Fats, oils and Lipids

Question 1

Difference between fats and oils?

Answer 1

Fats -solid at room temp
Oils-liquid at room temp

Question 2

Properties of fats and oils?

Answer 2

-are hydrophobic (can’t chemically mix with water )
-organic compounds composed of C, H and O (have low O2 content)
-Have high energy content due to high amount of C and H present

Question 3

Describe the structure of fats and oils?

Answer 3

-are triglycerides- made up of 3 fatty acids and glycerol

-have a carboxyl group at one end and a methyl group at the other end

Question 4

What is glycerol?

Answer 4

A polyhydric alcohol containing 3 carbon atoms joined to hydroxyl group

Question 5

Describe the difference between short, medium and long chain triglycerides?

Answer 5

short chain fatty acids are C4-8
Medium chain triglycerides are C10-C14 (are well absorbed in small intestines-useful for patients with bowel problems-helps to gain weight quickly)
Long chain triglycerides- C16-C22- includes essential fatty acids
-all triglycerides contain an even number of carbon atoms if naturally occurring in foods

Question 6

How are triglycerides formed?

Answer 6

-Each fatty acid can form an ester bond with hydroxyl (OH) group on glycerol via a condensation reaction so 3 water molecules are formed as biproduct

Question 7

Give 2 examples of other fatty substances?

Answer 7

-Phospholipids-also have a polar head group as well as fatty acid chains (non polar)- enables to mix with water due to polar head
-Cholesterol-found in animal sources, is transported around the body with proteins

Question 8

What is the difference between saturated and unsaturated fats?

Answer 8

Saturated-All bonds are saturated with hydrogen- there are no double bonds present between the carbons of the fatty acid chains. -normally solid at room temp and from animal sources, can be heated to high heats and maintain structure.

Unsaturated- contains double bonds, normally liquid at room temp and from plant sources (healthier-lower cholesterol)

Question 9

Types of unsaturated fats?

Answer 9

Monounsaturated- 1 double bond
Polyunsaturated- 2 double bonds

Question 10

How is the omega status of an unsaturated fat determined?

Answer 10

depends on where double bond is within chain-counting back from right side wherever last double bond is within chain is the omega number

Question 11

What are essential fatty acids?

Answer 11

Essential cannot be synthesised by body must be provided in diet eg.linoleic acid,Linolenic acid,Arachidonic acid

Question 12

What is hydrogenation?

Answer 12

When veg oils that tend to contain a large proportion of unsaturated fatty acids are either wholly (heated to 68c) or partially hydrogenated (heated to 44c) to make solid fats, eg.margarine

Question 13

Advantages of hydrogenation?

Answer 13

-A liquid oil is changed to a semi-solid or solid because the melting point of an unsaturated fat more becomes more like that of a saturated fat.(is increased)
-The rate of oxidation decreases (stability increases with increasing saturation)
-Increases hardness and plasticity .

Question 14

disadvantages of hydrogenation

Answer 14

-Monounsaturated and polyunsaturated fats are healthier for the heart than saturated fats
-Trans fatty acids can form which are hard to metabolize, accumulate in fatty tissue, are difficult to excrete from the body,
-Increase levels of LDL (bad) cholesterol and are a low-quality energy source

Question 15

What are the nutritional functions of fat?

Answer 15

-rich source of energy (1g provides 9kcal)
-act as insulating layer under skin
-protect vital internal organs
-act as a carrier for fat soluble vitamins A, D, E and K.
-prevent hair and skin becoming too dry,

Question 16

Effects of eating a diet high in saturated fats?

Answer 16

-means the body will decrease the amount of cholesterol it produces.
-it increases the amount of cholesterol in the bloodstream/arteries which can be linked to heart disease and stroke.(raise LDL cholesterol)

Question 17

Animal sources of fat?

Answer 17

Meat - visible and invisible fat
Fish - fatty fish, fish liver oils
Dairy foods - butter cream cheese

Question 18

Plant sources of fat?

Answer 18

Fruits and vegetables - avocado, olives
Nuts - brazil, walnuts,
Seeds - sesame, sunflower
Other - palm, coconut

Question 19

Difference between cis and trans fats?

Answer 19

Cis fatty acids- hydrogen bonds on same side- naturally occurring
Trans fatty acids- hydrogen bonds on opposite sides- manufactured, more unhealthy

Question 20

What is rancidity?

Answer 20

the deterioration of fats and oils leading to unpleasant odours and flavours

Question 21

How can rancidity occur?

Answer 21

-Can occur via 2 ways- hydrolytic or oxidative
-Hydrolyitic- affects dairy foods and caused by the enzyme lipase
-Oxidative- caused by contact with light, heat, oxygen or metals