week 2- lipids Flashcards
what is fat important for?
Insulation
Protection
Storage
Energy Production
Synthesis of hormones and lipoproteins
What are the most commonly ingested lipids?
triacylglycerols (TAGs)
What happens to TAGs in the mouth during digestion?
there is little effect on lipids as the enzymes in the mouth are aqueous
what happens to TAGs in the stomach during digestion?
TAGs are churned into droplets called CHYME
which enzyme begins actual lipid digestion
lipase
approximately how many TAGs are hydrolysed In the stomach
10%
which enzyme hydrolyses insoluble triglycerides
pancreatic lipase
how do pancreatic lipase hydrolyse insoluble triglyceride
by binding to the bile-salt micelles
how are TAGs partially hydrolysed and reformed again
they are partially hydrolysed ;having a monoacylglyceril and 2 fatty acid chains
they’re then formed into micelles with the help of bile salts
they are taken up the intestine and reformed into triacylglycerols
What is bile?
An emulsifier
how do bile salts aid in the formation of spherical micelle shapes formed by oil droplets
by clumping fatty acids and monacylglycerols
what is the structure of a fatty acid micelle?
Bile salts on the exterior
Hydrophobic fatty acids and monoacylglycerols in the interior
what are free fatty acids and monoglycerols reformed into
triacylglycerols
what is a chylomicron?
It is a lipoprotein.
It consists of TAGs, membranes and protein
What do chylomicrons do?
They transport TAGs from the intestinal cells to the bloodstream via the lymph system
Why do chylomicrons travel through the lymph system?
Because they are too large to fit in blood capillaries and may clog up blood vessels.
What are the uses of triacylglycerols after being transported by chylomicrons?
- absorbed by cells and processed for energy by forming Acetyl CoA
- Stored in adipose tissue/adipocytes (fat cells) as lipids
How are fats released from adipocytes when needed?
They are hydrolysed (broken down) in the adipocyte and released as fatty acids when needed
what are adipocytes?
They are fat cells in the adipose tissue found mostly in the abdominal cavity and subcutaneous tissue
what do adipocytes do?
They store energy
Used as insulation
Used as a shock absorber for organs
They are metabolically very active meaning they break down and synthesise TAGs constantly
What is lipolysis?
The breakdown of triglycerides by lipases.
Lipolysis is under hormonal control.
What are the hormones involved in lipolysis and what do they do?
Epinephrine and glucagon - promote lipolysis
Insulin - inhibit lipolysis
What is the structure of TAGs and what is their structure when they get hydrolysed (broken down)?
TAGs consist of 1 glycerol and 3 fatty acid chains
When they are hydrolysed , 1 fatty acid chain is released.
TAGs can keep getting hydrolysed (broken down) until there is just the glycerol molecule left
what happens to the glycerol molecule after the 3 fatty acid chains have been hydrolysed?
The glycerol molecule gets metabolised:
- It enters into the blood stream
- Travels to the liver OR kidney for processing
- It then gets converted to dihydroxyacetone phosphate
