Carbohydrate Metabolism-Glycolysis

Question 1

List common monosaccarides

Answer 1

fructose, galactose, glucose

Question 2

Can glucose cross the plasma membrane?

Answer 2

No; glucose is a very important molecule, but can’t cross the membrane readily so it needs to cross via GLUT transporter via facilitated diffusion.

Question 3

Tell me what cells have GLUT1 transporter

Answer 3

brain, cornea (so easy to get cataracts), erythrocytes(only source of energy)

1kM Affinity

Question 4

Tell me what cell have GLUT 2 Transporter

Answer 4

main transporter of LIVER and PANCREAS

• LOW AFFINITY
• 10mM

Question 5

Tell me what cell have GLUT3 Transporter

Answer 5

NUERONS

-kM 1mM

Question 6

Tell me what cells have GLUT 4 Transporter

Answer 6

Heart Cells, Adipose Cells, Skeletal Muscle Cells

-kM 5mM

Question 7

Where is GLUT4 found? What is its use?

Answer 7

GLUT4 Transporter is used in skeletal, cardiac, and adipose cells. GLUT4 Transporters are found in vesicles pre-made to respond to insulin receptors for the fusion and release into the plasma membrane.

Question 8

What is the net result of glycolysis?

Answer 8

2 pyruvate molecules, 2 NET ATP, 2 NADH Molecules

Question 9

What is the difference between hexokinase and glucokinase?

Answer 9

Hexokinase has lower kM and has greater affinity for glucose; found in all cells

Glucokinase has higher kM and is found in specifically liver and pancreatic cells. These cells have a MACROFUNCTION for regulating glucose. They are the LAST to uptake glucose after the whole body has finished.

Question 10

What is the rate limiting step of glycolysis?

Answer 10

Phosphofructokinase-1 Enzyme

Question 11

Which enzymes are the rate-limiting enzymes for glycolysis?

Answer 11

hexokinase/glucokinase
PFK-1
Pyruvate kinase***

Question 12

The rate-limiting enzymes are conrolled by which by-products?

Answer 12

ATP, AMP, INSULIN, GLUCOSE, GLUCAGON

Question 13

Why is glucokinase weakly inhibited by G6P, but hexokinase is strongly inhibited by G6P?

Answer 13

Glucokinase has a WEAK AFFINITY to GLUCOSE in the first place anyway! So, it makes sense that Glucokinase would weakly be allosterically inhibited by G6P.

Question 14

Is PFK-1 activated or de-activated by phosphorylation?

Answer 14

PFK-1 is deactivated by phosphorylation and ACTIVATED by dephosphorylation.

Question 15

What allosterically inhibits/ activates PFK-1?

Answer 15

Allosterically Activates: F2,6,BP; AMP

Allosterically Inhibits: ATP; Citrate

Question 16

So, according to the logic of PFK-1, would it be plausible to say that PFK-2 is also activated by dephosphorylation (specifically by protein phosphatase enzyme)?

Answer 16

Yes; PFk-2 is ALSO activated by dephosphorylation.

Question 17

What are the many different metabolic fats of G6P?

Answer 17

-Glycolysis, Pentose Phosphate Pathway, Glycogenesis, gluconeogenesis

Question 18

What would a disorder in the glycolitic pathway cause?

Answer 18

IT WOULD CAUSE IN ALMOST ALL DISORDERS; HEMOLYTIC ANEMIA BECAUSE ERYTHROCYTES USE GLYCOLYSIS TO CREATE ENERGY.

Question 19

What is Type 1 Diabetes caused by?

Answer 19

Loss of Pancreatic Beta Cells

Question 20

What is Type 2 Diabetes caused by?

Answer 20

insulin resistance; loss of Beta Cell Functionality

Question 21

What is Tarui Disease?

Answer 21

Disease that is associated with loss of functionality to PFK-1 enzyme.

Sx: Hemolytic Anemia
Jaundice/Bilirubin Accumulation
Excercise-Induced muscle weakness/fatigue