Cell Respiration Steps | Cell Respiration - Biology IB23

The four first steps of cell respiration.

Glycolysis

Glycolysis

The first step to both anaerobic and aerobic cell respiration which produces 2 ATP, 2 pyruvate molecules and NADH + H⁺ from 1 glucose molecule.

Glycolysis Steps

1. Happens in the cytoplasm where oxygen is not required.

2. Phosphorylation - 2 ATP molecules add phosphate to a glucose with 6-carbon atoms to energize it and make it unstable.

3. Lysis - The 6-carbon atom glucose will split into two 3-carbon molecules.

4. Oxidation - The sugars will be oxidized to convert them into pyruvates by having electron carriers NAD+ remove hydrogens from them, reducing them into NADH.

5. The phosphate molecules of the carbon molecules will be stripped away to ADPs to turn them into ATPs.

Link Reaction

The second steg of cell respiration which transfers pyruvate into the mitochondria. 2 pyruvates will turn into 2 acetyl-CoA, 2 CO₂, and 2 NADH + H⁺ for each glucose.

Link Reaction Steps

1. Happens in the mitochondria.

2. Decarboxylation - Pyruvate will be decarboxylated, meaning one carbon atom creating a 2-carbon molecule forming an acetyl compound. 2 CO₂ will be formed per glucose.

3. Oxidation - The pyruvate will be oxidized as hydrogens and electrons are removed and carried by the electron carrier NAD+.

4. A coenzyme, CoA, is added to the acetyl compound creating the final product, acetyl-CoA.

Krebs Cycle

The third stage of cell respiration, also knwon as the Citric Acid Cycle. 2 acetyl molecules per glucose will make 4 CO₂, 2 ATPs, 2 FADH₂ and 6 NADH + H⁺.

Krebs Cycle Steps

1. Happens in the matrix of the mitochondria where there’s several enzymes.

2. The coenzyme, CoA leaves.

3. The carbon acetyl molecule will enter the cycle and bind with a 4-carbon molecule to make a 6-carbon molecules known as citric acid.

4. Decarboxylation - Liberates two carbon atoms as two molecules of CO₂.

5. Oxidation - The acetyl groups will lose hydrogens to the electron carriers NAD+ and FAD, they’re then reduced to NADH + H⁺ and FADH₂.

6. Energy is released due to oxidation and will be carried to the cristae of the mitochondria through NADH + H⁺ and FADH₂.

7. 1 ATP is made per cycle, making 2 ATP per glucose molecule.

Electron Transport Chain

The fourth stage of cell respiration where electron carriers gather and are oxidized.

Electron Transport Chain Steps

1. Happens on the cristae where there’s enough surface area for several reactions to occur, various membrane proteins such as transport for ions, enzymes and electron carriers.

2. Oxidation - NADH + H⁺ and FADH₂ are oxidized, losing their electrons and hydrogens to the electron carriers within the cristae.

3. The electrons will be coupled to membrane proteins pumping H+ from the matrix into the intermembrane space to create a H+ concentration gradient.

4. Chemiosmosis - The H+ is only allowed back in through the enzyme ATP-synthase, the energy that’s used makes ATP from ADP and inorganic phosphate.

5. The final electron acceptor oxygen takes electrons and H+ to make water.

6. Oxygen binds with the free protons to maintain the gradient which is what forms water.