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Biology Unit 5
Topic 7: Run for your life
8. Describe the roles of glycolysis in aerobic and
anaerobic respiration, including the phosphorylation
of hexoses, the production of ATP, reduced coenzyme
and pyruvate acid (details of intermediate stages and
compounds are not required).
Respiration occurs in 2 stages:
Anaerobic respiration (Glycolysis)
Aerobic respiration (Krebs Cycle)
Anaerobic respiration is used when oxygen is not delivered quickly enough e.g., during a 100m
sprint. It is inefficient as less ATP is produced per glucose molecule, but the ATP is produced more
CHO 2CHO (Lactic Acid)
Literally means "sugar-splitting".
Takes place in the cytoplasm of the cell.
The glucose comes from the blood or from the breakdown of glycogen stores in muscle and
1 x Glucose provides:
2 x pyruvate
2 x reduced NAD
Net gain: 2 x ATP
Process of Glycolysis:
1. Pump priming 2 x ATP used to phosphorylate the glucose to hexose phosphate and then
to hexose diphosphate. (The sugar is now activated and can't leave the cell via the cell
2. This hexose diphosphate (6C) splits to make 2 x GALP (2 x 3C).
3. 1 x GALP reacts to make 1 x Pyruvic Acid, during which:
Hydrogen atoms are removed from GALP to form NADH, which go into the ETC in the
mitochondria to form ATP. 1 x GALP = 1 x NADH = 3 x ATP
Some ATP formed when GALP loses a phosphate in the forming of pyruvate.
Text Book: p.132 - 135
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Biology Unit 5
The Link Reaction:
The pyruvate formed during Glycolysis enters the mitochondrial matrix via the mitochondrial
membrane. The pyruvate undergoes a reaction before it enters the Krebs cycle. This is the Link
Reaction. The acetyl coA then enters the Krebs Cycle.
Pyruvate (3C) Acetyl coenzyme A (2C) + CO + HO
Controlling the rare of Glycolysis
The energy requirements of an organism vary over time. Consequently, Glycolysis and the Krebs
Cycle need to vary in rate.…read more