Oxygen is brought into the body through the nose. The air is warmed, and moistened in the sinuses. The air passes through the pharynx into the bronchi, through the bronchioles to the lungs. In the lungs, carbon dioxide and oxygen are exchanged.
Just as oxidation occurs in the internal combustion engine, oxidation in the cell produces the same by-products, carbon dioxide and water.
Where gasoline is the fuel in a car, sugar is the fuel in cells. In both cases energy is released from the chemical bonds of the fuel.
In the cell, this energy is used to perform life functions.
. Respiration is either aerobic or anaerobic. If it is aerobic, the cell takes in oxygen and gives off carbon dioxide. This is the most efficient form of respiration, yielding the most energy.
Anaerobic respiration does not require oxygen. This is fermentation. Anaerobic respiration occurs in muscle which is fatigued producing lactic acid. In fermentation by yeast, alcohol is produced.
This is the equation for the reaction involving the breakdown of glucose by oxidation into carbon dioxide and water. What is not shown in the equation, is the net yield of 36 ATP at the end of respiration. ATP is anmolecule used for storing energy. The energy is in the third phosphate bond of Adenosine Tri Phosphate.
As seen in the diagram below, respiration consists of three distinct chemical processes:
....glycolysis which is the splitting of sugar in the cytoplasm.
.....Kreb's cycle in the mitochondria where energy is released as bonds are borken.
......electron transport where the energy level of hydrogen is reduced through a series of cytochromes.
CGlycolysis refers to the breakdown of glucose. "Lysis" means to split. The result of glycolysis which occurs in the cytoplasm, is 2 molecules of ATP, 2 molecules of NADH, and two pyruvates. The pyruvates will enter the Krebs Citric Acid cycle to go through oxidation. Oxidation is defined as the addition of oxygen or the removal of electrons from an atom or molecule. Biochemically, oxidation and reduction are always linked. Reduction is the addition of electrons or hidrogyen ions.atoms to a molecule. The rsult isncrease in energy content of the molecule. This is synthesis.lick here to add your text.
Pyruvic acid is prepared for Krebs cycle by conversion to a two carbon comound, Acetyl group, followed by the addition of Coenzyme A to form Acetyl Coenzyme A.
In the process, two mroe molecules of NADH are formed.
The Krebs Cycle involves decarboxylations and oxidations and reductions of various organic acids that begins with and ends with Citric Acid. Each molecule of pyruvic acid that enters the Krebs Cycle will produce:
3 molecules of Carbon dioxide
3 molecules of NADH
1 molecule of FADH2
1 molecule of ATP.
The energy originally in glucose, and then pyruvic acid is now in the reduced nucleotides NADH and FADH2
The Electron Transport Chain
(Oxidative Phosphorylation)
The chain consists of a sequence of carrier molecules on the inner mitochondrial membrane that are capable of oxidation and reduction.
As electrons are passed throught the chain of hydrogen ion carrier proteins, there is a stepwise release of energy from the electrons for the generation of ATP. In aerobic respiration, the terminal electron acceptor of the chain is oxygen and teh final step is irreversible forming water. The process involves a series of redox reactions in which the potential energy in NADH and FADH2 is leberated and transferred to ATP for storage as a bio-fuel. The electron transport chain yields 32 molecules of ATP and water. About 47% of the energy originally in glucose is captured by ATP the remainder being liberated as heat.
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ETHANOL
LACTIC ACID
In fermentation or anerobic respiration , pyruvic acid is borken down into carbon dioxide and alcohol. No ATP is produced in this stage but there are two molecules of ATP generated int eh glycolysis phase. This process is used in the baking and brewing industry.
Anaerobic respiration also occurs in fatigued muscle wehre oxygen reserves have been depleted. The total products are 2 molecules of lactic acid, which causes muscle cramping, and 2 molecules of ATP. With rest, the muscle will return to normal as the lactic acid mixes with oxygen once again producing pyruvic acid which will then go through Kreb's cycle.
Other pages by Johnnie Bennett:
Johnnie Bennett is a teacher at the Montclair Kimberley Academy in Montclair, New Jersey
1993 New Jersey State Teacher of the Year
1997 New Jersey Biology Teacher of the Year
Although usually associated with the beverage industry, fermentation is important to other areas of the food industry. It is used to make cheeses, breads, root beer, and many other food items not associated with the process of anaerobic respiration and organisms such as yeast.
