Respiration 5.2 Flashcards
How does 2x pyruvate from glycolysis enter the mitochondria?
Via active transport
Describe the process of glycolysis
• Phosphorylation of glucose using energy from ATP;
• Oxidation of triose phosphate to pyruvate;
• Net gain of (+2) ATP;
• NAD reduced
Describe how oxidation takes place in glycolysis and in the Krebs cycle.
• Dehydrogenation (removal of H);
• by enzymes/dehydrogenases;
• NAD carrier is reduced;
• FAD carrier used in Krebs cycle
Water is a waste product of aerobic respiration. Describe how water is formed at the end of aerobic respiration (2)
• Oxygen is final/terminal electron acceptor;
• Combines with electrons and protons to form water
Explain how the amount of ATP is increased by reactions occurring inside a mitochondrion
• oxidation of pyruvate (removes e- and H+)
• Acetyl Co-enzyme A / 6C compound
• Substrate level phosphorylation of ATP (in Krebs cycle);
• Production of REDUCED NAD + FAD;
• in matrix of mitochondria;
• electrons fed into electron transport chain;
• through series of redox reactions releasing energy;
• Protons move into intermembrane space;
• ADP + Pi by ATP synthase
Describe the events of oxidative phosphorylation
OR
Describe the roles of the co-enzymes and carrier proteins in the synthesis of ATP
• NAD/FAD reduced (H+)
• H+ ions/electrons transferred from coenzyme to coenzyme / carrier to carrier (ETC on cristae of inner membrane);
• energy released through series of redox reactions;
• energy released used to pump H+ into intermembrane space forming an electro-chemical gradient;
• Protons flow back through ATP synthase to produce ATP from ADP + Pi
I’m many mammals ‘uncoupling proteins’ help to maintain a constant body temperature during hibernation.
Suggest and explain how (2)
- Allow passage of protons/H+
- (Energy) released as heat.
The mitochondria in muscles contain many cristae.
Explain the advantage of this (2)
• Larger surface area for electron carrier system / MORE oxidative phosphorylation;
• provide MORE ATP / energy for contraction
Give two reasons why the respirometer was left for 10 minutes when it was first placed in the water bath (3)
- Equilibrium reached;
- Allow for expansion (gases/liquids) / pressure change in apparatus;
- Allow respiration rate of seeds to stabilise.
Explain why a log scale is used to record the number of cells/bacteria (2)
- Large range/difference/increase in numbers;
- Accept reference to exponential (increase)
Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration (2)
- Regenerates NAD / Oxidises reduced NAD;
- (So) glycolysis continues;
Malonate inhibits a reaction in the Krebs cycle.
Explain why malonate would decrease the uptake of oxygen in a respiring cell (2)
- Less/no reduced NAD/coenzymes OR Fewer/no hydrogens/electrons removed (and passed to electron transfer chain);
- Oxygen is the final/terminal electron acceptor;
Name the 4 stages in respiration and where they occur
Glycolysis: cytoplasm
Link reaction: mitochondrial matrix
Krebs cycle: mitochondrial matrix
Oxidative phosphorylation via electron transport chain: membrane of cristae
Outline the stages of glycolysis
- glucose is phosphorylated to glucose phosphate by 2x ATP
- glucose phosphate splits into 2x triose phosphate
(ТР) - 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 1xCO. (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 + CO,
What happens in the Krebs cycle?
series of redox reactions produces:
• ATP by substrate-level phosphorylation.
• Reduced coenzymes.
• CO, from decarboxylation.
What is the electron transfer chain? (ETC) (2)
- 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 transport chain? (ETC) (3)
- Electrons 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 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? (3)
- 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 transfer chain rather than a single reaction? (2)
• 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
- Phosphorylation of glycerol -› TP for glycolysis.
- 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 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 (2)
• Glycolysis (anaerobic)
• Krebs cycle (aerobic)
What happens during anaerobic respiration in animals? (3)
• Only glycolysis continues
• Pyruvate acts as hydrogen acceptor (NADH + pyruvate)
Produces —>
• oxidised NAD (for further glycolysis) +
lactate
What happens to the lactate produced in anaerobic respiration? (2)
• Transported to liver via bloodstream, where it is oxidised to pyruvate.
• Can enter link reaction in liver cells or be converted to glycogen.
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 phosphorylation
• Produces fewer ATP (only 2 from glycolysis)
• produces ethanol/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 cause 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 CO, so that there is a net decrease in pressure as O, is consumed.
How could a student calculate the rate of respiration using a respirometer?
• Volume of O2 produced or CO, consumed/ time x mass of sample
• Volume = distance moved by coloured drop x (0.5 x capillary tube diameter)2 x Tr
