Glycolysis, TCA, ETC Flashcards
What are the two outcomes of glycolysis depending on oxygen availability?
Pyruvate and lactate
Mnemonic for Glycolysis enzymes?
High Profile (isomerase) People (Phosphorylate) Act Too Glamorous (Phos. And oxidation) Picture (ATP) Posing Every Place (ATP)
What are the four isozymes of hexokinase?
Hexokinase I,II,III = low Km
Glucokinase IV = high Km (lower on graph) = only in liver, activity high after a meal, glucose is trapped as G6P in liver with high blood glucose levels
What’s the rate determining step of glycolysis?
Reaction 3; F6P –> FBP (fructose-6-phosphate and fructose-1,6-bisphosphate) not readily reversible, only reversible via Fructose bisphosphatase 1
Which steps of glycolysis are not reversible?
3 and 10 (1)
How many ATPs are used during the energy investment phase?
2
How many ATP are made during the energy generating phase?
4 total, 2 net made
1,3BPG has high ____
Energy potential for next step (step 7)
What is unique about GAP? What can inhibit this?
Covalently bound to cysteine of enzyme GAPDH, where heavy metals (Hg2+) can irreversibly bind.
If NADH is not oxidized, rxn stops
What are the high energy potential steps?
PEP for the next reaction (rxn 9)
And
GAP for rxn 7
What hexoses other than glucose are metabolized?
Galactose –> G6P
Fructose –> DHAP
Mannose –> M6P –> F6P
Other fates of Pyruvate
- Aerobic = TCA cycle
- Anaerobic = CO2 and ethanol , nonhumans
- Anaerobic = lactate (fermentation= 2ATP, 100x slower than oxidative resp)
What is the cori cycle
When lactate is taken to liver and converted back to glucose
Control points of glycolysis (3)
- Hexokinase
- Phosphofructokinase 1
- Pyruvate kinase
All have negative delta Gs
What does G6P regulate?
Inhibits Hexokinase I,II,III
Function of glucagon
Signals liver to release glycogen stores and inhibits glucokinase. Glucokinase only active when glucose levels rise
What inhibits and regulates Phosphofructokinase?
ATP and citrate inhibit.
ADP and AMP relieve inhibition and activate PFK1
Regulated by glucagon
What activates Phosphofructokinase (PFK1)
F2,6BP
What inhibits hexokinase?
G6P
Function of glucagon?
Signals liver to release glycogen stores and inhibit glucokinase
What happens during a Fed state?
Insulin is released
PFK2 is dephosphorylated
High F2,6BP levels which stimulate kinase activity
What occurs during fasting state?
Glucagon is released
Protein kinase A activated
Phosphorylation of PFK2
Decreased F2,6BP
What inhibits Pyruvate kinase?
ATP and acetyl CoA (a sign of abundant energy in cell)
Can be inactivated by phosphorylation
Stimulated by F1,6BP
What are the alternative pathways of glycolysis?
2,3 BPG Shunt
Pentose phosphate shunt
What is the net payout for Glycolysis?
2 ATP, 2 NADH, 2 Pyruvate
Two shuttles that transport cytosolic NADH into mito
- Malate aspartate shuttle
2. Glycerol phosphate shuttle
Inhibitors of ETC (RMACCO)
Rotate - Rotenone Mouth - Malonate And - Antimycin A Cum - Carbon monoxide, cyanide Orally - oligomycin
Overall yield of TCA
2 CO2
3 NADH
1 FADH2
1 ATP
Five coenzymes needed for PDH
TPP (B1) Pantothenic acid b5 Lipoamide FAD (B2) NAD (B3)
How many cycles does TCA do?
2 because you have 2 Pyruvate from glycolysis
Cataplerotic pathways
Use TCA intermediates by avoiding built up
What are Anaplerotic pathways?
Make TCA intermediates
What are the environmental inhibitors of TCA
Arsenate, binds sulfhydryl compounds = lipoamide
Fluoroacetate (FAC) , binds aconitase as competitive inhibitor
Diseases associated with TCA disorders?
Alpha-ketoglutarate dehydrogenase
Fumarase
Succinate dehydrogenase
= cause neurological impairments, encephalitis
