4th Biochemistry Lecture Exam (Batch 2025) Flashcards
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The major control point of glycolysis is the reaction catalyzed by:
A. glucokinase
B. pyruvate kinase
C. phosphofructokinase
D. glyceraldehyde 3-phosphate dehydrogenase
C. phosphofructokinase
Regulatory/ Irreversible Steps
(1) Hexokinase/ Glucokinase
(3) Phosphofructokinase-1 (Rate-limiting step)
(10) Pyruvate Kinase
- Which of the following are intermediates of glycolysis that can be used to produce ATP by substrate-level phosphorylation?
A. 3-phosphoglycerate and 2-phosphoglycerate
B. 1,3-bisphosphoglycerate and phosphoenolpyruvate
C. glyceraldehyde 3-phosphate and dihydroxyacetone phosphate
D. glucose 6-phosphate and fructose 6-phosphate
B. 1,3-bisphosphoglycerate and phosphoenolpyruvate
Substate-level phosphorylation = 4 ATP
(7) Phosphoglycerate kinase (1,3-BPG -> 3-PG)
(10) Pyruvate Kinase (PEP->Pyruvate)
- The conversion of pyruvate to lactate in the red blood cells serves:
A. to regenerate NAD+
B. to synthesize additional ATP
C. to complete the oxidation of glucose to CO2 and H2O
D. to prevent accumulation of hydrogen peroxide that can cause hemolysis
A. to regenerate NAD+
Lactic acid fermentation, Anaerobic part of EMP, Major fate of Pyruvate in skeletal muscles and BC involves re-oxidation of NADH, ensures NAD supply.
- True of glucokinase:
A. present in the liver and pancreas
B. has higher affinity for glucose than hexokinase
C. can phosphorylate not only glucose but also fructose, galactose and mannose
D. inhibited allosterically by its product glucose 6-phosphate
A. present in the liver and pancreas
- How many ATP is produced for every glucose molecule oxidized in the muscles during high intensity exercise when supply of oxygen is limited?
A. 32
B. 30
C. 10
D. 2
D. 2
- The enzyme that converts pyruvate to acetyl CoA prior to its entry in the citrc acid cycle:
A. acetyl CoA carboxylase
B. pyruvate carboxylase
C. acetyl CoA synthetase
D. pyruvate dehydrogenase
D. pyruvate dehydrogenase
- Fill up the missing intermediate in the glycolytic pathway
Glyceraldehyde 3-phosphate ➝_______________ ➝ 3-Phosphoglycerate
A. phosphoenolpyruvate
B. 2-phosphoglycerate
C. 1,3 bisphosphoglycerate
D. dihydroxyacetone phosphate
C. 1,3 bisphosphoglycerate
- Glycolytic pathway regulation involves:
A. allosteric stimulation by ADP
B. allosteric inhibition by ATP
C. feedback, or product, inhibition by ATP
D. all of the above
D. all of the above
- Why does the glycolytic pathway continue in the direction of glucose catabolism?
A. There are essentially three irreversible reactions that act as the driving force for the pathway
B. High levels of ATP keep the pathway going in a forward direction
C. The enzymes of glycolysis only function in one direction
D. Glycolysis occurs in either direction
A. There are essentially three irreversible reactions that act as the driving force for the pathway
Regulatory/ Irreversible Steps
(1) Hexokinase/ Glucokinase
(3) Phosphofructokinase-1 (Rate-limiting step)
(10) Pyruvate Kinase
- Which of the following is not true of glycolysis?
A. ADP is phosphorylated to ATP via substrate level phosphorylation
B. The pathway does not require oxygen
C. The pathway oxidizes two moles of NADH to NAD+ for each mole of glucose that enters
D. The pathway requires two moles of ATP to get started catabolizing each mole of glucose
C. The pathway oxidizes two moles of NADH to NAD+ for each mole of glucose that enters
- Cleavage of a hexose bisphosphate:
A. Aldolase
B. Hexokinase
C. Fructose 2,6-bisphosphate
D. Lactate dehydrogenase
A. Aldolase
Hexoses
(Glucose, Galactose, Mannose) : Aldoses
(Fructose) : Ketoses
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Irreversible phosphorylation of glucose:
A. Aldolase
B. Hexokinase
C. Fructose 2,6-bisphosphate
D. Lactate dehydrogenase
B. Hexokinase
Regulatory/ Irreversible Steps
(1) Hexokinase/ Glucokinase
(3) Phosphofructokinase-1 (Rate-limiting step)
(10) Pyruvate Kinase
- Activates the rate-limiting glycolytic enzyme:
A. Lactate dehydrogenase
B. Hexokinase
C. Fructose 2,6 bisphosphate
D. Aldolase
C. Fructose 2,6 bisphosphate
- Reduction of pyruvate:
A. Forward glycolytic reaction with glucose-6-phosphate as substrate
B. Lactate dehydrogenase
C. Hexokinase
D. Fructose 2,6-bisphosphate
D. Fructose 2,6-bisphosphate
Gluconeogenesis (+) : Glucagon
Glycolysis (-) : Insulin
- Forward glycolytic reaction with glucose-6-phosphate as substrate
A. Isomerization
B. Reduction of pyruvate
C. Activates the rate-limiting glycolytic enzyme
D. Irreversible phosphorylation of glucose
A. Isomerization
- Which of the following is not accomplished in glycolysis?
A. Net ATP synthesis
B. Substrate level phosphorylation
C. Oxidative phosphorylation
D. Generation of reducing equivalents
C. Oxidative phosphorylation
Cellular Respiration:
Glycolysis (Catabolic)
Tricarboxylic Acid/ Kreb Cycle
Electron Transport Chain/ Oxidative phosphorylation
- What is the difference between hexokinase and glucokinase?
A. Hexokinase phosphorylates glucose; glucokinase does not
B. Hexokinase is absent in the liver; glucokinase is abundant in the liver
C. Hexokinase is inhibited by glucose-6-phosphate; glucokinase is not
D. Hexokinase has a low affinity for glucose; glucokinase has a high affinity for glucose
C. Hexokinase is inhibited by glucose-6-phosphate; glucokinase is not
- What is the main purpose of the hexokinase reaction?
A. To facilitate the exocytosis glucose from the interior of the cell
B. To activate glucose for glycolysis
C. To convert glucose to a 6-carbon ketose
D. A and B only
B. To activate glucose for glycolysis
Hexokinase/Glucokinase effectively traps glucose inside the cell after being transported by GLUT-2(Liver)/ GLUT-3 (Kidney)
**Hexoses **
(Glucose, Galactose, Mannose) : Aldoses
(Fructose) : Ketoses
- Where does glycolysis take place?
A. Mitochondrial matrix
B. Inner membrane of the mitochondria
C. Outer membrane of the mitochondria
D. Cytoplasm
D. Cytoplasm
- What type of metabolic process is glycolysis?
A. Anabolic
B. Catabolic
C. Amphibolic
D. Anaplerotic
B. Catabolic
Metabolism:
* Catabolism (Break down : produces energy) : -lysis, -oxidation
* Anabolism (Building up : uses energy) : -genesis, -synthesis
* Amphibolic (Both Catabolic and Anabolic)
* Anaplerotic (refill / replenish depleted intermediates in TCA which have been used for biosynthetic reactions; continuous functioning)
- Which of the following reactions are considered as gluconeogenic reactions or pathways?
A. Glycogen ➝ Glucose
B. Alanine ➝ Pyruvate
C. Acetoacetate ➝Glucose
D. Pyruvate ➝ Acetyl-CoA
B. Alanine ➝ Pyruvate
A. Glycogen ➝ Glucose (Glycogenesis)
B. Alanine ➝ Pyruvate (GNG : Glucose-Alanine Cycle)
C. Acetoacetate ➝Glucose (Cholesterol synthesis)
D. Pyruvate ➝ Acetyl-CoA (Transition State)
- Which of the following is not a gluconeogenic enzyme?
A. Glucose-6-phosphatase
B. Glyceraldehyde-3-phosphate dehydrogenase
C. Phosphoglycerate kinase
D. Pyruvate kinase
D. Pyruvate kinase
- What is the role of the enzyme** aldolase in gluconeogenesis?**
A. It synthesizes 2 triose phosphates for gluconeogenesis
B. It condenses 2 triose phosphates to form a 6-carbon compound
C. It converts aldoses to ketoses
D. It delivers adenosine triphosphate to the cytosol as a source of energy for gluconeogenesis
B. It condenses 2 triose phosphates to form a 6-carbon compound
- Why is gluconeogenesis not possible in skeletal muscles?
A. Skeletal muscles do not have the enzyme lactate dehydrogenase to convert lactate to pyruvate
B. Skeletal muscles do not have mitochondria for oxaloacetate synthesis
C. Skeletal muscles do not have the enzyme glucose-6-phosphatase
D. Skeletal muscles are deficient in fructose-1,6-bisphosphatase, the rate-limiting enzyme of gluconeogenesis
C. Skeletal muscles do not have the enzyme glucose-6-phosphatase
Both in cytosol and mitochondria in liver (90%) and renal cortex (10%)