Lecture 25 - Fatty acids as a fuel molecule #1 Flashcards
What is the chemical nature of lipids?
Hydrophobic or amphiphilic organic molecules
What are the three forms of lipid in the diet?
Phospholipids (membrane) , sterols, triacylglycerol
What is an example of a sterol?
Cholesterol
What is the role of cholesterol in the body?
A range including membranes, signalling (hormones) and forming bile salts
What is the chemical structure of cholesterol?
A hydrophobic ring structure
What is an example of a triacylglycerol (TAGs)?
fatty acids
What is a fatty acid?
Carbon chain attached to a carboxylic acid
What is a free fatty acid (FFA)?
A fatty acid not bound to any other molecule
What is the chemical nature of the carbon chain in fatty acids?
Hydrophobic
What is the structure of a triagylglycerol?
1x Glycerol (3C) with 3x fatty acids (acyl groups) attached
What component of the TAG is polar?
Glycerol
What component of the TAG is non-polar?
fatty acid (acyl group)
What type of enzyme breaks down TAGs?
Lipase
What does lipase do to TAGs?
Hydrolyses it to release the free fatty acids (FFAs)
What are bile acids?
Salts synthesised from cholesterol in the liver
How are bile acids synthesised?
By adding hydroxyl and/or carboxyl groups to create a hydrophilic face
What do bile acids form?
Micelles, multiple bile acids come together to form a hydrophobic core of TAGs inside to be absorbed into epithelial cells
What are exogenous fatty acids?
Fatty acids ingested from the diet
What is the path of exogenous fatty acid transport to the blood stream?
Consumed fats exist as TAGs, bile salts break these down into smaller droplets, pancreatic lipase breaks these down into MAG and 2FFAs which are then rearranged to form a micelle for transportation to SI lining for absorption. Once absorbed MAG and 2FFAs are rearranged back into a TAG which are packaged into chylomicrons along with apoproteins to enter capillaries
What is a chylomicron?
A type of large lipoprotein involved in TAG transport with low protein:lipid (~1:50)
What is a lipoprotein?
A type of ‘delivery system’ for lipid transportation, to help solubilise them
What are the components of a lipoprotein?
Phospholipids, unesterified cholesterol, esterified cholesterol, TAGs and apoproteins
What is unesterified and esterified cholesterol
Cholesterol without and with FFAs attached (respectively)
What is an apoprotein?
The protein component of the lipoprotein that can have several roles including; structural, ligand for receptors and enzyme co-factors
What are the classes of lipoprotein?
Chylomicron, VLDL, LDL, HDL
What is a VLDL?
Very low-density lipoprotein involved in TAG transport with medium lipid:protein (~1:9)
What is a LDL?
Low-density lipoprotein involved in cholesterol transport
What is a HDL?
High-density lipoprotein involved in cholesterol regulation
What happens to the chylomicron once it enters the blood stream?
Lipoprotein lipase hydrolyses the TAG into monoacylglycerol and fatty acids to enter the tissue
What is lipoprotein lipase activated by?
ApoCll
What happens to chylomicron remnants after?
They remain in blood
What can fatty acids be used for?
Fuel or storage
What is the preferred fuel for most tissues?
Fatty acids
Red Muscle Cells tend to use?
Fat (endurance)
White muscle cells tend to use?
Glucose (sprinting)
Why are fatty acids the preferred storage molecule?
Fatty acids are more reduced than carbohydrates (more energy released when oxidised)
Also takes up less room than carbohydrates (due to carbohydrates water retention)
Acetyl-CoA can be formed into ____ to make ____
Free fatty acids to make TAGs
Chylomicron remnants are absorbed in the?
Liver via receptors that recognise ligands on chylomicrons
Chylomicron remnants are recycled into:
VLDL (with TAGs)
Bile salts and cholesterol
What can remove TAGs from VLDL to make LDL?
Hepatic Lipase
