Respiration Flashcards
What are the stages of aerobic respiration?
- Glycolysis → phosphorylation and splitting of glucose (Cell Cytoplasm)
- Link Reaction → decarboxylation and dehydrogenation of pyruvate (Matrix of Mitochondria)
- Krebs cycle → cyclical pathway with enzyme-controlled reactions (Matrix of Mitochondria)
- Oxidative Phosphorylation → production of ATP through oxidation of hydrogen atoms (Inner Membrane of Mitochondria)
What is the site of aerobic respiration in eukaryotes
Mitochondria
Describe the process of glycolysis.
- Phosphorylation → glucose (6C) is phosphorylated by 2 ATP to form fructose bisphosphate (6C)
- Lysis → fructose bisphosphate (6C) splits into two molecules of triose phosphate (3C)
- Oxidation → hydrogen is removed from each molecule of triose phosphate and transferred to coenzyme NAD to form 2 reduced NAD
- Dephosphorylation → phosphates are transferred from the intermediate substrate molecules to form 4 ATP through substrate-linked phosphorylation
- Pyruvate is produced → the end product of glycolysis which can be used in the next stage of respiration
Describe the link reaction.
- Pyruvate is oxidised by enzymes to produce acetate and carbon dioxide, requiring the reduction of NAD to NADH
- Combination of pyruvate with coenzyme A to form acetyl coenzyme A (acetyl CoA)
Describe the Krebs cycle.
- Acetyl CoA (2C) enters the circular pathway from the link reaction in glucose metabolism
- Oxaloacetate (4C) accepts the 2C acetyl fragment from acetyl CoA to form citrate (6C) (Coenzyme A is released in this reaction)
- Citrate is then converted back to oxaloacetate through a series of oxidation-reduction (redox) reactions
- Decarboxylation of citrate (Releasing 2 CO2 as waste gas)
-
Oxidation of citrate (Releasing H atoms that reduce coenzymes NAD and FAD
3 NAD and 1 FAD → 3NADH + H+ and 1 FADH2) - Substrate-linked phosphorylation (A phosphate is transferred from one of the intermediates to ADP, forming 1 ATP)
Describe the process of oxidative phosphorylation.
- Hydrogen atoms are donated by reduced NAD (NADH) and reduced FAD (FADH2) from the Krebs Cycle.
- Hydrogen atoms split into H+ and electrons
- The high energy electrons enter the electron transport chain and release energy as they move through the ETC
- The released energy is used to transport protons across the inner mitochondrial membrane from the matrix into the intermembrane space, establishing a proton gradient between the intermembrane space and the matrix
- The protons return to the matrix via facilitated diffusion through the channel protein ATP synthase
- The movement of protons down their concentration gradient provides energy for ATP synthesis
- Oxygen acts as the final electron acceptor and combines with protons and electrons at the end of the electron transport chain to form water
How many reduced NAD made in aerobic respiration of a single glucose molecule?
- 2 x 1 = 2 from Glycolysis
- 2 x 1 = 2 from the Link Reaction
- 2 x 3 = 6 from the Krebs cycle
Total (10)
How many reduced FAD made in aerobic respiration of a single glucose molecule?
- 2 x 1 = 2 from the Krebs cycle
Total (2)
Describe the process of anaerobic respiration.
Lactate fermentation
- Reduced NAD transfers its hydrogens to pyruvate to form lactate
- Pyruvate is reduced to lactate by enzyme lactate dehydrogenase
- Pyruvate is the hydrogen acceptor
- The final product lactate can be further metabolised
Ethanol fermentation
- Reduced NAD transfers its hydrogens to ethanal to form ethanol
- Pyruvate is decarboxylated to ethanal, producing CO2
- Ethanal is reduced to ethanol by the enzyme alcohol dehydrogenase
- Ethanal is the hydrogen acceptor
- Ethanol cannot be further metabolised, it is a waste product
Metabolisation of lactate.
- It can be oxidised back to pyruvate which is then channelled into the Krebs cycle for ATP production
- It can be converted into glycogen for storage in the liver
What are possible respiratory susbstrates?
- lipids
- amino acids
- carbohydrates
