Lipids!

A lipid is an organic compound that is insoluble in water; notably fats, oils and steroids.

• Their low solubility in water is due to an absence of polar groups.

• They contain little oxygen and consist mostly of carbon and hydrogen atoms.

• The most familiar lipids are those found in fats and oils.

• Fats are usually from an animal origin(lard and butter) that are solid at room temperature.

• Oils which are usually from a plant origin(corn oil and soybean oil) are liquid at room temperature.

• Fat has many functions in the body:it is used for long term energy storage, it insulates against heat loss, and it forms protective cushion around major organs.

• Neutral fat is sometimes used because the molecule is non-polar.

Fatty acid- A molecule that contains a hydrocarbon chain and ends with an acid group. There are two types of fatty acids; saturated and unsaturated fatty acids.

Difference between unsaturated fatty acids and unsaturated fatty acids?

Saturated fatty acid- A molecule that lacks double bonds between the carbons and the hydrocarbon chain.The chain bears the maximum number of hydrogen's.

Unsaturated fatty acid- A fatty acid molecule that has one or more double bonds between the atoms of its carbon chain.

A phospholipid is a molecule that forms the bilayer of the cells of the cells membranes; has a polar, hydrophilic head bonded to two nonpolar, hydrophobic tails


Cholesterol and testosterone are the two steroid molecules; they act as chemical messengers.