Carbohydrate Metabolism Flashcards
Normal blood glucose level
90-108 mg/dl
hyperglycemic
elevated blood glucose
hypoglycemic
low blood glucose <45mg/dl
Glucose Transporter Isoforms
GLUT 1
GLUT 2
GLUT 3
GLUT 4
GLUT 5
GLUT 4
uptake of glucose from blood to cell in muscle, heart and adipose tissue
Pathways of glycolysis
Anaerobic
Aerobic
What is glycolysis
the breakdown of glucose to pyruvate
most common pathway
sole source of energy for erythrocytes
How many reactions take place in Anaerobic Glycolysis
10
how many times is glucose phosphorylated during anaerobic glycolysis, where do these take place?
2 times, during the first and third reactions
During glucose to pyruvate glycolysis how many carbons and how many phosphoryl groups are produced? What is the net cost?
Yield:
6 carbons
2 phosphoryl groups
Cost:
2 ATP
Which molecules are formed during the fourth anaerobic glycolysis reaction?
Dihydroxyacetone phosphate
glyceraldehyde 3 phosphate
What is Dihydroxey acetone phosphate converted to?
Glyceraldehyde 3 phosphate
Where does glyceraldehydde 3 phosphate get its second phosphoryl group from?
Inorganic Phosphate (Pi)
During the conversion of dihydroxyacetone phosphate to glyceraldehyde 3 phosphate which substance is reduced?
NAD+ to NADH
Where does 1,3 biphosphoglycerate donate its phosphoryl groups?
6th and 10th reaction
How many major phases does glycolysis have and what are they?
Preparatory phase (first 5 steps)
Payoff phase (last 5 steps)
Anaerobic Glycolysis Step 1
Prep Phase
-Phosphorylation of glucose
-Glucose + ATP >Hexokinase>ADP+ Glucose 6 phosphate
-Irreversible
-Control Point
Anaerobic Glycolysis Step 2
Prep Phase
Glucose 6 phosphate <phosphoglucomutase> Fructose 6 phosphate
-Aldose to Ketose
-Reversible</phosphoglucomutase>
Phosphoglucomutase
Phosphohexose Isomerase
Glucose 6 phosphate to Fructose 6 phosphate
Anaerobic Glycolysis Step 3
Prep Phase
Phosphorylation of Fructose 6 phosphate + ATP <Phosphofructokinase (PFK-1) to Fructose-1,6 Diphosphate (biphosphate) + ADP
-2nd priming reaction
-Irreversible
Importance of the PFK-1 Reaction
Rate limiting step in glycolysis
-inhibited by high ATP / High citrate
-Stimulated by Low atp/ low citrate
Why is PFK the key and not Hexokinase?
Glucose 6 phosphate, glycolytic intermediate can also be converted to clycogen, this is the first committed step and is catalyzed by PFK
Anaerobic Glycolysis Step 4
Prep Phase
Cleavage of Fructose 1,6 Diphosphate to BOTH Glyceraldehyde 3 phosphate (ALDOSE) and Dihydroxyacetone Phosphate (KETOSE) by aldolase
-Reversible
Anaerobic Glycolysis Step 5
Final Prep Phase
Interconversion of Triose PhosphatesOnly glyceraldehyde 3 phosphate (aldose) can be degraded in subsequent reactions
-Catalyzed by Triose Phosphate Isomerase
-Reversible
-Rapidly converts Dihydroxyacetone to glyceraldehyde 3 phosphate
Anaerobic Glycolysis Step 6
Payoff Phase
Oxidation of Glyceraldehyde 3 phosphate + NAD+ <glyceraldehyde 3 phosphate dehydrogenase> 1,3 Biphosphoglycerate + NADH + H+
-Reversible
-First of 2 energy conserving reactions
Importance of Glyceraldehyde 3 phosphate Dehydrogenase reaction
Uses NAD formed from lactate
Anaerobic Glycolysis Step 7
Payoff Phase
Transfer of phosphate from 1,3 Biphosphoglycerate to ADP
1,3 Biphosphoglycerate + ADP <Phosphoglycerate> ATP + 3 phosphoglycerate
-Reversible Reaction
-Substrate level phosphorylation</Phosphoglycerate>
Anaerobic Glycolysis Step 8
Payoff Phase
3 phosphoglycerate <phosphoglycerate> 2 phosphoglycerate
-moves phosphoryl group from C3 to C2
-Reversible</phosphoglycerate>
Anaerobic Glycolysis Step 9
Payoff Phase
Dehydration
2 phosphoglycerate <ENOLASE> phosphoENOpyruvate and H2O
Reversible</ENOLASE>
Anaerobic Glycolysis Step 10
Payoff Phase
Transfer of phosphate group to ADP
Phosphoenolpyruvate +ADP >Pyruvate Kinase> Pyruvate and ATP
Essentially irreversible
