Fats

Question 1

What are triglyceride molecules made up of?

Answer 1

One glycerol (or glycerin, a sugar alcohol) + three fatty acids attached

Question 2

Structure of fatty acids

Answer 2

A fatty acid is made up of a chain of carbon atoms with a methyl group at one end and an acid group at the other.

Attached to the carbon chain are hydrogen atoms

– the number of hydrogens per carbon atom depends on whether the fatty acid is

Saturated - Carry maximum number of hydrogen atoms (carbon atoms ARE SATURATED with hydrogen).

Unsaturated
Monounsaturated - One double bond within the hydrocarbon chain (UN-SATURATED).

Polyunsaturated - More than one double bond (UN-SATURATED).

Question 3

Solid (fats) and Liquid (oils)

Answer 3

Solid (fats)
• Triglycerides pack closely together.
• Attractive forces - higher melting point.

Liquid (oils)
• Unsaturated triglyceride molecules cannot pack closely together because of cis double bonds.
• Intermolecular forces are weaker.
• Less energy needed to separate molecules - lower melting point.

Question 4

Unsaturated Fatty Acids - cis isomer

Answer 4

Hydrogen atoms are on the same side of each double bond, causing the molecule to bend into a U-shape.

Question 5

Unsaturated Fatty Acids - trans isomer

Answer 5

Hydrogen atoms are on opposite sides of each double bond, causing the molecule to remain elongated.

Question 6

Trans Fats

Answer 6

• Caused by partial hydrogenation of unsaturated fats.
• Hydrogenated to produce a ‘harder fat’ with a higher melting point.
• ‘Not generally recognised as safe’ by the FDA.
• Found in hard margarines, biscuits, pastries, fast food.

Question 7

Fatty acids(number of carbons)

Answer 7

Short chain fatty acids (1 – 6 carbons).
Medium chain fatty acids (8 – 14 carbons).
Long chain fatty acids (> 14 carbons)

Question 8

Recommended blood lipid concentrations (Triglyceride, Total cholesterol)

Answer 8

Triglyceride: <1.1 mmol/L

Total cholesterol: <5.2 mmol/L

Question 9

Fat-soluble vitamins

Answer 9

Vitamins A, D, E, and K are fat-soluble, meaning they can only be digested, absorbed, and transported in conjunction with fats.

Question 10

Role of fats

Answer 10

Structural elements in all cell membranes 

Energy ~ 9 kcal per gram
(CHO is 3.75 kcal/g, protein 4 kcal/g and alcohol 7 kcal/g)

Insulation (reduces heat loss)

Protection of internal organs.

Question 11

Essential Fatty Acids

Answer 11

• The body can produce all the fatty acids it needs, except for linoleic acid (an omega-6 fatty acid), and alpha-linolenic acid (an omega- 3 fatty acid).
• Need correct ratio, and absolute amounts (0.6 and 1.2% of energy or 1-2 g/day)
• Concerns that intake of n-6:n-3 is too high