B1.1 Lipids

What are some examples of lipids in living organisms?

Fats, oils, waxes, steroids

What atoms do lipid macromolecules contain?

Carbon, hydrogen, oxygen

What is the polarity and solubility of lipids?

Hydrophobic, non-polar. Insoluble in water

What are triglycerides composed of?

1 glycerol molecule and 3 fatty acid molecules

How are triglycerides formed?

3 condensation reactions between glycerol and 3 fatty acids, releasing 3 water molecules

What is a phospholipid composed of?

1 glycerol molecule attached to 2 fatty acids and 1 phosphate group

How are phospholipids formed?

Esterification - ester bond forms between the hydroxyl (-OH) group of a glycerol molecule and the carboxyl group (-COOH) of a fatty acid

Condensation reaction - 3 water molecules are released

What is the polarity and solubility of phosphate and fatty acids?

• Amphipathic

• Phosphate head: polar, hydrophilic

• Fatty acid tails: non-polar, hydrophobic

What are fats?

Triglycerides, solid at room temperature, high melting points, saturated fatty acids

What are oils?

Triglycerides, liquid at room temperature, low melting points, unsaturated fatty acids

What are fatty acids composed of?

Carboxyl group, hydrocarbon chain, methyl group

What are the properties of saturated fatty acids?

• Single bonds between carbon atoms in hydrocarbon tail

• Each carbon atom is bonded to 2 hydrogen atoms

• Straight molecules - increases melting point, used as storage molecules in animals

What are the properties of unsaturated fatty acids?

• Not all single bonds

• Each carbon atom in carbon-carbon double bond can only bond to 1 hydrogen atom

• Kinked/bended hydrocarbon tail

What are monounsaturated fatty acids?

Fatty acid with one carbon-carbon double bond (C=C)

What are polyunsaturated fatty acids?

Many carbon-carbon double bonds (C=C)

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids have higher melting points than unsaturated fatty acids

Why are lipids ideal for long term energy storage?

• Contain 2x more energy per gram than most carbs

• Insoluble - not transported around body easily, remain in storage cells

• More water is produced during respiration than carbs - metabolic water, can be used as dietary water source

Where are lipids stored?

In adipose tissue under skin and around organs

How are triglycerides used in thermal insulation?

Low thermal conductivity, provides insulation, cushioning, and water-repellent energy stores. E.g. blubber layer in endotherms

What are endotherms?

Animals that rely on metabolic reactions to generate heat to maintain a constant internal body temperature

What are steroids?

Lipids with 4 fused carbon rings and a hydrocarbon chain

What are the properties of steroids?

Hydrophobic, non-polar - can pass through membranes

What are examples of steroid hormones?

Oestradiol and testosterone

What is the role of cholesterol within steroid hormoens?

Strengthens membranes