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Getting energy to make ATP
Cellular RespirationThe process by which mitochondria break
down food molecules to produce ATP is called cellular respiration. There are 3 stages of cellular respiration.1. Glycolysis (anaerobic)2. The citric acid cycle3. The electron transport chain. (aerobic)
Glycolysis
Energy used and made in glycolysisTakes 2 ATP to start glycolysisOnly 4 ATP are produced
4-2= 2 ATP gained (not very effective)Glycolysis uses an electron carrier called NAD+.NAD+ forms NADH which it accepts 2 electrons.
Glycolysis
Glycolysis is a series of chemical reactions in the cytoplasm of a cell that breaks down glucose into 2 molecules of pyruvic acid.
Glucose 2 pyruvic acidGlucose is a 6 carbon molecule.Pyruvic acid is a 3 carbon molecule.
Glycolysis
• Before citric acid cycle and electron transport chain stages begin, pyruvic acid undergoes a series of reactions in which it gives off a molecule of CO2 and bines with a molecule called coenzyme A to form acetyl-CoA.
The citric acid cycle
• Occurs in the mitochondria Citric acid cycle also called Krebs cycleFor every turn of the cycle, 1 ATP molecule of ATP and 2 molecules of carbon dioxide are produced.NAD+ and FAD+ (electron carriers) form NADH and FADH2 (carry electrons to electron transport chain)
Electron Transport chain
• Occurs in the inner membrane of the mitochondrion.
• Energized electrons are carried by NADH and FADH2 to the top of the chain.
• The electrons are passed from protein to protein within the membrane, slowly releasing their energy in steps. Some of that energy is used directly to form ATP.
Electron Transport Chain
• The final electron acceptor at the bottom of the chain is oxygen, which reacts with four hydrogen ions (4H+) and four electrons to form two molecules of (H2O). This is why oxygen is so important to our bodies.
• Without oxygen, the proteins in the electron transport chain cannot pass along the electrons.
Electron Transport Chain
• If a protein cannot pass along an electron to oxygen, it cannot accept another electron. Very quickly, the entire chain becomes blocked and ATP production stops.
• Overall, the electron transport chain add 32 ATP molecules.
• Aerobic process of ATP is very effective.
Other ways to make ATP
FermentationFermentation occurs after glycolysis.
Is a process of making ATP when there is no oxygen present. (Anaerobic process)Ex. Happens during heavy exercise, when your cells are without oxygen for a short period of time.
Fermentation
• There are two major types of fermentation
1. Lactic acid fermentation2. Alcoholic fermentation
Lactic acid fermentation
• Lactic acid fermentation is one of the processes that supplies energy when oxygen is scarce.
• Two molecules of pyruvic acid produced in glycolysis use NADH to form two molecules of lactic acid. This releases NAD+ to be used in glycolysis, allowing 2 ATP molecules to be formed for each glucose molecule.
Lactic acid fermentation
• The soreness feeling you get after you workout is due to the build up of lactic acid in the muscles cells.
• The lactic acid is transferred from muscle cells, where it is produced during strenuous exercise, to the liver that converts it back to pyruvic acid.
Alcoholic fermentation
• Is used by yeast cells and some bacteria to produce CO2 and ethyl alcohol.
Ex. When making bread, yeast cell produce CO2 that forms bubbles in the dough.