Glycolysis

Question 1

What is the major class of transmembrane proteins that are involved in sugar transport?

Answer 1

GLUT1-GLUT5

Question 2

GLUT2

Answer 2

Allows for the transport of glucose into and out of cells. Found in he liver, kidney, and pancreas. Relatively high Km, which means that it will only pick up Glucose in times of plentiful glucose.

Question 3

GLUT-4

Answer 3

It is insulin sensitive. Allows for the insulin regulated uptake of glucose in fat and muscle.

• “you need insulin 4 the Glut 4 in your 4 limbs of muscle and fat”
• more insulin will cause more Glut4 receptors to go to the cell surface and thus more glucose uptake.

Question 4

What is the point of phosphorylating glucose?

Answer 4

Basically it maintains the downhill gradient for glucose to get into the cells because only the intracellular glucose is phosphorylated. So now, the concentration of straight glucose goes down in the cell. This is called Glucose-6-phosphate

Question 5

WHat enzymes catalyze the reaction of Glucose –> Glucose-6-phosphate?

Answer 5

Hexokinase and Glucokinase

Question 6

Difference between Hexokinase and Glucokinase?

Answer 6

Hexokinase - Low Km and low Vmax. It is relatively broad with regards to what it can catalyze - it will catalyze many 6-carbon sugars.
Glucokinase - located in the liver and pancreas it has a high Km and a high Vmax.

Question 7

Feedback of Glucokinase

Answer 7

• inhibited by Fructose-6-phosphate because F6P goes into the nucleus and binds to the Glucokinase Regulatory protein.
• –This is reversed in times of high intracellular glucose content as well as high intracellular fructose-1-phosphate.
• Glucokinase expression is stimulated by insulin.

Question 8

What is the. First reaction in glycolysis??

Answer 8

Glucose to. Glucose-6-phosphate. ATP is. Used.

Question 9

What happens after the creation of glucose-6-phosphate?

Answer 9

G6P is isomerized into Fructose-6-phosphate

Question 10

What happens after F6P is made?

Answer 10

F6P gets phosphorylated by an enzyme called PFK-1 in order to make Fructose 1,6-bisphosphate.

Question 11

PFK-1

Answer 11

Phosphorylates F6P into Fructose 1,6-bisphosphate. This is the rate limiting step in glycolysis and is irreversible.

Question 12

Feedback of PFK1

Answer 12

Negative - ATP, CitraTe, and low pH
Positive - AMP and Fructose 2,6 - bisphosphate
- makes sense because when ATP is. Low you want ATP.

Question 13

What enzymes affect fructose 2,6 - bisphosphate levels?

Answer 13

PFK2 - Catalyzes the reaction: Fructose-6-phosphate –> Fructose 2,6 - bisphosphate
FBP-2 - Catalyzes the reverse reaction of: Fructose 2,6 - bisphosphate –> Fructose-6-phosphate

These 2 enzymes are technically found together on the same protein.

Question 14

How does PFK2/FBP2 get regulated? What regulates the thing. That regulates this?

Answer 14

Through phosphorylation events.

This is regulated through signal transduction cascades led by insulin/glucagon.

Question 15

What is the first step of the energy generation phase?

Answer 15

Aldosterone A converting Fructose 1,6 - bisphosphate into glyceraldehyde 3-phosphate dihydroxyacetone phosphate.

Question 16

What are the names of the two phases of glycolysis

Answer 16

Energy investment phase

Energy generation

Question 17

Glut-5

Answer 17

Primarily transports fructose as we saw in a different lecture.

Question 18

Glut-1

What happens if you have a deficiency?

Answer 18

Brain

- the brain doesn’t get enough glucose and therefore the patient has impaired neurological function.

Question 19

How is Glucokinase regulated??

Answer 19

By Fructose 6 phosphate - through a mechanism in the nucleus
- also by insulin (+) and glucagon (-)

Question 20

How does Fructose 2,6 bisphosphate get regulated?

Answer 20

Through PFK2.

• Insulin activates PFK-2 through dephosphorylation
• glucagon inactivates PFK-2 through phosphorylation.

— thin about it, PFK-1 makes Fructose 1,6 bisphosphate, PFK-2 makes Fructose-2,6 bisphosphate

Question 21

What is the difference bwteen liver PFK-2. And skeletal. Muscle PFK-2?

Answer 21

PFK-2 is regulated hormonally through insulin and glucagon in the liver
In skeletal muscle, PFK-2 is dependent on allosteric regulation by AMP.

Question 22

WHat regulation is there on pyruvate kinase?

Answer 22

\+ = Fructose 1,6 bisphosphate and insulin
- = glucagon

Question 23

How does pyruvate being shunted into lactate in a low low oxygen environment provide ATP?

Answer 23

Because it allows regeneration of NAD+ from NADH, which will allow glycolysis to repeat again for a 2 ATP gain each cycle.

Question 24

MODY

Answer 24

Mutations in Glucokinase

• causes mild diabetes
• monogenetic disorder
• apparently the reason patients get diabetes is because Glucokinase also acts as a glucose receptor for pancreatic beta cells so the insulin receptors won’t be as responsive.

Question 25

Pyruvate kinase deficiency

Answer 25

- hemolytic anemia - RBCs have insufficient ATP for their membrane pumps to they lyse. - -- the cells are speculated and look like the ghosts from pac-man. - results in an increase in 2,3 BPG

Question 26

What does PDH do? (Protein dehydrogenase)

Answer 26

Converts pyruvate to acetyl CoA to start the TCA cycle.

Question 27

What are the 5 cofactors that affect PDH?

Answer 27

``` Thiamine - 1 Pantothenic acid -2 Lipoic acid - 2 Riboflavin - 3 Niacin - 3 ``` - The Partly lying rabbinic nun

Question 28

Affect of arsenic and Mercury

Answer 28

Affects E2. Symptoms similar to beriberi.

Question 29

Tell tale sign of arsenic Poisening

Answer 29

Garlic scented breath | - also rice water stools and vomiting

Question 30

What provides negative feedback on PDH? How?

Answer 30

high energy molecules - acetyl CoA - ATP - NADH They do this by activating PDH kinase, which phosphorylates PDH and thus activates it. ---therefore pyruvate will not be converted into Acetyl CoA

Question 31

What provides positive feedback on PDH?

Answer 31

insulin (and calcium) - this makes sense because insulin indicates a fed state so there will be a lot of glucose and thus pyruvate so we want to convert all of that into energy. --- it does this by activating PDH phosphodiesterase, which de phosphorylates PDH and thus activates it

Question 32

Dichloroacetic acid

Answer 32

Pyruvate analog that binds to PDH kinase and therefore inhibits it. This means that PDH would remain in its de phosphorylated and active form.

Question 33

What would happen if you Have a pyruvate dehydrogenase complex deficiency?

Answer 33

You get accumulation of pyruvate and lactate. - associated with delayed muscle development and reduced muscle tone often associated with ataxia And seizures. Could also have congenital malformations of the brain.

Question 34

How do we treat patients with a pyruvate dehydrogenase complex deficiency?

Answer 34

A ketone if diet and severe restriction of protein and carbs. - this ensures that all the cells use acetyl-CoA from fat metabolism, so they don't need PHD. -- if the mutation is in the E1 part then giving thiamine could help potentially.

Question 35

How much does one cycle of the TCA cycle make?

Answer 35

3 NADH 1 FADH2 GTP 2 CO2 - in total this translates to 12 ATP

Question 36

Energy yield of Glycolysis + TCA

Answer 36

Glycolysis - 2 ATP and 2 NADH TCA = 2 ATP + 6 NADH + 2 FADH2 = 32 ATP Net. Energy production is 36 or 38 ATP for some reason

Question 37

What does fluoride do?

Answer 37

Inhibits enolase. The Km for bacteria is lower so it has a higher affinity for fluoride than humans do so it doesn't harm us, just them