Exam 4 Flashcards
Where does the TCA connect to gluconeogenesis and glycolysis?
Gluconeogenesis- via oxaloacetate
Glycolysis- pyruvate
What do dehydrogenases do?
Convert NAD to NADH, except succinate dehydrogenase it converts FAD to FADH2
What are the products of the TCA cycle?
1 ATP
3 NADH
1 FADH_2
2 CO_2
What is the mnemonic for TCA Cycle?
Can I Keep Selling Seashells for Money Officer?
Citrate, Isocitrate, a-Ketoglutarate, Succinyl COA, Succinate, Fumarate, Malate, Oxalacetate
What is the rate limiting step of TCA? Why?
Isocitrate dehydrogenase, loss of CO_2 drives rxn forward, low delta G
What happens when TCA intermediate concentrations are low and energy is high
Glycolytic intermediates can be converted for use
What are the activators of the TCA cycle?
ADP/AMP, Ca2+
What are the inhibitors?
ATP, too much product of a step
Oxidation of what forms the most energy than any form of carbon?
fatty acids
Function of fat?
main energy source of energy for liver, heart, and resting skeletal muscle
What are fatty acids initially present as?
Triacylglycerols
How are fatty acids released? Location from and to?
B-oxidation, cytosol to mitochondria
4 Steps of Fatty acid activation?
- fatty acid couples to COA
- Carnitine acyl transferase 1 catalyzes transesterification rxn to form fatty acyl carnitine
- acyl carnitine cotransporter allows for passive transport of fatty acyl carnitine
- Carnitine acyl transferase 2 transfers fatty acid group from carnitine back to coA for regeneration
What are the stages of catabolism?
- Acetyl-COA production
- Acetyl-COA oxidation
- Electron transfer oxidative phosphorylation
What does the production stage involve?
Glucose to Pyruvate to Acetyl-COA
What does the oxidation stage involve?
TCA Cycle
Describe the conversion of oxaloacetate and acetyl COA to Citrate
Oxaloacetate comes from gluconeogenesis, Citrate Synthesase and water push rxn, very delta neg so very favorable
Citrate to Isocitrate
Water shifts conformation of H and OH bond
Isocitrate to alpha Ketoglutarate
Isocitrate dehydrogenase, Isocitrate oxidized by NADP, MG2+ coordinate, carboxyl removal to CO_2
Alpha Ketoglutarate to Succinyl COA
A-Keto dehydrogenase complex, removal of CO_2 and addition of -S-COA
Succinyl COA Synthesase Rxn (Succinate)
-S-COA COA is replaced with P group, P removed and added to His, P then moves to GTP
Succinate to Fumarate
Succinate dehydrogenase, removal of two H+ and production of FADH_2, leads to fumarate
Fumarate to Malate
Hydration of Fumarate
Malate to Oxaloacetate
Double bond of C, two H+ leave
What are the products of TCA Cycle?
1FADH_2
3 NADH
1 ATP
TCA intermediates low but energy high?
Glycolytic intermediates converted for TCA
What does it mean that the TCA cycle is amphibolic?
Not just cyclical involved in catabolic and anabolic rxns
When energy is high?
TCA intermediates used in biosynthesis
Features of fats
pack tightly
main source of energy for heart, liver, skeletal muscle
stored in adipose tissue
source of metabolic water
What is required to bypass pyruvate kinase?
PEP and pyruvate carboxylase
General activators of TCA Cycle?
ADP, Ca2+
What is the immediate fate of fatty acids?
Bile salts breakdown fats, Mixed Micelles, Lipase degrade triacylglycerol, mixed with cholesterol/apolipoproteins into chylomicrons to lymph to bloodstream to tissues to lipase converts triacyclglycerols into fatty acids (either used as fuel or storage)
General inhibitors of TCA cycle?
ATP, NADH, precursors
Fat is very high in energy
T
What acts as an open gate for triacyclglycerols?
Perilipin
How are fatty acids activated and transported in the mitochondria?
- Fatty acids coupled to COA
- Transesterification to carnitine (Cotransporters allow for passive transport)
- CPT2 transesterifies fatty acyl carnitine back to COA (separates carnitine and fatty acyl COA)
Is B oxidation efficient?
Yes at 60%
Odd chain versus straight chain fatty acids?
Odd chain utilizes B12 and methomalonyl COA
How does fatty acid synthesis work?
High glucose leads to activation of insulin to fatty acid formation
MalonylCOA inhibits what?
Oxidation
During starvation, acetyl COA can be converted to what?
Ketone bodies
What are ketone bodies? Where are they formed?
Alternative source of energy for liver, heart, skeletal muscle, mitochondria
Ketone bodies can be converted back to COA. Why?
soluble, COA is often limiting, formation of ketone bodies produce COA
An increase in gluconeogenesis leads to depletion of oxaloacetate which slows TCA, leads to buildup of acetyl COA which then is converted to ketone bodies
________________
What happens in a long fasting period?
Production of glucogenic acids into liver
Kidney receives urea, TCA intermediate oxaloacetate shifts to gluconeogenesis, leads to buildup of acetyl COA which increases production of ketone bodies
fatty acids come in from adipose tissue in liver which is then oxidized for fuel which produces acetyl coa
An increase in gluconeogenesis decreases or increases TCA? Ketone formation?
Decreases TCA, Increases ketone body formation, can lead to ketoacidosis
In the well fed state what does insulin signal?
glucose to enter cells
fats to convert to fatty acids in muscle
fats converted to triacylglycerol in liver and adipose tissue
amino acids to go to liver to produce proteins, urea and a-keto acids
