Aerobic Cellular Respiration

Summary -

• Cell respiration: breaking down glucose to produce ATP

• Aerobic - living with oxygen

• Aerobic cell respiration

4 Stages:

Glycolysis

series of reactions that produce ATP by converting glucose to pyruvate

• Happens in the cytoplasm

• Happens twice at the same time

1. Glucose enters cell through transport protein - glucose to large to diffuse on own. ATP donates phosphate group to glucose

2. Another molecule of ATP donates a phosphate group too. Glucose + phosphate + phosphate

3. Splits into 2 molecules of PGAL. rest of glycolysis happens twice

4. PGAL donates H+ and electrons, makes NADH to be used later. Another phosphate group is added to PGAL

5. Phosphate group on PGAL is donated back to ADP

6. Second (the remaining) phosphate group is donated too. Left only with PGAL again

7. Donated phosphate group makes its way to another ADP to make ATP

8. PGAL - phosphate groups = pyruvate ; pyruvate is the final product

Pyuvate: used as a substrate for second stage of aerobic cell respiration

Acetyl CoA Formation

2 molecules of pyruvate enters mitochondrial matrix.

Acetyl CoA formation:

Both pyruvates split into - CO₂ and Acetyl group.

CO₂ leaves cell and then we exhale it. Acetyl group attaches to coenzyme A. Gives us two molecules of Acetyl CoA used in stage 3.

Citric Acid Cycle (Krebs Cycle)

1. Acetyl coA reacts with oxaloacetate. Product is citrate

2. Electrons and H+ added to NAD+, product is NADH. loses some carbon as CO₂

3. Carbon atoms removed as CO₂. NADH forms again

4. ATP forms by phosphorylation

5. Electrons and H+ are removed from compound. Added to coenzyme called FAD (flavin adenine dinucleotide). Becomes FADH2

6. Third molecule of NADH made

7. Final product is oxaloacetate. Used to start reaction again (cyclic)

Citric acid cycle runs twice: 2 molecules of Acetyl CoA made, citric acid cycle runs twice during aerobic cell respiration. Carbon backbone of glucose completely broken apart by now

Electron Transfer Phosphorylation

Similar to electron transfer phosphorylation in light-dependent reactions in photosynthesis

Starts along the mitochondrial membrane

1. NADH and FADH2 deliver electrons and H+. starts electron transfer chain

2. Energy from electron transfer chain moves H+ across membrane

3. H+ plus flows through ATP synthase making ATP

4. O₂ accepts electrons from transfer chain and other H+. creates H₂O