ascp mcq gycolysis

• RBC = glycolysis فقط

• Fluoride = يمنع glycolysis

• Hypoxia = ↑ lactate

• 2,3-BPG = ↓ O₂ affinity

• Pyruvate kinase deficiency = hemolytic anemia

In the Rappoport-Luebering shunt, which occurs in red blood cells, the intermediate 1,3-bisphosphoglycerate (1,3-BPG) is converted to 2,3-bisphosphoglycerate (2,3-BPG). What is the physiological significance of this shunt?

A) It increases the net yield of ATP in glycolysis.

B) It enhances the delivery of oxygen to tissues by decreasing hemoglobin's affinity for oxygen.

C) It provides NADPH for the reduction of glutathione.

D) It bypasses the need for the enzyme

It enhances the delivery of oxygen to tissues by decreasing hemoglobin's affinity for oxygen.

Which of the following conditions would result in a 'shift to the left' in the glycolytic pathway, specifically increasing the rate of glucose utilization in the liver?

A) High levels of Citrate.

B) Increased Glucagon secretion.

C) Increased levels of Fructose-2,6-bisphosphate.

D) High concentrations of Acetyl-CoA

Increased levels of Fructose-2,6-bisphosphate.

A deficiency in which of the following enzymes would specifically impair the production of NADH in the cytoplasm during glycolysis?

A) Hexokinase.

B) Glyceraldehyde-3-phosphate dehydrogenase (GAPDH).

C) Phosphoglycerate mutase.

D) Pyruvate kinase

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH).

In clinical chemistry, when a blood sample is collected in a tube without an antiglycolytic agent, the glucose concentration decreases at a rate of approximately:

A) 1% to 2% per hour at room temperature.

B) 5% to 7% per hour at room temperature.

C) 15% to 20% per hour at room temperature.

D) Glucose levels do not change unless the patient is diabetic.

5% to 7% per hour at room temperature.

Which enzyme is responsible for the 'trapping' of glucose within the cell by converting it to Glucose-6-Phosphate, and is characterized by a high affinity (low Km) for glucose in muscle tissue?

A) Glucokinase.

B) Hexokinase.

C) Glucose-6-Phosphatase.

D) Phosphoglucomutase.

Hexokinase

What is the net gain of ATP molecules from the metabolism of one molecule of glucose to two molecules of lactate in an erythrocyte?

A) 0 ATP.

B) 2 ATP.

C) 4 ATP.

D) 36 ATP.

B

Which of the following is the only enzyme in the glycolytic pathway that requires an input of inorganic phosphate (Pi) rather than ATP to phosphorylate its substrate?

A) Hexokinase

B) Phosphofructokinase

C) Glyceraldehyde-3-phosphate dehydrogenase (GAPDH)

D) Pyruvate Kinase

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH)

In a "Shift to the Right" of the Oxygen-Dissociation Curve, what is the effect on the glycolysis intermediate 2,3-BPG?

A) 2,3-BPG is decreased to allow more oxygen binding.

B) 2,3-BPG is increased, which is a common finding in high-altitude adaptation.

C) 2,3-BPG remains constant while pH changes.

D) 2,3-BPG is bypassed via the Entner-Doudoroff

2,3-BPG is increased, which is a common finding in high-altitude adaptation.

Which of the following metabolic pathways is the primary source of NADPH for maintaining reduced glutathione, which protects red blood cells from oxidative damage?

A) Embden-Meyerhof pathway (Glycolysis)

B) Hexose Monophosphate (HMP) Shunt

C) Tricarboxylic Acid (TCA) cycle

D) Rapoport-Luebering Shunt

B

During prolonged fasting, which enzyme's activity is significantly decreased in the liver to prevent the wasteful breakdown of glucose?

A) Glucose-6-phosphatase

B) Phosphofructokinase-1 (PFK-1)

C) Pyruvate carboxylase

D) Fructose-1,6-bisphosphatase

B

Which enzyme catalyzes the conversion of Phosphoenolpyruvate (PEP) to Pyruvate, producing the second "ATP payoff" of glycolysis?

A) Enolase

B) Pyruvate Kinase

C) Pyruvate Dehydrogenase

D) Lactate Dehydrogenase

B

Which pathway protects RBCs from oxidative damage?

Pentose phosphate pathway

Pyruvate kinase deficiency causes:

Hemolytic anemia

Increased 2,3-BPG causes the oxygen dissociation curve to

Shift right

What is the function of 2,3-BPG?

Decrease hemoglobin oxygen affinity

Which pathway produces 2,3-BPG in red blood cells?

Rapoport–Luebering shunt

If blood is left at room temperature without fluoride, glucose will

Decrease

Sodium fluoride prevents glycolysis by inhibiting which enzyme?

Enolase

Which tube additive prevents glycolysis in blood samples?

Sodium fluoride

Which enzyme converts pyruvate to lactate?

Lactate dehydrogenase

Increased lactate levels are associated with:

Tissue hypoxia

In anaerobic conditions, pyruvate is converted to:

Lactate

Why do mature erythrocytes use glycolysis only?

They have no mitochondria

What is the only source of energy for mature red blood cells?

Glycolysis

Which additive prevents glycolysis?

Sodium fluoride

Which condition would most increase glycolysis rate in RBCs?

A. Alkalosis

B. Increased ATP

C. Hypoxia

D. High citrate

Hypoxia

Which metabolite directly links glycolysis to lactic acidosis?

Pyruvate

A stored blood unit has decreased 2,3-BPG. What is the clinical effect?

Impaired oxygen release to tissues

Which condition would decrease 2,3-BPG levels?

Stored blood

Increased 2,3-BPG levels cause which effect?

Right shift of oxygen dissociation curve

Which pathway competes with glycolysis for glucose-6-phosphate?

Pentose phosphate pathway

Activation of the Rapoport–Luebering shunt results in:

A. Increased ATP

B. Decreased ATP

C. Increased glucose

D. Decreased lactate

Decreased ATP

The Rapoport–Luebering pathway functions to: Regulate hemoglobin oxygen affinity

Regulate hemoglobin oxygen affinity

If a blood sample is left at room temperature without preservative, glucose will:

A. Increase

B. Remain stable

C. Decrease

D. Convert to glycogen

Decrease

Sodium fluoride preserves glucose by inhibiting:

A. Hexokinase

B. Enolase

C. Pyruvate kinase

D. Lactate dehydrogenase

Enolase

Which additive best preserves glucose concentration in whole blood?

Sodium fluoride

Which disorder is directly related to impaired glycolysis in RBCs?

A. Iron deficiency anemia

B. Sickle cell disease

C. Pyruvate kinase deficiency

D. Thalassemia

Pyruvate kinase deficiency

A patient with severe hypoxia will most likely have increased:

Blood lactate

Pyruvate kinase deficiency results in:

Chronic hemolytic anemia

Hexokinase is inhibited by:

Glucose 6 phosphate

Which condition increases glycolysis in erythrocytes?

A. Alkalosis

B. Increased ATP

C. Hypoxia

D. High pH

Hypoxia

Which specimen handling error falsely decreases measured plasma glucose?

A. Delayed separation of plasma

B. Use of fluoride tube

C. Immediate centrifugation

D. Refrigeration

Delayed separation of plasma

What happens to ATP production when the Rapoport–Luebering shunt is activated?

ATP increases

B. ATP decreases

C. ATP unchanged

D. ATP doubles

ATP decreases

Which glycolytic intermediate is converted to 2,3-BPG?

A. Glucose-6-phosphate

B. Fructose-1,6-bisphosphate

C. 1,3-Bisphosphoglycerate

D. Pyruvate

1,3-Bisphosphoglycerate

Which enzyme deficiency leads to decreased ATP and hemolytic anemia?

A. Glucose-6-phosphate dehydrogenase

B. Pyruvate kinase

C. Lactate dehydrogenase

D. Hexokinase

Pyruvate kinase

What is the primary function of 2,3-BPG in red blood cells?

A. Increase ATP production

B. Increase hemoglobin oxygen affinity

C. Decrease hemoglobin oxygen affinity

D. Prevent hemolysis

Decrease hemoglobin oxygen affinity

Which glycolytic pathway produces 2,3-BPG in erythrocytes?

A. Embden-Meyerhof pathway

B. Pentose phosphate pathway

C. Rapoport–Luebering shunt

D. Hexose monophosphate shunt

Rapoport–Luebering shunt

Failure to inhibit glycolysis in a blood sample will result in:

A. Increased glucose

B. Decreased glucose

C. Increased pH

D. Increased bicarbonate

Decreased glucose

Which substance must be added to blood collection tubes to inhibit glycolysis?

A. Heparin

B. EDTA

C. Sodium fluoride

D. Oxalate

Sodium fluoride

Which enzyme converts pyruvate to lactate?

A. Pyruvate dehydrogenase

B. Lactate dehydrogenase

C. Hexokinase

D. Enolase

Lactate dehydrogenase

In anaerobic conditions, pyruvate is converted to:

A. Acetyl-CoA

B. Lactate

C. Oxaloacetate

D. Alanine

Lactate

Why do mature erythrocytes depend entirely on glycolysis?

A. Lack of nucleus

B. Lack of ribosomes

C. Lack of mitochondria

D. Lack of glucose transporters

Lack of mitochondria

What is the primary source of energy for mature red blood cells?

Glycolysis