Biochemistry - Endocrine Flashcards
which cells in the islets of langerhans secrete insulin?
beta cells
which cells in the islets of langerhans secrete glucagon?
alpha cells
which cells in the islets of langerhans secrete somatostatin?
delta cells
what is the initial structure that is cleaved to form insulin?
preproinsulin
true or false: there is great variation in the amino acid sequence of insulin between species
false
very little variation
what is the effect of insulin upon amino acids, glucose and lipids?
increases uptake into respective tissues
true or false: insulin inhibits lipolysis
true
through which transporter does glucose enter beta cells in the pancreas?
GLUT2
what happens to glucose once in the beta cell in the pancreas?
phosphorylated to glucose 6 phosphate
which enzymes carry out glucose phosphorylation?
glucokinase
hexokinase (RBCs)
which two proteins make up a functional Katp channel?
Kir 6.1
sulphonylurea receptor (SUR1)
what inhibits the Katp channel?
intracellular ATP
what happens as a result of inhibition of the Katp channel?
depolarisation, causing opening of calcium channels to allow insulin exocytosis
what is MODY?
maturity onset diabetes of the young
what causes MODY?
a genetic defect in beta cell function, causing early onset type II diabetes
which enzyme is impaired in MODY?
glucokinase
how are ketone bodies formed?
derived from acetyl-CoA in beta oxidation
name three ketone bodies
acetone
acetoacetic acid
B-hydroxybutric acid
which type of diabetes is ketoacidosis most associated with?
type 1
true or false: sodium follows water everywhere
false
water follows sodium
true or false: concentration of sodium inside the cell is greater than outside the cell
false
what does mineralocorticoid activity refer to?
sodium retention in exchange for potassium and/or hydrogen ions
what is the main steroid in the body with mineralocorticoid activity?
aldosterone
what does excess mineralocorticoid activity cause?
sodium retention ‘
what effect does sodium loss have upon water?
sodium loss means water loss
outline what happens in terms of sodium and water when BP drops
decreased BP causes sodium and water retention, in order to compensate and bring blood pressure up
which hormone controls water reabsorption?
ADH
what effect does ADH have on water reabsorption and thus urine output?
causes increased water reabsorption producing low volume concentrated urine
true or false: concentrated/small volume urine has a high osmolality
true
what are the main causes of decreased sodium levels/
too much water
too little sodium
what are the main causes of increased sodium levels?
too little water
too much sodium
how can too much water cause decreased sodium levels?
SIAD
compulsive water drinking
how can too little sodium cause decreased sodium levels?
sodium loss
decreased sodium intake
how can increased sodium levels be due to too little water?
water loss
decreased water intake
how can too much sodium increase sodium levels?
IV medication
drowning in the sea
high salt foods
outline the pathogenesis of addison’s disease
- adrenal insufficiency
- cant make enough aldosterone
- cant retain enough sodium
- lose sodium and water
- low ECFV, patient is dehydrated and dizzy
what is the main osmotic stimulus for ADH release?
high sodium causes increased ADH
does hypovolaemia cause increased or decreased ADH release?
increased to compensate for fluid loss
outline pathogenesis of diabetes insipidus
- disrupted pituitary
- can’t secrete ADH
- less water reabsorption
- lots of water lost in urine
- sodium is high to reflect water deficit
