Cell metabolism 1 & 2 Flashcards
steps of cellular metabolism?
glycolysis, krebs/TCA cycle, oxphos
types of reactions which define metabolism?
redox, litigation requiring ATP cleavage, isomerisation, group transfer, hydrolytic, addition/removal of functional groups
overall process of glycolysis?
glucose forms 2 three carbon pyruvate
does glycolysis need oxygen?
no, it’s an anaerobic process
two stages of glycolysis?
formation of a high-energy compound, splitting of high-energy compound
step one of glycolysis
glucose –> glucose-6-phosphate
ATP –> ADP
enzyme is hexokinase
this is a GROUP TRANSFER
why is step one of glycolysis important?
commits glucose-6-phosphate to cell as it’s negatively-charged so cannot leave cell via glucose transporters
step 2
glucose-6-phosphate —-> fructose-6-phosphate
enzyme = phosphoglucose isomerase
it’s an ISOMERISATION reaction
step 3
fructose-6-phosphate —> fructose-1,6-bisphosphate
ATP - ADP
enzyme = phosphofructokinase
= GROUP TRANSFER
step 4
fructose-1,6-bisphosphate —> glyceraldehyde-3-phosphate and dihydroxyacetone phosphate
enzyme = aldolase
this is a HYDROLYTIC reaction
step 5
dihydroxyacetone phosphate —-> glyceraldehyde-3-phosphate
enzyme = TPI
ISOMERISATION reaction
step 6
glyceraldehyde-3-phosphate –> 1,3-bisphosphoglycerate
enzyme = glycerade-3-phosphate dehydrogenase
= REDOX and GROUP TRANSFER
step 7
1,3-bisphophoglycerate –> 3-phosphoglycerate
ADP –> ATP
enzyme = phosphoglycerate kinase
= GROUP TRANSFER
step 8
3-phosphoglycerate —> 2-phosphoglycerate
enzyme = phosphoglycerate mutase
reaction = ISOMERISATION
step 8
3-phosphoglycerate —> 2-phosphoglycerate
enzyme = phosphoglycerate mutase
reaction = ISOMERISATION
step 9
2-phosphoglycerate —-> phosphoenol pyruvate
enzyme = enolase
reaction = GROUP REMOVAL
step 10
phosphoenol pyruvate —> pyruvate
enzyme = pyruvate kinase
ADP —-> ATP
reaction = GROUP TRANSFER
net result of glycolysis?
2 pyruvate, 2 NADH, 2 ATP
three fates of pyruvate?
alcoholic fermentation (anaerobic)
pyruvate —-> acetaldehyde
enzyme = pyruvate decarboxylase
acetaldehyde —> ethanol
enzyme = alcohol dehydrogenase
lactate fermentation
pyruvate —-> lactate
enzyme = lactate dehydrogenase
main concept of these two reactions is regenerating NAD+ so glycolysis can continue in anaerobic conditions
third fate:
pyruvate —-> acetyl CoA
enzyme = pyruvate dehydrogenase complex
this produces NADH
why is NAD+ needed?
dehydrogenation of glyceraldehyde-3-phosphate, first step in generating ATP
creatine phosphate?
ATP buffer when exercising
creatine phosphate —> creatine
ADP —> ATP
enzyme = creatine kinase
creatine kinase?
the enzyme which is used to catalyse the reaction from creatine phosphate to creatine
used by athletes as a dietary supplement
what bond in acetyl CoA?
thioester bond
high-energy bond that is readily hydrolysed so acetyl CoA can donate acetate to other molecules
beri-beri
caused by a thiamine deficiency
symptoms include damage to peripheral nervous system, decreased cardiac output and weakness of cardiac musculature
brain is particularly vulnerable as it relies heavily on glucose metabolism
what does each turn of the TCA/krebs cycle produce?
2 x CO2
3 x NADH
1 x GTP
1 x FADH2
when is the bulk of ATP generated?
oxidative phosphorylation
which other molecules can enter TCA cycle?
amino acids, fatty acids
two types of amino acid
glucogenic - can produce glucose via gluconeogenesis
ketogenic - can produce acetyl CoA
how many molecules can be created by the degradation of all 20 amino acids?
seven
how do proteins enter the TCA cycle?
transamination reactions, then carbon skeleton is funnelled into cycle
transamination reaction?
= transferral of amine group
nh4+ generated which is converted to urea and excreted as waste product
an amino acid and keto acid form another pair of amino acid and keto acid
alanine metabolism?
alanine + a-ketoglutarate —-> pyruvate + glutamate
NADH transportation?
NADH needs to be transported into the mitochondria so it can be used in oxidative phosphorylation and so NAD+ is regenerated as there is only a finite amount
the high-energy electrons are transported into the mitochondria
two methods of NADH transport and where?
malate-aspartate shuttle - in kidney, lung and heart
glycerol-phosphate - in skeletal muscle and brain
glycerol-phosphate shuttle?
only electrons from NADH move
glycerol-3-phosphate dehydrogenase transfers electrons from NADH to DHAP generate glycerol-3-phosphate
membrane-bound form of the same enzyme transfers electrons to FAD, these then get passed to co-enzyme Q (part of electron transport chain)
