5.2 Respiration Flashcards
Name the 4 main stages in aerobic respiration
- Glycolysis
- Link reaction
- Krebs cycle
- Oxidative phosphorylation
Where does glycolysis occur?
Cell cytoplasm
Where does the link reaction occur?
Mitochondrial matrix
Where does the Krebs cycle occur?
Mitochondrial matrix
Where does oxidative phosphorylation occur?
Via electron transfer chain, in the inner mitochondrial membrane (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 and 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 1x CO2 (decarboxylation) and 2H atoms (used to reduce 1x NAD) - 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 reactions 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 electron transfer chain?
Electrons released from reduced NAD and FAD undergo successive redox reactions
The energy released is coupled to maintaining proton gradient or released as heat
Oxygen acts as final electron acceptor
How is proton concentration gradient established during chemiosmosis in aerobic respiration?
Some energy released from the ETC is coupled to the active transport of H+ ions from the mitochondrial matrix into the inter membrane space
How does chemiosmosis produce ATP during aerobic respiration?
Protons move down their concentration gradient from the inter membrane 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
What is the benefit of an electron transfer 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 an alternative respiratory substrate?
Lipid —> glycerol + fatty acids
1. Phosphorylation of glycerol —> TP for glycolysis
2. Fatty acid —> acetate
acetate enters link reaction
H atoms produced for oxidative phosphorylation
How can amino acids act as an alternative respiratory substrate?
Deamination produces:
1. 3C compounds –> pyruvate for link reaction
2. 4C / 5C compounds –> 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 + 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 ethanol 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
Results in muscle fatigue
Compare aerobic and anaerobic 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 ethanol or lactate
Anaerobic:
- Substrate-level phosphorlyation 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 (pressure changes in boiling tube causes a drop of coloured liquid to move)
- Use a dye as the 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 carbon dioxide so that there is a net decreases in pressure as oxygen is consumed
How could a student calculate the rate of respiration using a respirometer?
Volume of oxygen produced or carbon dioxide consumed / time x mass of sample
Volume = distance moved by coloured drop x (0.5 x capillary tube diamater)^2 x pie
