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27 Cards in this Set
- Front
- Back
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What sugar results from the breakdown of starch?
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glucose
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What sugar results from the breakdown of sucrose?
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glucose and fructose
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What sugar results from the breakdown of glycogen?
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glucose
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What sugar results from the breakdown of lactose?
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galactose and fructose
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What is the structure of Galactose?
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6-C
C4 OH to left |
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What is the structure of glucose?
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6C sugar
C4 OH to right D sugar |
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What is the structure of fructose
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6C sugar
C2 is a ketone C4 to right C5 OH to right |
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How is glucose transported into hepatocytes? (macro and micro)
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sugars go directly to liver via portal blood flow, transported into liver via GLUT2
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What is a D sugar? What is significance?
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C5 OH group on right, our body only metabolizes D sugars
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What is the Km property of GLUT2?
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Very high so glucose will only get transorted into liver if the concenteration is super high
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Does insulin stimulate fructose transport into liver?
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NO!
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What does glucokinase do and what is it specific to?
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Converts glucose to G-6-P and is specific to liver and B-cells in pancreas
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What is the activity of glucokinase under normal blood glucose levels?
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glucokinase has a Km of 8 mM, blood glucose is 5 mM so generally not active stroing of glucose
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What regulates glucokinase, what DOES NOT
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Regulation:
1) insulin induced transcription 2) glucokinase regulatory protein NOT regulation 1) glucose-6-P |
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How does insulin regulate glucokinase?
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-causes rapid increase of glucokinase mRNA meaning increase in amount
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How does cAMP affect insulin?
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turns of transcription of insulin
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What all is missing in diabetics?
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insulin and therefore glucokinase
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How does GRP fucntion
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It binds to GK and deactivates it
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What substrates affect deactivation of GK?
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1) F-6-P stimulates deactivation (and disassociation from GK)
2) F-1-P inhibits deactivation |
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What substrates affect activation of GK?
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1) Glucose stimulates activation
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What does aldolase B work on and what does it produce, and where?
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1) works only in liver
2) substrate= fructose-1-P 3) products: glyceraldehyde and dihydroxyacetone phosphate |
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Name the key enzymes and process in conversion of galactose to glucose-1-phosphate
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1) galactokinase phosphorylates galactose-->galac-1-P
2) galac-1-P exchanges with UDP-glucose via galactose trasferase enzyme to form UDP-galactose and glucose-1-P 3) UDP glucose generated from UDP galactose via epimerase enzyme |
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What enzyme is defective in most cases of galactosemia?
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galactose-1-P uridylyl tranferase
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What reactions are involved in cataract formation and when do they occur?
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1) aldose reductase converts galactose and glucose (aldehydes) to galacitol and glucitol (alcohols).
2) This occurs only when there is high concentration b/c Km is ~200 |
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Where does gluconeogenesis take place?
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liver, lesser extent in kidney
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What are the major carbon sources and where do they come from?
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1) amino acids from dietary proteins and tissues in starvation
2) lactate from muscle and erythrocytes 3) fructose and galactose 4) glycerol from triglyceride breakdown in adipose tissue |
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What is the role of the TCA cycle in gluconeogenesis?
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it rolls in different biomolecules amino acids such as glutamate from muscle getting converted to a-ketoglutarate. These different carbon backbones from amino acid breakdown are components of the TC A cycle, via the cycle, they get converted to oxaloacetate, which is the first molecule in glucose produciton.
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