Intro to Metabolism, Regulation of Glucose Metabolism by insulin and glucose- Lecture 60

Question 1

What is metabolism?

Answer 1

a sequence of enzyme-catalyzed reactions that brings about the transformation of substrate to products

Question 2

What are the major functions of metabolism?

Answer 2

obtain and trap chemical energy from substrate, build precursors of macromolecules from the substrates, assemble the precursors into macromolecules, degrade macromolecules into simpler molecules

Question 3

What is catabolism?

Answer 3

oxidative degradation of large nutrient macromolecules into smaller, simpler compounds
usually coupled with the release of energy

Question 4

What is anabolism?

Answer 4

enzyme synthesis of larger molecular components of the cell from simpler precursors
usually requires input of energy

Question 5

What are the means of regulation for metabolism?

Answer 5

Availability and concentration of substrates and cofactors
Availability/need for ATP
Enzyme characteristics
Regulatory enzymes-often allosteric
Genetic control of amount of enzyme in the cell
Hormone regulation (chemical messenger increase or decrease the rate of a metabolic rxn in another cell

Question 6

What vitamins are fat soluble?

Answer 6

A (retinol), Provitamine A (beta-carotene), D, E, K

Question 7

What vitamins are water soluble?

Answer 7

Thiamin, riboflavin, niacin, pantothenic acid, vitamin b, biotin, folate, vitamin b 12, vitamin c

Question 8

Name the kinds of glucose transporters.

Answer 8

GLUT1 through GLUT5

Question 9

Describe the high affinity glucose transporters.

Answer 9

GLUT 1 and 3 have a Km of 1 mM and are responsible for basal glucose uptake for almost all tissues (RBC, brain, heart, liver, etc.)

Question 10

Describe the low affinity glucose transporter.

Answer 10

GLUT2 has a Km of 15-20 mM and senses high gluose levels; it is present only in the liver and the pancreas

Question 11

Describe the intermediate affinity glucose transporter.

Answer 11

GLUT4 has a Km of 5 mM and is present in adipose and muscle, the amount of this is increased with insulin translocation from Golgi to plasma membrane

Question 12

Describe the activity of GLUT5.

Answer 12

Mainly a fructose transporter; present primarily in GI tract and kidneys

Question 13

What is passive carrier-medicated glucose transport?

Answer 13

ATP not required because glucose moves down its concentration gradient; blood glucose levels is maintained between 4-8 mM

Question 14

What is active transport of glucose?

Answer 14

Moves molecules of glucose against their concentration gradient, so requires ATP or other energy source

Question 15

What is insulin?

Answer 15

A peptide hormone released by the pancreatic beta cells in response to high glucose

Question 16

What are the functions of insulin?

Answer 16

Increase glut4 in the membrane
Increase glycolysis (decrease gluconeogenesis)
Increase glycogen synthesis (decrease glycogen breakdown)
Increase fatty acid synthesis and protein synthesis (decrease their breakdown)

Question 17

How does insulin work?

Answer 17

Activates or inhibits rate-limiting enzymes in the pathways or increasing or decreasing synthesis of these enzymes at transcriptional or post-transcriptional levels

Question 18

Glucagon is made by the _______ and works in the ______ by activating ______. Epinephrine is made by the _________ and works in ________ .

Answer 18

Alpha cells of the pancreas
Liver and adipose
g-protein coupled receptors
Adrenals
Most tissues (except RBCs)

Question 19

Glucagon is released in response to _________ whereas epinephrine is released in response to _______.

Answer 19

Low blood glucose

Stress

Question 20

What are the functions of glucagon and epinephrine?

Answer 20

Increase production of glucose, especially for use by brain, RBC, muscle/heart

Question 21

How do glucagon and epinephrine function?

Answer 21

Increased gluconeogenesis and glycogen/fat/protein breakdown (opposite of insulin)

Question 22

What is Type I DM?

Answer 22

Failure to produce insulin because of the destruction of pancreatic beta cells

Question 23

What is Type II DM?

Answer 23

Failure to respond to the actions of insulin (insulin resistance)

Question 24

What is the result of DM?

Answer 24

High blood glucose
Impaired glucose utilization
High glucose production
Bioenergetic problems/failure to thrive
Ketosis due to increased fatty acid metabolism
Protein breakdown
Increased glycosylation reactions (HbA1C)
Osmotic pressure in eyes

Question 25

______ pathways have both catabolic and anabolic components.

Answer 25

Amphibolic

Question 26

Inhibitors of _______ will inhibit the enzyme but not likely the overall pathway.

Answer 26

non-rate-limiting enzymes

Question 27

How much energy is release in the hydrolysis of one ATP?

Answer 27

7-8 Kcal/mol

Question 28

As a general ‘rule’, glucagon and epi promote ________, whereas insulin promotes _______.

Answer 28

the phosphorylation of enzymes by activating cAMP-dependent PKA
the dephosphorylation of enzymes by activating certain phosphatases