What does glycolysis make?
Pyruvate from glucose
Describe glycolysis
Phosphorylation
- Glucose is phosphorylated using a phosphate from a molecule of ATP, creating 1 molecule of glucose phosphate and 1 molecule of ADP
- ATP is then used to add another phosphate, forming hexose bisphosphate
- hexose bisphosphate is then split into 2 molecules of triose phosphate
Oxidation
- Triose phosphate is oxidised (loses hydrogen), forming 2 molecules of pyruvate
- NAD collects the hydrogen ions, forming 2 reduced NAD
- 4 ATP are produced, but 2 were used up during phosphorylation, so there’s a net gain of 2 ATP
Where does glycolysis take place?
Cytoplasm of cells
In anaerobic respiration (in plants and yeast) what is pyruvate converted into?
Pyruvate —> Ethanal —-> Ethanol
In anaerobic respiration (in animal cells and some bacteria) what is pyruvate converted to?
Pyruvate —> Lactate (lactic acid)
Describe what happens during the link reaction
- Pyruvate is decarboxylated (1 carbon atom is removed from pyruvate in the form of CO2)
- Pyruvate is oxidised to form acetate and NAD is reduced to form reduced NAD
- Acetate is combined with coenzyme A (CoA) to form acetyl coenzyme A (acetyl CoA)
- No ATP is produced in this reaction
Where does the link reaction take place?
Matrix of mitochondria
How many times does the link reaction occur for 1 glucose molecule?
2
Describe 3 things that happen from the link reaction for 1 glucose molecule
- 2 molecules of acetyl CoA go into the Krebs cycle
- 2 CO2 molecules are released as a waste product of respiration
- 2 molecules of reduced NAD are formed and go to the last stage (oxidative phosphorylation)
What does the Krebs cycle involve?
A series of oxidation-reduction reactions
Where does the Krebs cycle take place?
Matrix of mitochondria
How many times does the Krebs cycle happen for each pyruvate molecule?
1
How many times does the Krebs cycle happen for each glucose molecule?
2
Describe the Krebs cycle
- Acetyl CoA from the link reaction combines with a 4C molecule (oxaloacetate) to form a 6C compound (citrate)
Coenzyme A goes back to the link reaction to be used again
- The 6C citrate molecule is converted to a 5C molecule
Decarboxylation occurs, where CO2 is removed
Dehydrogenation also occurs, where hydrogen is removed
The hydrogen is used to produce reduced NAD from NAD
- The 5C molecule is then converted to a 4C molecule
Decarboxylation and dehydrogenation occur, producing 1 molecule of reduced FAD and 2 molecules of reduced NAD
ATP is produced by the direct transfer of a phosphate group from an intermediate compound to ADP. When a phosphate is directly transferred from 1 molecule to another it’s called substrate-level phosphorylation. Citrate has now been converted into oxaloacetate
