Lipids (transport/storage/oxidation) Flashcards
What are the functions of a fatty acid?
It is a direct fuel source
A cell membrane constituent and is involved in cell signaling
What is esterification?
The formation of a bond (ester bond) between an alcohol and an organic acid with the removal of water
How are glycerides formed?
By the process of esterification
What are some functions of triglycerides?
- A storage of fuel
- They are the largest fuel store in the body
- The splitting of triglycerides liberates fatty acids
What are phospholipids made up of and what is their main function?
Fatty acid, phosphate, a backbone (normally glycerol) and alcohol
Main function is the lipid bilayer
What are phosphoglycerides?
Derived from phosphotidate and alcohol
Inositol,choline and serine can combine with phosphotidate to form a phosphoglyceride
What is cholesterol?
- A cell membrane and a blood lipid
- required to build and maintain cell membranes and regulate fluidity
- used in the formation of other circulating steroid hormones
- required for formation of bile salts used in lipid digestion
What happens if the lipid is not water soluble (isn’t stored/utilized straight away)
It requires transport in the blood
What do lipoproteins do?
They carry TG and cholesterol in the blood stream
VLDL and LDL carry cholesterol/TG from the liver and tissues
HDL carries cholesterol/TG from bloodstream back to liver for recycling
Can fatty acids be transported in the blood?
Yes, not only as triglycerides in lipoproteins
99.9% of all FFA in plasma are
Bound to albumin
Is more energy stored in adipose tissue or glycogen?
Adipose! 108,000 compared to 2,000
How do the triglycerides provide fuel for exercise?
TG can be broken down to fatty acids in both adipose tissue and muscle
Are triglycerides taken into adipocytes?
No, they are first hydrolysed to fatty acids by LPL
Then the fatty acids are freed in capillaries by LPL and flow down a concentration gradient into adipocytes with the aid of a carrier protein
Describe the set of stages in using fatty acids as a fuel for exercise?
- mobilization - lipolysis, adipose tissue/IMTG/VLDL-TG
- transport into blood stream (FA with albumin)
- transport into the muscle cell - transport into mitochondria
- oxidation in beta-oxidation pathway and TCA cycle
How do adrenaline and insulin affect the mobilization of lipid fuel from adipose tissue?
Adrenaline increases the hormone sensitive lipase which breaks down TG to glycerol and 3FFA which then go into the capillary
Insulin decreases this enzyme
Explain fatty acid uptake in muscle?
VLDL/chylomicron broken down to FA by LPL. The FA then use a transport protein to get Into the muscle
Also FA from the blood bound to albumin go through same process
What is fatty acid muscle uptake directly related to?
Plasma FFA concentration
By what process does transport across the membrane into muscle (fatty acids) occur
Facilitated diffusion
Can the FA transporter protein become saturated?
Yea it can, an increase of lipolysis = an increase of glycerol in the blood
What happens to the fatty acids upon uptake into muscle
They are converted to a conenzyme A derivative
Where preparation for B-oxidation occurs, this priming reaction requires ATP catalyses by fatty-acyl-CoA synthetase
How are the fatty acyl-CoA molecules transported from the muscle sarcoplasm into the mitochondria?
Via an ester bond with carnitine (can’t just diffuse across)
Discuss carnitine
Carnitine is synthesised by liver from methionine and lysine and derived from the diet, it is present in tissues that are able to oxidise fatty acids
What is the key enzyme in beta oxidation?
3-HAD
Where does beta-oxidation occur?
In the mitochondrial matrix
What is beta-oxidation?
The sequential removal of 2 carbon fragments from a fatty acid which yields the produces acetyl CoA, NADH and FADH2 (oxidized in ETC)
What does beta oxidation produce ATP wise?
It produces 5 ATP molecules per 2 carbon acetyl-CoA unit cleaved from the FFA chain
Where do the ATP produced in beta oxidation come from?
3 ATP from NADH
2 ATP from FADH2
