5.2 - Respiration Flashcards
Name the 4 main stages in aerobic respiration and where they occur.
- Glycolysis: cytoplasm
- Link reaction: mitochondrial matrix
- Krebs cycle: mitochondrial matrix
- Oxidative phosphorylation (ETC): membrane of cristae
Outline the stages of glycolysis.
- Glucose is phosphorylated to glucose phosphate by 2x ATP.
- Glucose phosphate splits into 2x triose phosphate (TP).
- 2x TP is oxidised to 2x pyruvate
Net gain of 2x reduced NAD & 2x ATP per glucose.
How does pyruvate from glycolysis enter the mitochondria?
Via active transport
What happens during the link reaction?
- Oxidation of pyruvate to acetate.
Per pyruvate molecule: net gain of 1xCO2 (decarboxylation) & 2H atoms (used to reduce 1xNAD). - Acetate combines with coenzyme A (coA) to form acetylcoenzyme A.
Give a summary equation for the link reaction.
pyruvate + NAD + CoA —> acetyl CoA + reduced NAD + CO2
What happens in the Krebs cycle?
series of redox produces:
- ATP by substrate-level phosphorylation.
- Reduced coenzymes.
- CO2 from decarboxylation.
What is the electron transfer chain?
- Series of carrier proteins embedded in membrane of the cristae of mitochondria.
- Produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration.
What happens in the ETC?
- Electron s released from reduced NAD & FAD undergo successive redox reactions.
- The energy released is coupled to maintaining proton gradient or released as heat.
- Oxygen acts as a final electron acceptor.
How is a proton concentration gradient established during chemiosmosis in aerobic respiration?
- Some energy released from the ETC is coupled to the active transport of H+ ions (protons) from the mitochondrial matrix into the intermembrane space.
How does chemiosmosis produce ATP during aerobic respiration?
- H+ ions (protons) move down their concentration gradient from the intermembrane space into the mitochondrial matrix via the channel protein ATP synthase.
- ATP synthase catalyses ADP + Pi –> ATP.
State the role of oxygen in aerobic respiration.
- Final electron acceptor in electron transfer chain (produces water as a byproduct).
What is the benefit of an electron tranfer chain rather than a single reaction?
- energy is released gradually
- less energy is released as heat
Name 2 types of molecule that can be used as alternative respiratory substrates.
- Amino acids from proteins
- glycerol and fatty acids from lipids
How can lipids act as alternative respiratory substrate?
lipid –> glycerol + fatty acids
1. Phosphorylation of glycerol –> TP for glycolysis.
2. Fatty acid –> acetate.
a. acetate enters link reaction.
b. H atoms produced for oxidative phosphorylation.
How can amino acids act as an alternative respiratory substrate?
Deamination produces:
1. 3C compunds –> pyruvate for link reaction.
2. 4C/5C compunds –> intermediates in Krebs Cycle.
Name the stages in respiration that produce ATP by substrate-level phosphorylation?
- Glycolysis (anaerobic)
- Krebs cycle (aerobic)
What happens during anaerobic respiration in animals?
Only glycolysis continues reduced NAD + pyruvate –> oxidised NAD (for further glycolysis) + lactate
What happens to the lactate produced in anaerobic respiration?
- Transported to liver via bloodstream, where it is oxidised to pyruvate.
- Can enter link reaction in liver cells or be converted to glycogen.
What happens during anaerobic respiration in some microorganisms e.g. yeast and some plant cells?
- Only glycolysis continues.
- Pyruvate is decarboxylated to form ethanal.
- Ethanal is reduced to ethanal using reduced NAD to produce oxidised NAD for further glycolysis.
What is the advantage of producing ethanol/lactate during anaerobic respiration?
Converts reduced NAD back into NAD so glycolysis can continue
What is the disadvantage of producing ethanol during anaerobic respiration?
- Cells die when ethanol concentration is above 12%.
- Ethanol dissolves cell membranes.
What is the disadvantage of producing lactate during anaerobic respiration?
Acidic, so decreases pH which results in muscle fatigue.
Similarities between anaerobic and aerobic respiration.
- Both involve glycolysis
- Both require NAD
- Both produce ATP
Contrast aerobic and anaerobic respiration.
Aerobic:
- Produces ATP by substrate-level phosphorylation and oxidative phosphorylation
- produces much more ATP
- does not produce ehtanol or lactate
Anaerobic:
- substrate-level phosphorylation only
- produces fewer ATP
- produces ethanol or lactate
Suggest how a student could investigate the effect of a named variable on the rate of respiration of a single-celled organism.
- Use respirometer
- Use a dye as a terminal electron acceptor for the ETC
What is the purpose of sodium hydroxide solution in a respirometer set up to measure the rate of aerobic respiration?
Absorbs CO2 so that there is a net decrease in pressure as O2 is consumed.
How could a student calculate the rate of respiration using a respirometer?
- Volume of O2 producd or CO2 consumed/ time x mass sample
- Volume = distance moved by coloured drop x (0.5 x capillary tube diameter)2 x pie
