METABOLISM Flashcards
Glycolysis, Citric Acid Cycle, etc.
What are anabolic pathways?
biosynthetic, reductive
build complex molecules from simpler ones and typically need an input of energy.
require:
- an energy source
- reducing equivalents - source of H+ (e.g NADPH, NADH)
What are catabolic pathways?
degradative, oxidative
involve the breakdown of complex molecules into simpler ones and typically release energy.
provide:
- energy
- reducing equivalents
- precursors
STAGE 1 OF GLYCOLYSIS
1) Glucose receives a phosphate group from ATP - irreversible
2) Hexokinase catalyses the change from glucose to Glucose-6-phosphate
3) Phosphoglucose isomerase catalyses the isomerising of Glucose-6-phosphate into Fructose-6-phosphate
4) Phosphofructokinase catalyses the phosphorylation of fructose-6-phophate into fructose-1,6-biphosphate (rate-limiting step)
STAGE 2 OF GLYCOLYSIS
1) Fructose-1,6-biphosphate is split into two 3-carbon molecules
- Glyceraldehyde 3-phosphate (GP)
- Dihydroxyacetone phosphate
What catalyses Fructose 1,6-biphosphate to Glyceraldehyde
Aldolase
What catalyses Fructose-1,6-biphosphate to Dihydroxyacetone phosphate
trios phosphate isomerase
STAGE 3 OF GLYCOLYSIS
G-3-p to … catalysed by…
1,3-biphosphoglycerate by G-3-P dehydrogenase
1,3-biphosphoglycerate to …. by ….. generating ….
3-phosphoglycerate by phosphoglycerate kinase
- generates ATP
phosphoenolypyruvate to …. by… generating….
pyruvate by pyruvate kinase
- generates ATP
ATP produced in glycolysis
2
First reaction in the citric acid cycle
aldol condensation reaction followed by hydrolysis
oxaloacetate to citrate
what catalyses the reaction of oxaloacetate to citrate
citrate synthase
Second reaction in the citric acid cycle
citrate to isocitrate
what is the intermediate? (citrate to isocitrate)
cis-aconitate
Second reaction in the citric acid cycle is catalysed by…
aconitase
What is Aconitase? How does it work?
An iron-sulphur protein used in the two-part second reaction of the citric acid cycle.
- one of the iron atoms binds to the citrate
- facilitates the dehydration/hydration reactions
Third reaction in the citric acid cycle
isocitrate to oxalosuccinate to alpha-ketogluterate
catalysed to isocitrate dehydrogenase
Fourth reaction in the citric acid cycle
alpha-ketoglucerate to succinylcholine coa
catalysed by a-ketoglucerate dehydrogenase complex
production of NADH
Fifth reaction in the citric acid cycle
succinyl CoA to Succinate
catalysed by succinyl CoA synthase
production of CoA + GTP
Sixth reaction in the citric acid cycle
succinate to fumirate
catalysed by succinate dehydrogenase
key step in production of FADH2
7th reaction in the citric acid cycle
fumerate to malate
catalysed by fumerase
8th reaction in the citric acid cycle
malate to oxaloacetate
catalysed by malate dehydrogenase
key step in the production of NADH
What is type of reaction does PYRUVATE DEHYDROGENASE have
irreversible reaction
Isocitrate dehydrogenase is inhibited by …
ATP and NADH
A-ketogluterate dehydrogenase is inhibited by …
ATP, succinyl CoA and NADH
Pyruvate dehydrogenase is inhibited by …
ATP, acetyl CoA and NADH
Arsenic and Mercury inhibit Citric Acid Cycle. How?
inhibiting pyruvate dehydrogenase complex by inactivating the dihydrolipomide component of the transacetylase
Overall reaction of Citric Acid Cycle
Acetyl CoA + (3NAD+) + FAD + GDP + Pi ——> 2CO2 + 3NADH + FADH2 + GTP + CoA
Product yields in citric acid cycle
CO2
2
Product yields in citric acid cycle
GTP
1
Product yields in citric acid cycle
NADH
3 (six electrons)
Product yields in citric acid cycle
FADH2
1 (two electrons)
Citric acid cycle location in eukaryotic cell
mitochondrial matrix
Citric acid cycle location in prokaryotic cell
cytoplasm (mesosomes)
ATP YIELD FROM OXIDATION OF PALMITATE
Net yield of 106 ATP
8 acetyl CoA - 8 X 10 ATP = 80 ATP
7 NADH - 7 X 2.5 ATP = 17.5 ATP
7 FADH2 - 7 X 1.5 ATP = 10.5 ATP
108 ATP - 2 ATP (cost of activation to palmitoyl-CoA)
Function of the carnitine shuttle
used to transport fatty acyl coA from the cytoplasm to the mitochondrial matrix
Does the carnitine shuttle require ATP AND NADPH?
no.
Requires no chemical energy supply
What inhibits the carnitine shuttle?
Malonyl-CoA
