Section 5 - Unit 12: Respiration Flashcards
Describe how ATP is made in mitochondria (6 marks)
- Substrate level phosphorylation / ATP produced in Krebs cycle
- Krebs cycle / link reaction produces reduced coenzyme / reduced NAD /
reduced FAD - Electrons released from reduced / coenzymes / NAD / FAD
- (Electrons) pass along carriers / through electron transport chain / through
series of redox reactions - Energy released
- ADP / ADP + Pi
- Protons move into intermembrane space
- ATP synthase
Explain why it is important for plants to produce ATP during respiration
in addition to during photosynthesis (5 marks)
- In the dark no ATP production in photosynthesis
- Some tissues unable to photosynthesise / produce ATP
- ATP cannot be moved from cell to cell / stored
- Plant uses more ATP than produced in photosynthesis
- ATP for active transport / synthesis (of named substance)
Why does anaerobic respiration produce far less ATP than aerobic respiration? (3 marks)
- Anaerobic respiration relies on substrate level phosphorylation in the glycolytic pathway to produce a net 2 ATP per glucose
- Aerobic respiration produces 2 ATP from substrate-level phosphorylation in glycolysis, 2 ATP from substrate-level phosphorylation in the Krebs cycle and around 32 ATP from oxidative phosphorylation.
Explain why in the presence of oxygen, respiration yields more ATP per molecule of glucose than it does in the absence of oxygen (3 marks)
- Oxygen as terminal hydrogen / electron acceptor allowing operation of electron transport chain / oxidative phosphorylation
- Fate of pyruvate
- Significance of ATP formed in glycolysis
Where in a cell does glycolysis take place (1 mark)
Cytoplasm
Explain how fermentation allows glycolysis to occur (2 marks)
- Regenerates NAD
- NAD reduced in glycolysis
Explain why aerobic respiration produces more ATP per molecule of glucose than anaerobic respiration (2 marks)
- Oxygen combines with electrons and protons
- Electron transfer chain occurs in aerobic respiration in oxidative phosphorylation
- In anaerobic respiration, only glycolysis occurs
Describe how Acetylcoenzyme A is formed in the link reaction (2 marks)
- Hydrogen removed from pyruvate and carbon dioxide released
- Addition of coenzyme A
Explain why converting pyruvate to lactate allows the continued production of ATP during anaerobic respiration (2 marks)
- Regenerates NAD
- NAD used in glycolysis
In muscles, some of the lactate is converted back to pyruvate when they are well supplied with oxygen. Suggest one advantage of this (1 mark)
- Pyruvate used in aerobic respiration
OR - Lactate is toxic/harmful
Describe the part played by the inner membrane of a mitochondrion in producing ATP (3 marks)
- Electrons transferred down electron transport chain
- Provide energy to take H+ into space between membranes
- H+ pass back, through membrane through ATPase
- Energy used to combine ADP and phosphate to produce ATP
Name one step in which carbon dioxide is produced in aerobic respiration (1 mark)
- Krebs cycle
OR - Link reaction
Explain why oxygen is needed for the production of ATP on the cristae of the mitochondrion (3 marks)
- ATP formed as electrons pass along transport chain
- Oxygen accepts electrons from electron transport chain
- Forms H₂O / accepts H+ from reduced NAD
Where in a cell does the Krebs cycle take place (1 mark)
Mitochondrial matrix
Describe what happens to pyruvate in anaerobic conditions and explain why anaerobic respiration is advantageous to human skeletal muscle (4 marks)
- Forms lactate
- Use of reduced NAD
- Regenerates NAD
- NAD can be re-used to oxidise more respiratory substrate/allows glycolysis to continue
Name two substances formed from pyruvate during respiration (1 mark)
- CO₂
- Water
- ATP
- Reduced NAD
If there is a shortage of oxygen in muscle cells during exercise, some pyruvate is converted into lactate. Explain why muscles become fatigued when insufficient oxygen is available (2 marks)
- Build up of lactate lowers the pH
- Enzyme activity inhibited
Some of the lactate is oxidised to pyruvate by muscles when they are well-supplied with oxygen. Suggest an advantage of the lactate being oxidised in the muscles (2 marks)
- Lactate / pyruvate is an energy source
- Muscles have immediate ATP supply
- Restores pH levels
Describe the role of oxygen in aerobic respiration (2 marks)
- Final acceptor for hydrogen
- To form water
Name 3 substances produced in the Krebs cycle (3 marks)
- NADH
- FADH
- ATP
Explain the advantage of mitochondria in muscle cells having more cristae than in skin cells (2 marks)
- Larger surface area for electron transport chain / more enzymes for ATP production
- Muscle cells use more ATP (than skin cells)
Describe the roles of the coenzymes and carrier proteins in the synthesis of ATP (3 marks)
- NAD / FAD reduced
- Electrons transferred via a series of redox reactions
- Energy made available as electrons passed on
- Energy used to synthesise ATP from ADP and phosphate using ATPase
- Protons passed into intermembrane space
- Protons flow back through stalked particles / enzyme;
During respiration, where does the electron transfer chain take place (1 mark)
- Inner membrane of mitochondrion cristae
DNP inhibits respiration by preventing a proton gradient being maintained across
membranes. When DNP was added to isolated mitochondria the following changes were
observed
• less ATP was produced
• more heat was produced
• the uptake of oxygen remained constant.
Explain how DNP caused these changes (3 marks)
- No H+ movement so no ATP produced
- Heat released from electron transport / redox reactions - Oxygen used as final electron acceptor / combines with electrons (and protons)
Explain the process of glycolysis (4 marks)
- Phosphorylation of glucose
- Oxidation of triose phosphate
- Net gain of ATP
- Reduction of NAD to NADH
Explain why a Krebs cycle inhibitor would decrease the rate of oxygen uptake in a respiring cell (2 marks)
- NADH and FADH2 would not be produced ??
- Oxygen is the final electron acceptor
The change to the dissociation curve is one of a number of ways in which the total oxygen supplied to muscles is increased during exercise. Give two other ways in which the total oxygen supplied to muscles during exercise is increased (2 marks)
- Increase stroke volume
- Arterioles supplying the muscles dilate / vasodilation
Explain why people with faulty mitochondria have a higher than normal concentration of lactate in their blood after exercise (3 marks)
- Mitochondria / aerobic respiration not producing any ATP
- Increased use of ATP supplied by increase in anaerobic
respiration - More lactate produced and leaves muscle by (facilitated) diffusion
Explain why faulty mitochondria could lead to muscle weakness (3 marks)
- Reduction in ATP production by aerobic respiration
- Less force generated because fewer actin and myosin interactions in muscle
- Fatigue caused by lactate from anaerobic respiration
