9- Metabolism 2 - fate in pyruvate Flashcards
(35 cards)
where is NAD+ derived from?
niacin, a vitamin
- there’s only limited amounts of NAD+ present in a cell
how is NAD+ regenerated and why does it need to be?
in glycolysis: NAD+ reduced to NADH & H+
NADH must be re-oxidised to let glycolysis continue
NAD+ is regenerated through oxidative metabolism of pyruvate
what is general function of NADH?
to deliver electrons (to respiratory chain)
where does the citric acid cycle occur?
in mitochondria
what are cristae?
the folds of the inner membrane of mitochondria
what is mitochondrial matrix space?
space between the folds of inner membrane
where are the enzymes for the TCA cycle?
in matrix of mitochondria
what does the inner membrane of mitochondria contain?
proteins for electron transport chain, ATP synthase and transport proteins
how does pyruvate enter mitochondrial matrix?
pyruvate transporter: H+/pyruvate symporter by facilitated diffusion
(very large H+ gradient from cytosol to matrix - pH gradient)
how does ATP, ADP & inorganic phosphate (Pi) move in/out of mitochondria?
through a similar process as pyruvate - voltage gradient drives ADP, ATP exchange and PH gradient drives phosphate import
how does pyruvate make acetyl CoA?
- The pyruvate dehydrogenase complex (PDC) catalyses the oxidative decarboxylation of pyruvate to acetyl-CoA
what is PDC?
- pyruvate dehydrogenase complex (PDC) consists of 3 enzymes
- is allosterically regulated by phosphorylation
- it catalyses pyruvate -> acetyl CoA
- PDC activity determines glucose oxidation in well oxygenated tissues
is pyruvate →acetyl CoA reversible or irreversible reaction?
irreversible (Acetyl-CoA cannot be converted back to pyruvate)
how many reactions in total are in TCA cycle?
8 reactions - all homeostatic = always return to same starting part if precursor available
what are the process of TCA cycle? (describe the pathway of all the carbons)
- 2 carbon unit (from acetyl CoA) condenses to 4 carbon unit resulting in 6 carbon unit (citrate)
- 6 carbon unit decarboxylated twice = yields 2 CO2 and 2 NADH
- this makes 4 carbon unit = yield NADH, FADH2, GTP
another 2 carbon unit from acetyl CoA then joins to 4 carbon unit and cycles again
does TCA cycle generate energy?
it makes reducing equivalents - it generates 1 GTP per turn and that can be turned to ATP so tiny energy yield but insignificant
what catalyses the first starting reaction of acetyl CoA to CoA-SH (coenzyme A) ?
citrate synthase
what is the only enzyme of TCA cycle not located in mitochondrial matrix?
succinate dehydrogenase - it’s integrated in the inner mitochondrial membrane
what does succinate dehydrogenase catalyse?
succinate + FAD -> fumarate + FADH2
what happens to electrons in each turn of TCA cycle?
in each turn:
3 pairs of electrons + NAD+ →NADH + H+
transfer of 1 pair of electrons to reduce FAD →FADH2
what is GTP formed from?
GDP + Pi by substrate level phosphorylation
how many carbons are uptaken and how many released in 1 TCA cycle? and in what form?
uptake of 2 carbon atoms in form of acetyl-CoA and release of 2 carbon atoms in form of CO2
what is an example of stage 2 metabolic disorder?
PDC deficiency = PDCD
pyruvate hydrogenase (PDH) is enzyme of pyruvate dehydrogenase complex
- gene located on X chromosome so survivable for females but not males
how many NADH produced overall per 1 glucose molecule?
10
(2 from glucose - pyruvate and then 3 in TCA cycle x 2 = 10)
