Lecture 31 Flashcards
What is metabolic homeostasis
The body’s ability to maintain various metabolic processes to ensure molecules essential for life are kept at an optimal level
What does metabolic homeostasis require?
The interplay of the digestive system, endocrine system, nervous system and many different signal transduction events
What is the preferred fuel type for the brain?
Glucose but can use ketone bodies as well
What is the preferred fuel type for skeletal muscle?
Fatty acids, however, can use all especially when exercising
What does skeletal muscle store and export?
Stores glycogen
Exports lactate and alanine
What is the preferred fuel type for cardiac muscle?
Fatty acids
What is the preferred fuel type for the adipose tissue?
Fatty acids
What fuel is stored in and transported from adipose tissue?
Stores triacylglycerols
Exports fatty acids and glycerol
What is the preferred fuel type for the liver?
Amino acids, glucose and fatty acids
What fuel is stored in and exported from the liver?
Stores glycogen
Exports triacylglycerols, glucose, ketone bodies
What is the prefered fuel for RBCs and why?
Glucose as RBCs lack mitochondria for any other metabolic pathway to occur
What fuel is exported from RBCs?
Lactate
Why can the brain not use FAs?
They cannot cross the blood-brain barrier
What is insulin?
A peptide hormone synthesised in and secreted by the pancreatic beta cells in response to high blood glucose levels
What does insulin do?
Acts on the liver, muscle and adipose tissues to promote glucose transport into cells to be used for energy or stored as glycogen
What happens to the body without insulin?
It starves
What is type 1 diabetes?
An early onset form of diabetes, diagnosed by symptoms, blood glucose and glycated haemoglobin
What are common symptoms of diabetes?
Glycosuria (glucose in urine) and the presence of ketones in the blood
What causes type 1 diabetes?
An autoimmune condition leading to the loss of pancreatic beta cells and therefore no insulin secretion
What is preproinsulin?
Initial form of insulin synthesised from transcription and translation in the ER, containing the A-chain, B-chain, C-peptide, and a signal sequence
What is the signal sequence?
A chain that helps direct the protein into the ER but is removed by signal peptidase, leaving proinsulin
What is proinsulin?
The A-chain, B-chain, and C-peptide of insulin. It is folded and stabilised by disulfide bonds and moves to the Golgi and is packaged into secretory granules. Proprotein convertase enzymes in the granules cleave proinsulin to release active insulin (A-chain and B-chain) and C-peptide.
What is the C-peptide?
A chain released during the cleavage of proinsulin along with insulin, has a longer half-life than insulin and can be used as a marker of insulin secretion
What is the c-peptide important for?
Distinguishing between endogenous insulin and exogenous insulin
