Lipids

What are lipids?

fats, oils, waxes, insoluble in water, most fats and oils are triglycerides

What are lipids made up of?

carbon, hydrogen, oxygen (lower proportion of oxygen than carbohydrates)

What are triglycerides?

Three fatty acids combined with glycerol, formed by esterification (condensation reactions, forms ester bond)

Properties of triglycerides

• Large ratio of energy-storing carbon-hydrogen bonds compared to no. Carbon atoms so a lot of energy is stored in the molecule

• High ratio of hydrogen to oxygen atoms act as a metabolic water source- releases oxygen when oxidised

• Large and hydrophobic so are insoluble in water so wont affect water potential

• Low mass to energy ratio so a lot can be stored in a small volume

What are phospholipids?

One fatty acid molecules is replaced by a phosphate molecule. Whilst fatty acid molecules repel water (hydrophobic), phosphate molecules attract water (hydrophilic)

What two parts is a phospholipid made up of?

Hydrophilic head which interacts with water (is attracted to it) but not with fat, and a hydrophobic tail which orients itself away from water but mixes readily with fat

Properties of phospholipids

• 2 charged regions so are polar

• positioned in water so that heads are exposed to water and tails aren't forming a phospholipids bilayer membrane structure which makes up the plasma membrane around cells.

• phospholipid structure allows them to form glycolipids by combining carbohydrates within the cell-surface membrane which are important in cell recognition

What are saturated fatty acids?

The hydrocarbon chain has only single bonds between carbons

What are unsaturated fatty acids?

have one or more double bonds between carbon atoms

Cause bends/kinks in fatty acid tail so phospholipids further apart

Increase fluidity

Function of lipids

• Protection of vital organs,

• insulate the body

• insoluble so prevent evaporation in plans and animals- waxy cuticle

• form the meyelin sheath around some neurones

• water source

• source of energy as when oxidised provide more than twice the same energy as the same mass of carbohydrates