Question

Aerobic Cellular Respiration (getting energy from food) involves four steps: Glycolysis, the Intermediate Acetyl CoA Reaction (Prep Reaction), the Citric Acid (Krebs) Cycle, and the Electron Transport Chain. State:

where each of the four steps takes place in a cell

how many ATP are generated at each step, if at all

what is the starting (ie. glucose or pyruvate) and ending substance for each step

Answer 1

Glycolysis occurs in cytosol. Two ATP are generated in glycolysis. Glucose (substrate) is broken down into two pyruvate (end product) molecules in glycolysis. Two NADH2 are also formed here.

Acetyl CoA reaction occurs in mitochondria. Pyruvate (substrate) is converted into Acetyl CoA (end product). No direct ATP is produced here. NADH is formed here which goes in electron transport chain to yield ATP.

Krebs cycle also occurs in mitochondria. It is a cyclic process, therfore no end product is formed. Acetyl CoA combines with oxaloacetate and forms citrate and at the end again oxaloacetate is formed which again combines with Acetyl CoA. Two ATP (2 GTP) are dirctly formed during Krebs cycle. Further NADH and FADH2 are formed.

Electron transport chain occurs in inner mitochondrial membrane. There is no product formed in this step. NADH and FADH2 formed during glycolysis, Acetyl CoA reaction and krebs cycle are converted into ATP in electron transport chain. 32 ATP are formed in electron transport chain.