What's the main conversion in glycolysis?
1 glucose ---> 2 Pyruvate
What can pyruvate be further metabolized into?
Anaerobic conditions- Lactate (muscles) or ethanol (microorganisms)
Aerobic conditions- Acetyl CoA
What is the net energy generation of glycolysis?
-2 ATPs are produced
-2 NAD+ reduced to 2 NADH
What's the glycolysis equation?
Glucose + 2 ADP + 2NAD+ + 2Pi ---->
2 Pyruvate + 2ATP + 2NADH + 2 H+ +2H20
How is pyruvate metabolized to ethanol?
Two reactions are required, catalysed by:
1. Pyruvate decarboxylase
2. Alcohol dehydrogenase
(acetaldehyde = ethanal)
Why is pyruvate made into lactate in muscles rather than ethanol?
Muscles lack pyruvate decarboxylase (which miscroorganisms have).
Musces have lactate dehydrogenase which converts pyruvate to lactate.
What do the anaerobic metabilizing reactions of pyruvate generate?
They regenerate NAD+ for use by GAPDH in glycolysis. Hence glycolysis can continue to generate ATP.
Which steps of glycolysis are irreverible and why?
Steps 1,3 and 10.
They have large ∆G. The other steps ∆G is close to zero and these ar reversible.
What regulates glycolysis?
1. Metabolites in the pathway (feedback inhibition)
2. Availability of substrates
3. Hormonal regulation (linked to kinases and phosphatases)
What does hexokinase catalyse?
An irreversible step at the start of glycolysis.
Glucose to glucose 6-phosphate
What is hexokinase inhibited by?
Glucose 6-phosphate (its product)
When enough product is made, negative feedback
What happens differently in the liver for the 1st raction of glycolysis?
A seperate enzyme is used0 GLUCOKINASE.
Not inhibited by its product. Important because high levels of glucose 6 -phosphate needed in the liver for glycogen storage.
How is phosphofructokinase-1 (PFK-1) inhibited?
ATP is a substrate and inhibitor of PFK-1.
AMP acitvates PFK-1 by relieving the ATP inhibition.
Elevated citrate also inhibits PFK1.
How is pyruvate kinase regulated? (step 10)
It's inhibited by ATP (a product). Feedback inhibition.
Activated by fructose 1,6 bisphosphate - feed forward activation
What is GLUT?
A family of 6 passive hexose transporters
How does insulin affect the GLUT fam?
Glucose uptake mediated by GLUT4 is stimulated by insulin
The other GLUT transporters mediate glucose transport in and out of cells in the absence of insulin
What are the general inhibitors of glycolysis?
High ATP/citrate conc., low blood glucose levels
What are the general activators?
High AMP, high levels of bloog glucose
What is made when these other sugars enter glycolysis?
a. Fructose- glyceraldehyde 3 phosphate
b. Galactose- glucose 6 phosphate
c. Mannose- fructose 6-phosphate
What are the steps of glycolysis?
Glucose 6 phosphate
Fructose 6 phosphate
Fructose 1,6 phosphate
What are the enzyme in each step of glycolysis?