Lipids

What are lipids primarily composed of?

Lipids are comprised of carbon, hydrogen, and oxygen.

Lipids include:

Triglycerides, steroids, waxes, and phospholipids.

What are lipids?

Hydrophobic and insoluble in water due to their structure

Why are lipids considered hydrophobic?

Their hydrocarbon molecules contain many non-polar covalent bonds.

How can the solubility of lipids be improved?

By combining it with other molecules e.g. glycolipids and lipoproteins

What are triglycerides and phospholipids types of?

Glycerides

Triglycerides

Stored as fat in adipose tissue (humans) and as oil (seeds of plants)

What form are fats in at body temperature and at room temperature?

Liquid in body temperature

Solid at room temperature

What form are oils in at body temperature and at room temperature?

Liquid in both

How are triglycerides made?

By combining three fatty acids with one glycerol

What makes up one end of the fatty acid?

Carboxylic acid

What does the carboxylic acid connect to?

The glycerol in the condensation reaction

What can be of varying length?

The hydrocarbon tail containing many carbon atoms joined together

How are triglycerides formed?

By a process known as esterification forming an ester bond

When does as ester bond form?

When the hydroxyl (-OH) group of a glycerol molecule bonds with the carboxyl group (-COOH) of a fatty acid

What is the formation of an ester bond?

A condensation reaction releasing three water molecules for every triglyceride formed

What are phospholipids formed from?

Two fatty acids bonded to a glycerol molecule

What is the third fatty acid replaced by?

A phosphate ion

What do the two fatty acids form with the glycerol?

An ester bond

What is the phosphate molecule?

It is polar making it hydrophilic and soluble in water

What are the fatty acid chains?

Non-polar making it hydrophobic and insoluble in water

Similarities between triglycerides and phospholipids

• both are formed through condensation reactions

• three molecules of water are formed

• both are types of lipids/glycerides

• both have ester bonds

Differences (triglycerides)

• only fatty acids with glycerol

• mostly non-polar and hydrophobic

• 3 ester bonds

Differences (phospholipids)

• one phosphate group and two fatty acids

• amphipathic (hydrophilic and hydrophobic)

• 2 ester bonds