Cellular Respiration and Glycolysis

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Questions and Answers

In cellular respiration, what is the primary role of ATP?

  • To act as an electron carrier.
  • To be oxidized into water.
  • To store and transport energy for cellular work. (correct)
  • To serve as the final electron acceptor.

During glycolysis, a single molecule of glucose is converted into:

  • one molecule of pyruvate.
  • two molecules of pyruvate. (correct)
  • one molecule of Acetyl CoA.
  • two molecules of Acetyl CoA.

Which of the following is NOT a product of glycolysis?

  • Pyruvate
  • ATP
  • FADH2 (correct)
  • NADH

What is the direct fate of pyruvate if oxygen is absent from a cell?

<p>It is reduced to either ethanol or lactate. (A)</p> Signup and view all the answers

The oxidation of pyruvate to Acetyl CoA occurs in which cellular location?

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

How many molecules of $CO_2$ are produced by the Krebs cycle from one molecule of Acetyl CoA?

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

How many ATP molecules are produced by substrate level phosphorylation (SLP) directly during the Krebs cycle per Acetyl CoA?

<p>1 (B)</p> Signup and view all the answers

In total, how many ATP molecules can be produced from 1 molecule of NADH via Oxidative Phosphorylation/Electron Transport Chain?

<p>3 (B)</p> Signup and view all the answers

Where is the electron transport chain (ETC) located in eukaryotic cells?

<p>The inner mitochondrial membrane (cristae) (D)</p> Signup and view all the answers

What is the role of NADH and FADH2 in oxidative phosphorylation?

<p>To donate electrons to the ETC. (B)</p> Signup and view all the answers

What is the function of the proton gradient generated by the ETC?

<p>To provide the energy for ATP synthesis via ATP synthase (D)</p> Signup and view all the answers

How many ATP molecules are synthesized for each NADH molecule that donates its electrons to the ETC in the mitochondrial matrix?

<p>3 ATP (C)</p> Signup and view all the answers

Why does FADH2 produce fewer ATP molecules than NADH in oxidative phosphorylation?

<p>FADH2 enters electrons into the ETC further down the chain, bypassing the first proton pump (B)</p> Signup and view all the answers

How many ATP molecules are generated when the cytoplasmic NADH produced during Glycolysis donates its electrons to the ETC?

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

What is the significance of the inner mitochondrial membrane's impermeability to NADH?

<p>It requires the usage of a shuttle mechanism resulting in fewer ATP from NADH generated during Glycolysis. (C)</p> Signup and view all the answers

Which process directly generates the proton gradient used for ATP synthesis in cellular respiration?

<p>The exergonic flow of electrons through the electron transport chain. (C)</p> Signup and view all the answers

During the oxidation of pyruvate to acetyl CoA, how many molecules of CO2 are evolved per molecule of glucose?

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

What is the net gain of ATP produced by substrate-level phosphorylation (SLP) during glycolysis per glucose molecule?

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

How many molecules of NADH are produced from one molecule of glucose during the Krebs cycle?

<p>6 (B)</p> Signup and view all the answers

Under anaerobic conditions, what is the primary role of fermentation?

<p>To regenerate NAD+ from NADH (A)</p> Signup and view all the answers

How many total ATP molecules are ideally generated per glucose molecule through oxidative phosphorylation in aerobic respiration?

<p>34 (D)</p> Signup and view all the answers

What is the location of beta oxidation of lipids within the cell?

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

If a molecule of glucose undergoes fermentation to ethanol, how many molecules of carbon dioxide are produced?

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

How many ATP equivalents are generated from the 2 FADH2 molecules produced during the Krebs cycle?

<p>4 (A)</p> Signup and view all the answers

Flashcards

Cellular Respiration

The process of converting macromolecules into ATP.

ATP

A small, usable form of energy produced in cellular respiration.

Stages of Cellular Respiration

Four key phases: Glycolysis, Oxidation of Pyruvate, Kreb's Cycle, Oxidative Phosphorylation.

Glycolysis

The first stage of cellular respiration, occurring in the cytosol, splitting glucose into pyruvate.

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Fate of Pyruvate

Determines if pyruvate undergoes further oxidation or fermentation based on oxygen presence.

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Oxidation of Pyruvate

The process in which pyruvate is converted to Acetyl CoA in the mitochondrial matrix.

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Kreb's Cycle

A series of reactions that oxidizes Acetyl CoA to produce ATP, NADH, and FADH2.

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Productions of Kreb's Cycle

Produces 2 CO2, 1 ATP, 1 FADH2, and 3 NADH per Acetyl CoA input.

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Oxidative Phosphorylation (OP)

Process of ATP production using the electron transport chain and oxygen.

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Electron Transport Chain (ETC)

A series of protein complexes that transfer electrons from NADH and FADH2 to oxygen.

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NADH and FADH2

Reduced coenzymes that deliver electrons to the ETC.

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Proton Gradient

Difference in H+ concentration across the mitochondrial membrane generating potential energy.

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ATP Synthase

Enzyme that synthesizes ATP by utilizing the energy from protons flowing back into the matrix.

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NADH ATP yield

Each NADH typically produces 3 ATP during oxidative phosphorylation.

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FADH2 ATP yield

Each FADH2 typically produces 2 ATP during oxidative phosphorylation.

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Glycolysis NADH exception

NADH from glycolysis yields only 2 ATP due to transport issues into mitochondria.

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Substrate Level Phosphorylation (SLP)

ATP production directly in glycolysis and Krebs cycle, without electron transport.

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Total ATP from Glycolysis

Glycolysis yields 4 ATP total, but 2 ATP are net gain after energy investment.

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Fermentation

Anaerobic process converting pyruvate into ethanol or lactate, regenerating NAD+.

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Beta Oxidation of Lipids

Process in the mitochondrial matrix that breaks down fatty acids for energy when O2 is present.

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NADH production

NADH is produced during glycolysis, oxidation of pyruvate, and Krebs cycle, critical for ATP generation.

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Study Notes

Cellular Respiration

  • Cellular respiration is a metabolic pathway that converts large energy molecules into smaller, more usable energy called ATP.
  • The overall reaction is: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (ATP)
  • Cellular respiration has four stages: Glycolysis, Oxidation of Pyruvate to Acetyl CoA, Krebs Cycle, and Oxidative Phosphorylation/Electron Transport Chain.

Glycolysis

  • Occurs in the cytoplasm, whether or not oxygen is present.
  • One 6-carbon glucose molecule is oxidized and split into two 3-carbon pyruvate molecules.
  • Two NAD+ are reduced to two NADH (each worth 2 ATP through OP/ETC).
  • Two ATP are consumed ("energy investment phase").
  • Four ATP are produced via Substrate-level phosphorylation ("energy yielding phase").
  • No FADH2 or CO2 is produced during glycolysis.

Oxidation of Pyruvate to Acetyl CoA

  • Occurs in the mitochondrial matrix only if oxygen is present.
  • Each 3-carbon pyruvate molecule is oxidized to a 2-carbon molecule of acetyl CoA.
  • One NAD+ is reduced to NADH (worth 3 ATP through OP/ETC) per pyruvate.
  • One molecule of CO2 is produced per pyruvate.
  • No ATP is consumed or produced by substrate-level phosphorylation.
  • No FADH2 is produced.

Krebs Cycle

  • Occurs in the mitochondrial matrix only if oxygen is present.
  • Acetyl CoA enters the cycle, and is completely oxidized to two CO2 molecules.
  • For every 2-carbon molecule of acetyl CoA that enters, the following are produced:
    • 2 CO2
    • 1 ATP by substrate-level phosphorylation
    • 1 FADH2 (worth 2 ATP by OP/ETC)
    • 3 NAD+ are reduced to 3 NADH (each worth 3 ATP by OP/ETC), for a total of 9 ATP.

Oxidative Phosphorylation (OP/ETC)

  • The electron transport chain (ETC) is located in the inner mitochondrial membrane (cristae).
  • It is only operational if oxygen is present.
  • Electrons from NADH and FADH2 enter the ETC.
  • Kinetic energy from the electron flow is used to pump H+ ions (protons) from the matrix into the intermembrane space.
  • The potential energy of the H+ gradient is converted to kinetic energy as the H+diffuse back into the matrix through ATP synthase, producing ATP.
  • Each NADH yields 3 ATP, and each FADH2 yields 2 ATP.

Fate of Pyruvate

  • If oxygen is present, pyruvate enters the mitochondrial matrix and is further oxidized to acetyl CoA.
  • If oxygen is absent, pyruvate remains in the cytosol and is reduced to either ethanol (alcohol fermentation) or lactate (lactic acid fermentation).

Beta Oxidation of Lipids

  • Occurs in the mitochondrial matrix if oxygen is present.
  • Lipids are broken down into 2-carbon molecules of acetyl CoA.
  • Acetyl CoA enters the Krebs Cycle.
  • For each 2-carbon molecule of acetyl CoA, following are produced:
    • 2 CO2
    • 1 ATP by substrate-level phosphorylation
    • 1 FADH2 (worth 2 ATP)
    • 3 NADH (worth 9 ATP)

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