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8.3 Outside the Mitochondria: Fermentation
So far, we have accounted for only 2 of the 36 to 38 ATP molecules that are theoretically possible when glucose is completely broken down to CO2 and H2O.
pyruvate enters the mitochondria when O2 is available.
If O2 isn't available, fermentation occurs.
Represent the location, inputs, and outputs of glycolysis.
Discuss the two pathways.
Oxygen is needed to keep the electron transport chain working.
In the absence of oxygen, the process of Fermentation produces a limited amount of ATP.
pyruvate, the end product of glycolysis, is reduced in animal cells.
Depending on the type ofbacteria, they can either produce an organic acid, such as lactate, or an alcohol and CO2.
A good example of organisms generating alcohol and CO2 is the yeasts.
There is a reduction of pyruvate in the process of fermentation.
It picks up more electrons when it recycles NAD+.
Each step is catalyzed by a specializedidase.
When oxygen is absent, the cell still needs energy.
The first step in the energy-harvesting phase of glycolysis involves the regeneration of NAD+.
The NAD+ is now free to return to the earlier reaction and become reduced once more.
When oxygen is present and the cell is able to convert sugar into CO2 and H2O, there is enough energy for the cell to continue working.
The chemicals of industrial importance produced by otherbacteria include isopropanol, butyric acid, proprionic acid, and acetic acid when they ferment.
breads are made using yeasts.
Wine, beer, and other alcoholic beverages are produced through alcoholic fermentation.
Lactic acid fermentation is essential to certain animals and tissues despite its low yield.
The animals use lactic acid for a rapid burst of energy.
When muscles are working hard over a short period of time, lactic acid fermentation provides them with the oxygen they need.
Alcoholic and Lactic acid ferments produce equivalent to 14.2 kcal/mol glucose.
A possible energy yield of 686 kcal/mol is represented by the complete breakdown to CO2 and H2O.
The complete breakdown of glucose can be achieved with an efficiency of only 2.1%.
The theoretical 36 to 38 ATP molecule that may be produced by cellular respiration is far short of what is produced by fermentation.
It is necessary to move on to the reactions and pathways that occur with oxygen in the mitochondria in order to achieve this number.
You can find items like bread, yogurt, soy sauce, and even beer or wine at the grocery store.
These are just a few of the many foods that are produced when the organisms ferment.
Many of the vitamins and minerals that would attract other organisms have been removed by the organisms that ferment.
When yeast are killed by alcohol, it can be dangerous to the organisms that produced them.
The alcohol produced by the yeast is lost during baking.
sourdough breads are made from a starter composed of yeast andbacteria from the environment.
The flavor of the bread can be sour and salty, as in San Francisco-style sourdough, to a milder taste, such as that produced by most Amish friendship bread recipes.
Beer and wine have alcohol produced when yeast ferment.
Wine is made when yeast ferment fruit.
Distilling to concentrate the alcohol content is required for stronger alcoholic drinks.
acetic acid can be found in wine and cider.
The process of pasteurization was invented by Louis Pasteur.
The process of pasteurization was originally developed to make milk safe to drink, so that limited acetic acid would be produced.
The pursuit of scientific knowledge can have a positive effect on our lives.
Milk to sour is caused by the action of various lactic acidbacteria that produce yogurt, sour cream, and cheese.
Lactose is found in milk, which thesebacteria use as a source of energy.
Rennin must be added to the milk in order for it to coagulate and become solid in the cheese making process.
Cucumbers, sauerkraut, and kimchi are produced by the action of acid-causing, fermentablebacteria that can survive in high-salt environments.
Salt is used to draw liquid out of vegetables.
The mold breaks down the starch and gives the microorganisms sugar to make alcohol and organic acids.
Scientists use the process of fermentation to improve our lives because it is a biologically and economically important process.
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