Cellular Respiration Overview and Stages

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Questions and Answers

What is the main role of the electron transport chain in cellular respiration?

To facilitate fermentation pathways in the absence of oxygen.

To directly produce ATP through oxidative phosphorylation.

To convert NADH back to NAD+ in the mitochondrial matrix.

To break the free-energy drop from glucose to O2 into smaller steps. (correct)

How does the proton-motive force contribute to ATP synthesis?

By accumulating protons in the intermembrane space for storage.

By allowing protons to enter the mitochondrial matrix freely.

By creating a gradient that drives the action of ATP synthase. (correct)

By directly converting ADP to ATP.

During glycolysis and fermentation, what is the ultimate fate of NADH?

It is used to produce ATP directly.

It combines with oxygen to form water.

It is converted to glucose for energy storage.

It is oxidized back to NAD+ by transferring electrons to pyruvate. (correct)

What is the maximum yield of ATP from one glucose molecule during cellular respiration?

32 ATP Signup and view all the answers

Which of the following is a product of alcohol fermentation?

Ethanol Signup and view all the answers

In lactic acid fermentation, which compound is produced from pyruvate?

Lactate Signup and view all the answers

What does chemiosmosis specifically refer to in cellular respiration?

The utilization of H+ gradients to drive ATP synthesis. Signup and view all the answers

How does the energy released during the electron transport chain get utilized?

To drive the phosphorylation of ADP to ATP through the action of ATP synthase. Signup and view all the answers

What is the primary site of cellular respiration in a cell?

Mitochondrion Signup and view all the answers

Which process precedes the citric acid cycle during cellular respiration?

Glycolysis Signup and view all the answers

During glycolysis, what is the overall net gain per molecule of glucose?

2 NADHs and 2 ATPs Signup and view all the answers

What molecule is formed after pyruvate undergoes oxidation in the mitochondria?

Acetyl CoA Signup and view all the answers

What is produced as a waste product in the citric acid cycle?

CO2 Signup and view all the answers

How many ATP molecules are generated per turn of the citric acid cycle?

1 ATP Signup and view all the answers

What is the role of NAD+ during the oxidation of pyruvate?

To be reduced to NADH Signup and view all the answers

In oxidative phosphorylation, what happens to electrons as they move through the electron transport chain?

They lose free energy Signup and view all the answers

Study Notes

Cellular Respiration Overview

Cellular respiration is a set of catabolic pathways that break down nutrients into usable chemical energy (ATP)
It includes both aerobic and anaerobic respiration.
Mitochondrion is the site for cellular respiration

Stages of Cellular Respiration

Glycolysis: Breaks down glucose into two pyruvate molecules in the cytosol
- Two stages: energy investment, energy harvest
- Net gain: two NADHs, two ATPs per glucose molecule
Pyruvate Oxidation: Pyruvate moves into the mitochondrial matrix and is further oxidized to Acetyl CoA
- A molecule of CO2 is removed and NAD+ is reduced to NADH during this step
- Acetyl CoA enters the Krebs cycle
Krebs Cycle (Citric Acid Cycle):
- Oxidizes organic fuel derived from pyruvate generating 1 ATP, 3 NADH, and 1 FADH2 per turn
- Produces 2 CO2 as a waste product (total of 3 CO2, including one from pyruvate oxidation.)
- The cycle runs twice per glucose molecule consumed.
- Has eight steps, each catalyzed by a specific enzyme
- Acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate
- The next seven steps decompose citrate, making the process a cycle.
- NADH and FADH2 carry electrons to the electron transport chain.
Oxidative Phosphorylation:
- Electrons drop in free energy as they are transferred down the chain.
- It finally passes to O2 to form H₂O
- Electron transport chain breaks the large free-energy drop from glucose to O2 into smaller steps.
- This releases energy in manageable amounts.
- No ATP is produced directly by the chain
- Chemiosmosis is the energy coupling mechanism in this stage.
  - Electrons are passed down the electron transport chain. H+ is pumped from the mitochondrial matrix to the intermembrane space.
  - H+ moves down its concentration gradient back across the membrane, passing through the protein complex ATP synthase.
  - This causes ATP synthase to spin, catalyzing the phosphorylation of ADP to ATP.
  - The H⁺ gradient is referred to as a proton-motive force.
  - Certain electron carriers accept and release H⁺ along with the electrons.
About 34% of the energy in glucose is converted into ATP (30 or 32) during cellular respiration. The rest is lost as heat

Anaerobic Respiration (Fermentation):

Fermentation is an extension of glycolysis that oxidizes NADH by transferring electrons to pyruvate
Two common types:
- Alcohol fermentation (used in brewing, winemaking, and baking)
- Lactic acid fermentation (used in cheese and yogurt production; muscle cells use this during strenuous exercise when oxygen is scarce)

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Description

This quiz explores the fundamental processes of cellular respiration, including both aerobic and anaerobic pathways. It covers key stages such as glycolysis, pyruvate oxidation, and the Krebs cycle, while highlighting the production of ATP and other byproducts. Test your understanding of how cells convert nutrients into usable energy.