Metabolism Overview and Reaction Types

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Questions and Answers

What is the primary function of catabolic pathways in metabolism?

  • To break down complex molecules and release energy (correct)
  • To synthesize complex molecules from simple molecules
  • To facilitate oxidation reactions alone
  • To store energy in the form of ATP

Which of the following accurately describes a redox reaction?

  • Always results in the formation of ATP
  • Only occurs in the mitochondria
  • Involves the transfer of electrons between species (correct)
  • Involves only the loss of oxygen

What is produced from the hydrolysis of ATP?

  • Only ADP and water
  • ADP, Pi, and protons (H+) (correct)
  • ADP and GTP
  • AMP and inorganic phosphate (Pi)

Where does glycolysis occur within a cell?

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

What role does phosphofructokinase play in glycolysis?

<p>It regulates the rate of glycolysis by responding to ATP levels (B)</p> Signup and view all the answers

What is the energy currency in living cells and what is its primary source of energy?

<p>ATP, released through hydrolysis (D)</p> Signup and view all the answers

What happens if a system is left without an input of energy?

<p>It will enter a state of energetic equilibrium (C)</p> Signup and view all the answers

Which of the following statements about anabolic pathways is true?

<p>They synthesize complex molecules from simpler ones using energy (D)</p> Signup and view all the answers

What is the final product of glycolysis?

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

Which molecule is regenerated by the reduction of pyruvate to lactate during anaerobic conditions?

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

What is the net ATP production during glycolysis?

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

What activates the pyruvate dehydrogenase enzyme complex?

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

Which metabolic pathway occurs in the mitochondrial matrix?

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

How many NADH molecules are produced in glycolysis?

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

What is the primary purpose of gluconeogenesis in the liver after intense exercise?

<p>To produce glucose-6-phosphate (A)</p> Signup and view all the answers

Which enzyme is primarily responsible for converting pyruvate to acetyl-CoA?

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

What is the overall equation representing gluconeogenesis?

<p>2 pyruvate + 4 ATP + 6 H2O -&gt; 1 glucose + 4 ADP + 2 GDP + 2 NAD+ (D)</p> Signup and view all the answers

What happens to acetyl-CoA excess in the liver?

<p>It is converted to fatty acids (A)</p> Signup and view all the answers

Flashcards

What is metabolism?

The sum of all chemical reactions occurring within a living organism, essential for maintaining life.

What are catabolic pathways?

Metabolic pathways that break down complex molecules into simpler ones, releasing energy in the process.

What are anabolic pathways?

Metabolic pathways that build complex molecules from simpler ones, requiring energy from ATP.

What is phosphorylation?

A chemical reaction involving the addition of a phosphate group to a molecule.

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What is oxidation?

The process of removing electrons from a molecule, often accompanied by the gain of oxygen.

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What is reduction?

The process of adding electrons to a molecule, often accompanied by the loss of oxygen.

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What is ATP?

The cell's primary energy currency, used to power various cellular processes.

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What is glycolysis?

The process of breaking down glucose to produce ATP, occurring in the cytosol.

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What is the first step in glycolysis?

A six-carbon sugar molecule, such as glucose, is broken down into two three-carbon molecules: glyceraldehyde 3-phosphate (GA-3-P) and dihydroxyacetone phosphate (DAP).

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How is DAP converted to GA-3-P?

Dihydroxyacetone phosphate (DAP) is converted into glyceraldehyde 3-phosphate (GA-3-P) by the enzyme triosephosphate isomerase.

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What happens to GA-3-P after it's formed?

Glyceraldehyde 3-phosphate (GA-3-P) is oxidized by NAD+ to produce NADH and is dephosphorylated twice, generating two ATP molecules per GA-3-P molecule.

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What is the final product of glycolysis?

The final product of glycolysis is two pyruvate molecules, each containing three carbons.

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What is the net energy yield of glycolysis?

Glycolysis produces a net gain of two ATP molecules and two NADH molecules, while using up two NAD+ molecules.

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What happens to pyruvate in anaerobic conditions?

In anaerobic conditions, the lack of oxygen prevents the regeneration of NAD+ through oxidative phosphorylation, making it a limited resource. The cell regenerates NAD+ by reducing pyruvate to lactate, oxidizing NADH back to NAD+.

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What causes muscle pain during intense exercise?

The buildup of lactate in muscles during anaerobic respiration can cause muscle pain.

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What is the Cori cycle?

The Cori cycle is a metabolic pathway in the liver that converts lactate back to glucose, using up ATP and GTP.

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What is the process of converting pyruvate to glucose called?

The Cori cycle uses two pyruvate molecules to produce glucose-6-phosphate, a process called gluconeogenesis.

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What happens to pyruvate in the mitochondrial matrix?

Oxidative decarboxylation is the process in the mitochondrial matrix where pyruvate is decarboxylated to form acetyl-CoA, using NAD+ to produce NADH and releasing CO2.

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Study Notes

Metabolism Overview

  • Metabolism encompasses all chemical processes in a living organism for life maintenance.
  • Metabolic pathways involve reactants, products, and enzymes.
  • Metabolism can be categorized as catabolic (breaking down complex molecules) and anabolic (building complex molecules).
  • Specific pathways occur in specific locations, like glycolysis in the cytosol and the TCA cycle in the mitochondrial matrix.
  • Glucose metabolism involves many interlinked metabolic pathways.

Reaction Types

  • Hydrolysis: Breaking down molecules by adding water.
  • Condensation: Joining molecules, releasing water.
  • De/phosphorylation: Removal/addition of phosphate groups.
  • De/carboxylation: Removal/addition of CO2.
  • Oxidation: Gain of oxygen, or loss of electrons.
  • Reduction: Loss of oxygen, or gain of electrons.
  • Redox reactions commonly occur together, transferring electrons between species.

Energy in Cells

  • Systems without energy input reach thermodynamic equilibrium (death).
  • Cells store energy as fat or glycogen.
  • ATP (adenosine triphosphate) is the energy currency of cells.
  • ATP's high-energy phosphate bonds release energy via hydrolysis (adding water).
  • ATP production occurs via oxidative phosphorylation or substrate-level phosphorylation.

Energy Generation (Respiration)

Glycolysis

  • Occurs in the cytosol.
  • Glucose is phosphorylated, priming the molecule, using 2 ATPs.
  • The 6-carbon molecule is split to two 3-carbon molecules (glyceraldehyde-3-phosphate).
  • These are further modified, releasing energy to produce 4 ATPs and 2 NADHs.
  • Net product: 2 ATPs and 2 NADHs from 1 glucose molecule.

Anaerobic Conditions

  • Without oxygen, NAD+ regeneration cannot occur via oxidative phosphorylation.
  • Cells convert pyruvate to lactate, oxidizing NADH to NAD+.
  • Lactate buildup causes muscle pain; it's transported to liver cells.
  • The Cori cycle converts lactate back to glucose.
  • This cycle consumes significant ATP.

Oxidative Decarboxylation

  • Occurs in the mitochondrial matrix.
  • Pyruvate is converted to acetyl-CoA, releasing NADH and CO2.
  • Pyruvate dehydrogenase can be regulated by phosphorylation (inhibited) or dephosphorylation (activated).
  • Other molecules, like amino acids and fatty acids, can also be converted to acetyl-CoA.

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