Glycolysis Flashcards
Name all of the steps of glycolysis
Glucose – hexokinase, glucose 6- phosphate- phosphoglucoisomerase, fructose 6- phosphate- phosphofructokinase, Fructose 1,6-bisphosphate- aldolase, dihydroacetone phosphate- triose phosphate isomerase, glyceraldehyde 3- phosphate- glyceralderhyde 3- phosphate dehydrogenase, 1,3 bisphosphoglycerate- phosphoglycerate kinase, 3-phosphoglycerate- phosphoglycerate mutase, 2-phosphoglycerate- Enolase, phosphenol pyruvate- pyruvate kinase, pyruvate
What is the purpose of phosphorylating glucose?
Increases specificity of reaction
How is phospho-fructo-kinase-1 inhibited/activated?
A high energy state with high ATP (liver and muscle) H+ (muscle), and Citrate (liver) inhibits PFK1 allosterically (binding)
AMP (muscle) increases activity (low energy) as does fructose-2,6-bisP (liver)
Anaerobic glycolysis is the only source of energy where?
Red blood cells Cornea and lens of eye, and certain regions of the retina Renal medulla Testis Leukocytes
What are the irreversible steps of glycolysis? Why?
Hexokinase (equilibrium is far towards products), Phosphofructo Kinase, and Pyruvate Kinase are irreversible.
Which steps of Glycolysis produce/use ATP?
ATP is used up in the steps:
Glucose to Glucose-6-phosphase via Hexokinase
Fructose-6-phosphate to Fructose-1,6-biphosphate
ATP is MADE in the steps:
1,3-biphosphoglycerate to 3-Phosphoglycerate via Phosphoglycerate kinase
Phosphoenol pyruvate to Pyruvate via Pyruvate Kinase
Where is NADH used/produced in glycolysis?
2 NADH is produced in the step:
Glyceraldehyde-3-Phosphate to 1,3-biphosphoglycerate
We get 2 NADH because aldolase converts F-1,6-BP into Glyceraldehyde-3-phoshate and dihydroxyacetone phosphate (DHAP). The DHAP gets get converted to a Glyceraldehyde-3-Phosphate by Triose Phosphate isomerase. Then the 2 G3P’s get converted into 1,3-biphosphoglycerate by GAP dehydrogenase. NAD+ gets reduced in the process
Why does phosphoenolpyruvate have a higher phosphoryl transfer potential than ATP? (based on structure)
Resonance, product has better Solvation, and Electrostatic forces can be decreased
Describe the role of each enzyme in glycolysis
Hexokinase: slowest part, rate determining step. converts glucose to glucose-6-phosphate using Mg2+ and ATP
Phosphoglucoisomerase: converts g-6-p into Fructose-6-phosphate
Phosphofructokinase: Uses ATP and Mg2+ to convert F-6-P into fructose-1,6-biphosphate. FIRST COMMITTED STEP
Aldolase: Converts fructose-1,6-biphosphate into 1 glyceraldehyde-3-phosphate and a Dihydroxyacetone phosphate.
Triose Phosphate isomerase: converts DHAP into a 2nd glyceraldehyde-3-phosphate (the reason why we have 2 pyruvate at the end)
GAP dehydrogenase (glyceraldehyde-3-phosphate dehydrogenase): converts the 2 G3P’s into 1,3-bisphosphoglycerate. PRODUCES 2 NADH
Phosphoglycerate kinase: converts 1,3-bisphosphoglycerate into 3-phosphoglycerate using Mg2+. PRODUCES AN ATP
Phosphoglycerate Mutase: Converts 3-phosphoglycerate into 2-phosphoglycerate using Mg2+
Enolase: converts 2-phosphoglycerate into Phospho Enol Pyruvate.
Pyruvate Kinase: converts Phospho Enol Pyruvate into Pyruvate using Mg2+. PRODUCES AN ATP
How is glycolysis regulated based on energy charge in muscle?
Inhibited by ATP and Alanine (high energy state) (Pyruvate Kinase PK)
Activated by Fructose-1,6-biphosphate (Low energy state) (Pyruvate Kinase PK)
How is blood sugar regulating glycolysis in the liver?
PFK is upregulated by Fructose-2,6-BisP in Liver
Pyruvate Kinase is L type here and under hormonal control, insulin to stimulate activity and Glucagon to inhibit it. (more active when dephosphorylated)
What are the various isozymes of the glucose transporter protein? Function?
GLUT 1 and GLUT 3 are found in all mammalian cells
GLUT 4 is in Muscle and Fat cells
GLUT 2 is in liver and pancreatic beta cells
What are the three stages of glycolysis?
- Conversion of glucose to fru-1,6-bisphosphate (uses 2 ATPs)
- Cleavage of Fru-1,6-bisphosphate to DHAP and glyceraldehyde-3-phosphate (G3P)
- Conversion of G3P to pyruvate (produces 4 ATPs and 2 NADHs)
What are the 2 fates of pyruvate?
Complete oxidation to CO2 or fermentation into lactate
Lactate builds up in absence of O2 (anaerobic exercise)
Why is AMP a better sensor of energy levels than ADP in the cell?
Adenylate kinase tranfers Phosphate groups to make ATP.
ATP>ADP>AMP (also ADP + ADP = ATP + AMP)
A slight decrease in ATP leads to a large increase in AMP which upregulates glycolysis.
