Lipids Flashcards
What are lipids?
1.Water-insoluble molecules that can be extracted from tissues by non polar solvents
2.They are not polymers
What reaction releases large amount of energy in lipids
Oxidation of lipids releases large amount of energy
Four functions of lipids
1.Energy storage
2.Insulation
3.Cell membrane structure
4.Communication
5 Types of Lipids
1.Fatty acids
2.Triglycerides (TAGs)
3.Phospholipids
4.Sphingolipids
5.Steroids (Cholesterol)
Fatty Acids exist either as?
FAs exist either as free or esters (TAGs)
Found at high levels in plasma during fasting
How do FAs circulate in the body?
They circulate bound to Albumin
Empirical formula for FAs
(H(CH2)nCOOH)
How long are FA chains usually?
4-40 carbons long
Also have an amphipathic nature (hydrophilic/phobic)
What parts of FAs are hydrophilic/phobic?
The carboxyl head is Polar
The fatty acid chain is non polar
What number carbon FAs are most common in plants and animals?
C16 and C18
Difference between saturated and unsaturated fatty acids
1.Saturated fatty acids have no double bonds and are solid at room temp (animals, humans)
2.Unsaturated fatty acids have one or more double bonds cause chain to bend and are liquid at room temp (fish, oils)
Are fatty acids common in nature?
Fatty acids are rare to find in nature and a lot of the times combined to glycerol via condensation reactions to form an ester bond (TAG)
What percentage of lipids consumed are TAGs? Where are they also produced?
90%
The liver also produces them which is transferred to tissues in lipoproteins
TAGs, which are fats, are hydrolysed via what enzyme?
Lipase separates FAs and Glycerol
Can FAs in TAGs be different?
Yes they can be homogenic or heterogenic FAs within the TAG
What are the functions of fats within mammals
They are stored in adipose tissue and cushion vital organs and insulate the body
N.B They contain twice the energy of polysaccharides like glycogen
What is a phospholipid made of?
2 FAs + glycerol + phosphate group
What two forms of complex lipids can phospholipids form?
1.sphingolipid
2.phosphoglyceride
How long are FAs on Phospholipids?
14-24 Carbons long
What is the PL called when the R group on the Phosphate head is choline?
Glycerophosphatiydlcholine
What does GPI stand for?
Glycerophosphatidylinositol
What are GPIs and what do they do?
They are glycolipids attached to proteins as membrane anchors (role in cell signalling)
What is Sphingosine and what is the major difference in a Sphingolipid?
Sphingosine is a C18 amine alcohol
A sphingolipid has a Sphingosine instead of glycerol and a FA and R group are added to it
What are three functions of a Sphingolipid
1.Cell recognition
2.Signalling
3.Lipid Rafts
What is the major glycolipid in humans?
Glycosphingolipids are the major glycolipids in humans
What is the major glycolipids in humans?
The major glycolipids in humans are glycosphingolipids
What Sphingolipid can be found at the myelin sheath?
Sphingomyelin
What is the main steroid in mammals and how is it gained?
Cholesterol is the main steroid of mammals and its made in the liver and some from diet
What is the precursor of all steroids?
Cholesterol is the precursor
Where is cholesterol mainly found?
90% of cholesterol is found within the cell membrane (150g total in the average body)
What is a major control point in the synthesis of cholesterol?
HMG coA Reductase is a major control point which statin drugs can inhibit this enzyme to stop cholesterol synthesis
What are steroids?
Lipids with a common carbon skeleton of four fused rings which depend on the functional group attached to the rings
Name four main steroid categories?
1.glucocorticoids
2.mineralocorticosteroids
3.Oestrogen,androgen,and progestogens
4.Base for Bile acids
What are most lipids digested as?
Most are digested as triglycerides which are insoluble and difficult to digest so the solution is bile
How are lipids transport?
Dietary lipids are exogenously transported from the intestines to the liver
Then endogenously transported from the liver peripheral tissues (ALL via alipoproteins which wrap around the lipid)
Rank lipoproteins classes from lowest to highest
1.Chylomicron
2.VLDL
3.LDL
4.HDL
Rank lipoprotein classes from lowest to highest
1.chylomicron
2.VLDL
3.LDL
4.HDL
What do lipids move around as?
Lipids are metabolised and carried as lipoproteins
