Biology Stage 2: Krebs Cycle (Aerobic)

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Questions and Answers

What is the main purpose of Acetyl CoA in the Krebs Cycle?

It acts as an oxygen donor in the process.
It enters a series of reactions to release energy. (correct)
It is used to produce ATP directly.
It initiates the breakdown of glucose into pyruvic acid.

Which component is formed when NAD+ combines with hydrogen ions and high-energy electrons?

FADH2
NADH (correct)
Adenosine Triphosphate
Carbon Dioxide

Which of the following is NOT a product of the Krebs Cycle?

Hydrogen Ions
Glucose (correct)
ATP
Carbon Dioxide

In which part of the cell does the Krebs Cycle occur?

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

What role do the hydrogen ions play in the Krebs Cycle?

<p>They help in forming NADH for the electron transport system. (C)</p> Signup and view all the answers

Flashcards

Krebs Cycle

A metabolic cycle occurring in the mitochondrial matrix that breaks down Acetyl CoA, releasing carbon dioxide, hydrogen ions, and electrons.

Acetyl CoA

A 2-carbon molecule that enters the Krebs Cycle, formed from the breakdown of pyruvate.

NAD+

An electron carrier that picks up electrons and protons during the Krebs Cycle, ultimately transporting them to the electron transport chain.

ATP

The primary energy currency of the cell, produced in various cellular respiration processes.

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Electron Transport Chain

A series of reactions that occurs in the inner mitochondrial membrane, using electrons carried by NADH to generate a proton gradient, driving ATP production.

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Study Notes

Stage 2: Krebs Cycle (Aerobic)

Krebs cycle occurs in the mitochondrial matrix
Requires oxygen (aerobic)
Pyruvic acid, a molecule from glycolysis, enters the mitochondrion
Each molecule of pyruvic acid is broken down to one molecule of carbon dioxide and a 2-carbon molecule called Acetyl CoA
Acetyl CoA enters the Krebs cycle, a series of reactions
In the reactions of the Krebs cycle, the molecule breaks down and releases carbon dioxide molecules, hydrogen ions (protons), and electrons
Hydrogen ions and high-energy electrons combine with the electron acceptor NAD+ to form NADH
NAD+ is short for nicotinamide adenine dinucleotide

Products of Krebs Cycle (Fate)

ATP: releases energy, e.g. for active transport
Carbon dioxide: released into the atmosphere. Used in photosynthesis by plants
Hydrogen ions (H+) and electrons: Trapped by NAD+ to form NADH. This NADH is transported to the electron transport system.