Krebs Cycle Notes

The Krebs cycle is a crucial part of cellular respiration, following glycolysis.
Glycolysis involves taking a glucose molecule and accessing the hydrogens attached to it. These hydrogens provide the energy to make ATP (adenosine triphosphate).
The Krebs cycle harvests hydrogen molecules from the compound produced at the end of glycolysis.
After collecting hydrogens, the process moves to oxidative phosphorylation, where ATP is formed using the energy from the harvested hydrogens.

At the end of glycolysis, two pyruvic acid molecules are produced.
If oxygen is present, pyruvic acids are converted into acetyl, a two-carbon molecule.
Coenzyme A assists acetyl by speeding up reactions, forming acetyl coenzyme A.

Acetyl coenzyme A enters the mitochondria (glycolysis occurs in the cytosol).
Acetyl breaks off, leaving a two-carbon structure.
Coenzyme A transports acetyl into the mitochondria and then returns to glycolysis to repeat the process.

A two-carbon compound joins with a four-carbon compound to form a six-carbon compound.
The six-carbon compound breaks down, losing a carbon atom which forms carbon dioxide ( $CO_2$ ), which is then exhaled.
Hydrogen atoms are also released during this breakdown.
After losing a carbon, the compound becomes a five-carbon compound.
The five-carbon compound then loses another carbon atom (forming $CO_2$ ) and another hydrogen atom, resulting in a four-carbon compound.
The four-carbon compound restarts the cycle by combining with another two-carbon compound.

Hydrogen atoms, when isolated, tend to react with other atoms, potentially disrupting chemical reactions.
NAD (nicotinamide adenine dinucleotide) is a hydrogen carrier.
NAD picks up a hydrogen atom and becomes NADH.
NADH transports the hydrogen to the final cycle, oxidative phosphorylation.
The Krebs cycle breaks down acetyl and harvests hydrogens which are then attached to NAD for delivery to oxidative phosphorylation.
Oxidative phosphorylation uses hydrogen to form 32 ATP molecules.

Decarboxylized: The process where carbon molecules break off, forming carbon dioxide ( $CO_2$ ).
Dehydrogenized: The process where hydrogen atoms are removed or harvested.

Glycolysis produces pyruvic acid, which, in the presence of oxygen, turns into acetyl.
Coenzyme A picks up acetyl, forming acetyl coenzyme A, and delivers it to the mitochondria.
The Krebs cycle requires oxygen and is thus an aerobic reaction.
Dehydrogenized: removal of hydrogens.
Decarboxylized: removal of carbon dioxide ( $CO_2$ ).
NAD: A hydrogen carrier that picks up hydrogen to form NADH and delivers it to oxidative phosphorylation.