Describe the process of glycolysis
glucose —–> pyruvate
1. activate glucose by phosphorylation. This requires the hydrolysis of 2 molecules of ATP to 2 x ADP to provide the 2 phosphates
2. glucose phosphate then splits into 2 x triose phosphate
3. triose phosphate is then oxidised to pyruvate which involves the loss of H which reduces the hydrogen carrier molecule NAD to NADH2 ATP is also produced directly at this stage via substrate level phosphorylation
What are the glycolysis of glucose yields
- 2 NET ATP directly by substrate level phosphorylation
- 2 reduced NAD
- 2 molecules of pyruvate
Describe the link reaction
- pyruvate actively transported into mitochondrial matrix
- pyruvate converted to acetyl co A
- pyruvate oxidised to acetate & the hydrogen removed is used to reduce the hydrogen carrier ‘NAD’ to form reduced NAD (NADH2) and a molecule of coenzyme A is also required
- a molecule of CO2 is also lost
- NO ATP is produced directly in the link reaction
What are the link reaction yields?
- reduced NAD
- 2 acetyl co A
- CO2
Describe the process of the Krebs cycle
- 2C acetyl co A combines with 4C molecule to form 6C compound
- 6C compound loses CO2 & Hydrogen to convert to a 4C compound and 1 x ATP (via SLP)
What are the yields of the krebs cycle?
- 2 x CO2 produced
- some ATP produced directly by substrate level phosphorylation
- 3 x reduced NAD and 1 x FAD produced to be used in oxidative phosphorylation
- 1 molecule of glucose
- 2 molecules of acetyl co enzyme A = krebs cycle happens twice
Describe how oxidation takes place in glycolysis and in the krebs cycle (3)
- removal of hydrogen
- by enzymes
- Hydrogen accepted by NAD
- in krebs cycle, FAD used aswell
Describe the electron transport chain (ETC)
- reduced H carriers are oxidised losing hydrogen
- electrons from hydrogen pass down a series of electron carriers within mitochondrial membranes in a series of REDOX reactions
- as electrons pass along ETC they lose energy some of which is used to pump H+ into intermembrane space
- some energy is also lost as heat
- the H+ diffuse down proton gradient across inner membrane into matrix via ATP synthase, as they pass down enough energy is provided to form ATP
- electrons and H+ recombine with O2 to form water
- oxygen is terminal electron acceptor
- without oxygen removing H+ and electrons, there would be a ‘back up’ of electrons along ETC & process of cellular respiration will come into halt
water is a waste product of aerobic respiration. Describe how water is formed at the end of aerobic respiration
- oxygen is terminal electron acceptor
- combines with electrons and protons to form water
Describe the role of co enzymes and carrier proteins in the synthesis of ATP (3)
- reduced NAD and reduced FAD
- electrons transferred from coenzyme to co enzyme
- energy released as electrons passed down
- energy used to synthesise ATP from ADP and Pi using ATP synthase
- H+ pumped into intermembrane space
- H+ diffuse back through ATP synthase
Describe how ATP is made in mitochondria
- substrate level phosphorylation
- krebs cycle and link reaction produces reduced NAD & FAD
- electrons released from reduced NAD & FAD pass along ETC
- energy released
- protons pumped into intermembrane space
- ADP + Pi
- ATP synthase
Describe the events of oxidative phosphorylation
- reduced NAD & FAD
- ETC on cristae
- electrons transferred from coenzyme to coenzyme
- energy released as electrons passed on
- protons pumped into intermembrane space
- protons flow back through stalked particles
- energy used to synthesise ATP from ADP and phosphate using ATP synthase
Explain how the amount of ATP is increased by reactions occurring inside a mitochondrion
- removal of electrons and H+
- from pyruvate
- acetyl co A
- substrate level production of ATP
- production of reduced NAD & FAD
- in matrix of mitochondria
- electrons fed into ETC
- electrons pass along ETC
- energy released
- protons move into intermembrane space
- ADP + Pi
- ATP synthase
What are respirometers?
As animal or plants respire:
- oxygen is used for aerobic respiration
- this reduced the volume of oxygen in the tube therefore reducing the pressure
- solution of KOH absorbs the CO2 released by animal or plant
- therefore the ink in the connecting tube moves from higher to lower pressure along the graduated scale
- measure time taken
Describe the process of glycolysis (3)
- phosphorylation of glucose using ATP
- oxidation of triose phosphate to pyruvate
- net gain of ATP
- NAD reduced
In many mammals, ‘uncoupling proteins’ help to maintain a constant body temperature during hibernation.
Suggest and explain how.
- allow passage of protons
- energy released as heat
The mitochondria in muscles contain many cristae. Explain the advantage of this.
- larger surface area for ETC
- provide more ATP
Give two reasons why the respirometer was left for 10 minutes when it was first placed in the water bath.
- equilibrium reached
- allow pressure change in apparatus
- allow respiration rate of seeds to stabilise
explain why a log scale is used to record the number of bacteria
- large range/difference in numbers
(increase)
Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration
- regenerates 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.
- less reduced NAD
- fewer electrons removed
- oxygen is the terminal electron acceptor
