Metabolism and Cellular Respiration

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Questions and Answers

What role does NADH play in cellular respiration?

It directly produces ATP by itself.

It serves as the final electron acceptor.

It transports protons to other cellular membranes.

It is oxidized to NAD+ and carries electrons to the ETC. (correct)

How does FADH2 differ from NADH in terms of ATP production?

FADH2 contributes to fewer ATP molecules compared to NADH. (correct)

FADH2 produces the same amount of ATP as NADH.

FADH2 produces more ATP than NADH.

FADH2 carries electrons to an earlier point in the ETC than NADH.

What is the final electron acceptor in the electron transport chain?

FADH2

NADH

Oxygen (correct)

Carbon dioxide

What happens in the absence of oxygen during cellular respiration?

Oxidative phosphorylation halts and cells rely on fermentation. Signup and view all the answers

During the process of cellular respiration, what happens to hydrogen atoms from glucose?

They are transferred to NAD+ to form NADH before reaching oxygen. Signup and view all the answers

What is the primary difference between fermentation and cellular respiration?

Cellular respiration produces more ATP than fermentation. Signup and view all the answers

Which of the following statements correctly describes catabolism?

It is the process of breaking down molecules to release energy. Signup and view all the answers

What is produced when pyruvate is oxidized to acetyl CoA?

Carbon dioxide and NADH Signup and view all the answers

During which stage of cellular respiration is glucose completely oxidized?

Citric acid cycle Signup and view all the answers

Which type of phosphorylation occurs during cellular respiration when ATP is formed from ADP using energy from the electron transport chain?

Oxidative phosphorylation Signup and view all the answers

What is the role of enzymes in the context of cellular respiration?

To catalyze the breakdown of organic molecules to release energy. Signup and view all the answers

What is the yield of ATP from one molecule of glucose during fermentation?

2 Signup and view all the answers

Which molecule is primarily used by cells for energy storage and transfer?

ATP Signup and view all the answers

What is the primary purpose of cellular respiration?

To release energy by breaking down complex molecules Signup and view all the answers

What happens to glucose during cellular respiration?

It is oxidized, releasing energy Signup and view all the answers

What role do electron carriers like NADH and FADH serve in cellular respiration?

They transfer electrons during energy production Signup and view all the answers

What is produced as a result of the oxidation of glucose in cellular respiration?

ATP and heat along with carbon dioxide and water Signup and view all the answers

What happens to ATP after it transfers its energy to a molecule?

It converts into adenosine diphosphate (ADP) Signup and view all the answers

During cellular respiration, what is the final electron acceptor?

Oxygen Signup and view all the answers

Which statement accurately describes oxidation in the context of cellular respiration?

It is the loss of electrons from a molecule Signup and view all the answers

Why is the 'fall' of electrons during cellular respiration described as stepwise?

It prevents a sudden release of energy Signup and view all the answers

What occurs during phosphorylation related to ATP?

ATP transfers a phosphate group, activating a molecule Signup and view all the answers

What is the general equation for cellular respiration?

C6H12O6 + 6O2 → 6H2O + 6CO2 + energy Signup and view all the answers

Study Notes

Metabolism

Anabolism builds complex molecules from simpler ones, using energy (e.g., protein synthesis).
Catabolism breaks down molecules, releasing energy (e.g., cellular respiration).

Catabolism

Fermentation occurs without oxygen, producing ATP only through glycolysis (2 ATP per glucose).
Cellular Respiration requires oxygen and produces ATP via glycolysis, the citric acid cycle, and oxidative phosphorylation (up to 32 ATP per glucose).

Energy Harvest Principles

Cellular respiration and fermentation are catabolic energy-yielding pathways.
Cells use ATP for work.
Redox reactions release energy as electrons move between atoms.
Cellular respiration involves electrons “falling” from organic molecules to oxygen.
The "fall" of electrons is stepwise and requires carriers.

Cellular Respiration

Cellular respiration is a catabolic pathway that breaks down complex molecules, releasing energy.
Food is fuel for cellular respiration.
It involves movement of electrons (gain or loss).
The equation is: Organic compounds + O2 → CO2 + H2O + energy.
We will study the breakdown of glucose as an example.

ATP (Adenosine Triphosphate)

Consists of adenine, ribose (a sugar), and three phosphate groups.
Stores energy in the high-energy bonds between its phosphate groups.
Transfers energy for cellular work by releasing one phosphate group to form ADP.

Phosphorylation

The transfer of the terminal phosphate group from ATP to another molecule.
Changes the shape of the receiving molecule to become active.
When the phosphate group leaves, the molecule returns to its inactive shape.

Redox Reactions in Cellular Respiration

Glucose and fuel molecules are oxidized, releasing energy.
Glucose is oxidized, oxygen is reduced, and electrons lose potential energy.
H+ is the source of electrons transferred to O-.
Glucose has abundant hydrogen, a source of electrons that “fall” to oxygen.
Enzymes (dehydrogenases) lower activation energy, allowing fuels to be oxidized.
The resulting energy is used for ATP synthesis.

Oxidation and Reduction

Oxidation: loss of electrons from a molecule.
Reduction: gain of electrons by a molecule.
Redox reactions are essential for energy production in cells.

Role of NADH in Cellular Respiration

Carries electrons to the electron transport chain (ETC).
NADH is oxidized back to NAD+ in the ETC, allowing ATP production through oxidative phosphorylation.

Role of FADH2 in Cellular Respiration

Carries electrons to the ETC but feeds them at a later point than NADH.
Contributes to the production of fewer ATP molecules compared to NADH.

Role of Oxygen in Cellular Respiration

Oxygen is the final electron acceptor in the ETC.
Without oxygen, the ETC cannot function.
Oxygen combines with electrons and protons to form water, by-product of cellular respiration.
Without oxygen, oxidative phosphorylation halts, forcing cells to rely on fermentation or anaerobic respiration.

Summary of Electron "Fall" Steps during Respiration

The process of electrons falling from glucose to oxygen is gradual, not a single event.
Each step is catalyzed by a specific enzyme.
Hydrogen atoms from glucose first pass to the coenzyme NAD+ to form NADH.
Then, electrons from NADH move to the electron transport chain and finally to oxygen, releasing energy to form ATP.

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Description

Explore the concepts of metabolism, including anabolism and catabolism, with a focus on cellular respiration and fermentation. This quiz will test your knowledge on energy harvest principles and the pathways that yield energy in cells. Delve into how ATP is produced and the role of redox reactions in cellular processes.