Integrating metabolic response to starvation

Question 1

Glucagon

Answer 1

Secreted by alpha cell, which is inhibited by paracrine action of insulin
Suppression relieved by fall in glucose which causes fall in insulin

Question 2

Epinephrine

Answer 2

When hypothalamus senses low glucose, it causes sympathetic nervous system to secrete epinephrine, which stimulates alpha cell to release glucagon

Question 3

GLP-1

Answer 3

Glucagon-like-peptide 1 is produced from small intestine and secreted into blood stream after high carb meal–stimulates beta cells to make and secrete insulin

Question 4

Adenylate Cyclase

Answer 4

Produces cyclic AMP from ATP when activated by subunit of G-protein. Epinephrine and Glucagon cause G protein to activate it.

Question 5

Protein Kinase A (PKA)

Answer 5

Activated by cyclic AMP to initiate phosphorylation changes in many proteins

Question 6

cAMP phosphodiesterase (PDE)

Answer 6

Breaks down cyclic AMP, determines intracellular concentration of cyclic AMP and therefore activation of PKA
-Favors TG storage

Question 7

Tyrosine Kinase

Answer 7

Activated when Insulin attaches to extra cellular part of insulin receptor.
Leads to tyrosine phosphorylation of intracellular “docking proteins” which recruits other proteins necessary for downstream signaling events, especially protein Kinase Akt

Question 8

cAMP/PKA pathway

Answer 8

Used by glucagon and Epinephrine, antagonized by Insulin

Question 9

Glucuneogenisis

Answer 9

Energy for gluconeogenesis provided by fatty acid oxidation
Provides ongoing availability of glucose during nutrient limitation (even between meals/overnight), along with glycogenolysis (brain and RBCs almost always need glucose)
Mainly happens in Liver and Kidney

Question 10

Glucose-6-phosphate

Answer 10

Not expressed in muscle, so muscle can’t export glucose into blood.
Is expressed in liver, so liver is source of glucose to blood

Question 11

Anabolic Phase

Answer 11

Period from ingestion of nutrients until completion of utilization or storage of nutrients
Stimulated by rise in Insulin

Question 12

Catabolic Phase

Answer 12

Period from termination of anabolic phase to next meal
-When stored energy sources are mobilized
Stimulated by fall in insulin

Question 13

Substrate regulation of metabolism

Answer 13

Glucose stimulates its own storage by enhancing fatty acid and glycogen synthesis
Fatty Acid diminish the rate of FA synthesis and increase rate of FA oxidation

Question 14

Adenylate Kinase

Answer 14

Catalyzes production of ATP and 5’AMP from 2 ADPs

-senses ATP availability and alters usage and generation of ATP via its products

Question 15

AMP Activated Protein Kinase (AMPK)

Answer 15

Senses 5’-AMP (made from 2ADP–>ATP + AMP) and increases pathways that generate ATP, decreases synthesis activity

Question 16

Insulin

Answer 16

Initiate uptake of glucose into cells and suppresses Glucagon and Epinephrin Secretion.
Corresponds to Anabolic phase of metabolism
Also stimulates fatty acid and TV synthesis, and VLDL export from skeletal muscle

Question 17

Beta-cells of Pancreatic Islets and C chain

Answer 17

Secrete insulin in preproform.
“Pre” is an N sequence that directs peptide chain to ER and is removed there.
“Pro” is a biologically inactive “C chain” that directs folding and is secreted with insulin after detachment via proteases.
C chain is useful in measuring insulin levels

Question 18

GLUT-4

Answer 18

Cell surface transport protein that allows glucose to enter cell, stimulated by insulin.
With low insulin concentration (like nutrient limitation), glucose is rerouted to cells that are independent of GLUT4 in uptake of glucose, like brain and RBC