12. Energy And Respiration Flashcards
Why is ATP such a good energy currency molecule?
- ATP can be regenerated after being hydrolyzed
- ATP can be easily hydrolyzed- so you can release energy.
- ATP cannot spontaneously hydrolyzed but can be broken down using ATP-ase
- Hydrolysis of ATP releases large amounts of energy
What is the respiratory quotient?
The ratio of the number of molecules of carbon dioxide produced to the number of molecules of oxygen taken in as a result of respiration.
State the 4 stages of aerobic respiration and where each of them occurs in eukaryotic cells.
- glycolysis in the cytoplasm
- link reaction in the mitochondrial matrix
- Krebs cycle in the mitochondrial matrix
- oxidative phosphorylation on the inner membrane of
mitochondria
Explain what happens in glycolysis.
- Phosphorylation- glucose is phosphorylated by 2 ATP to form fructose bisphosphate.
- Lysis- fructose bisphosphate splits into two molecules of triode phosphate.
- 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
Explain what happens in the Link reaction.
When oxygen is available pyruvate will enter the mitochondrial matrix and aerobic respiration will continue.
It moves across the double membrane of the mitochondria via active transport.
1. Decarboxylation and dehydrogenation of pyruvate by enzymes to produce an acetyl group
2. Combination with coenzyme A to form acetyl CoA, co2 and reduced NAD
Outline the steps in the Krebs cycle.
- The 2C Acetyl group is accepted by the 4C oxaloacetate to form 6C citrate
- Decarboxylation and dehydrogenation of 6C nitrate to form a 5C compound, carbon dioxide and reduced NAD
- The compound then undergoes further Decarboxylation and dehydrogenation until eventually 4C oxaloacetate is reformed.
- It undergoes substrate link reaction- where a little energy is released and ADP and phosphate is synthesized into ATP.
- Dehydrogenation- FAD will accept a hydrogen molecule and become reduced FAD
- Dehydrogenation- NAD will accept a hydrogen molecule and become reduced NAD.
Describe the role of NAD and FAD in transferring hydrogen to carriers in the inner mitochondrial membrane.
Reduced NAD and reduced FAD transfer the hydrogen atoms from the different stages of respiration to the electron transport chain on the inner mitochondrial membrane, the site where hydrogens are removed from the coenzymes
A
Explain what happens during oxidative phosphorylation.
- Hydrogen atoms split into protons and energetic electrons.
- Energetic electrons release energy as they pass through the electron transport chain
- The released energy is used to transfer protons across the inner mitochondrial membrane.
- Protons return to the mitochondrial matrix by facilitated diffusion through ATP synthase providing energy for ATP synthesis.
- Oxygen acts as the final electron acceptor to form water.
Explain why aerobic respiration produces significantly more ATP than anaerobic respiration.
It allows for complete oxidation of glucose and utilizes the electron transport chain, which generates a large amount of ATP through oxidative phosphorylation. Anaerobic respiration is less efficient, producing only 2 ATP, as it relies solely on glycolysis.
Why is oxygen so important in aerobic respiration
Oxygen acts as the final electron acceptor. Without oxygen the electron transport chain cannot continue as the electrons have nowhere to go. Without oxygen accepting the electrons (and hydrogens) the reduced
coenzymes NADH and FADH2 cannot be oxidised to regenerate NAD and FAD, so they can’t be used in further hydrogen transport.
Explain how the link reaction begins following glycolysis
- When oxygen is available pyruvate will enter the mitochondrial matrix and aerobic respiration will continue
- It moves across the double membrane of the mitochondria via active transport, requires a transport protein and ATP.
- Once in the mitochondrial matrix pyruvate takes part in the link reaction
Explain what the role of Coenzyme A is.
A coenzyme is a molecule that helps an enzyme carry out its function but is not used in the reaction itself.
