EXAM3_Gluconeogenesis

Question 1

What are the four regulatory enzymes of Gluconeogenesis?

Answer 1

1. Pyruvate Carboxylase (requires ATP)
2. PEP carboxylase (via malate aspartate shuttle)
3. FBPase-1* (step 3)
4. G6Pase (step 1)

Question 2

What/how much energy carriers needed for gluconeogenesis for each glucose?

Answer 2

4 ATP (pyruvate to OAA, and 1,3BPG)
2GTP (OAA to PEP)
2NADH (1,3BPG to GA3P)

Question 3

What are 4 types of precursors that can be used for gluconeogenesis?

Answer 3

GLYCOGEN IS GLYCOGENOLYSIS NOT GLUCONEOGENESIS FAG!

1. Lactate
2. Glycerol
3. AA’s (glucogenic)
4. Propionyl-CoA (odd chain FA’s only!)

Question 4

What are the products of Beta oxidation

Answer 4

Acetyl-CoA
NADH
FADH2

Question 5

When using beta oxidation during fasting, we have a surplus of Acetyl coA, NADH, FADH2 which inhibits the TCA cycle (slows it down). We will have plenty of energy in the form of ATP but what is Lacking?
What is done to compensate?

Answer 5

Glucose for the brain and RBC’s

Gluconeogenesis makes glucose from AA’s/Muscle breakdown

FAT USED for ATP Energy but
Glucose required/used for brain and RBCs

Question 6

When you see a CARBOXYLASE what should you immediately think?

Answer 6

BIOTIN (coenzyme of carboxylase)

Biotin Attaches CO2 to the molecule!

GET IT STRAIGHT!

Question 7

During fasting, Beta oxidation produces acetyl-CoA which allosterically activates what enzyme of gluconeogenesis?

Answer 7

Pyruvate carboxylase

Question 8

Pyruvate carboxylase has what two roles in the fasting state?

Answer 8

TCA Priming

Gluconeogenesis

Question 9

The malate aspartate shuttle is used for what?

What energy used/required?

Answer 9

used to transfer OAA into cytosol.
(using pep carboxylase) OAA-> PEP
USES 2 GTP

Question 10

GTP in glycolysis is used for what?

Answer 10

OAA to PEP (pep carboxylase)

Question 11

What is the rate limiting step in gluconeogenesis?

What is it inhibited by?

Answer 11

FBPase-1

inhibited by high levels of F2,6-BisP

Question 12

What activates the rate limiting step of gluconeogenesis?

think basic concept first then dive deeper:
Gluconeogenesis= low IG = phosphorylation of target enzy
FBP2 complex= activated>decreases F26bisP- low glycolysis- activated fbpase1- activates gluconeogenesis

Answer 12

Low IG > phosphorylation of FBP2 > active FBP2 > Decreases F2,6-bisP

Low F2,6-bisP:

• Inhibits PFK1 –> Glycolysis not active
• Activates FBPase1 –> Gluconeogenesis active

Question 13

G6Pase is shared in two liver pathways:

Answer 13

Liver glycogenolysis
Liver gluconeogenesis

Converts g6p to glucose into blood stream

Question 14

what AA from muscle? what does it influence?

Answer 14

Alanine from muscle- influences rate of hepatic glucose synthesis

Question 15

Cori Cycle links what two pathways in what two tissues?

Answer 15

1. Anaerobic glycolysis (muscle and RBC’s) and

2. Liver gluconeogenesis (liver)

Question 16

What is the physiological significance of the Cori Cycle?

Answer 16

Shifts the burden of RBC metabolism and Exercising muscle metabolism to the liver

Question 17

What molecules cycle in the cori cycle? (what changes to what)

Answer 17

GLUCOSE >liver> LACTOSE >muscle> GLUCOSE»liver
Glucose in liver (via gluconeogenesis) is anaerobically used in muscles and converted to LACTATE which is then used as a precursor in the liver again (in gluconeogenesis) to reform glucose

Question 18

Why is starving yourself to lose weight (anorexia) such a bad idea?

Answer 18

Your brain requires glucose to live-
when no glucose is available, your body breaks down muscle (aa’s) to make glucose.

Breaks down your skeletal and cardiac muscle

Question 19

What are 3 protein sparing molecules?

Answer 19

1. Ketone bodies
2. Dietary Carbohydrates
3. Liver Glycogen

Question 20

In beta oxidation (high NADH, FADH2, Acetyl CoA) what regulatory TCA enzyme is inhibited?
Why is that good?

Answer 20

Isocitrate Dehydrogenase

- ensures OAA enters into gluconeogenesis

Question 21

What is HMG-CoA synthase? what causes its activation?

Answer 21

HMG-CoA synthase causes synthesis of Ketone Bodies

is Activated by high levels of Acetyl-CoA (caused by beta oxidation)