Biochem Exam 4: Insulin And Glucagon

Front 1

Obj.
Indicate the specific sites of insulin and glucagon synthesis

Back 1

insulin:
synthesized by beta cell in pancreas

glucagon:
synthesized by alpha cells in pancreas

Front 2

What 4 organs play a major role in metabolism?

How do they communicate?

Back 2

liver
adipose
muscle
brain

-communicate via nervous system, availability of substrates, & variation in plasma hormone levels

Front 3

Obj.
List the effects of insulin rise in patients blood

Back 3

decreases blood glucose

Front 4

The energy metabolism is controlled by what (5/6) hormones?

These hormones induce storage when food is available & degradation of storage when it is not

Back 4

1. insulin
2. glucagon
3. epinephrine
4. norepinephrine
5. cortisol (chronic stress)
& GH

Front 5

Insulin affects the anabolism (building) of what (3)?

Back 5

glycogen
triacylglycerols
protein

Front 6

Obj.
Cite the regulators of insulin secretion

Back 6

Stimulated by-
1. glucose (strongest stimuli, more secreted)
2. AAs (Arg)
3 GI hormones

Inhibited by-
1. low dietary fuel (glucose, ATP)
2. stress, trauma, extreme exercise (presence of epinephrine)

Front 7

Active insulin results from posttranslational cleavage of what two precursors?

Back 7

preporinsulin
proinsulin

Front 8

Obj.
Predict the metabolic effects of insulin on:
carbohydrates
triacylglycerides
protein synthesis

Back 8

carbohydrates:
-increases glycogen synthesis & glucose uptake
-inhibits gluconeogenesis & glycogenolysis

triacylglycerides:
-inhibits hormone-sensitive lipase, decreasing release of FAs (decrease degradation in ADIPOSE)
-increases glucose uptake by adipose, increasing G-3-P
-activates lipoprotein lipase (LPL), increasing free FAs

protein synthesis:
-stimulates AA uptake & protein synthesis

Front 9

Insulin secretion is measured using the plasma concentration of what?

Back 9

C-peptide
(concentrations are directly proportional)
-has longer half life, is degraded in kidney

Front 10

Effects of Insulin

Back 10

*insulin is stored in granules & secreted by exocytosis when needed, has a 6 min half life

Inhibits:
gluconeogenesis (liver)
glycogenolysis (liver)

Activates:
glycogen synthesis (muscle & liver)
glucose uptake (muscle & adipose)(NOT RBCs, brain, or liver!!!!)

=decreased blood glucose

Front 11

What is insulin degraded by?

Back 11

insulinase

*degraded in liver and kineys

Front 12

Obj.
General consequences of hypoglycemia

Back 12

-confusion
-aberrant behavior
-blood glucose < or = 40 mg/dL
-coma

Front 13

Beta cells sense glucose via ___________ activity, and secrete insulin in response.

Back 13

glucokinase

Front 14

Obj.
What are the two types of hypoglycemia symptoms/onset?

Back 14

1. sudden lowering of glucose (Adrenergic)
-symptoms due to epinephrine release

2. gradual decrease of brain glucose (Neuroglycopenic)
-symptoms due to brain malfunction

Front 15

Obj.
What are the symptoms of each type

Back 15

Andrenergic:
-anxiety
-palpitations
-tremors
-sweating

Neuroglycopenic:
-headache
-confusion
-slurred speech
-seizures
-coma
-death

Front 16

The absorption of a carbohydrate rich meal results in:

Back 16

insulin secretion
glucagon inhibition

--> overall increase in glucose an insulin

Front 17

T/F
Insulin stimulates the synthesis of enzymes necessary for protein sythesis

Back 17

TRUE

Front 18

Obj
what hormonal changes accompany hypoglycemia

Back 18

-decreased (low) insulin*
-increased (high) glucagon*
-increased (high) epinephrine*
-increased cortisol
-increased growth hormone

Front 19

Glucagon & epinephrine are important for (short/long) term regulation of blood glucose

Back 19

short term

**cortisol and growth hormone are important for long term**

Front 20

Obj.
Why is hypoglycemia a medical emergency?

How can it be corrected?

Back 20

CNS requires continuous supply of glucose
Severe prolonged hypoglycemia causes brain death

*treated w/ glucose administration!

Front 21

Epinephrine induces:

Back 21

glycogenolysis
lipolysis

*epinephrine OVERRIDES normal glucose-stimulated release of insulin= even if glucose is present, if epinephrine is there, insulin will not be secreted

Front 22

Obj.
Cite different types of hypoglycemia

Back 22

Insulin-induced hypoglycemia:
-caused by diabetic (type 1) ppl taking insulin
-treated w/ carb/glucose, eaten/injected depending on consciousness

Postprandial hypoglycemia:
-caused by high insulin release after meal
-transient, recovers after eating
-avoided by eating frequent small meals

Front 23

Obj.
Explain insulin's mechanism of action

Back 23

1. Receptor tyrosine kinase phosphorylates Insulin receptor Substrates (IRS)
2. Phosphorylated IRS promotes activation of other protein kinases & phosphatases
3. Activation of enzymes leads to biological effects of insulin:
increase:
glucose uptake
glycogen synthesis
protein synthesis
fat synthesis
decrease:
gluconeogenesis
glycogenolysis
lipolysis

--altered gene expression

Front 24

Obj
what are the effects of hypoglycemia and alcohol intoxication?

Back 24

-Degradation of ethanol leads to increased cystolic NADH
^reduction of pyruvate to lactate (lactic acidosis)
^conversion of OAA to malate
-Decrease in pyruvate & OAA leads to decreased gluconeogenesis (bc precursors unavailable)
^leads to hypoglycemia

Front 25

Formation of NADH can be decreased by taking ___________
This intake will result in what?

Back 25

Disulfram (aldehyde dehydrogenase inhibitor, halts ethanol metabolism)

Results in:
flushing
tachycardia
hyperventilation
nausea

Front 26

T/F
glucagon and GLP-1 ("glucagon-like" incretin) are secreted by the same cells

Back 26

FALSE

glucagon is secreted by alpha cells in pancreas, GLP-1 secreted by neuroendocrine (L cells) in gut!

-have similar function

Front 27

Glucagon w/ epinephrine, cortisol, and growth hormone has (same/opposite) effect of insulin

Back 27

opposite

Front 28

In the liver, what does glucagon increase?

Back 28

glycogenolysis
gluconeogenesis
FA oxidation (forming ketone bodies & acetyl CoA)
AA uptake (for gluconeogenesis)

(= opposite effect of insulin!!!)
(glucagon + epi also activate ketogenesis, where insulin inhibits)

Front 29

Stimulation/inhibition of glucagon secretion

Back 29

Stimulation:
low blood glucose (hypoglycemia)
high AA (hypoglycemia caused by insulin)
epinephrine (increase glucose use)

Inhibition:
high blood glucose
high insulin

Front 30

Obj
Fasting hypoglycemia is rare but can occur under what conditions?

If untreated what may occur?

Back 30

-hepatocellular damage (low glucose production)
-adrenal insufficiency
-fasting + large alcohol intake
-overuse of glucose by body in presence of pancreatic beta tumor (elevated insulin)

pt may:
lost consciousness
have convulsions
slip into coma

Front 31

alcohol consumption should be avoided in individuals that are ___________, _____________, or _______________

Back 31

fasting, engaged in prolonged strenuous exercise, or taking insulin