That takes place in the non organ part of the cytoplasm (cytosole) of the cell.

Krebs cycle

Electron transport

Those take place both inside the mitochondria, where respiratory enzymes, water, phosphate groups, co-enzymes, and electron-carrier molecules (cytochromes) exist.

Hydrogen Carriers:

During Glycolysis (break down of glucose), and Krebs cycle, Hydrogen atoms are removed from the Carbon skeleton of the glucose molecule that pass to co-enzymes (NAD+ and FAD) which act as Hydrogen carriers:

Reduction

NAD+ + H2 NADH + H+

Reduction

FAD + H2 FADH2

1. Glycolysis:

Glycolysis takes place in both aerobic and anaerobic respiration to produce energy. In Glycolysis one molecule of glucose breaks down forming two molecules of pyruvic acid (3-carbon), two molecules of ATP, and two molecules of NADH + H+ passing through a group of reactions through which glucose is converted into:

Glucose 6-phosphate (6-carbon)

Fructose 6-phosphate (6-carbon)

Fructose 1-6-diphosphate (6-carbon)

Two molecules of PGAL (phosphoglyceraldehyde) (3-carbon)

Two molecules of pyruvic acid (3-carbon).

So, the oxidation of the glucose molecule into 2 pyruvic acid molecules is accompanied with:

- The reduction of 2 molecules of NAD+ into 2 molecules NADH + H+

- The production of 2 molecules of ATP in the cytosole of the cell.

NAD+ : Nicotine amide adenine di-nucleotide.

FAD : Flaven adenine di-nucleotide.

All these reactions occur in the absence of Oxygen, so they are called anaerobic respiration. The energy resulted is not enough to perform all the vital activities of living organisms. Therefore, in the presence of Oxygen, pyruvic acid molecules pass into the mitochondria to produce more energy. This takes place in two consecutive stages: Krebs cycle, and electron transport.

Anaerobic respiration

C6H12O6 2C3H6O3 + 2ATP

Date: 2015-12-11; view: 794