Medicina

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paNeL 2–4
FATTY ACIDS
All fatty acids have carboxyl groups with long hydrocarbon tails. COOH COOH COOH CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3
stearic acid (C18)fatty acids and other lipids
Hundreds of different kinds of fatty acids exist. Some have one or more double bonds in their hydrocarbon tail and are said to be unsaturated. Fatty acids with nodouble bonds are saturated. –O –O O O C C

CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3
palmitic acid (C16)

CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH CH CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3
oleicacid (C18) space-filling model carbon skeleton oleic acid

This double bond is rigid and creates a kink in the chain. The rest of the chain is free to rotate about the other C–C bonds.

stearicacid

UNSATURATED

SATURATED

TRIACYLGLYCEROLS
O H2C HC O C O C O C

Fatty acids are stored as an energy reserve (fats and oils) through an ester linkage to glycerol to formtriacylglycerols.

H2 C HC H2 C

OH OH OH

O

glycerol

H2C

O

CARBOXYL GROUP
If free, the carboxyl group of a fatty acid will be ionized. O C O

PHOSPHOLIPIDS

Phospholipids are the majorconstituents of cell membranes.
hydrophilic group choline

O O
_

P O CH2

O

_

CH2 But more often it is linked to other groups to form either esters O C O or amides. O C N H C

CHhydrophobic fatty acid tails phosphatidylcholine

general structure of a phospholipid

In phospholipids two of the –OH groups in glycerol are linked to fatty acids, while the third –OH group is linkedto phosphoric acid. The phosphate is further linked to one of a variety of small polar groups (alcohols).

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LIPID AGGREGATES
Fatty acids have a hydrophilic head and a hydrophobic tail.micelle

POLYISOPRENOIDS
long-chain polymers of isoprene O– O P O O–

In water they can form a surface film or form small micelles.

Their derivatives can form larger aggregates held together by...