Basic Science Flashcards
What cells secrete insulin and glucagon?
- insulin: Beta cells
- glucagon: Alpha cells
What so delta and PP cells secrete?
- delta cells: somatostatin
- PP cells: pancreatic polypeptide
What is the simple pathway for the production of insulin?
- made in the RER of pancreatic beta cells as preproinsulin
- this is cleaved to make insulin
- C peptide is made in a 1:1 ratio (no known function)
What is the short-acting form of insulin?
lispro= most rapid acting and is used in combination with longer acting types
What is the long-acting form of insulin?
glargine= released slowly into the blood and the level is maintained during sleep
What is the process of secretion of insulin?
- glucose enters beta cells through GLUT2
- glucose is phosphorylated by glucokinase
- increase in glucose metabolism so increase in intracellular ATP from respiration
- ATP inhibits ATP-sensitive K+ channels
- this causes depolarisation
- voltage-gated Ca2+ channels open
- an increase in Ca2+ causes insulin to be released
What are the features of glucokinase?
- Km is at ideal glucose concentration
- action increased as glucose increases
What is the fasting glucose in diabetics?
above 7
What is the pattern of release of insulin from a beta cell?
it is biphasic with a reserve pool and a readily releasable pool (RRP)
What is the structure of a Katp channel?
- 4x Kir6
- 4x SUR1
this forms an octomeric structure
What are the factors that can cause change in Katp?
- normally, ATP inhibits Katp to cause depolarisation
- Katp can be inhibited by sulphonylurea
- Katp can be stimulated by diazoxide
(overwork Beta cells)
What mutation can lead to neonatal diabetes?
Kir6.2 which is part of the Katp channel as there will be more Katp channels and they will be overactive
What is MODY?
Maturity-onset diabetes of the young
- familial disease with beta cell genetic defect
- associated with transcription factors
- MODY2 involves glucokinase impairment
What are the definitions of the types of diabetes?
- Type 1= loss of insulin secreting beta cells
- MODY= defective glucose sensing and/or loss of insulin secretion
- Type 2= hyperglycaemia with hyperinsulinaemia so there is decreased insulin sensitivity in tissues
What are the processes that insulin promotes?
this is an anabolic hormone
- amino acid uptake in the muscle
- DNA synthesis
- protein synthesis
- growth repossess
- glucose uptake in muscles and adipose tissue
- lipogenesis in adipose tissue and liver
- glycogen synthesis in liver and muscle
What are the processes that insulin inhibits?
- gluconeogenesis in the liver
- lipolysis in the adipose tissues
What is the outline of insulin sensing?
- insulin receptors = receptor tyrosine kinase
- signalling pathways = PI3K and RAS which are regulated by growth factors
What are the features of Leprechaunism?
- association with dwarfism
- defects in insulin binding or insulin receptor signalling
- growth problems
What are the main features of DKA?
- increased HR
- vomiting
- dehydration
- smell of ketones on breath
Where are ketone bodies made?
liver mitochondria
How are ketone bodies made?
when the ration of carbohydrates:fatty acids is changed when there is an increase in FAs the more ketone bodies are made from acetyl-coA
What are ligand-gated ion channels?
- in neurones and muscle cells
- bound and activated by hormones and neurotransmitters
- these cause a response in milliseconds
What happens to open ligand-gated ion channels?
there is a chemical change when the hormone binds so there is structural change
What disease occurs when ligand-gated ion channels are distrupted?
Myasthenia Gravis- autoimmune condition with loss of ACh receptors
