 26

Which enzyme catalyzes the rate limiting step of cholesterol synthesis? a) HMG-CoA synthase b) HMG-CoA reductase c) Acetyl CoA carboxylase d) Fatty acid synthase

Answer 26

b) HMG-CoA reductase

Question 27

What happens to HMG-CoA reductase when phosphorylated? a) Activated b) Inactivated c) No change d) It undergoes proteolysis

Answer 27

b) Inactivated

Question 28

Which molecule acts as an allosteric activator of phosphofructokinase-2 (PFK-2)? a) ATP b) ADP c) Fructose 2,6-bisphosphate d) Citrate

Answer 28

c) Fructose 2,6-bisphosphate

Question 29

Noncompetitive inhibition of an enzyme is characterized by: a) Inhibitor binds only to the active site b) Inhibitor binds to an allosteric site independent of substrate binding c) Inhibitor binds only to the enzyme-substrate complex d) Inhibitor permanently inactivates the enzyme

Answer 29

b) Inhibitor binds to an allosteric site independent of substrate binding

Question 30

Which enzyme is irreversibly activated through proteolytic cleavage? a) Pyruvate kinase b) Trypsin c) Hexokinase d) Acetyl CoA carboxylase

Answer 30

b) Trypsin

Question 31

Which enzyme is allosterically inhibited by citrate in glycolysis? a) Hexokinase b) Phosphofructokinase-1 c) Pyruvate kinase d) Glucokinase

Answer 31

b) Phosphofructokinase-1

Question 32

During fasting, which hormone increases the activity of PKA leading to phosphorylation of key enzymes? a) Insulin b) Glucagon c) Epinephrine d) Both b and c

Answer 32

d) Both b and c

Question 33

Which enzyme's activity is enhanced by glucose 6-phosphate binding in glycogenesis? a) Glycogen phosphorylase b) Glycogen synthase c) Glucose 6-phosphatase d) Phosphorylase kinase

Answer 33

b) Glycogen synthase

Question 34

Which enzyme catalyzes the conversion of malate to pyruvate? a) Malic enzyme b) Malate dehydrogenase c) Pyruvate carboxylase d) Citrate lyase

Answer 34

a) Malic enzyme

Question 35

What is an example of a suicide inhibitor used in cancer treatment? a) Statins b) 5-fluorouracil c) Malonate d) Phenylalanine

Answer 35

b) 5-fluorouracil

Question 36

Which of these enzymes is repressed by insulin? a) Glucose 6-phosphatase b) Hexokinase c) Glycogen synthase d) Phosphofructokinase-1

Answer 36

a) Glucose 6-phosphatase

Question 37

Which enzyme is repressed by glucagon during fasting? a) Fructose 1,6-bisphosphatase b) Pyruvate kinase c) Phosphofructokinase-1 d) Pyruvate carboxylase

Answer 37

b) Pyruvate kinase

Question 38

What enzyme does AMP activate to increase both glycolysis and fatty acid oxidation in muscle? a) Phosphofructokinase-1 b) Acetyl CoA carboxylase c) Hexokinase d) Fatty acid synthase

Answer 38

a) Phosphofructokinase-1

Question 39

During exercise, most ATP in muscle is generated from: a) Blood glucose b) Liver glycogen c) Muscle glycogen d) Ketone bodies

Answer 39

c) Muscle glycogen

Question 40

Which molecule acts as an allosteric inhibitor of hepatic glycogen phosphorylase? a) cAMP b) Ca2+ c) Glucose 6-phosphate d) AMP

Answer 40

c) Glucose 6-phosphate