Cellular Respiration: Lesson 9.2 - The Krebs Cycle

acetyl-CoA combines with a 4-carbon compound in the krebs cycle to produce citric acid

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during the krebs cycle, pyruvic acid is broken down into carbon dioxide in a serious of energy-extracting reactions

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krebs cycle begins when pyruvic acid, produced by glycolyisis, passes through the 2 membranes of the mitochondria and into the matrix

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ultimate yield for krebs cycle

2 ATP, 8 NADH, 2FADH2

the acetyl part of coenzyme A is made up of 2 carbon atoms, 1 oxygen atom, 3 hydrogen atoms)

As the krebs cycle begins acetyl-CoA adds the 3 carbon acetyl group to a 4-carbon molecule already resent in the cycle, producing a 6-carbon molecule called citric acid

pyruvic acid from glycolysis reacts to form acetyl-CoA, which enters the Krebs cycle.

In the process, a molecule of CO2 is produced and 2 high energy electrons are passed to NAD+ to produce NADH.

for each turn of the cycle

a molecule of ADP is converted to a molecule of ATP

each molecule of glucose results in 2 turns of the krebs cycle

and therefore 2 ATP molecules

the krebs cycle is also known as the citric acid cycle

because citric acid is the first compound formed in this series of reactions

ATP molecules are very useful for the cell

become immediately available to power cell activities

during the Krebs cycle, pyruvic acid from glycolysis is used to make

carbon dioxide, NADH, ATP, and FADH2.

at 5 places, electron carriers accept a pair of high energy electrons,

changing NAD+ to NADH and FAD to FADH2.

this 4-carbon compound can then start the cycle over again by combining with acetyl-CoA.

energy released by the breaking and rearranging of carbon bonds is captured in the forms of ATP, NADH, and FADH.

FAD

flavine adenine dinucleotide similar to NAD respectively

the krebs cycle is named after

hans krebs. british biochemist who demonstrated its existence in 1937

carrier molecules such as NADH, in the presence of oxygen, the electrons they hold are used to generate

huge amounts of ATP

as the cycle continues, citric acid is broken down into a 4-carbon molecule, more carbon dioxide is released, and electrons are transferred to electron carriers.

one atom is removed from the 6-carbon citric acid, then another, releasing 2 molecules of carbon dioxide and leaving a 4-carbon molecule

in the presence of oxygen,

pyruvic acid passes to the krebs cycle

through a series of many reactions citric acid is broken down into a 5-carbon compound and then a 4-carbon compound

releasing 2 CO2 molecules along the way

the krebs cycle is a cycle because

the 4-carbon molecule produced in the last step is the same molecule that accepts the acyetal-CoA in the first step. The molecule needed to start the reactions of the cycle is remade with every turn

matrix

the innermost compartment of the mitochondria and the site of the krebs cycle reactions

in the inside of the matrix, one carbon atom from pyruvic acid becomes part of a molecule of carbon dioxide

which is eventually released into the air

the other 2 carbon atoms from the pyruvic acid rearrange and form acetic acid

which is joined to a compound called coenzyme A the resulting molecule is called acetyl CoA