Exam 3 - pancreas

what are the 4 cells within the islets of langerhans

alpha

beta

delta

PP

which cell found in the islets of langerhans make up 75%? what do they secrete

beta, insulin

which cell found in the islets of langerhans make up 20%? what do they secrete

alpha

glucagon

what do delta cells produce

somatostatin

what chromosome controls insulin synthesis

11

mRNA directs ribosomal synthesis of preproinsulin, what does this molecule contain

signal peptide

A and B chains of insulin

connecting peptide - C peptide

what is cleaved from preproinsulin to create proinsulin

signal peptides

once proinsulin is formed and sent to the RER, what produces a folded insulin molecule

disulfide bridge formation

the folded insulin is packaged in the goli apparatus and turned into insulin once what is cleaved

C peptide

what are insulin and the cleaved connecting peptide (C-peptide) packaged together in

secretory granules

which pool is insulin more commonly in? which is it less in?

reserve pool of granules

ready releasable

which pool is initially released when beta cells are activated? which comes next?

releasable pool

reserve pool

how long does insulin circulate in its free form

3-8 minutes

what results in equal release of insulin and C-peptide

exocytosis of secretory granule contents

is c-peptide readily degraded by the liver?

no

what is used as an index of secretory capacity of the pancreas

c-peptide

t/f

insulin is only released in response to one hormone

false, there are many

what is the main stimulus for insulin release from pancreatic beta cells

glucose

what transport molecule moves glucose from blood into cell via facilitated diffusion

GLUT 2

GLUT 2 brings glucose into the cell which causes ___ channels to close and ___ channels to open causing depolarization. The calcium then causes insulin secretory granules to undergo ____ into the pancreas venous blood

potassium, calcium, exocytosis

what enzyme does insulin trigger in the liver to control how fast glucose is processed

glucokinase

what transport molecule does insulin stimulate

GLUT4

what is the mechanism of action for insulin

tyrosine kinase

at the target tissue, what pathways does insulin use to determine what happens to glucose

PI3K

MAPK

what cells are GLUT 2 found in? what type of transport do they use? are they sensitive to insulin? does it have high or low affinity

pancreatic beta cells, hepatocytes

facilitated diffusion

no

low

what tissues are GLUT 4 found in? what transport do they use? are they sensitive to insulin? does it have high or low affinity

skeletal muscle, adipose tissue

facilitated diffusion

yes

high

in the liver and muscle, insulin binds to its tyrosine kinase receptor and causes glucose to be converted into ___ and ____ for what processes?

what is the difference between these two locations?

glycogen, pyruvate, glycogenesis and glycolysis

liver: GLUT 2

muscle: GLUT 4, amino acid channel for protein synthesis

in adipose tissue, insulin uses ___ and glucose is converted into ___ and ___ to make ____

GLUT 4, glycerol, FFA, TGs

what two enzymes are needed in order for insulin to convert glycogen into glucose

phosphorylase, glucose phosphate

does a trained or untrained muscle have a higher glycogen capacity

trained

how quickly should glycogen stores be replenished after exercise

30-60 minutes

insulin increases the use of glucose by most body tissues to decrease blood glucose, at the same time it decreases utilization of what energy source?

fat

what happens when there are more carbs ingested than the liver and muscle can use

FA synthesis

in adipose tissue, what hormone does insulin inhibit to prevent fatty acids from leaving the tissue and entering the blood

hormone sensitive lipase

what mechanism does adipose tissue use to grow

hypertrophy

what hormones have we discussed in class so far that have increased blood glucose

GH, cortisol, TH< catecholamines

what stimulates insulin secretion? what inhibits it?

hyperglycemia

normal blood glucose

what are insulin's primary actions in the liver? muscle? adipose?

L: glycogenesis, glycolysis

M: glycogenesis, glycolysis, protein synthesis

A: lipogenesis

what cells release glucagon

alpha cells

what kind of hormone is glucagon? what mechanism does it use?

peptide

adenylyl cyclase

what stimulates glucagon release? what inhibits it?

hypoglycemia (low bld glucose)

hyperglycemia (high bld glucose)

what are glucagon's primary actions in the liver?

glycogenolysis (glycogen to glucose)

gluconeogenesis (new glucose)

release glucose to blood

what is glucagon's primary action in adipose tissue

lipolysis

in adipose tissue, what enzyme does glucagon stimulate to break down triglycerides into ffa and diacyglycerol

hormone sensitive lipase

in the liver, FFA undergo what reaction? what is produced in excess?

beta oxidation

ketone bodies

what process is regulated by the balance between the effects of glucagon and insulin at their target organs

ketogenesis

what affect on HSL does the absence of insulin have

unable to inhibit HSL = more TGs = more glucose and ketones = diabetic ketoacidosis if a diabetic