Krebs Cycle and Cellular Respiration Quiz

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Questions and Answers

What molecule is produced when flavin adenine dinucleotide (FAD) accepts two hydrogen atoms?

NADH

TPP

FADH2 (correct)

FADH

Which coenzyme is NOT required for the oxidation of pyruvate to Acetyl-CoA?

CoA-SH

ATP (correct)

NAD+

FAD

What is the main function of the intermediates produced during the Krebs cycle?

To facilitate protein synthesis

To transport electrons in glycolysis

To be used in fatty acid and sterol synthesis (correct)

To generate ATP only

The overall reaction of decarboxylation and oxidation of pyruvate requires which component?

TPP Signup and view all the answers

What is the purpose of the mnemonic for memorizing the names of the Krebs cycle intermediates?

To facilitate memorization for synthesis applications Signup and view all the answers

What defines a reducing equivalent in biochemistry?

A chemical species which transfers the equivalent of one electron in redox reactions Signup and view all the answers

Which is the last electron acceptor in the electron transport chain?

Oxygen Signup and view all the answers

What is the function of ATP synthase in oxidative phosphorylation?

To synthesize ATP from ADP and Pi Signup and view all the answers

What is the primary role of the malate-aspartate shuttle in cellular respiration?

To transport NADH across the mitochondrial membrane Signup and view all the answers

How many ATP molecules are produced per molecule of NADH in oxidative phosphorylation?

2.5 Signup and view all the answers

How many ATP molecules are generated from one full cycle of the Krebs cycle?

2 ATP Signup and view all the answers

Which complex in the electron transport chain is inhibited by cyanide?

Complex IV Signup and view all the answers

Which complex is NADH first transferred to in the electron transport chain?

Complex I Signup and view all the answers

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

O2 Signup and view all the answers

What is the primary role of protons in oxidative phosphorylation?

To build a concentration gradient used to generate ATP Signup and view all the answers

In which organs is the glycerol 3-phosphate shuttle primarily active?

Skeletal muscle and brain Signup and view all the answers

Which of the following best describes oxidative phosphorylation?

The process of ATP formation from electron transfer via electron carriers Signup and view all the answers

In which part of the mitochondria does the electron transport chain occur?

Inner mitochondrial membrane Signup and view all the answers

How many molecules of ATP are produced from one FADH2 in the electron transport chain?

1.5 ATP Signup and view all the answers

What type of molecules serve as the primary energy source during cellular respiration?

Carbohydrates, lipids, and proteins Signup and view all the answers

Which reaction releases the most NADH molecules in the Krebs cycle?

Conversion of isocitrate to alpha-ketoglutarate Signup and view all the answers

What is the main product of the oxidative phosphorylation stage of cellular respiration?

ATP and water Signup and view all the answers

Which electron carriers are involved in cellular energy metabolism?

NADH and FADH2 Signup and view all the answers

In which part of the mitochondria does the citric acid cycle occur?

Mitochondrial matrix Signup and view all the answers

What is produced from the oxidation of glucose, fatty acids, and other metabolic fuels?

Acetyl-CoA Signup and view all the answers

Which component of the mitochondria is primarily involved in ATP synthesis during oxidative phosphorylation?

Cristae Signup and view all the answers

What is a primary function of the mitochondria aside from generating ATP?

Regulating cellular metabolic activity Signup and view all the answers

Which statements about NADH are true?

It is produced during glycolysis. Signup and view all the answers

Which vitamin is necessary for the formation of FAD, an important electron carrier?

Vitamin B2 (riboflavin) Signup and view all the answers

Study Notes

Energy Metabolism

Energy metabolism is the process where organisms transform and use energy from food.
The source of energy for cells is the oxidation of fuel molecules (carbohydrates, lipids, and proteins).
It's a series of complex chemical reactions to produce ATP, the cell's primary energy currency.

Cellular Respiration Stages

Metabolic fuel oxidation (acetyl-CoA production): This initial stage involves breaking down fuels like glucose, fatty acids, and amino acids to produce acetyl-CoA.
Citric Acid Cycle (Krebs Cycle): Pyruvate is converted to CO2 and reduced electron carriers (NADH and FADH2) within the mitochondrial matrix.
Oxidative Phosphorylation: Electrons from NADH and FADH2 are transferred along the electron transport chain, generating ATP and water. This final stage occurs on the inner mitochondrial membrane.

Mitochondria Structure and Function

Mitochondria are double-membrane organelles often called the "powerhouses of cells" due to their role in ATP production.
Double membrane: An outer membrane and an inner membrane.
Intermembrane space: The space between the outer and inner membranes.
Cristae: Inward folds of the inner membrane where the electron transport chain proteins are located.
Matrix: The space enclosed by the inner membrane containing enzymes, proteins, DNA, and ribosomes.
DNA: Mitochondria contain their own DNA, allowing them to self-replicate to some degree.

Electron Carriers

NADH (Nicotinamide Adenine Dinucleotide): An important electron carrier, crucial for cellular respiration.
FADH2 (Flavin Adenine Dinucleotide): Another critical electron carrier often associated with the citric acid cycle.
Both NADH and FADH2 are reduced forms of these carriers. They pick up electrons from other reactions and carry them to the ETC and participate in electron transfer.

Oxidative Phosphorylation (OXPHOS) and Electron Transport Chain (ETC)

OXPHOS: The process that generates a majority of the cell's ATP.
ETC: A series of electron carriers embedded in the inner mitochondrial membrane. Electrons are passed along this chain, releasing energy used to pump protons (H⁺) across the membrane, creating a gradient.
Protons flow back across the membrane through ATP synthase, a protein that uses the energy to produce ATP.
This proton gradient is driven by the reactions of the electron transport chain.
Oxygen is the final electron acceptor in this chain.

Shuttles (NADH Transport)

NADH produced in glycolysis is typically not capable of directly crossing into the mitochondria.
Special "shuttles", such as the glycerol-3-phosphate shuttle and malate-aspartate shuttle, carry electrons from NADH in the cytoplasm to produce NAD+ in the mitochondrial matrix to allow participation in the ETC process. These shuttle systems efficiently transfer electrons to produce ATP.
Different tissues/organs may utilize different shuttles.

ATP Yield

The complete oxidation of a glucose molecule can result in a variable number of ATP molecules, depending on the specific shuttle mechanisms used.
Various factors affect the final ATP yield.

Inhibitors of OXPHOS

Certain molecules interfere with the electron transport chain or ATP synthase, hindering ATP production.
Examples include rotanones, cyanide, oligomycin, and others.

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Description

Test your knowledge on the Krebs cycle and the processes of cellular respiration. This quiz will cover key aspects such as coenzymes involved, the role of intermediates, and important reactions like decarboxylation. Prepare to challenge your understanding of these crucial biochemical pathways!