Metabolism and its controll Flashcards
What is metabolism?
is the sum of the chemical processes that occur within an organism to maintain life
What is catabolism
Breaking down of complex molecules into smaller ones releasing energy
What is anabolism?
building up of a complex molecule from two smaller ones requiring energy input
What is oxidation
Oxidation is loss of electrons
What is reduction
gain of electrons
What are the functions of NAD+ and FADH
Are coenzymes act as hydrogen carriers transport hydrogen to the ETC to release e and allow generation of ATP
What are some of the specialisation’s of the mitochondria
double membrane
forms inter-membrane space to allow accumulation of protons
lots of cristae increase the SA for ETC and ATP synthases
matrix contains specific enzymes for TCA cycle as well as for B oxidation . these are encoded for by the mitochondria’s own plasmid
Where does glycolysis occur
in the cytosl
What are the inputs and the outputs of hlycolysis
Inputs:
Glucose, 2ATP, 4ADP, 2Pi, 2NAD+
Outputs
2 pyruvate, 2NADH, 2 net ATP
What is the priming phase
conversion of glucose into fructose 1-6-bisphosphate required 2 ATP.
What are the two irreversible enzymatically controlled steps in the priming phase
conversion of glucose to glucose 6 phosphate via hexokinase (uses an ATP)
conversion of fructose 6 phosphate to fructose 1-6-bisphosphate via 6 phosphofructokinase
this directs molecules to ATP production
What are the final major two phases of glycolysis
splitting phase conversion of F1-6BP to 2GA3P
oxidoreduction phase whereby 2G3P is converted to pyruvate via pyruvate kinase this is irreversible
What then happens to the pyruvate produced from glycolysis
shuttled into mitochondrial matrix
What is pyruvate decarboxylation and where does it occur.
occurs in the mitochondrial matrix
pyruvate dehydrogenase converts pyruvate and CoA to aCoA and CO2.
also produces a NADH
this happens twice as there are 2 pyruvates produced from one glucose!
why is the control of pyruvatedecarboxylase so essential?
How is it controlled?
this is an irreversible step. A gaseous product is produced that cannot be trapped
this directs pyruvate into generation of ATP
is inhibited by high [ATP], high [NADH], and high [aCoA]
tightly controlled enzymatic feedback mechanism
citric acid cycle
Where does it occur
what is produced in one turn?
in the mitochondrial matrix
1 turn produces: 3NADH 1FADH2 1GTP 2CO2
what are the important irreversible control points in the citric acid cycle?
What are they controlled/inhibited by?
citrate synthase (adds aCoA to oxaloacetate to produce citrate and CoA)
isocitrate dehydrogenase which converts isocitrate to alpha ketoglutarate
a ketoglutarate dehydrogenase
that producess succinyl-CoA
All are inhibited by high [ATP] and high [NADH]
what happens to molecules in the TCA cycle when there is no need for the TCA cycle to turn?
can be filtered off for use in anaplertoic reactions
e.g. pyruvate can be used to produce alanine
or oxaloacetate can be used to produce aspartate
Outline the Electron transport chain
reduced hydrogen carriers bind to enzyme complexes embedded in the inner mitochondrial membrane
causes oxidation of h carrier and reduction of enzyme e- are donated and H+ are release into matrix
e- are passed from carrier to carrier passing into a lower energy state each time. release of energy as they pass from carriers allows pumping of H+ into inter-membrane space
generating a proton motive force
each H carrier will enter at different points and therefore pump a different amount of ATP across the membrane
O2 acts as the final electron acceptor taking e-, and using H+ from matrix forming H2O . Essential to allow ETC to continue
What is chemisomosis
H+ that have accumulated in the inter-membrane space may then move back through ATP synthases done a electrochemical gradient causing a conformational change in the enzyme allowing for the production of ATP via oxidative phosphorylation
What happens in brown adipose tissue
Mitochondria are uncoupled
therefore H+ that are pumped into inter-membrane space pass freely through UCP1 channels –> this releases heat energy allowing for thermogenesis in neonates
What is anaerobic respiration and what occurs?
Oxidative phosphorylation cannot occur as there is not enough O2 getting to respiring tissues.
To allow glycolysis to continue and some ATP to be generated there must be a supply of NAD+ (is no longer being oxidised in the ETC)
as such Pyruvate is converted to lactate and in this process pyruvate accepts e- from NADH to produce NAD+ and lactate. This allows Glycolysis to continue
What is the fate of lactate
lactate build up cause lactic acidosis so majority of it is transported to the liver
It is converted back to pyruvate via lactate dehydrogenase
this pyruvate can then be used by hepatocytes to produce new glucose molecule via gluconeogenesis this is known as the Cori cycle
What is gluconeogenesis? what does it require?
Production of glucose form non carbohydrate soucres
costly process requires: Pyruvate 4ATP 2GTP 2NADH to make a single glucose
