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Cell respiration - Biology SL Topic 2.8 production of ATP, glycolysis, alcoholic fermentation,
Biology SL
IB
High School - US
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Cell respiration Topic 2 Biology SL
Production of ATP ➢ Each covalent bond in a glucose, amino acid or fatty acid represents stored chemical energy ➢ Example: the burning of wood is a release of storedchemical energy in the form of heat and light ○ Burning is the release of chemical energy calledrapid oxidation ➢ Cells metabolise/break down their organic nutrientsbyslow oxidation ➢ Enzymes catalyse the breakdown of one covalent bondat a time in a glucose, amino acid or fatty acid molecule ○ Every time a covalent bond is broken a small amountof energy is released ➢ The goal of releasing energy in a controlled way isto trap the released energy in the form of ATP ➢ Cell respirationis the production of ATP ○ Can be either anaerobic or aerobic ■ There are two types of anaerobic ● Alcoholic fermentation ● Lactic acid fermentation
Glycolysis ➢ All kinds of cellular respiration begin withglycolysis ○ The metabolic pathway that is common on all organisms of Earth ➢ Process ○ Glucose enters the cytoplasm of the cell through the plasma membrane ■ Facilitated diusion ○ Enzymes modify the molecule ○ The 6-carbon molecule is cleaved into 2 3-carbon molecules calledpyruvate ○ 4 ATP molecules are formed, but 2 are needed to start glycolysis making the net gain 2 ATP molecules ➢ Not all the covalent bonds in glucose are broken
Anaerobic respiration ➢ Organisms can derive their ATP without the use of oxygen and are referred to as anaerobic ➢ Fermentationis the breakdown of organic molecules for ATP production in an anaerobic way ➢ Alcoholic fermentation
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Cell respiration Topic 2 Biology SL
○ Many bacteria and fungi rely on it, for example yeast ○ Glycolysis takes place ○ Each pyruvate is converted to an ethanol (2 carbons) molecule ○ The lost 2 carbons form 2 carbon dioxide molecules ○ Both ethanol and carbon dioxide are waste products ■ That is why yeast is used in baking and in alcohol production ○ The only ATP produced comes from glycolysis ➢ Lactic acid fermentation ○ Happens in organisms that use oxygen during cell respiration ○ Some of the glucose entering into cell respiration will follow this anaerobic pathway when the organism exceeds its body’s capacity to supply oxygen ○ Lactic fermentation allows glycolysis to continue ○ Glycolysis takes place ○ 2 3-carbon pyruvate molecules are converted into 2 3-carbon lactic acid ○ There are converted back into pyruvate when oxygen levels rise and aerobic respiration proceeds ○ The only ATP produced comes from glycolysis
Aerobic respiration ➢ Occurs in mitochondria ➢ Oxygen is needed ➢ Process ○ Glycolysis takes place ○ The 2 pyruvate molecules enter a mitochondrion ○ Each pyruvate loses a carbon dioxide and becomesacetyl-CoA ■ Acetyl-coenzyme A has 2 carbon atoms ○ The 2 acetyl-CoA molecules enter theKrebs cycle ■ A series of reactions ■ A cycle because it starts and ends with the same molecule ○ Through many reactions the 2-carbon acetyl-CoA are broken down into 2 carbon dioxide molecules ■ 3 oxygens are needed to break down each acetyl-CoA ○ 30-36 ATP molecules are generated ○ Aerobic cell respiration completely oxidizes a glucose molecule and the end-products are carbon dioxide , water and ATP C 6 H 12 O 6 + 6O 2 ⇒ 6CO 2 + 6H 2 O
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Cell respiration - Biology SL Topic 2.8 production of ATP, glycolysis, alcoholic fermentation,
Subject: Biology SL
IB
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