Biochemistry Flashcards
What type of hormone is insulin?
Peptide hormone
Which cells secrete insulin?
Pancreatic beta-cells
What do pancreatic alpha cells secrete?
Glucagon
Which cells secrete somatostatin?
Delta cells
Where specifically is insulin made?
Rough ER
What is insulin made from?
preproinsulin
What else is produced alongside insulin?
C-peptide
What proteins make up the ATP sensitive K channel?
Kir6
SUR1
Which type of diabetes is caused by mutations in Kir6?
Neonatal diabetes
Mechanism of T1DM?
Autoimmune destruction of pancreatic beta cells
Mechanism of T2DM?
beta cells try to compensate for hyperglycaemia (caused by insulin resistance) then the beta cells lose function due to over-compensation
Mechanism of MODY?
Defective glucose sensing in pancreas and/or loss of insulin secretion
Where are the targets for insulin signalling?
Liver
Muscle
Adipose tissue
Does insulin inhibit lipolysis?
Yes
List some biological effects that are “switched on” by insulin?
Amino acid uptake in muscle Glucose uptake in muscle and adipose tissue Lipogenesis in adipose tissue and liver Glycogen synthesis in liver and muscle DNA and protein synthesis
What is leprechaunism caused by?
mutations in the gene for insulin receptor which results in severe insulin resistance
What is rabson Mendenhall syndrome?
Severe insulin resistance that results in developmental abnormalities, hyperpigmentation, hyperinsulinaemia and DKA
What causes DKA?
build up of ketone bodies
When glucose is not available, fatty-acids are oxidised for energy. Excess acetyl-CoA is then converted to ketone bodies which leaves to acidosis
How do you treat DKA?
Insulin
Rehydration
How does glucose enter pancreas?
through GLUT2 transporters
What happens to glucose after it enters pancreas?
Phosphorylated to glucose-6-phosphate
Which enzymes phosphorylate glucose?
Glucokinase
hexokinase
What happens in the pancreas once glucose is phosphorylated?
Insulin is released
Intracellular ATP increases ATP inhibits ATP sensitive K channel Depolarises cell membrane Ca2+ channel opens Secretory vesicles fuse Insulin is released
When is insulin released?
When blood glucose >5mM
Insulin release in biphasic
true or false
true
What is the general rule for sodium and water?
Water follows sodium
Which hormone controls water balance?
ADH
Where is ADH released from?
posterior pituitary
What is the result of increased ADH?
small volume, concentrated urine (high osmolality)
What is the result of decreased AFH?
high volume, diluted urine (low osmolality)
What does ADH cause?
water reabsorption
Which hormone controls sodium balance?
Steroids
Where are steroid hormones released from?
Adrenals
What else is sodium balance known as?
Mineralocorticoid activity
What does an increased mineralocorticoid activity cause?
Na+ gain
What does an decreased mineralocorticoid activity cause?
Na+ loss
Where is sodium confined to?
extracellular fluid
What does Addison’s disease cause?
Decreased sodium
What is diabetes insipidus?
Pituitary can’t secrete ADH so there’s too much water therefore too much sodium
