PoH: Lipids Flashcards
Name the 4 types of fatty acids
Saturated
Mono-unsaturated
Poly-unsaturated
Trans fats
Name the 4 major lipid classes
Triacylglycerol
Phospholipid
Glycolipid
Steroids
What is triacylglycerol made of, and why do we need them?
Esters of FAs and glycerol
Provide dietary fuel and insulation
Are phospholipids water-soluble, fat-soluble or both? What 3 functions do they perform in the body
Both - amphipathic
Membranes
Lipid droplets
Local signalling molecules
What sort of ring system do steroids have? Provide 3 examples of steroids in the body
4 Ring system
Cholesterol – starting material for synthesis of bile salts, steroid hormones and other components
Steroid hormones – serve as chemical messengers (corticosteroids, sex hormones)
Bile salts – sodium salts of steroid use for emulsification
Describe the 2 functions of cholesterol
Component of cell membranes, e.g. plasma lipoproteins
Precursor to sterol hormones, vitamin D, bile acids and protein modification
Describe the structure of cholesterol
C27H46O
It has a central sterol nucleus of four hydrocarbon rings
What is eicosanoid derived from?
Oxidation of 20-carbon unsaturated fatty acids (omega 3 or 6)
What 2 functions do eicosanoids have, and what’s their half-life like?
They’re signalling molecules
Precursors to prostaglandins
Short half life
What is a steroid lipid made from and what is it a starting material for?
From cholesterol
Starting material for synthesis of bile salts, steroid hormones and other components
Lipid digestion mainly occurs where?
Small intestine
In what 3 ways are fats digested in the stomach?
· Pancreatic enzymes (lipates)
· Emulsification (dispersion) by bile salts
Peristalsis (mixing)
How are FAs packaged and released?
Packaged into chylomicrons
Released by exocytosis
How are chylomicrons broken down?
In tissues, TAG in chylomicrons is hydrolysed to FA and glycerol by lipoprotein lipase. Chylomicrons depleted of TAG are called chylomicron remnants which go to the liver
After chylomicrons are degraded, what happens to the FAs?
The FAs are used for energy or re-esterified to TAG for storage.
In what complex are free FAs transported around the body?
In a complex with serum albumin
90% of FAs are esterified (not free)
Define essential fatty acid
Polyunsaturated fatty acids that we must get from the diet because they’re needed for health but we cannot synthesise these in the body.
Where do FAs come from?
Diet
Stored lipid/tryglyceride (released from adipose tissue)
Synthesised in body through Citrate Shuffle (via palmitate from Acetyl CoA)
What 3 places does free FA synthesis occur in the body?
Liver
Lactating mammary gland
Adipose tissue
What does the Citrate Shuffle do?
Synthesises FAs
Where does the Citrate Shuffle take place? Where does modification occur?
Mitochondria and cytosol
Further modification in mitochondria and ER
Which of the following can be used in the Citrate Shuffle to make FAs: Fat, protein, carbohydrate
All
What does b oxidation involve?
It involves taking a long FA chain and nibbling bits off to produce FADH, ATP, NADH and Acetyl CoA
Name the 3 steps of b oxidation
1) Oxidation of FAs
2) Carnitine shuttle to transport into mitochondrial matrix
3) Degradation with 4 main enzyme reactions
What type of chemical reactions are the steps of b oxidation?
Dehydrogenation
Hydration
Dehydrogenation
Thiolysis
Describe the function of ketone bodies
Provide energy when fasting, as there’s no glucose to use. If there’s no insulin it impairs use and leads to diabetic ketoacidosis
Where are ketone bodies produced?
Liver
How are ketone bodies produced and what happens to the product?
β-oxidation of fatty acids => Acetyl CoA
Acetyl CoA + Pyruvate enter Citric Acid Cycle to form ATP
In what part of cells are KBs metabolised? What do they yield? What are they reconverted into?
KB can be oxidised in the mitochondria to yield 2 GTP and 22 ATP
They’re transported to tissues and reconverted to Acetyl CoA
In b oxidation, what transports oxidised fatty acids into the mitochondrial matrix?
Carnitine shuttle
