Lipids

Question 1

Explain the structure and solubility of lipids in the diet

Answer 1

Organic compounds composed of a carbon skeleton with hydrogen and oxygen substitutions

Do not readily dissolve in water but they dissolve in organic solvents (e.g. hexane)

Oils (liquid at room temperature( and fats (solid at room temperature)

Question 2

Name and explain the 3 different classes of lipids and give examples

Answer 2

Simple lipids - fatty acids esterified with alcohols (e.g. triglycerides, sterol esters)

Complex lipids - fatty acids esterified with alcohols plus other groups (e.g. phospholipids, glycoproteins)

Derived lipids - lipids obtained by hydrolysis of simple or complex lipids (e.g. fatty acids

Question 3

Explain the structure of lipids

Answer 3

90% found in the form of triacylglycerols (triglycerides)

Glycerol (backbone) + 3 fatty acids

Other lipids: Phospholipids
Sterols (cholesterol)

Question 4

Explain the bonding in lipids

Answer 4

Saturated - no bond

Unsaturated - contains a double bond

Monounsaturated (1 double bond)

Polyunsaturated
(more than 1 bond)

Question 5

Explain the structure of fatty acid

Answer 5

Even number chain of carbon atoms with hydrogen attached, a methyl group (CH3) and a carboxylic acid group (-COOH)

Question 6

Name common saturated, monosaturated and polyunsaturated fatty acids

Answer 6

Saturated:

Palmitic

Stearic

Monosaturated:

Oleic

Polyunsaturated:

Linolenic
a- linolenic

Eicosapentaeonic (EPA)
n-3 Docosapentaenoic

Docosahecaenoic

Question 7

Explain the structure of cis and trans isomers

Answer 7

Cis - Hydrogens on the same side

Trans - Hydrogens are opposite each other

Question 8

Explain the genera hydrogenation process

Answer 8

Hydrogen gas into chamber - hydrogen gas is added under pressure in the form of tiny bubbles at the base of the agitator

Nickel catalyst slurry - Nickel catalyst is added in an oil slurry

Question 9

Explain what happens to a cis unsaturated fat if it is hydrogenated and if its is partially hydrogenated - what product is created

Answer 9

Hydrogenation - Saturated fat

Partial Hydrogenation - Trans Unsaturated Fat

Question 10

Name the 2 essential fatty acids (EFA)

Why does the body need these fatty acids

Answer 10

Linoleic acid

alpha-Linolenic acid

The body cannot synthesis/produce EFAs

EFAs must be include din the diet

Question 11

What is the the DRV for essential fatty acids

Answer 11

1-2% of total energy intake

Linolenic acids should be at least 1% of total energy. Alpha-Linolenic acids should be at least 0.2% of total energy

Question 12

Give the DRV for omega 6 and omega 3 for males and females

Answer 12

Omega 6:
Females: 11 -12g/day
Males@ 16-17 g/day

Omega-3:
Females: 1.1 g/day
Males: 1.6g/day

Question 13

Give some features of essential fatty acid deficiency

Answer 13

Hair loss

Scaling dermatitis

Increased trans epidermal water loss

Poor wound healing

Growth retardation

Renal failure

Reproductive failure

Question 14

Give the dietary recommendations for the following:

Total fat
Saturated fat, Polyunsaturated fat
Monounsaturated fat Trans fat

Answer 14

Total fat: less than 35% of food energy

Saturated fat: less than 11% of food energy

Polyunsaturated fat: 6.5% of energy

Monosaturated fat: 13% of energy

Trans fat: less than 2% of energy

Question 15

Name the 3 main functions of fat

Answer 15

Structural - component of cell membrane

Storage - storing energy for later use, insulating and protecting the body

Metabolic - providing energy for the body, transporting fat-soluble vitamins

Question 16

Explain the function of fat in the cell membrane

Answer 16

Fats form an internal part of cell membranes, which form a barrier between the cell and the external environment

Membranes’ basic structural unit is phospholipids

Cholesterol is also found in lipid membranes

Question 17

Explain why fat is the main energy store in the body

Answer 17

Majority of fats are triglycerides in adipose tissue

Adipose tissue represents the large reservoir of storage lipids

Triglycerides are highly concentrated stores of metabolic energy

Triglycerides are very non-polar, so they are stored without water, unlike carbohydrates and proteins

Question 18

Explain how visceral fat and subcutaneous fat protects the body

Answer 18

Visceral fat - protects the vital organs

Subcutaneous fat - shock absorber, maintenance of body temperature

Question 19

Explain what lipoprotein are

Answer 19

Lipoprotein are the major form of lipid transported in the bloodstream