Glucose is an energy rich molecule. If the energy were released quickly in an uncontrolled manner enough heat can be released to destroy the cell. Click to see a demonstration of the amount of energy in glucose. Energy is released from a glucose molecule in the cell slowly and in a controlled manner involving many chemical reactions. The amount of energy that can be released from these reactions depends on the presence of oxygen.
Aerobic respiration involves the breakdown of organic molecules in a three part process, which includes glycolysis, the Krebs cycle and the mitochondrial electron transport chain. Glycolysis produces products that feed into the Krebs cycle and the Krebs cycle produces products that feed into the electron transport chain. Click to see a summary of inputs and outputs of each stage of aerobic cellular respiration process
The first step to the breakdown of glucose is glycolysis. Glycolysis occurs in the cytosol and through a number of chemical reactions glucose is split into two pyruvate molecules with the net release of two ATP molecules. It takes two ATP molecules to split the glucose molecule but four molecules of ATP are produced.
Glycolysis occurs rapidly and in the absence of oxygen.
The next step in the breakdown of glucose depends on the absence or presence of oxygen.
If there is no oxygen present pyruvate is converted into lactic acid in most animals and into ethanol and carbon dioxide as occurs in certain microorganisms. This is known as fermentation and no more ATP is produced.
However, in the presence of oxygen, pyruvate enters the mitochondria, bonded to a coenzyme, where it undergoes complete breakdown in a process called the Krebs Cycle. Products of the Krebs cycle are then fed into the electron transport chain where the bulk of ATP molecules are produced. Below is the breakdown of ATP molecules produced at each step.
Glycolysis => 2 ATP
Krebs Cycle =>2 ATP
Electron Transport Chain:=> 32-34 ATP
So net energy production = 36-38 ATP
Carbon and hydrogen atoms, stripped off the pyruvate molecules, form carbon dioxide and water respectively. Electrons go through a number of reactions to release their energy in the formation of ATP. Finally, the electrons combine with hydrogen ions (H+) and oxygen to form water. The simplified overall aerobic breakdown of glucose is shown below.
C6H12O6 + 6O2 => 6CO2 + 6H2O + 36-38 ATP
The breakdown of glucose yields energy. The amount of energy released by a single glucose molecules depends on:
Glucose is split into two pyruvate molecules:
Aerobic respiration:
The purpose of coenzymes during cellular respiration is to:
Most of the ATP produced during aerobic respiration occurs:
When an athlete is undergoing strenuous exercise, most of the energy comes from:
Water is formed during respiration:
Most of the ATP formed during aerobic respiration is formed by:
A simplified overview of the aerobic cellular respiration process is given on the left.
In the absence of oxygen for every glucose molecule
The overall equation for aerobic cellular respiration is
C6H12O6 + 6O2 => 6CO2 + 6H2O
.
The water is produced in the
Processes in the brown and red region take place in the
and only in the presence of
Consider the animation on the right.
Water is produced in the
Pyruvate is converted to acetyl CoA in the
Cytochromes are proteins that makeup the
The bulk of the ATP molecules produced during aerobic cellular respiration are produced in the .
The Krebs cycle occurs in the and is where pyruvate acetyl CoA is broken down into carbon dioxide with the net release of
The reaction represented by the equation below is that of
C6H12O6 + 6O2 ---> 6CO2 + 6H2O
The process by which chemical energy in food is converted into ATP is known as
NAD+ and FAD are molecules that take part in the process of aerobic cellular respiration. What is their function?
