Macromolecule Metabolism Overview
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Questions and Answers

Which of the following macromolecules is primarily broken down in the glycolytic pathway?

  • Proteins
  • Carbohydrates (correct)
  • Nucleic acids
  • Lipids

Which metabolic process is responsible for synthesizing new proteins in the body?

  • Protein synthesis (correct)
  • Lipogenesis
  • Glycolysis
  • Gluconeogenesis

Which of the following is NOT a major end product of lipid catabolism?

  • Acetyl-CoA
  • Amino acids (correct)
  • Fatty acids
  • Glycerol

Nucleic acid metabolism involves the synthesis and breakdown of:

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

What is the net gain of ATP molecules produced per molecule of glucose during glycolysis?

<p>2 ATP (C)</p> Signup and view all the answers

Which enzyme catalyzes the conversion of glucose to glucose-6-phosphate in the first step of glycolysis?

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

In the process of glycolysis, which molecule acts as the final electron acceptor to form lactate in anaerobic conditions?

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

Which step in glycolysis is considered the ‘rate-limiting step’?

<p>Fructose-6-phosphate to fructose-1,6-bisphosphate (B)</p> Signup and view all the answers

During glycolysis, glucose is ultimately broken down into:

<p>Two molecules of pyruvate (B)</p> Signup and view all the answers

Which enzyme in glycolysis catalyzes the substrate-level phosphorylation that produces ATP?

<p>Pyruvate kinase (B)</p> Signup and view all the answers

In which cellular organelle does glycolysis take place?

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

Which metabolic pathway is responsible for generating glucose from non-carbohydrate sources?

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

In aerobic conditions, pyruvate from glycolysis is converted into:

<p>Acetyl-CoA (A)</p> Signup and view all the answers

How many NADH molecules are produced per molecule of glucose during glycolysis?

<p>2 NADH (D)</p> Signup and view all the answers

Which pathway involves the breakdown of triglycerides into fatty acids and glycerol?

<p>Lipolysis (A)</p> Signup and view all the answers

What is the main purpose of the urea cycle in amino acid metabolism?

<p>To excrete nitrogen (D)</p> Signup and view all the answers

The breakdown of glucose in glycolysis produces pyruvate. In the presence of oxygen, pyruvate enters which cycle?

<p>Citric acid cycle (Krebs cycle) (B)</p> Signup and view all the answers

Which coenzyme is regenerated during the conversion of pyruvate to lactate under anaerobic conditions?

<p>NAD+ (B)</p> Signup and view all the answers

Which of the following molecules provides feedback inhibition to hexokinase in glycolysis?

<p>Glucose-6-phosphate (D)</p> Signup and view all the answers

Which enzyme in glycolysis catalyzes the cleavage of fructose-1,6-bisphosphate into two three-carbon molecules?

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

The final step of glycolysis, catalyzed by pyruvate kinase, produces pyruvate and:

<p>ATP (A)</p> Signup and view all the answers

During fatty acid oxidation, each cycle of beta-oxidation produces which of the following?

<p>Acetyl-CoA, NADH, and FADH2 (D)</p> Signup and view all the answers

Which of the following is a precursor molecule for triglyceride synthesis?

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

The presence of high levels of which molecule signals cells to start glycogen synthesis?

<p>Insulin (A)</p> Signup and view all the answers

Which hormone stimulates the breakdown of glycogen to glucose in response to low blood sugar?

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

Flashcards

Glycolysis

The metabolic pathway that breaks down carbohydrates (primarily glucose) into pyruvate, generating a small amount of ATP and NADH.

Citric Acid Cycle (Krebs Cycle)

A series of reactions that occur in the mitochondria, oxidizing pyruvate from glycolysis to carbon dioxide, generating ATP, NADH, and FADH2.

Protein Synthesis

The process of synthesizing new proteins from amino acids.

Lipolysis

The process of breaking down lipids (fats) into fatty acids and glycerol.

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Glycogenolysis

The breakdown of glycogen (stored glucose) into glucose.

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Glycogenesis

The process of synthesizing glycogen from glucose.

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Lipogenesis

The process of synthesizing new lipids from non-lipid sources, like carbohydrates or proteins.

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Gluconeogenesis

The process of producing glucose from non-carbohydrate sources, like amino acids or glycerol.

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Lactate Fermentation

The process of converting pyruvate to lactate in anaerobic conditions. This allows glycolysis to continue even without oxygen.

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Inhibitor

A molecule that inhibits the activity of an enzyme, often by binding to the active site.

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ATP Yield in Glycolysis

The net gain of ATP molecules produced per molecule of glucose during glycolysis is 2 ATP.

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Hexokinase

Hexokinase is the enzyme that catalyzes the conversion of glucose to glucose-6-phosphate, the first step in glycolysis.

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Phosphofructokinase

Phosphofructokinase is the enzyme that catalyzes the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate, the rate-limiting step in glycolysis.

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Rate-Limiting Step in Glycolysis

The step in glycolysis where fructose-6-phosphate is converted to fructose-1,6-bisphosphate is the rate-limiting step, meaning it controls the overall rate of glycolysis.

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Final Step in Glycolysis

The final step in glycolysis, catalyzed by pyruvate kinase, produces pyruvate and ATP.

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Location of Glycolysis

Glycolysis occurs in the cytoplasm of the cell.

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Pyruvate to Acetyl-CoA Conversion

The process of converting pyruvate to acetyl-CoA, which then enters the citric acid cycle, occurs in the mitochondria.

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Urea Cycle

The urea cycle is responsible for excreting nitrogen waste produced during amino acid metabolism.

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Beta Oxidation Products

During fatty acid oxidation, each cycle of beta-oxidation produces one molecule of acetyl-CoA, one molecule of NADH, and one molecule of FADH2.

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Insulin & Glycogen Synthesis

Insulin is a hormone that stimulates glycogen synthesis, promoting the storage of glucose.

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Glucagon & Glycogen Breakdown

Glucagon is a hormone that stimulates glycogen breakdown, releasing glucose into the bloodstream.

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Glucose to Glucose-6-Phosphate

The process of converting glucose to glucose-6-phosphate is the first step in glycolysis.

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End Product of Glycolysis

Pyruvate is the end product of glycolysis.

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Pyruvate Enters Citric Acid Cycle

The breakdown of glucose in glycolysis produces pyruvate, which then enters the citric acid cycle in the presence of oxygen.

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Glycerol in Lipid Synthesis

Glycerol is a precursor molecule for triglyceride synthesis.

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Aldolase

Aldolase is the enzyme that catalyzes the cleavage of fructose-1,6-bisphosphate into two three-carbon molecules during glycolysis.

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Glucose-6-Phosphate Feedback Inhibition

The presence of high levels of glucose-6-phosphate inhibits the activity of hexokinase, creating a feedback loop to regulate glycolysis.

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NAD+ Regeneration

The coenzyme NAD+ is regenerated during the conversion of pyruvate to lactate under anaerobic conditions.

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Fatty Acid Oxidation

Fatty acids are broken down through a process called beta-oxidation, generating acetyl-CoA, NADH, and FADH2.

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Study Notes

General Overview: Macromolecule Metabolism

  • Carbohydrates are broken down in glycolysis.
  • Protein synthesis is responsible for creating new proteins.
  • Lipid catabolism does not produce amino acids. It creates fatty acids, glycerol, and acetyl-CoA.
  • Nucleic acid metabolism involves DNA and RNA synthesis and breakdown.

Carbohydrate Metabolism: Glycolysis

  • Glycolysis produces 2 ATP per glucose molecule.
  • Hexokinase is the enzyme that converts glucose to glucose-6-phosphate in the first step of glycolysis.
  • The rate-limiting step is the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate.
  • Glucose is broken down into two pyruvate molecules during glycolysis.

Integration of Metabolic Pathways

  • Glycolysis occurs in the cytoplasm of the cell.
  • Gluconeogenesis produces glucose from noncarbohydrate sources.
  • Pyruvate is converted to acetyl-CoA in aerobic conditions.
  • Pyruvate is converted to lactate in anaerobic conditions. NAD+ is regenerated.
  • Glucose-6-phosphate inhibits hexokinase through feedback inhibition.
  • Aldolase cleaves fructose-1,6-bisphosphate to two three-carbon molecules.
  • The final step of glycolysis, catalyzed by pyruvate kinase, produces pyruvate and ATP.

Lipid Metabolism

  • Lipolysis breaks down triglycerides into fatty acids and glycerol.
  • Acetyl-CoA, NADH, and FADH2 are produced in each cycle of beta-oxidation.
  • Glycerol is used to create triglycerides.

Metabolic Regulation

  • Insulin signals cells to begin glycogen synthesis.
  • Glucagon causes glycogen to be broken down to glucose when blood sugar is low.

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Description

This quiz covers the essential concepts of macromolecule metabolism, including carbohydrate metabolism through glycolysis, protein synthesis, lipid catabolism, and nucleic acid metabolism. Understand the key processes and pathways that integrate these macromolecules in biological systems.

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