Gluconeogenesis Flashcards by Mind Med

Which organs perform gluconeogenesis?

A) Liver and kidney
B) Muscle and adipose tissue
C) Liver and muscle
D) Liver and spleen

A) Liver and kidney

Liver is the main gluconeogenic organ; kidney contributes about 40% during fasting state.

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Which of these is NOT a major gluconeogenic precursor?

A) Lactate
B) Glycerol
C) Fatty acids
D) Glucogenic amino acids

C) Fatty acids

Fatty acids are not direct substrates but provide energy via β-oxidation.

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Which amino acid is a principal gluconeogenic precursor?

A) Lysine
B) Leucine
C) Alanine
D) Valine

C) Alanine

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What metabolic state favors gluconeogenesis predominance over glycogenolysis?

A) Fed state (1-4 hours post meal)
B) Early fasting (4-8 hours)
C) Starvation (12-14 hours onward)
D) Exercise state only

C) Starvation (12-14 hours onward)

In starvation, glycogen stores deplete, gluconeogenesis provides glucose predominantly.

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How does gluconeogenesis differ from glycolysis?

A) Uses same enzymes and steps
B) Is identical process in reverse
C) Bypasses three irreversible glycolytic steps with different enzymes
D) Occurs only in muscle

C) Bypasses three irreversible glycolytic steps with different enzymes

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What is the rate-limiting enzyme of gluconeogenesis?

A) Phosphofructokinase-1
B) Fructose-1,6-bisphosphatase
C) Pyruvate kinase
D) Glucokinase

B) Fructose-1,6-bisphosphatase

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Pyruvate carboxylase requires which cofactor for its activity?

A) NADH
B) ATP
C) Biotin
D) FAD

C) Biotin

It also requires energy of ATP

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What is the function of PEP carboxykinase (PEPCK) in gluconeogenesis?

A) Converts PEP to pyruvate
B) Converts oxaloacetate to phosphoenolpyruvate (PEP)
C) Converts glycerol to DHAP
D) Converts fructose-1,6-bisphosphate to fructose-6-phosphate

B) Converts oxaloacetate to phosphoenolpyruvate (PEP)

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Which enzyme catalyzes the final step, releasing glucose into the blood?

A) Glucokinase
B) Hexokinase
C) Glucose-6-phosphatase
D) PFK-1

C) Glucose-6-phosphatase

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During starvation, which metabolic precursor usage increases for gluconeogenesis?

A) Fatty acids directly converted to glucose
B) Amino acids and glycerol from triacylglycerol breakdown
C) Glucose from diet
D) Direct use of ketones

B) Amino acids and glycerol from triacylglycerol breakdown

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How does ethanol inhibit gluconeogenesis?

A) By depleting ATP
B) By increasing NADH
C) By decreasing biotin availability
D) By blocking pyruvate carboxylase directly

B) By increasing NADH

This inhibited lactate to pyruvate conversion leading to increased lactate in the body = acidosis

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What effect does insulin have on gluconeogenesis?

A) Stimulates pyruvate carboxylase and PEPCK
B) Inhibits gluconeogenic enzymes, suppressing gluconeogenesis
C) Has no effect
D) Increases glucose-6-phosphatase activity

B) Inhibits gluconeogenic enzymes, suppressing gluconeogenesis

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What hormone primarily activates gluconeogenesis during fasting?

A) Insulin
B) Glucagon
C) Cortisol only
D) Epinephrine only

B) Glucagon

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Which cycle describes the movement of alanine from muscle to liver for gluconeogenesis?

A) Cori cycle
B) Krebs cycle
C) Alanine cycle
D) Urea cycle

C) Alanine cycle

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Which of these reactions is not an irreversible step in gluconeogenesis?

a. glucose 6-phosphate to glucose
b. pyruvate to PEP
c. oxaloacetate to PEP
d. fructose-1,6-bisphosphate to fructose-6-phosphate

c. oxaloacetate to PEP

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Which of the following is most likely to happen in a normal person after consuming a high-carb meal?

a. Insulin secretion falls
b. Insulin production rises
c. The glucagon level rises
d. The levels of glucagon and insulin both drop

b. Insulin production rises

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Which of the following is most likely to be high in the blood in Type 1 diabetes due to the lack of insulin synthesis and a persistent glucogenic state?

a. Ketone Production
b. Blood glucose
c. Insulin sensitivity
d. Glycogen Storage

a. Ketone Production

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True/False: Alanine, a key gluconeogenic amino acid, is mostly obtained from the liver and utilized in the production of glucose.

False

Alanine is primarily produced in skeletal muscle, not the liver. It is released from muscles via transamination and transported to the liver, where it enters gluconeogenesis to produce glucose

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True/False: Pyruvate is converted to OAA during gluconeogenesis instead of acetyl-CoA due to activation of pyruvate carboxylase and inhibition of pyruvate dehydrogenase.

True

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Which of the following cannot be used as a source of glucose?

a. Acetyl-CoA
b. Alanine
c. Glycerol
d. Lactate

a. Acetyl-CoA

Acetyl-CoA cannot serve as a substrate for gluconeogenesis because its formation from pyruvate is irreversible. It is a ketogenic precursor

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Gluconeogenesis usually derives its energy from which metabolic pathway?

a. Β-oxidation
b. Glycolysis
c. HMP shunt
d. Krebs cycle

a. Β-oxidation

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Conversion of PEP from Pyruvate is possible during gluconeogenesis because of the:

a. Decreased activity of PEPCK
b. Enhanced activity of pyruvate kinase
c. Inactivity of pyruvate dehydrogenase
d. Inhibition of pyruvate carboxylase

c. Inactivity of pyruvate dehydrogenase

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What is the common substrate of glycogenolysis and gluconeogenesis in the liver?

a. Fructose-1,6-bisphosphate
b. Fructose-6-phosphate
c. Glucose-6-phosphate
d. Phosphoenolpyruvate

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c. Glucose-6-phosphate

Which of the following organs does not directly contribute to the synthesis of glucose?

a. Kidneys
b. Liver
c. Muscle
d. RBCs

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c. Muscle

Muscle lacks glucose-6-phosphatase and cannot release free glucose into the blood; it only uses glucose internally.

Which enzyme converts pyruvate to oxaloacetate and is allosterically activated by acetyl-CoA? a) Pyruvate dehydrogenase b) Pyruvate carboxylase c) Phosphoenolpyruvate carboxykinase (PEPCK) d) Pyruvate kinase

b) Pyruvate carboxylase

Fructose-1,6-bisphosphatase, a rate-limiting enzyme of gluconeogenesis, is inhibited by which molecule? a) AMP b) ATP c) Acetyl-CoA d) NADH

a) AMP it is also inhibited by Fructose-2,6-bisphosphatase

Glucagon increases the level of which second messenger to regulate gluconeogenic enzymes? a) cGMP b) cAMP c) ATP d) NADH

b) cAMP

Which enzyme is inhibited by glucagon through cAMP-mediated protein kinase A activation to prevent the conversion of phosphoenolpyruvate to pyruvate? a) Pyruvate carboxylase b) Pyruvate kinase c) Phosphofructokinase-1 d) Glucose-6-phosphatase

b) Pyruvate kinase

In the fed state, insulin increases the activity of which enzyme to promote glycolysis? a) Phosphofructokinase-2 (PFK-2) b) Fructose-1,6-bisphosphatase c) PEP carboxykinase (PEPCK) d) Glucose-6-phosphatase

a) Phosphofructokinase-2 (PFK-2)

During prolonged fasting and starvation, which metabolic pathway is most predominant to maintain blood glucose levels? a) Glycolysis b) Glycogenolysis c) Gluconeogenesis d) Lipogenesis

c) Gluconeogenesis

What effect does insulin have on fructose-2,6-bisphosphate levels and what is the consequence on glycolysis and gluconeogenesis? a) Increases fructose-2,6-bisphosphate, stimulating glycolysis and inhibiting gluconeogenesis b) Decreases fructose-2,6-bisphosphate, stimulating gluconeogenesis and inhibiting glycolysis c) No effect on fructose-2,6-bisphosphate d) Increases fructose-2,6-bisphosphate, stimulating gluconeogenesis

a) Increases fructose-2,6-bisphosphate, stimulating glycolysis and inhibiting gluconeogenesis

Which enzyme is responsible for converting glucose-6-phosphate to glucose in the liver and kidney, facilitating glucose release into the bloodstream? a) Glucokinase b) Glucose-6-phosphatase c) Hexokinase d) Phosphoglucomutase

b) Glucose-6-phosphatase

Glucagon inhibits glycolysis and stimulates gluconeogenesis. Which of the following enzyme modifications by glucagon is responsible for this? a) Dephosphorylation of pyruvate kinase b) Phosphorylation of pyruvate kinase c) Activation of phosphofructokinase-1 d) Inhibition of glucose-6-phosphatase

b) Phosphorylation of pyruvate kinase

During the early fasting state (4-18 hours post-meal), which pathway predominates for glucose production? a) Gluconeogenesis only b) Glycogenolysis only c) Both glycogenolysis and gluconeogenesis equally d) Neither pathway is active

b) Glycogenolysis only

What is a common cause of hypoglycemia in a patient with heavy alcohol intake and prolonged fasting? a) Increased gluconeogenesis b) Increased NADH inhibiting gluconeogenesis c) Increased glycogenolysis d) Increased insulin secretion

b) Increased NADH inhibiting gluconeogenesis

In insulin-induced hypoglycemia, what is the likely reason for the drastic drop in blood glucose after insulin administration? a) Overactivation of gluconeogenesis b) Suppression of glycogenolysis during fasting c) Increased lipolysis d) Increased glucagon secretion

b) Suppression of glycogenolysis during fasting

Why are premature neonates at risk of hypoglycemia? a) They have high glycogen stores b) Their gluconeogenic enzymes are underdeveloped c) They have excess adipose tissue d) They have elevated insulin levels

b) Their gluconeogenic enzymes are underdeveloped

In diabetic ketoacidosis (DKA), why does ketone body production increase? a) Insulin stimulates ketogenesis b) Persistent gluconeogenesis and lipolysis due to lack of insulin c) Glycogen synthesis is increased d) Glucose uptake by muscles is increased

b) Persistent gluconeogenesis and lipolysis due to lack of insulin

What leads to hyperglycemia in Type 2 diabetes mellitus? a) Increased insulin sensitivity b) Destruction of insulin receptors by inflammatory mediators and ROS c) Increased glucose uptake by muscle cells d) Increased gluconeogenesis suppression

b) Destruction of insulin receptors by inflammatory mediators and ROS

What is the primary defect in Type 1 diabetes mellitus related to gluconeogenesis? a) Excess insulin secretion b) Lack of insulin leading to unregulated gluconeogenesis and lipolysis c) Increased glycogenolysis inhibition d) Decreased ketone body production

b) Lack of insulin leading to unregulated gluconeogenesis and lipolysis

Which of the following is true regarding glucosuria? a) It occurs when blood glucose concentrations are below the renal threshold b) It occurs when blood glucose concentrations exceed the renal threshold (~10 mmol/L) c) It is caused by increased insulin secretion d) It decreases excretion of glucose in urine

b) It occurs when blood glucose concentrations exceed the renal threshold (~10 mmol/L)

How does ethanol metabolism impair gluconeogenesis? a) By increasing the conversion of lactate to pyruvate b) By increasing NADH which inhibits conversion of lactate to pyruvate c) By increasing glycogen storage d) By activating pyruvate carboxylase

b) By increasing NADH which inhibits conversion of lactate to pyruvate

In starvation, which metabolic adaptation helps to spare muscle protein? a) Increased glycogenolysis b) Elevated ketone body levels as an alternative energy source c) Increased gluconeogenesis from muscle protein d) Decreased fatty acid oxidation

b) Elevated ketone body levels as an alternative energy source

What happens to blood glucose levels during prolonged starvation (5-6 weeks)? a) They rise significantly b) They stay in a low normal range c) They become undetectable d) They increase due to increased glycogenolysis

b) They stay in a low normal range (~65 mg/dL)

Which compound does a biotin carry & transfer to pyruvate ?

Carbon Dioxide CO2 Hence, OAA is pyruvate + CO2

Acetyl-Coa and ATP inhibits what enzyme?

Pyruvate D.H. therefore, no glycolysis occurs in gluconeogenesis

Enumerate the difference of malate, lactate, and aspartate in producing PEP

malate: Pyruvate > OAA > Malate > OOA > PEP lactate: Pyruvate > OAA > PEP aspartate: Pyruvate > OAA > aspartate > OOA > PEP

How many pyruvate is required to make glucose

How many ATP and NADH is required to make glucose

Normal Blood Glucose?

80-100 mg/dL In fed state, it increased to 120-140 mg/dL (normal hyperglycemia)

In the fed state, which hormones stimulate insulin release at the pancreas?

Arginine and Leucine

After a carbohydrate rich meal, how long does the body take in order to bring glucose level back to normal?

2 hours

How much glucose is present in the body when a person has starved for 6 wks? A. 20 mg/dL B. 40 mg/dL C. 50 mg/dL D. 65 mg/dL

D. 65 mg/dL

How much glucose is present in the body when a person has starved for 3 days? A. 80 mg/dL B. 90 mg/dL C. 70 mg/dL D. 120 mg/dL

C. 70 mg/dL

How much glucose is present in the body when a person has been fasting for 12 hours? A. 80 mg/dL B. 90 mg/dL C. 70 mg/dL D. 120 mg/dL

A. 80 mg/dL

How much glucose is present in the body when a person has been given a glucose IV? A. 100 mg/dL B. 90 mg/dL C. 140 mg/dL D. 120 mg/dL

A. 100 mg/dL

Gluconeogenesis Flashcards

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