Post on 02-Jan-2016
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Regulation of Calvin cycle
Rubisco is a prime target for regulation
Activation of rubisco by carbamate
Rubisco is activated by carbamylation
CO2 concentration?
pH?
Mg2+ concentration?
Alkaline pH favors
fig20-34
high light
Stroma pHAnd Mg2+
conditions regulate stromal FBP-1
Activation of Rubisco
Redox regulation of Calvin cycle with Thioredox: Activation of enzymes by regulating redox states of a disulfide bond
fig20-36
high light Th-SHenz
activity
redox regulation of Calvin cycle enzymes via thioredoxin
Coordination of the light and dark reactions
Electron transfer
Reduced ferrodoxin
Thioredoxin
Regulatory disulfide bonds in Calvin cycle enzymes
Light reactions
Dark reactions
Coordination of the light and dark reactions
Electron transfer
Reduced ferrodoxin
Thioredoxin
Regulatory disulfide bonds in Calvin cycle enzymes
Light reactions
Dark reactions
pHMg2+
Fat Metabolism
Americans are getting fatter, so do the people in other developed countries
Triacylglycerol: Fatty acids and glycerol
Also called triglycerides or neutral fats
Fatty acids
Various lipids
Dietary fats form micelles with the help of Bile salts
Lipases release fatty acids and monoacylglycerol
Transport lipids in Chylomicrons
from McDonalds to Metabolism…
Summary of dietary lipids processing
Molecular structure of Chylomicrons
Mobilization of the stored Triacylglycerol in adipose tissue
Transport fatty acids from adipose tissue to muscle or other tissue
Serum albumin
Fatty acids and glycerol are the products from lipase cleavage
Fate of glycerol
Physiological roles for fatty acids
Building blocks for phosphalipis and glycolipids
Covalent modification of proteins
Fuel
Precursor for hormones and signaling molecules
Fatty acids are oxidized in matrix of mitochondria
Activation and transport fatty acids to mitochondria
Three enzymatic reactions:
Acyl CoA synthetase
Carnitine acyl transferase I
Carnitine acyl transferase II
Activates fatty acid to form Acyl CoA
Driving by hydrolysis of pyrophosphate
Transport Fatty acids into mitochondria
Carnitine acyltransferase I
Carnitine acyltransferase II
Formation of Acyl carnitine
Normally, the transfer of an acyl group from an alcohol to sulfhyfryl group is thermodynamically unfavorable
Four basic steps in -oxidation
Recurring metabolic motifs
Acyl-CoA dehydrogenase: an enzyme similar to succinate dehydrogenase
The enzyme is located on the inner membrane
The product is always trans
fig19-8
Complex II succinate dehydrogenase
Electron-transferring flavoprotein
Enoyl-CoA hydratase: similar to fumarase
Always L configuration
B-hydroxyl-CoA dehydrogenase: similar to malate dehydrogenase
Only use L type of substrate
Thiolase
-oxidation challenges
monounsaturated FA
polyunsaturated FA
odd-carbon FA
An isomerase is needed for unsaturated
-oxidation ofpolyunsaturatedfatty acids
fig17-10
-oxidation ofpolyunsaturatedfatty acids
fig17-10
A reductase and an isomerase
Odd-chain fatty acids yield propionyl CoA
Propionyl CoA carboxylase: biotin Mutase
the coenzyme B12 reaction
box17-2
Ketosis and ketone bodies
Synthesis of ketone bodies
Ketone bodies can be regarded as a water-soluble, transportable form of acetyl units,
provide alternative fuels
Ketone bodies are produced in liver and are a major source of energy for some tissues
From ketone bodies to acetyl CoA
Unselfish liver
Diabetes and starvation leads to ketosis