Fats and Lipids

Question 1

Define lipid.

Answer 1

• A fat or oil
• Found in food, visceral fat in body, cell membranes, brain, nervous tissue
• Deposited subcutaneously
• Have highest energy value
• Insoluble in water (hydrophobic)
• Composed of carbon, hydrogen and oxygen- long hydrocarbon chain

Question 2

How are triglycerides formed?

Answer 2

• Glycerol and three fatty acids
• The bonds, formed through condensation reactions, between carboxylic group of glycerol molecule and hydroxyl group of fatty acids form ester bonds.

Question 3

What are unsaturated fatty acids?

Answer 3

• Branched chain

- C=C: double bond so less space for hydrogen atoms (not saturated with hydrogen)

Question 4

What are saturated fatty acids?

Answer 4

• Straight chain

- No double bonded carbons so space for hydrogen atoms

Question 5

How does the structure of a lipid determine its physical properties?

Answer 5

• Unsaturated fatty acids are generally oils and have lower melting point than saturated fatty acids because they have weaker intermolecular forces of attraction between chains
• This is because they are more spread out in the oil
• Saturated fats are closer together and have stronger intermolecular forces of attraction between chains which is why they have a higher melting point.

Question 6

What are triglycerides’ fatty acid tails?

Answer 6

Hydrocarbons and are also hydrophilic.

Question 7

Describe the function and features of HDL.

Answer 7

• Mainly protein, small amounts of cholesterol
• Smaller, higher density
• Transport cholesterol from body tissues to liver where it is recycled or excreted
• Reduce total blood cholesterol when levels are too high

Question 8

Describe the function and features of LDL.

Answer 8

• More cholesterol, mainly lipid, less protein
• Larger, small density
• Transport cholesterol from liver to the blood where it circulates until needed by cells
• Increase total blood cholesterol when levels are too low