Integrative Metabolism

Question 1

Why is the liver special in regard to glycolytic pathways?

Answer 1

Because the liver can utilize nearly all the glycolytic pathways

-It is the main reservoir for glucose and decides what to do with the glucose based on signals from the brain and pancreas (deliver it to other organs)

Question 2

What three types of molecules are involved in energy utilization and are broken into subunits?

Answer 2

carbohydrates -> saccharides
proteins -> amnio acids
lipids -> fatty acids

Question 3

How do cells (hepatocytes) ensure that glucose stays in the cell, after glucose uptake?

Answer 3

Phosphorylation: glucose -> glucose-6-P by Hexokinase (with ATP)

-> because it doesn’t fit the transporter anymore and it is charged and cant diffuse through the membrane anymore

Question 4

What happens if other types of sugars enter the cell?

Answer 4

They get converted into glucose or other glycolytic intermediates

Question 5

What are the first two priorities of the liver regarding glucose?

Answer 5

1. Glucose -> Glucose-6-P -> secrete into the blood to transport it tissues that need glucose
2. Build up glycogen (polymer) if needed later

Question 6

What is priority number 3 in the liver for glucose utilization?

Priorities 4 and 5?

Answer 6

-Degrade glucose-6-P
-put it into the Krebs cycle and convert it into electrons (e-)
-make ATP through oxidative phosphorylation

Priority 4 and 5:
store as fat Acetyl-CoA to form lipids
make nucleotides by the pentose phosphate pathway

Question 7

Which priorities are mostly disrupted in diabetes?

Answer 7

Priority 1: Glucose secretion into the body because there is no signal for glucose uptake
Priority 2: Production of glycogen because there is no GLUCOSE to store

Question 8

What is the key molecule in the glycolytic pathway in the liver?

Answer 8

Glucose-6-P

Question 9

What are the first two priorities of the liver regarding amino acid utilization?

Answer 9

1. Produce proteins needed in the liver (for itself)
2. Provides amino acids and plasma proteins to other tissues
3. Make other molecules: nucleotides, hormones, porphyrins

Question 10

What is priority number 4 and 5 of the liver regarding amino acid utilization?

Answer 10

4. Excess of amino acid is going out as waste in form of UREA
5. Excess of amino acids converted into pyruvate to make glucose (GLYCONEOGENESIS) -> in DT2 it is hyperactive

Question 11

Why is priority number 5 (amino acid utilization) dangerous for DT2 patients?

Answer 11

Because more glucose is produced even though there is enough glucose available

Question 12

Where does glucose from diet go first?

Answer 12

From the small intestine to the liver through the portal vein

Question 13

What are normal blood glucose levels?

Answer 13

65-95 mg/dl or 4 - 4.5 mM

Question 14

What signals are sent by the brain and pancreas in response to low blood glucose (hunger)?

Answer 14

Pancreas: Glucagon
Brain: Cortisol, epinephrine -> puts you under stress (headache, sweating, HR)

Question 15

What are the most important glucose transporters?

Answer 15

GLUT 1- GLUT-5

GLUT-2: in the liver, small intestine, kidney, ß-cells -> rapid uptake or release of glucose

GLUT-3: brain

GLUT-4: in the heart, skeletal muscle, fat tissue -> insulin-stimulated glucose uptake

GLUT-5: small intestine

SGLT-1- in small intestine and kidney

Question 16

Which processes are not working properly in T2D?

Answer 16

in T2D:
-Gluconeogenesis in the liver is stimulated after meal -> bc no signal of sufficient glucose in the blood(suppressed in non-diabetic)

-Glucose uptake to the liver is suppressed

-Glucose uptake to peripheral tissues is suppressed

-Glycogenesis (making glycogen, priority 2) in the liver is suppressed -> bc we don’t get enough glucose into the liver

-Excess glucose is stored as fatty acid and exported to adipocytes even though glucose is not used properly (in a higher priority than it should -> list of priorities messed up)