CHO Metabolism Revision Quiz
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Questions and Answers

What is the primary action of glycogen phosphorylase?

  • Breaks α-1,6 glucosidic bonds
  • Synthesizes glucose from glycogen
  • Inhibits glycolysis
  • Breaks α-4 glucosidic bonds (correct)

Which conversion is necessary for synthesizing glucose from propionol?

  • Converted to dihydroxyacetone
  • Converted to acetyl CoA
  • Converted to glucose-6-phosphate
  • Converted to succinyl CoA (correct)

Which of the following pathways can be classified as amphibolic?

  • Glycolysis
  • Krebs cycle (correct)
  • Glycogenolysis
  • Glycogenesis

What is a characteristic of glycolysis in red blood cells?

<p>Ends with the production of lactate (C)</p> Signup and view all the answers

Which statement about ATP generation from glucose metabolism is true?

<p>Complete oxidation of one molecule of glucose gives 36-38 ATP. (A)</p> Signup and view all the answers

What occurs during the oxidative decarboxylation of pyruvate?

<p>Formation of acetyl CoA (C)</p> Signup and view all the answers

What is one key enzyme in the process of glycogenesis?

<p>Glycogen synthase (B)</p> Signup and view all the answers

Which enzyme acts on fructose to produce fructose-1-phosphate?

<p>Fructokinase (D)</p> Signup and view all the answers

In which pathway does the production of NADPH+H and ribose-5-phosphate occur?

<p>HMP shunt (C)</p> Signup and view all the answers

Why can't glycogenolysis in muscles yield free glucose?

<p>Muscles lack glucose-6-phosphatase enzyme. (C)</p> Signup and view all the answers

Flashcards

Anabolic Pathway

A metabolic pathway that constructs complex molecules from simpler ones.

Catabolic Pathway

A metabolic pathway that breaks down complex molecules into simpler ones, releasing energy.

Amphibolic Pathway

A metabolic pathway that can function both as anabolic and catabolic, depending on the cell's needs.

Glycolysis

Metabolic pathway that breaks down glucose into pyruvate.

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Krebs Cycle

A series of reactions in mitochondria that further oxidizes acetyl-CoA, producing ATP and electron carriers.

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Substrate-level phosphorylation

A metabolic reaction that directly produces ATP by transferring a phosphate group to ADP.

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HMP Shunt

A metabolic pathway that produces NADPH and ribose-5-phosphate from glucose.

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Uronic Acid Pathway

A metabolic pathway that produces glucuronic acid, important in detoxification and vitamin C synthesis.

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Aerobic Glycolysis

Glucose breakdown with oxygen, yielding higher ATP.

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Anaerobic Glycolysis

Glucose breakdown without oxygen, yielding lower ATP.

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Glycogenesis

The synthesis of glycogen from glucose.

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Glycogenolysis

Breakdown of glycogen to glucose.

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Gluconeogenesis

The synthesis of glucose from non-carbohydrate precursors.

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Glucose-6-phosphatase

Enzyme crucial for releasing free glucose from glycogen.

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Mitochondria

Cell organelle where Krebs cycle occurs.

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Cytoplasm

The gel-like substance inside the cell where glycolysis and HMP shunt occur.

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Glycogen phosphorylase action

Breaks α-1,4 glycosidic bonds in glycogen by adding inorganic phosphate (phosphorylysis).

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Glycerol to glucose synthesis

Glycerol needs conversion to dihydroxyacetone before glucose synthesis.

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Propionol to glucose synthesis

Propionol needs conversion to succinyl CoA before glucose synthesis.

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Fructose-2,6-bisphosphate

A molecule that stimulates glycolysis, and inhibits gluconeogenesis.

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Fanconi syndrome

Renal disorder causing decreased reabsorption of glucose, amino acids, and phosphate, leading to excretion in urine.

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Pyruvate to Acetyl CoA

Conversion of pyruvate to acetyl CoA, a crucial step of cellular respiration using the pyruvate dehydrogenase complex.

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RBC Glycolysis

Anaerobic glycolysis in red blood cells producing lactate, 2 ATPs, and 2,3-BPG; independent of insulin.

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Fasting Blood Glucose

Normal range for fasting blood glucose: 70-110 mg/dL.

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Renal glucose threshold

Blood glucose level (180 mg/dL) above which glucose starts to appear in the urine.

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Glucokinase/Hexokinase function

Convert glucose to glucose-6-phosphate.

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Fructokinase action

Converts fructose to fructose-1-phosphate.

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Hexokinase action on fructose

Converts fructose to fructose-6-phosphate.

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Galactokinase action

Converts galactose to galactose-1-phosphate.

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Hexokinase action on galactose

Converts galactose to galactose-6-phosphate.

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Study Notes

CHO Metabolism Revision

  • Anabolic Pathways: Glycogenesis, Gluconeogenesis
  • Catabolic Pathways: Glycolysis, Oxidative decarboxylation, Krebs cycle, HMP shunt, Uronic acid pathway, Glycogenolysis
  • Amphibolic Pathway: Krebs cycle
  • Aerobic Glycolysis: 36-38 ATP from glucose
  • Anaerobic Glycolysis: 2 ATP from glucose
  • Oxidative Decarboxylation of Pyruvate: 6 ATP
  • Acetyl CoA Oxidation (Krebs): 12 ATP per molecule
  • Substrate Level Phosphorylation (Examples):
    • Glycolysis: Phosphoglycerate kinase, pyruvate kinase
    • Krebs cycle: Succinate thiokinase
  • Coenzymes:
    • HMP shunt: NADP
    • Glyceraldehyde-3-phosphate dehydrogenase: NAD
    • Succinate dehydrogenase: FAD
  • Uronic Acid Pathway: Production of Glucuronic acid (UDP-glucuronic acid), used in detoxification, synthesis of vitamin C (in animals not humans)
  • HMP Shunt: Important for NADPH + H and ribose-5-phosphate production
  • Key Enzymes (Glycolysis): Hexokinase, glucokinase, phosphofructokinase-1, pyruvate kinase
  • Key Enzymes (Krebs Cycle): Citrate synthase, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase
  • Key Enzymes (HMP Shunt): Glucose-6-phosphate dehydrogenase
  • Key Enzymes (Glycogenesis): Glycogen synthase
  • Key Enzymes (Glycogenolysis): Glycogen phosphorylase
  • Key Enzymes (Gluconeogenesis): Pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose 1,6-biphosphatase, glucose-6-phosphatase
  • Glycogenesis Requirements: Glycogen synthase, UDP-glucose, branching enzyme, glycogen primer
  • Glycogenolysis Requirements: Glycogen phosphorylase, inorganic phosphate, glucan transferase, debranching enzyme
  • Glycogenolysis (Liver vs. Muscles): Liver glycogenolysis produces free glucose due to glucose-6-phosphatase; muscle glycogenolysis does not
  • Cytoplasmic Cycles: Glycolysis, oxidative decarboxylation, HMP shunt, uronic acid pathway, glycogenesis, glycogenolysis
  • Mitochondrial Cycle: Krebs cycle
  • Gluconeogenesis: Cytoplasmic and mitochondrial
  • Glycerol Conversion to Glucose: Dihydroxyacetone
  • Propionol Conversion to Glucose: Succinyl CoA
  • Fructose 2,6-bisphosphate: Stimulates glycolysis, inhibits gluconeogenesis
  • Fanconi Syndrome: Reduced renal tubular reabsorption of glucose, amino acids, and phosphate
  • Pyruvate to Acetyl CoA: Pyruvate dehydrogenase complex, 5 coenzymes (NAD, FAD, CoASH, TPP, lipoic acid)
  • α-ketoglutarate to Succinyl CoA: α-ketoglutarate dehydrogenase complex, 5 coenzymes (NAD, FAD, CoASH, TPP, lipoic acid)
  • RBC Glycolysis: Anaerobic; ends with lactate; produces 2 ATP; independent of insulin; produces 2,3-BPG;
  • Normal Fasting Blood Glucose: 70-110 mg/dL
  • 2-hour postprandial blood glucose: up to 140 mg/dL
  • Hypoglycemia: Blood glucose below 60 mg/dL
  • Renal Threshold: 180 mg/dL
  • Glucose-6-Phosphate Production: Glucokinase, hexokinase on glucose
  • Fructose-1-Phosphate Production: Fructokinase on fructose
  • Fructose-6-Phosphate Production: Hexokinase on fructose
  • Galactose-1-Phosphate Production: Galactokinase on galactose
  • Galactose-6-Phosphate Production: Hexokinase on galactose

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Revision On CHO Metabolism PDF

Description

Test your knowledge of carbohydrate metabolism in this comprehensive quiz. Explore topics such as anabolic and catabolic pathways, ATP yield in glycolysis, and important coenzymes. Ideal for students revising for exams or anyone interested in biochemistry.

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