Lecture 19

Question 1

Describe the general pathway of glucose in primary metabolism

Answer 1

glucose -> blood vessels -> brain, muscle, or pyruvate -> acetyl CoA -> TAG -> VLDL -> TAG

Question 2

Describe the general pathway of amino acids in primary metabolism

Answer 2

aa -> blood vessels -> protein synthesis OR alpha-keto acids -> NH3 + urea

Question 3

Describe the general pathway of fats in primary metaboism

Answer 3

fats -> TAG in lymph system -> fatty acids in muscle

Question 4

In which body organ is amino acid synthesis the most high in demand?

Answer 4

Liver

Question 5

In which state is insulin present? Well-fed or starved?

Answer 5

Well-fed

Question 6

Where is insulin made? What type of molecule is it?

Answer 6

It’s made in pancreatic beta-islet cells. It’s a polypeptide hormone.

Question 7

Describe insulin synthesis

Answer 7

1. mRNA
2. preproinsulin (has signal sequence a N-terminus)
3. ER import (signal sequence cleaved off)

Question 8

Describe insulin protein structure.

Answer 8

Peptides A, B, and C. 2 disulfide bonds between peptides A and B, 1 disulfide bond within peptide B

Question 9

Lack of which peptide in insulin is bad for Type I diabetes patients? What does it cause?

Answer 9

Lack of peptide C linked to neuropathy

Question 10

Why can’t diabetics take insulin pills? Why inject instead?

Answer 10

Enzymes will degrade the protein in the stomach. Inject into bloodstream to bypass

Question 11

Adding what to insulin extends its lifespan in the blood?

Answer 11

Adding fatty acid to insulin makes it so that it can be transported by serum albumin, so insulin will stay in the bloodstream longer

Question 12

According to research, how does caloric restriction appear to affect lifespan?

Answer 12

Increases lifespan

Question 13

Describe fuel sources during a short fast (about 12 hrs)

Answer 13

Mostly glucose

Question 14

Describe fuel sources during early starvation (12-24 hrs)

Answer 14

Liver glycogen is almost depleted so fatty acid mobilization occurs. Brain still uses glucose

Question 15

Describe later starvation (4-10 days)

Answer 15

Protein gets broken down into alanine, which can make glucose. Ketone bodies start to be made, which the brain starts to use. The brain also still uses some glucose

Question 16

Describe much later starvation (10+ days)

Answer 16

Ketone bodies are the main fuel source in the brain, which frees up some glucose for the body. Protein continues to be broken down into Ala for glucose. acetyl-CoA builds up -> ketone bodies. Excess ketone bodies excreted in the urine

Question 17

What is the fuel source that is required for starvation to continue?

Answer 17

Adipose. If fat gets completely depleted, then ketone bodies can’t be made anymore. So, protein gets broken down until essential proteins get catabolized and cause organ failure. Increased fat reserves allow for longer short-term starvation survival.