This document requires Netscape 3.x or compatible Web Browser.

DB Logo

DENF 1521 Biochemistry

blue line

Oxidative Phoshorylation

Lesson 5.1
Overview

Instructions
  1. Please enter both your name & student identification number first below to be sure you get credit (before doing anything else).
  2. Then study Lesson 5.1 at your own pace. When Practice Exercises appear, click the appropriate button to choose your answer. Then press the "Get Feedback..." button to find out how you did. Continue to try again if you miss.
  3. After studying Lesson 5.1, and responding to all practice exercises, follow instructions at the end to submit your responses for Lesson 5.1 participation credit.
NAME:
ID # (No dashes please):
Dental Biochemistry Brush
DB Bullet Lesson 5.1 Oxidative phosphorylation overview

5.1 An overview of the reactions of the
oxidative phosphorylation pathway

5.1A Lesson objectives

The objectives of this lesson are to understand the

  1. Function of oxidative phosphorylation in the cell
  2. Importance of the mitochondrial structure
  3. Sources of NADH and FADH2 for electron transport
  4. Basis of oxidation/reduction reactions

5.1B Introduction

Oxidative phosphorylation is the process by which ATP is formed as electrons are transferred from NADH or FADH2 to molecular oxygen (O2) by a series of electron carriers. The energy released form the oxidation of glucose, fatty acids, and amino acids is stored as the reduced coenzymes NADH or FADH2. There is a step by step transfer of electrons from NADH or FADH2 to specific complexes which are part of the electron transport chain. These respiratory assemblies are located in the inner mitochondrial membrane. The ulimate acceptor of these electrons is O2. Another important feature to remember is that the process of electron transport and ATP synthesis are distict, but coupled processes.

The structure of the mitochondria is a very important feature of the oxidative phosphorylation process. The diagram below reviews the important properties of the mitochondria with respect to oxidative phosphorylation. It is very important to remember that the inner mitochondrial membrane is impermeable to ions and small molecules.

This structure is very important because the process of electron transport establishes a proton gradient which is then used to synthesize ATP. If the inner mitochondrial membrane was not impermeable to protons, no gradient could be extablished. In a later lesson, you will see how compounds which break down the permeability barrier prevent the synthesis of ATP. The following diagram illustrates the relationship between electorn transport and ATP synthesis.

5.1C Sources of reduced coenzymes

The sources of the reduced coenzymes NADH and FADH2 come mainly from the oxidation of glucose, fatty acids, and amino acids to form Acetyl CoA.

Dental Biochemistry Brush
DB Bullet Lesson 5.1 Oxidative phosphorylation overview

CAC introduction
Practice
Exercise 1: 		The inner mitochondrial membrane is impermeable to ions and small molecules.

No Response
True
False

Practice
Exercise 2: 		The ultimate acceptor of the electrons from the reduced coenzymes which enter oxidative phosphorylation is

No Response
ATP
Acetyl CoA
Cytochrome c
O2


Practice
Exercise 3: 		The establishment of a proton gradient across the inner mitochondrial membrane is due to the

No Response
Synthesis of ATP
Passage of electrons between carriers
Conversion of NADH to NADPH
Hydrolysis of ATP


Practice
Exercise 4: 		The respiratory assemblies required for the reactions of oxidative phosphorylation are found on the outer mitochondrial membrane.

No Response
True
False

Dental Biochemistry Brush
DB Bullet Lesson 5.1 Oxidative phosphorylation overview

5.1D Redox potential and Free Energy

This section is a review of the basic principles needed to understand biological oxidative phosphorylation. If you need additional information consult a basic biochemistry or chemistry text or see Oxidation - Reduction - "REDOX" Reactions.

Oxidation-reduction (Redox) reactions involve the transfer of electrons from one substance to another. Redox reactions must occur together. One compound must lose electrons and the other gain electrons. The substance which loses electrons is called the reducing agent while the substance which gains electrons is called the oxidizing agent. The reduction potential is the measure of the ability of one compound to reduce another. For example, in the following reaction O2 is the reducing agent (and is oxidized) and NADH is the oxidizing agent (and is reduced).

1/2 O2 + NADH + H+ H2O + NAD+

Dental Biochemistry Brush
DB Bullet Lesson 5.1 Oxidative phosphorylation overview

Redox potential/Free energy
Practice
Exercise 5: 		A compound which loses electrons as part of a reaction is classified as an oxidizing agent.

No Response
True
False


Practice
Exercise 6: 		If a reaction has an overall E0' which is positive, then the reaction is a favorable reaction.

No Response
True
False


Dental Biochemistry Brush
DB Bullet Lesson 5.1 Oxidative phosphorylation overview

5.1E Summary

After completing this lesson you should understand the following general aspects concerning oxidative phosphorylation.
  1. The transport of electrons form NADH and FADH2 provide "energy" for the synthesis of ATP
  2. The integrety of the mitochondrial structure is essential for oxidative phosphorylation
  3. NADH and FADH2 used for electron transport result from the oxidation of fuels, mainly glucose
  4. Oxidation/reduction reactions are coupled
  5. The ultimate acceptor of electrons in oxidative phosphorylation is molecular oxygen (O2)

line
Final Instructions

Press Button below for your score.

  • After completing Lesson 5.1, including all practice exercises, press the "Submit... " button below for Lesson 5.1 research participation credit.
  • After you press "Submit..." it is possible Netscape may tell you it is unable to connect because of unusually high system demands. If you receive no error message upon submission you're OK. But, if Netscape gives you an error message after you press the "Submit..." button, wait a moment and resubmit or consult the attendant.
  • Finally, press the "Table of Contents..." button below to correctly end Lesson 5.1 and return to the Table of Contents so you may continue with Lesson 5.2.

End Lesson 5.1
Overview of oxidative phosphorylation



red line