Metabolism Flashcards
Glycolysis occurs where?
cytoplasm (of all cells)
Does glycolysis require oxygen?
no
Per 1 glucose, glycolysis yields ____ ATP
2
Glucokinase
liver, low affinity for glucose compared to hexokinase, acts when BG is high, induced by insulin
G –> G-6-P
step 1 of liver glycolysis & glycogen synthesis
Hexokinase
traps glucose
G –> G-6-P
PFK-1
rate limiting step
F-6-P –> F-1,6-BP
PFK-2
makes the F-2,6-BP that activates PFK-1
F-6-P –> F-2,6-BP
GAPDH
produces NADH
GA-3-P –> 1,3-BPG
Pi + NAD+ –> NADH + H+
3-phosphoglycerate kinase
substrate level phosphorylation
ADP –> ATP
pyruvate kinase
substrate level phosphorylation
ADP –> ATP
which enzymes catalyze irreversible reactions in glycolysis?
glucokinase/hexokinase
PFK-1
pyruvate kinase
How is the NADH produced from glycolysis oxidized aerobically?
mitochondrial ETC
How is the NADH produced from glycolysis oxidized anaerobically?
cytoplasmic lactate dehydrogenase
pyruvate dehydrogenase
pyruvate –> acetyl-CoA + NADH
____ stimulates pyruvate dehydrogenase
insulin
____ inhibits pyruvate dehydrogenase
acetyl-CoA
Citric acid cycle occurs where?
mitochondrial matrix
pyruvate & fatty acyl CoA cross the membranes, and acetyl CoA is made in matrix
What is the purpose/products of the citric acid cycle?
to oxidize acetyl-CoA to CO2
generates:
NADH
FADH2
GTP
ETC occurs where?
inner mitochondrial membrane
Reduction potentials ____ down the ETC until the electrons end up on _____ which has the _____ reduction potential.
increase
oxygen
highest
____ can’t cross the inner mitochondrial membrane
NADH
What are the 2 shuttle mechanisms used to transfer electrons to mitochondrial matrix
glycerol 3 phosphate shuttle
malate-aspartate shuttle
Complex I
NADH –> NAD+ + H+
2e- –> Q
4H+ to inter membrane space
Complex II
succinate –> fumarate + 2H+
e- –> Q via FAD
0H+ transfer in this step
Complex III
receives e- from Q –> passes to cytochrome c
4H+ to inter membrane space
Complex IV
receives e- from cytochrome c
reduces O2:
O2 + 4H+ –> 2H2O
2H+ to inter membrane space
ATP synthase
ADP + Pi –> ATP
3H+ returns to matrix
What force is used as energy to make ATP in the ETC?
Proton-motive force, made by the proton gradient between the inter membrane space and the mitochondrial matrix
What is the energy yield from glycolysis of 1 glucose molecule?
2 NADH
2 ATP
= 7 ATP
What is the energy yield from pyruvate dehydrogenase of 2 pyruvate molecules (1 glucose molecule)?
2 NADH
= 5 ATP
What is the energy yield from citric acid cycle x2 (1 glucose molecule)?
6 NADH
2 FADH2
2 GTP
= 20 ATP
What is the total energy yield from metabolism of 1 glucose molecule?
32 ATP
How much ATP does 1 molecule of NADH yield?
2.5 ATP
How much ATP does 1 molecule of FADH2 yield?
1.5 ATP
Glycogenesis
glycogen synthesis
Glycogenolysis
breakdown of glycogen
Gluconeogenesis
reverse of glycolysis (generation of glucose from lactate, glycerol, some amino acids)
Gluconeogenesis occurs where?
cytoplasm & mitochondria, mostly in liver
What enzymes in gluconeogenesis bypasses pyruvate kinase?
Pyruvate carboxylase
PEP carboxykinase
What enzyme in gluconeogenesis bypasses PFK-1?
F-1,6-BP-ase
What enzyme in gluconeogenesis bypasses hexokinase/glucokinase?
G-6-P-ase
What 2 enzymes are used for glycogenesis?
glycogen synthase
branching enzyme
Glycogen synthase creates _______ ________ between _____ molecules
alpha 1,4 glycosidic links between glucose molecules
Glycogen synthase is activated by _____ in the ____ and ____
insulin in the liver and muscles
Branching enzyme moves a block of oligoglucose from ______ and connects it as a ______ using ________
one chain
branch
alpha 1,6 glycosidic link
What 2 enzymes are used for glycogenolysis?
glycogen phosphorylase
debranching enzyme
glycogen phosphorylase breaks _______, removing _______
alpha 1,4 glycosidic links
G-1-P molecules
Glycogen phosphorylase is activated by _____ in the ____ and by ____ & ____in ____
glucagon in the liver
epi & AMP in exercising muscle
Debranching enzyme moves a block of oligoglucose from ______ and connects it to the ______ using ________
one branch
chain
alpha 1,4 glycosidic link
Pentose Phosphate Pathway
generates NADPH and sugars
what is the rate limiting step of the PPP?
G-6-P dehydrogenase (activated by NADP+ & insulin)
PPP occurs where?
cytoplasm of most cells
How many electrons does cytochrome c carry?
1
How many electrons does coenzyme Q carry?
2
How does active muscle generate energy?
anaerobic metabolism (glycolysis) oxidative phosphorylation (ETC) direct phosphorylation (CP) fatty acid oxidation
How does cardiac muscle generate energy?
fatty acid oxidation
How does the brain generate energy?
1 glucose
2 starvation –> ketolysis
What does resting muscle use for energy?
free fatty acids
conserves carbs as glycogen
What is the key enzyme in cholesterol biosynthesis?
HMG-CoA reductase
What is the only fatty acid that humans can synthesize? Where is it made? From what?
Palmitic acid
Cytoplasm
Acetyl-CoA
Fatty acid oxidation occurs where?
Mitochondria
Beta oxidation reaction
acyl CoA + FAD + NAD+ + H2O + CoA → acyl CoA (less 2 carbons) + FADH2 + NADH + H+ + acetyl CoA
Beta oxidation generates _____ to enter the _______
acetyl CoA
citric acid cycle
_____ is transported into the mitochondria via the ______ ______ for use in beta oxidation
acyl CoA
carnitine shuttle
_____ form during prolonged periods of starvation due to excess ______ in the liver
ketone bodies
acetyl CoA
ketolysis breaks down _____ _____ into ________
ketone bodies
acetyl CoA
Carbon skeletons of amino acids are used for energy in ______ or ______
gluconeogenesis
ketone body formation
amino groups from amino acids are fed into the _____ _____ for excretion
urea cycle
In the absence of oxygen, _____ from glycolysis will be converted into ______ in the _______
pyruvate
lactate
cytoplasm
