Lipids

Question 1

List 3 types of lipids

Answer 1

• steroids
• phospholipids
• triglycerides

Question 2

What is the function of steroids

Answer 2

hormones in the human body
- used as structural component

Question 3

What is the chemical composition of steroids

Answer 3

they are 4 carbon rings backbone

Question 4

What is the function of phospholipids

Answer 4

components of cell membranes

Question 5

What is the chemical composition of a phospholipid

Answer 5

• 1 glycerol, 2 fatty acids and 1 phosphate group
• amphipathic (polar phosphate head and non-polar hydrocarbon tail)

Question 6

What is the function of triglycerides

Answer 6

energy storage and thermal insulation

Question 7

What is the chemical composition of a triglyceride

Answer 7

• 1 glycerol + 3 fatty acids
• non-polar and hydrophobic
• ester linkage
• ex: fats and oil

Question 8

What is the general formula of lipids

Answer 8

• CH3 (CH2)n COOH
• methyl group and carboxylic acid group and hydrocarbon chain

Question 9

What are the two main types of fatty acids

Answer 9

• saturated (only have single bonds)
• unsaturated (one of more carbon double bonds

Question 10

What are the features of saturated fatty acids

Answer 10

• straight structure
• more tightly packed together and have a greater surface area
• greater melting point than unsaturated fats

Question 11

What are the features of unsaturated fatty acids

Answer 11

• bent or straight structure depends on trans and cis
• tend to be liquid at room temp.

Question 12

What are the features of trans fatty acids

Answer 12

• have a hydrogen on either side of the C=C
• have a straight structure
• this gives them a larger surface area and there are more LDFs between the fatty acid molecules as they can be packed together more tightly and have a higher melting point

Question 13

What are the features of cis fatty acids

Answer 13

• have a hydrogen on the same side of the C=C
• have a bent structure
• this gives them a smaller surface area, less LDFs between the fatty acid molecules & less packed together, lower melting point

Question 14

What are the properties of lipids

Answer 14

• non-polar and thus insoluble
• work as chemical messengers (hormones)
• transporters of lipid-soluble vitamins and hormones
• used for electrical and thermal insulation
• structural components of cell membranes

Question 15

Why are lipids a greater source of energy than carbohydrates

Answer 15

they release more energy per grm than carbohydrates because they are less oxidised than carbohydrates (lipids have a higher proportion of C-H bonds which store more energy/higher energy density)

Question 16

Outline the use of steroids

Answer 16

use: build up muscle, oral contraceptive pill

Question 17

Outline the abuse of steroids

Answer 17

infertility, breast development, deepening of the voice, unfair advantage in sports

Question 18

How is cholesterol transported in the body

Answer 18

lipoproteins

Question 19

What are the 2 main types of lipoproteins

Answer 19

low-density & high-density

Question 20

What are the features of low-density lipoproteins (LDL)

Answer 20

• it has less proteins and more fat
• they deposit cholesterol in the arteries

Question 21

What are the features of high-density lipoproteins (HDL)

Answer 21

• it has more proteins and less fat
• they remove cholesterol from the arteries

Question 22

What is the health risk of cholesterol

Answer 22

Too much cholesterol can lead to blocked arteries and increase the risks of heart disease and obesity

Question 23

What types of fats are bad for the body

Answer 23

Trans and saturated fatty acids tend to increase LDL

Question 24

What is the rancidity of fats

Answer 24

refers to the unpleasant smell and texture of fats, when they go bad

Question 25

What are the two types of rancidity of fats

Answer 25

oxidative and hydrolytic

Question 26

Outline the hydrolytic rancidity

Answer 26

• when ester links are broken by water and produce glycerol (& fatty acid)

Question 27

What are the conditions that favour hydrolytic rancidity

Answer 27

• water
• the enzyme lipase
• high temperatures
• acidic or alkaline conditions

Question 28

Outline the oxidative rancidity

Answer 28

when fatty acid chains are broken down when oxygen reacts with the C=C bonds of unsaturated lipids and produce bad smelling ketones, alcohols and aldehydes

Question 29

What are the conditions that favour oxidative rancidity

Answer 29

• high proportion of unsaturated fatty acids
• high temperatures
• high oxygen availability
• high light intensity
• the presence of metals (copper and nickel)

Question 30

How can oxidative rancidity be controlled

Answer 30

anti-oxidants

Question 31

What are the different ways which triglycerides can be broken down

Answer 31

• acid hydrolysis (in the presence of heat and strong acid)
• alkaline hydrolysis (in the presence of strong base and produces salt of fatty acid)
• enzymes (lipase)

Question 32

What is alkaline hydrolysis also refered as

Answer 32

saponification

Question 33

What is the iodine number

Answer 33

• can be used to determine the number of C=C in the fat
• number of grms of iodine that reacts with a 100g of fat

Question 34

Why are saturated fats good electrical/thermal insulators

Answer 34

they have no delocalised electrons

Question 35

Outline alkaline hydrolysis

Answer 35

• saponification
• strong base reacts with triglyceride
• products are water soluble
• produces glycerol and salt of fatty acid