Lipids

What are the two types of lipids?

Triglyceride

Phospholipids

What is triglyceride composed of?

3 fatty acids attached to a glycerol

What bonds join the fatty acids to the glycerol? (2)

Ester bonds

They are formed 3 times between the hydroxyl group of the glycerol and the OH of the carboxyl group on the fatty acids

Roles of Lipids: Source of energy (2)

When oxidised - lipids provide more than twice the amount of energy as from the same mass of carbohydrate

Release valuable water

Roles of lipid: Waterproofing

Lipids are insoluble and so have a waterproofing affect

Roles of lipids: Insulation (3)

Lipids are slow conductors of heat

Fat is stored under the surface of organism to retain heat

Also act as electrical insulators (myelin sheath in nerves)

Roles of Lipids: Protection

Stored around delicate organs such as the kidneys

What is the function of triglycerides?

Energy storage

Triglycerides: Carbon-Hydrogen bonds (2)

Have a high ratio of carbon-hydrogen bonds compared to carbon atoms

Therefore are an excellent store of energy - lots of energy released when the bonds are broken

Triglycerides: Mass:Energy ratio (2)

Have a low mass to energy ratio

Make them a good energy store because lots of energy can be stored in a small space

Triglycerides: Water solubility (2)

Insoluble in water

Do not affect water potential of cells

Triglycerides: Hydrogen:Oxygen ratio (2)

High ratio of hydrogen to oxygen atoms so release water when oxidised

Provide a valuable source of water, especially for organisms living in dry deserts

Phospholipids: Structure

2 fatty acids + glycerol + phosphate group

What bonds are found in phospholipids? (2)

Ester bond between the glycerol and fatty acids tail

Phosphoester bond between the phosphate group head and the glycerol

What is the function of phospholipids?

Form cell membranes

What is the fatty acids tail compared to the phosphate head? (2)

Fatty acids tail = hydrophobic whereas phosphate head = hydrophilic

This makes phospholipids polar - made of two ends that behave differently

How do phospholipids form a bilayer? (2)

Hydrophilic phosphate heads face aqueous solution - acts as a barrier, blocking large, water soluble molecule

Hydrophobic fatty acid tails face inwards - shielded from water

Phospholipids: Glycolipids (3)

Phospholipid structure allows them to form glycolipids

This is by combining with carbohydrates within the cell surface membrane

These glycolipids are important in cell recognition

Glycerol (2)

A molecule which combines with three fatty acids to form triglycerides

It is a 3- carbon chain with 3 hydroxyl groups

Hydrophilic

Section of a molecule which is attracted to water

Hydrophobic

Section of a molecule which is repulsed by water

Lipid (2)

A class of organic compounds that are derived of fatty acids and are insouble in water but soluble in organic solvents

Triglycerides, phospholipids, waxes and steroids

Mono-unsaturated fatty acid

Fatty acid which possesses a carbon chain with a single double bond between carbon atoms

Mono-unsaturated fatty acid

Fatty acid which possesses a carbon chain with a single double bond between carbon atoms

Phospholipid (2)

Triglyceride in which one of the three fatty acid molecules is replaced by a phosphate molecule

Phospholipids are important in the structure an functioning of plasma membranes

Poly-unsaturated fatty acid

Fatty acid which possesses a carbon chain with many double bonds between carbon atoms

Saturated fatty acid

A fatty acid in which there are no double bonds between the carbon atoms

Triglyceride (2)

An individual lipid molecule made up of a glycerol molecule and three fatty acids

Contains ester bonds