Topic 5—A: Photosynthesis And Respiration- 7. Aerobic Respiration- The Mitochondrial Reactions Flashcards
What happens in the link reaction?
- It converts the pyruvate produced in glycolysis to acetyl coenzyme A
Link reaction (stages)
- Pyruvate is decarboxylated so one carbon atom is removed from pyruvate in the form of carbon dioxide
- At the same time pyruvate is oxidised to form acetate and NAD is reduced to form reduced NAD (NADH)
- Acetate is then combined with coenzyme A to form acetyl coenzyme A
Is ATP produced in the link reaction?
No
How many times does the link reaction occur per glucose molecule?
It happens twice for every glucose molecule
Why does the link reaction happen twice for every glucose molecule?
- Two pyruvate molecules are made for every glucose molecule that enters glycolysis
What are the products of the link reaction? (For one glucose molecule) = 2 link reactions
- 2 reduced NAD
- 2 carbon dioxide
- 2 acetyl coenzyme A
What is the Krebbs cycle?
- It produces reduced coenzymes and ATP
- Happens twice for every glucose molecule (once for every pyruvate molecule)
- It involves a series of oxidation-reduction reactions which take place in the matrix of the mitochondria
Krebbs cycle (stages)
- Acetyl coenzyme A (2 carbons) from the link reaction combines with 4 carbon molecule (oxaloacetate) to form a 6 carbon molecule (citrate)
- Coenzyme A goes back to the link reaction to be used again
- The 6 carbon citrate molecule is converted to a 5 carbon molecule. Decarboxylation occurs where carbon dioxide is removed. Dehydrogenation also occurs. The hydrogen is used to produce reduced NAD (NADH) from NAD
- The 5 carbon molecule is then converted to a 4 carbon molecule. Decarboxylation and dehydrogenation occurs producing one molecule of carbon dioxide, 2 molecules of NADH, molecule of FADH
- ATP is produced by the direct transfer of a phosphate group from ADP
- Citrate has now been converted into oxaloacetate
What is it called when a phosphate group is directly transferred from one molecule to another?
Substrate-level phosphorylation
What are the products of the Krebbs cycle? (2 cycles) per glucose molecule
- 2 coenzyme A
- 4 carbon dioxide
- 6 NADH
- 2 FADH
- 2 ATP
- 2 oxaloacetate
How many times does the Krebbs cycle occur per glucose molecule ?
2 times out of
What is oxidative phosphorylation?
- It’s the process where the energy carried by electrons, from reduced coenzymes (NADH & FADH) is used to make ATP.
- It involves the electron transport chain and chemiosmosis
Oxidative phosphorylation (stages)
- Hydrogen atoms are released from reduced NAD and reduced FAD as they are oxidised to NAD and FAD. The hydrogen atoms split into protons (H+) and electrons (e-)
- The electrons move down the electron transport chain (made up of electron carriers losing energy at each carrier
- This energy is used by the electron carriers to pump protons from the mitochondrial matrix into the intermembrane space
- The concentration of protons is now higher in the intermembrane space than in the mitochondrial matrix- this forms an electrochemical gradient
- Protons them move down the electrochemical gradient back across the inner mitochondrial membrane and into the mitochondrial matrix via ATP synthase (which is embedded in the inner mitochondrial membrane). This movement drives the synthesis of ATP from ADP and inorganic phosphate
- This process of ATP production driven by the movement of H+ ions across a membrane (due to electrons moving down an electron transport chain) is called chemiosmosis
- In the mitochondrial matrix, at the end of the transport chain, the protons, electrons and oxygen (from the blood) combine to form water. Oxygen is said to be the final electron acceptor
What is chemiosmosis?
- Production of ATP driven by the movement of H+ ions across a membrane (due to electrons moving down an electron transport chain)
How many ATP are produced from each reduced NAD?
2.5 ATP
