Lipids Flashcards
What are some properties of lipids
Heterogeneous organic molecules
Hydrophobic
Exist in cell membranes, as lipid droplets in adipose tissue, as lipoproteins in blood
What is the biological function of lipids
Stored form of energy Structural element of membranes Enzyme cofactors Hormones Vitamins A D E K Signalling molecules
Lipid classes
Fatty acids Triacylglycerol (TAG) Phospholipids Glycolipids Steroids
What are the two types of fatty acids and what is the difference between them
Unsaturated - one or more double bond that kink hydrocarbon chain
Saturated - solid with no double bonds
Which fatty acids are essential
Linoleic and alpha linolenic
Where do you get essential fatty acids from
Plants
What are some ‘good fats’ and what makes them so
Vegetable oil e.g. olive or sunflower
They’re high in polyunsaturated fatty acids
What are some ‘bad fats’ and why
Stearic (beef)
High in saturated fatty acids
What is a ‘really bad fat’ and why is it so
Trans fatty acids, result from hydrogenation of vegetable oils e.g. man made hard margarine
After which point can humans not introduce double bones
Carbon 9
What are omega 3 fatty acids derived from
Linolenic acid
What does omega 3 FA do
Lowers plasma cholesterol, prevents atherosclerosis, lowers TAG, prevents obesity, reduces inflammation
Classis symptoms of essential fatty acid deficiency
Growth retardation Reproductive failure Skin lesions Kidney and liver disorders Subtle neurological and visual problems
What are triacylglycerols
Esters of fatty acids and glycerol
Function of triacylglycerols
Dietary fuel
Insulation
Water insoluble TAG coalesce into lipid droplets in adipose tissue
Major lipid component of adipose tissue
What are phospholipids composed of
Glycerol bonded to 2 fatty acids and a phosphate group
Describe amphiphatic nature of phospholipids
Positively charged head is hydrophilic
Hydrophobic tail repels water
What is the main dietary lipid
Triacylglycerol
Where is the main site of digestion
Small intestines
What are some other dietary lipids
Phospholipids, cholesterol, free fatty acids and cholesterol ester
What digests lipids and what is it promoted by
Lipids are digested by pancreatic enzymes called lipases and is promoted by emulsification by bile salts and peristalsis
What are bile salts
Derivatives of cholesterol
Saves lipids coalescing in an aqueous enviroment
Act as a biological detergents to form emulsions and mixed micelles
How do we digest TAG
Most degraded in small intestine by pancreatic lipase to monoacylglycerol and 2 FA
What are cholesterol esters digested to
Cholesterol and free FA
How are phospholipids digested and what too
Converted to FAs and lysophospholipids by hydrolysation
Which of short, medium and long FAs require micelles for absorption
Long
What is steatorrhea
Excess fat in faeces, stools float, have oily appearance and are foul smelling
What happens if the gallbladder is removed
Inhibition of digestion and absorption of fats
How is TAG stored in adipose cells
Droplets that constitute the depot fat
Why is TAG the most efficient storage form of fuel
It’s highly reduced, nearly anhydrous
How are FA released from stored TAG in adipose tissue
Hormone Sensitive Lipase (HSL) activated by phosphorylation in response to epinephrine. High plasma glucose and insulin promote dephosphorylation of lipase (deactivation)
How are FA transported in the blood
Free FA transported through blood in complex with serum albumin
What is the most abundant plasma protein and how many FA binding sites does it have
Albumin, 2-7
What occurs when there is too much LDL
Atherosclerosis, lipid develops into fatty streaks and plaque within an artery
What does the beta oxidation pathway do
Degrades fatty acids 2 carbons at a time
Produces acetyl CoA and NADH and FADH2
Where does beta oxidation occur
Mitochondrial matrix
What happens in beta oxidation?
Three stages:
- activation of fatty acids in cystole
- transport by carnatine shuttle into the mitochondria
- degradation to 2 carbon gragments (as acetyl CoA) in the mitochondrial matrix - energy
What happens in fatty acid activation
Fatty acid activated to form fatty acyl CoA in cytoplasm
What is the Carnitine shuttle
Major site of regulation
Prevents synthesis and degradation occurring simultaneously
Carton from diet or made from lysine/methionine in liver/kidney
What is CAT-1
Carnitine palmitoyl-transferase deficiency
A carnatine associated defect in liver fatty acid beta oxidation impairs the livers capacity to use fatty acids as fuels and puts and extra burden on its capacity to generate glucose through glucneogenesis
What happens during degradation stage of beta oxidation
- Dehydrogenation to produce FADHs
- Hydration
- Dehydrogenation to produce NADH
- Thiolysis (cleaved) to produce acetyl CoA
