Lipids Flashcards
(46 cards)
What is a lipid?
A biomolecule that is soluble in nonpolar solvents
What is a fatty acid?
Monocarboxylic acid with long unbranched hydrocarbon chain
Most animal fatty acids have … numbers of carbon atoms
Even
What are fats?
Triglycerides: 3FA chains esterified to one glycerol molecule
What are sources of fatty acid?
Diet: triglycerides absorbed across intestinal epithelium and transported in blood by chylomicrons to liver and adipose tissue (hydrolysed to free fatty acids)
De Novo synthesis in liver: carried by VLDL to other tissue (often stored in adipose)
How is digested FA carried to liver?
Chylomicrons
How are newly synthesised FA carried from the liver to tissue?
VLDL
What are essential fatty acids, why are they essential?
Linoleic and Linolenic acid (can’t be made in the body)
Body can’t introduce C=C beyond C9
What is the structure of a phospholipid, how is it made?
Diacylglycerol molecule (2 FA, one glycerol via ester linkages)
Headgroup attached to 3rd position via phosphodiester bond and an alcohol
How many water molecules to make a phospholipid?
4
What are the roles of phospholipid?
Component of cell membrane lipid bilayer
Component of pulmonary surfactant (maintain lung structure)
What are different classes of phospholipid, how do they arise?
Dictated by their head group:
No head group apart from glycerol –> phosphatidylglycerol
Serine head group –> phosphatidylserine
Ethanolamine head group –> phosphatidylethonalamine
Choline –> phosphatidylcholine
Inositol –> phosphpatidylinositol (forms PIP2)
What is the name of a phospholipid with Serine head group?
Phosphatidylserine
What is the name of a phospholipid with no head group apart from glycerol?
Phosphatidylglycerol
What is the name of a phospholipid with choline head group?
Phosphatidylcholine
What is the name of a phospholipid with Inositol head group?
Phosphpatidylinositol (forms PIP2)
What is structure of cholesterol what’s it made from?
27C 4 ring, acetyl CoA
What are the roles of cholesterol (5)?
Component of plasma membrane - decrease fluidity
Precursor of steroid hormones
Precursor of bile salts
Precursor of vitamin D
Component of lipoproteins (e.g. Chylomicrons, VLDL, HDL)
What do lipoproteins do?
Transport triglycerides and cholesterol in blood between tissues of body
Why is LDL considered bad?
Depositis cholesterol in plaques which can block blood vessels
What are the roles of lipids (3)?
1) Energy source: higher specific energy than glycogen or protein, lower hydration level than glycogen
2) Structural role (1:component of bilayer membrane e.g. phospholipids, 2: stabilise fat water interfaces)
3) Signalling molecule (extracellular: steroid hormones and eicosanoids e.g. prostaglandis) (Intracellular: second messengers from PIP2 breakdown e.g. IP3 and DAG)
How do lipids stabilise water fat interfaces?
Bile salts in intestine emulsify dietary lipids
Pulmonary surfactant (mixture of phospholipid and protein) reduce surface tension at interface of alveolar lining fluid and air in lung - prevent alveolar collapse
Describe role of cholesterol in membrane?
Inserts into hydrophobic portion so sterically inhibit fatty acyl chains movement so membrane less fluid
Describe structure of plasma membrane bilayer in terms of phospholipids , what’s the significance of the tails?
Polar headgroups facing aqueous environment
Hydrophobic tails point inwards - diffusion barrier to prevent ions/hydrophilic molecules crossing
