Cell Respiration: Oxidative Phosphorylation

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Questions and Answers

What is the primary function of oxidative phosphorylation in cellular respiration?

To convert ADP into ATP (correct)

To break down glucose into acetyl CoA

To produce glucose from pyruvate

To synthesize NADH and FADH2

Which component of the Electron Transport Chain (ETC) is responsible for carrying a single electron from complex III to complex IV?

Coenzyme Q

NADH dehydrogenase

Succinate dehydrogenase

Cytochrome c (correct)

Which of the following statements accurately describes a role of Coenzyme Q in oxidative phosphorylation?

It oxidizes NADH to form ATP

It carries two electrons from complex IV to complex III

It can freely diffuse within the lipid bilayer of the inner mitochondrial membrane (correct)

It is a water-soluble protein in the intermembrane space

How many ATP are generated from one glucose molecule during glycolysis?

2 ATP (net) Signup and view all the answers

What type of reaction primarily occurs at Complex I of the Electron Transport Chain?

Oxidation of NADH Signup and view all the answers

Which of the following is NOT a byproduct of one glucose molecule during oxidative phosphorylation?

2 ATP Signup and view all the answers

During oxidative phosphorylation, the reduced electron carriers primarily originate from which metabolic processes?

Glycolysis and the TCA cycle Signup and view all the answers

Which of the following best represents the role of ATP in cellular metabolism?

It is used as the immediate source of energy for cellular processes Signup and view all the answers

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

Oxygen Signup and view all the answers

How many protons are transported across the inner mitochondrial membrane to synthesize one ATP molecule?

3 H+ Signup and view all the answers

What is the primary function of ATP synthase?

To phosphorylate ADP Signup and view all the answers

What role do uncouplers like DNP play in oxidative phosphorylation?

Reduce ATP production Signup and view all the answers

What is the purpose of the binding-change model in the function of ATP synthase?

To eject ATP from the β-ATP site Signup and view all the answers

Which of the following statements is true regarding the proton gradient produced during oxidative phosphorylation?

It decreases the pH in the intermembrane space Signup and view all the answers

What effect does oligomycin have on cellular respiration?

Inhibits ATP synthase Signup and view all the answers

Which complex in the electron transport chain is known to be blocked by cyanide?

Complex IV Signup and view all the answers

What is one outcome of the electrochemical gradient created by redox reactions in mitochondria?

Increased oxygen consumption Signup and view all the answers

What is thermogenin, also known as UCP1, primarily responsible for?

Generating heat Signup and view all the answers

Study Notes

Oxidative Phosphorylation Overview

Cellular respiration involves breaking down glucose to produce ATP, the energy currency of cells.
The process occurs in three major stages:
- Acetyl CoA production (glycolysis)
- Acetyl CoA oxidation (TCA cycle)
- Electron transfer and oxidative phosphorylation.

Glycolysis and Energy Yield

Glycolysis produces a net yield of 2 ATP and 2 NADH per glucose molecule.
Pyruvate decarboxylation generates 2 NADH (one for each pyruvate).
The TCA cycle, which runs twice per glucose, yields:
- 6 NADH
- 2 FADH2
- 2 GTP (converted to ATP).

Role of ATP and Electron Carriers

ADP is compared to a partially charged battery, while ATP is a fully charged battery.
The electron transport chain (ETC) acts like a charger, converting ADP into ATP.
The conclusion of energy production is through oxidative phosphorylation, utilizing reduced electron carriers from previous processes.

Electron Transport Chain Components

The ETC consists of 5 protein complexes:
- Complex I: NADH dehydrogenase
- Complex II: Succinate dehydrogenase
- Complex III: Ubiquinone:cytochrome c oxidoreductase
- Complex IV: Cytochrome oxidase
Additionally, two mobile electron carriers are involved:
- Coenzyme Q (ubiquinone) shuttles electrons between complexes.
- Cytochrome c transfers electrons from complex III to complex IV.

Electron Flow Dynamics

Electron flow within the ETC is driven by increasing standard electrode potentials from negative to positive.
Electrons lose energy as they move through the chain, which can be harnessed for work, with oxygen serving as the final electron acceptor.

Chemiosmotic Coupling and ATP Synthesis

Protons (H+) are pumped into the intermembrane space, creating an electrochemical gradient known as chemiosmotic coupling.
Protons flow through ATP synthase (Complex V) to convert ADP and inorganic phosphate (Pi) into ATP.
ATP synthase comprises two components:
- FO: Transports H+ across the membrane.
- F1: The catalytic site in the matrix that synthesizes ATP.

ATP Yield and Mechanism

Approximately 30-32 ATP molecules are generated from the complete oxidation of one glucose molecule.
The actual yield can vary due to proton leakages across the inner mitochondrial membrane.

Uncoupling Mechanisms in Oxidative Phosphorylation

Uncoupling disconnects the ETC from ATP synthesis and can be caused by uncouplers that allow protons to move across membranes independently.
Uncoupling results in reduced ATP production, increased O2 consumption, and heat generation.
Examples of uncouplers include:
- Cyanide, which blocks Complex IV.
- Venturicidin/oligomycin, which inhibits ATP synthase.
- Dinitrophenol (DNP): an early diet pill that acts as a protonophore, bypassing ATP synthase, potentially leading to lethal effects.

Uncoupling Protein

Uncoupling protein 1 (UCP1 or thermogenin) facilitates heat generation by dissipating the proton gradient, promoting energy expenditure without ATP production.

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Description

This quiz covers the process of oxidative phosphorylation within cell respiration. It reviews how glucose is broken down to produce ATP, the role of adenosine tri-phosphate as the energy currency, and the stages involved, from glycolysis to the TCA cycle and electron transfer. Test your understanding of these critical biochemical processes!