Where does Glycolysis occur?

In the cytoplasm of every cell

Which OH on glucose is most likely to be phosphorylated? 

The OH on carbon 6

[image]

Which steps of glycolysis are irreversible and what is special about them? 

1,3 and 10

all kinases with 

large ΔG's makes them irreversible in the given direction 

What occurs in stage 1 of glycolysis?

How many enzymes are involved?

Glucose is converted into fructose 1,6-bisphosphate.

3 enzymes are involved.

What occurs in Stage 2 of Glycolysis?

Fructose 1,6 bisphosphate is cleaved into 2 molecules of Glyceraldehyde 3-phosphate

What occurs in Stage 3 of Glycolysis?

Glyceraldehyde 3-phosphate is converted into pyruvate in order to harvest ATP

Describe Hexokinase and its relationship with glucose

Hexokinase is a type of transferase, that specifically is a kinase that phosphorylates any 6 carbon sugar. It has a preference to certain sugars like glucose for which it has a small K_m. 

The reaction is reversible in ideal conditions but is metabolically reversible.

How does the hexokinase reaction work?

The lone pair on the 6-OH of glucose attacks MgATP. The Mg bridges the β and γ phosphates. When the attack occurs, the MgATP loses a phosphate and the Mg now bridges β and α making it more stable. The end result is MgADP and Glucose 6-phosphate.

Why is Glucose phosphorylated immediately upon entering the cell?

Phosphorylating glucose reduces its desire to leave by a large amount because it makes it larger, more polar and charged

Which binds first, ATP or glucose? And how do you know?

• ATP fits first because glucose wont bind if ATP is absent .

• ATP will not be hydrolyzed if Glucose is not present .

•Upon Glucose binding the enzymes changes shape via induced fit

What are Isozymes? And which ones are important for glucose?

Isozymes are different forms of hexokinases. They catalyze the same reaction but have different K_m values (different affinities) for glucose.

Hexokinase I,II and III are active at normal glucose  concentrations and are regulated. Hexokinase IV aka. Glucokinase is active at higher glucose levels -Larger K_m (when all other kinases are occupied) and is not regulated.

What is step 2 of Glycolysis?

Isomerization of Glucose 6-phosphate (G-6P) to Fructose 6-phosphate (F-6P).

The ring form of G-6P becomes the open chain form. The open chain form then isomerizes because the Carbonyl changes from carbon 1 to carbon 2. This creates F-6P which then adapts to its more stable ring form.

What happens in step 3 of glycolysis?

 Phosphofructokinase catalyzes the addition of a phosphate to the carbon 6 of F-6P by ATP into Fructose 1,6 bisphosphate (F-1, 6-BP) 

Metabolically irreversible

Key regulatory step

What happens in step 4 of glycolysis?

Fructose 1,6 bisphosphate is cleaved into Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate by Aldose(lyase) 

Not a 50/50 split.

What happens in step 5 of glycolysis?

What happens in step 6 of glycolysis?

What happens in step 7 of glycolysis?

What happens in step 8 of glycolysis?

What happens in step 9 of glycolysis?

What happens in step 10 of glycolysis?