Cellular Respiration in Eukaryotic Cells
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Questions and Answers

Citrate synthase catalyses the condensation of acetyl-CoA and oxaloacetate to form ______.

citrate

Isocitrate dehydrogenase converts isocitrate to ______ while reducing NAD+ to NADH.

a-ketoglutarate

Oxidative phosphorylation occurs in the inner ______ membrane.

mitochondrial

Complex IV, known as Cytochrome c oxidase, facilitates the transfer of electrons to ______, forming water.

<p>oxygen</p> Signup and view all the answers

ATP synthase uses the proton gradient generated by the ______ to synthesize ATP.

<p>ETC</p> Signup and view all the answers

GLYCOLYSIS is the first stage of cellular respiration, it occurs in the ______ and involves the breakdown of one molecule of glucose.

<p>cytoplasm</p> Signup and view all the answers

The investment phase of glycolysis uses 2 ______ molecules to phosphorylate glucose.

<p>ATP</p> Signup and view all the answers

Phosphofructokinase is a key regulatory enzyme in glycolysis that is activated by ______.

<p>AMP</p> Signup and view all the answers

In the payoff phase, glycolysis yields 4 ______ molecules and 2 NADH molecules.

<p>ATP</p> Signup and view all the answers

The pyruvate generated in glycolysis is transported to the ______ for further oxidation.

<p>mitochondria</p> Signup and view all the answers

Pyruvate is oxidized into acetyl-CoA in a reaction catalyzed by the ______ dehydrogenase complex.

<p>pyruvate</p> Signup and view all the answers

For each acetyl-CoA molecule, the citric acid cycle produces 3 ______ and 1 FADH.

<p>NADH</p> Signup and view all the answers

The citric acid cycle releases 2 ______ molecules as waste products.

<p>CO2</p> Signup and view all the answers

Flashcards

Oxidative Phosphorylation

The process of generating ATP by using the proton gradient across the inner mitochondrial membrane, driven by the electron transport chain.

Electron Transport Chain (ETC)

A series of protein complexes and electron carriers embedded in the inner mitochondrial membrane, transferring electrons from NADH and FADH2 to oxygen, releasing energy for ATP synthesis.

Chemiosmosis

The movement of protons across the inner mitochondrial membrane, driven by the ETC, creating a proton gradient that powers ATP synthase.

ATP Synthase

An enzyme complex embedded in the inner mitochondrial membrane that uses the proton gradient generated by the ETC to synthesize ATP from ADP and inorganic phosphate.

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Citric Acid Cycle (CAC)

The citric acid cycle is a series of chemical reactions that occur in the mitochondria of cells, breaking down acetyl-CoA to produce energy in the form of ATP.

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Glycolysis

The first stage of cellular respiration, occurring in the cytoplasm. It breaks down one glucose molecule (6C) into two pyruvate molecules (3C).

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Investment Phase of Glycolysis

The investment phase requires 2 ATP molecules to phosphorylate glucose and fructose-6-phosphate, preparing for molecule cleavage.

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Payoff Phase of Glycolysis

This phase yields 4 ATP molecules and 2 NADH molecules through substrate-level phosphorylation. The 2 3C molecules are further metabolized.

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Phosphofructokinase

A key regulatory enzyme in glycolysis, converting fructose-6-phosphate into fructose-1,6-biphosphate. It is activated by AMP and inhibited by ATP, tightly controlled by cellular energy levels.

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Pyruvate Dehydrogenase Complex

This multi-enzyme complex involves 3 enzymes (E1, E2, E3), decarboxylating pyruvate (removing CO2), reducing NAD+ to NADH, and attaching Coenzyme A to the resulting 2C acetyl group.

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Citric Acid Cycle

The second stage of cellular respiration, taking place in the mitochondrial matrix. It completes the oxidation of an acetyl-CoA molecule, generating 3 NADH, 1 FADH2, 1 GTP, and 2 CO2 molecules.

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Acetyl-CoA

It is a molecule that enters the citric acid cycle and is derived from pyruvate through the action of pyruvate dehydrogenase.

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Study Notes

Cellular Respiration in Eukaryotic Cells

  • Cellular respiration is a multi-step process converting glucose into ATP
  • Primarily occurs in the cytoplasm and mitochondria
  • Consists of three main stages: glycolysis, citric acid cycle, and oxidative phosphorylation

Glycolysis

  • First stage of cellular respiration, occurring in the cytoplasm
  • Breaks down one glucose molecule (6C) into two pyruvate molecules (3C)
  • Anaerobic process (does not require oxygen)
  • Divided into two phases: investment and payoff
  • Investment phase: Uses 2 ATP to phosphorylate glucose, preparing it for cleavage
    • Hexokinase phosphorylates glucose to glucose-6-phosphate
    • Phosphofructokinase converts fructose-6-phosphate to fructose-1,6-bisphosphate
      • Key regulatory enzyme; activated by AMP, inhibited by ATP
  • Payoff phase: Further metabolizes 3C molecules, yields 4 ATP and 2 NADH (substrate-level phosphorylation)
    • Pyruvate kinase converts phosphoenolpyruvate to pyruvate
    • Pyruvate production
  • Pyruvate transported to mitochondria in presence of oxygen for further oxidation

Pyruvate Oxidation (Bridge reaction)

  • Occurs in the mitochondrial matrix
  • Pyruvate dehydrogenase complex oxidizes pyruvate to acetyl-CoA
  • Multi-enzyme complex (E1, E2, E3)
  • Decarboxylates pyruvate, reduces NAD+ to NADH, attaches CoA to the 2C acetyl group
  • Produces one CO2 per pyruvate

Citric Acid Cycle (Krebs Cycle)

  • Completes oxidation of acetyl-CoA molecule
  • Per acetyl-CoA molecule: 3 NADH, 1 FADH2, 1 GTP (converted to ATP) produced
  • Releases 2 CO2 molecules as waste products
  • Key enzymes:
    • Citrate synthase (condensation of acetyl-CoA and oxaloacetate to citrate)
    • Isocitrate dehydrogenase (conversion of isocitrate to α-ketoglutarate; produces NADH and releases 2 CO2)
    • α-ketoglutarate dehydrogenase (conversion of α-ketoglutarate to succinyl-CoA; produces NADH and releases CO2)
    • Succinate dehydrogenase (oxidation of succinate to fumarate; reduces FAD to FADH2)

Oxidative Phosphorylation

  • Final stage in cellular respiration, occurs on the inner mitochondrial membrane
  • Two stages: electron transport chain (ETC) and chemiosmosis
  • Electron Transport Chain (ETC):
    • NADH and FADH2 donate electrons to the ETC, composed of protein complexes and electron carriers
    • Electrons lose energy as they pass through complexes, releasing energy that pumps H+ into the intermembrane space
    • Complexes:
      • Complex I (NADH dehydrogenase): Oxidizes NADH, transfers electrons to ubiquinone (Q), pumps protons
      • Complex II (Succinate dehydrogenase): Transfers electrons from FADH2 to Q, no proton pumping
      • Complex III (Cytochrome bc1 complex): Passes electrons, pumps protons
      • Complex IV (Cytochrome c oxidase): Transfers electrons to oxygen (final electron acceptor), forms water
  • Chemiosmosis:
    • ATP synthase uses the proton gradient generated by the ETC to synthesize ATP from ADP and inorganic phosphate
  • Outputs approximately 26-28 ATP per glucose molecule.

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Description

This quiz explores the process of cellular respiration, focusing on glycolysis, the first stage that occurs in the cytoplasm. Participants will learn about the investment and payoff phases, key enzymes involved, and the overall conversion of glucose into ATP. Test your understanding of how energy is produced in eukaryotic cells.

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