Triglyceride structure & function (Lipids)

Describe lipids

• Lipids are macromolecules that contain carbon hydrogen & oxygen atoms. However unlike carbohydrates, lipids contain a lower proportion of oxygen

• Some Lipids are non-polar & hydrophobic - repels water molecules & insoluble

What are the two main groups of lipids?

1. Triglycerides (Main component of fats & oils)

2. Phospholipids (A type of lipid molecule that is a major component of cell membranes)

Which monomers make up a triglyceride?

1 Glycerol & 3 fatty acids

Why is glycerol classed as a alcohol?

Chemical structure features Hydroxyl (-OH) groups attached to saturated carbon atoms

What functional groups do fatty acids contain?

• Methyl group (-CH3) at one end of a hydrogen carbon chain (R-group) & at the other is a carboxylic group (-COOH)

How do fatty acids vary?

1. Length of the hydrocarbon chain (R-group)

2. The fatty acid chain (R-group) may be saturated or unsaturated

Define the terms saturated & unsaturated

Saturated - No double bonds

Unsaturated - Double bonds

What bond forms between glycerol & fatty acids to make triglyceride molecules?

Ester bonds

What type of reaction forms a triglyceride?

Condensation reaction

How many fatty acids are there in a triglyceride?

3 Fatty acids join to one glycerol molecule

How many water molecules are released in the formation of one triglyceride?

3

Describe properties of triglycerides - Energy storage

• Many C–H bonds → release lots of energy when oxidised in respiration.

• High energy-to-mass ratio → lots of energy stored without adding much mass

• Being hydrophobic, they do not cause osmotic water uptake & affect water potential, allowing efficient storage in cells

Describe the insulation property of triglycerides

• Triglycerides are part of the myelin sheath, insulating nerves & speeding up nerve impulse transmission

• Stored in adipose tissue under skin to reduce heat loss

Describe the buoyancy property of triglycerides

• Fat has a low density, aiding buoyancy in aquatic animals

Describe the protection property of triglycerides

• Adipose tissue cushions & protects internal organs from damage

Draw a diagram below to show a glycerol & 3 fatty acids forming a triglyceride. Highlight the ester bond formation & annotate the water lost

What is the general formula of a fatty acid?

RCOOH

‣ where R = the variable hydrocarbon chain

‣ COOH = a carboxyl group