BCH Hormone Regulation of Carbohydrates

Question 1

Metabolism of carbohydrates is regulated by_________

Answer 1

Insulin and glucagon

Question 2

Action of insulin

Answer 2

decrease plasma levels of glucose by promoting glucose uptake by tissue following an increase in plasma levels of glucose

Question 3

Action of glucagon and other anti-insulin hormones

Name the other hormones

Answer 3

increases plasma levels of glucose
Hormones are: epinephrine, glucocorticoids, ACTH etc

Plasma insulin/glycogen ratio is delicately maintained for glucose homeostasis

Question 4

Major organs dominant in CHO metabolism

Answer 4

liver
adipose tissue
muscle
brain

Question 4

Function of major organs dominant in CHO and how they work together

Answer 4

These tissues contain sets of enzymes such that each organ is specialized for:
1. storage
2. use
3. and generation of specific fuels

These tissues act in concert with a coordinated network in which one tissue may provide a substitute for another or process compounds produced by the other

Question 4

Hormone supporting insulin and glucagon (an its functions)

Answer 4

catecholamines
changes in plasma levels of this hormone make the body store energy or make energy available as the case arises

Question 4

Chains of insulin are joined by________

Answer 4

intermolecular disulfide bonds at A7,B7 and A20, B19
There is also an intramolecular disulfide bond on A chain at 6th and 11th

Question 5

Discuss Insulin

Answer 5

It is an anabolic hormone of the well-fed state and it is an important signal to stimulate the storage of excess nutrients such as glycogen and triglycerides
It is a polypeptide molecule of 51 arranged in 2 chains ( a and b)
Chain A has 21 aa
Chain B has 30 aa residues

Question 6

Communication between tissues is mediated by________

Answer 6

1. nervous signals
2. variation in the hormonal level or
3. availability of substitutes

Question 7

Insulin is produced by what?

Answer 7

β cells of islets on langherhans of the pancreas

Question 8

How does insulin mature?

Answer 8

In a cascade of cleavage from pre-proinsulin or proinsulin and finally insulin in response to increased blood glucose

Question 9

Regulation of insulin and glucagon secretion to maintain glucose homeostasis

Answer 9

The amount of Insulin and Glucagon released by the pancreas are regulated so that hepatic glucose production is kept equal to the used glucose by peripheral tissues to maintain a delicate balance in the ins-glu ratio to maintain glucose homeostasis

Question 10

insulin secretion is increased by

Answer 10

1. glucose or carbohydrate
2. amino acid
3. certain GIT hormones e.g. CCK

Question 10

insulin secretion is decreased/inhibited by

Answer 10

when there is a scarcity of dietary fuel, or a period of stress

Question 11

Metabolic effects of insulin on carb metabolism

Answer 11

mainly promotes storage

Question 11

Insulin is prominent in 3 tissues

Answer 11

liver
muscle
adipose tissue

the brain and RBC have no insulin receptors hence no insulin action is in them

Question 11

action of liver and muscle

Answer 11

increase glycogenesis (glycogen synthesis)
decrease glycogenolysis
decrease gluconeogenesis

Question 11

action of adipose and muscle

Answer 11

increase glucose uptake

Question 11

Mechanism of action of insulin

Answer 11

Insulin binds to specific high affinity receptors in the cell membrane of most tissues including:
liver
muscle and
adipose, causing a cascade of reactions leading to its biological effects. Such reactions include:
Receptor recruitmen
signal transduction
dephosphorylation of enzymes etc

Question 12

What is the hormone of the fasting state

Answer 12

Glucagon

Question 13

Discuss glucagon

Answer 13

It is a polypeptide molecule of 29 aa arranged in a single chain of insulin. Glucagon is a catabolic hormone produced by alpha cells of the pancreatic Islets of langerhans in response to decrease plasma levels of glucose. It works in concert with the cathecols and corticosteroid to antagonize on the target tissues

Question 14

Regulation of glucagon secretion

Answer 14

Glycogen responds to stimuli that signal actual or potential hyperglycemia
A decrease in plasma glucose Is the primary stimulus for glucagon release

A protein meal also stimulates glucagon release just as it has a counterforce to prevent hypoglycemia that may accompany increase insulin release

Paradoxically, in periods of stress, elevated levels of calthecoloamines also stimulates the production of glucagon in anticipation of increased utilization of glucose

Question 15

Glycogen secretion is inhibited by

Answer 15

high levels of glucose and by insulin

Question 16

Metabolic Effects of Glucagon in CHO metabolism

Answer 16

Glucagon acts on the liver to cause increase glycogenolysis and increase gluconeogenesis this can be demonstrated by an IV administration of glucagon which leads to immediate rise in blood glucose

Glucagon also causes a decrease in glycogenesis

Question 17

Mechanism of action of glucagon

Answer 17

Glucagon binds to G- protein receptor on the membranes of hepatocytes resulting in a cascade of reactions by activating cAMP leading onwards to phosphorylation of specific enzymes induces….. in site metabolism