Carbohydrate (4) Flashcards
What is the role of Pyruvate dehydrogenase ?
Used to convert Pyruvate into acetyl coA.
What are key features of the link reaction ?
- irreversible reaction as co2 is released.
- NAD is converted into NADH.
- happens in the mitochondrial matrix.
Explain the key principles of the TCA cycle (Krebs)
- oxidative ( requires NAD+ , FAD+)
- some energy produced ATP/GTP
- irreversible reaction ( produces co2)
- substrate level phosphorylation occurs to make ATP
- produces precursors for biosynthesis
- ## does not function in the absence of O2.
How is the TCA cycle regulated ?
- ATP/ADP ratio
- NADH/NAD+ ratio
- for example high energy signal NADH inhibits the TCA cycle , whereas the TCA cycle is activated by low energy signal ADP.
Summarise the catabolism of glucose so far in the TCA cycle
- all C-c bonds broken
- all C atoms are oxidised to co2.
- all C-H bonds broken
- all H atoms are transferred to NAD+ and FAD
Outlinethe process the process of oxidative phosphorylation
Electrons are transferred across the carrier molecules.
- they lose energy as they move across the carrier molecules.
- this energy is used to actively pump H+ ions from the matrix of the mitochondria into the inter membrane space.
- this builds up an electrochemical gradient
- h + enters ATP synthase which uses the proton motive force to generate ATP,
- oxygen acts as the final electron acceptor to make water.
What happens when there is low ADP concentration , but high ATP concentration in oxidative phosphorylation? ( an example of regulation)
- less ADP means there is less substrate for ATP synthase.
- inward flow of H+ ions into the matrix via atp synthase stops.
- concentration of H+ increases in the intermembrane space.
- prevents further pumping of H+
- electron transport chain is halted
What is an example of inhibition of oxidative phosphorylation ?
- anaerobic respiration which can occur through cyanide or carbon monoxide being present.
- they bind to cytochrome C oxidase , this prevents oxygen being used as a the final electron acceptor
- this prevents the flow of electrons across electron transport chain , less H+ pumped too,
What is the role of uncouplers ?
- theythey uncouple the electron transport chain from ATP to produce heat.
- increase permeability of thr inner mitochondrial membrane to H+ ions. H+ enters mitochondria which ruins the proton gradient. This prevents P.M.F SO ATP IS NOT MADE.
- ECT continues , so O2 can still act as an electron acceptor And heat is still produced.
What is an example of an uncoupler ?
Thermogenin ( UCP1)is found in brown adipose tissue.
Explain the role of thermogenin ( UCP1) in brown adipose tissue ?
- non-shivering thermoregulation : noradrenaline is produced.
2. this stimulates lipolysis by lipase which releases fatty acids.
3. beta oxidation of fatty acids occur which produces NADH/FADH2. The H+ from these molecules can enter two different pathways : either through ATP synthase where ATP would be produced OR through UCP1 where ATP is not produced and instead heat would be produced in the matrix of the mitochondria.
4. So UCP1 dissipates the proton gradient and PMF no longer occurs regularly. So energy by proton motive force is dissipated as heat.
Where is brown adipose tissue found in ?
- newborn infants to maintain heat.
- hibernating animals to generate heat to maintain body temperature
What are 3 differences between oxidative phosphorylation
And substrate level phosphorylation ?
SL - can occur with limited O2 , whereas OP cannot.
- OP is a major process of ATP production , whereas SL is a minor process for ATP synthesis
- OP requires membrane associated complexes , whereas SL requires soluble enzymes in matrix and cytoplasmic.
What is Pyruvate dehydrogenase activated by ?
- ADP
- NAD+
- INSULIN
- PYRUVATE
-
What is Pyruvate dehydrogenase inhibited by ?
- acetyl coA
- NADH
- ATP
- citrate
