lipids

Question 1

state two biological functions of lipids

Answer 1

-lipids form a protective layer that surrounds delicate organs, e.g. kidneys
-lipids provide the body with the essential fatty acids that cannot be made by the body, e.g. linoleic acid

Question 2

describe how the chemical structure of cis fatty acids and trans fatty acids differ(CIS)

Answer 2

the hydrogen atoms on either side of the double bonds are both above or both below the carbon chain

Question 3

describe how the chemical structure of cis fatty acids and trans fatty acids differ(TRANS)

Answer 3

the hydrogen atoms on either side of the double bond are on opposite side of the carbon chain

Question 4

explain oxidative rancidity

Answer 4

occurs when oxygen in the air combines with the carbons in a double bond of the unsaturated fatty acids

Question 5

explain hydrolytic acid

Answer 5

occurs when enzyme or bacteria break down lipids into glycerol and fatty acids

Question 6

state two functions of omega 3 fatty acids in the diet

Answer 6

-reduce the risk of coronary heart disease, heart attacks and stokes by raising HDL and lowering LDL
-decrease the viscosity of blood, preventing clots to blockages in the coronary arteries

Question 7

explain hydrogenation

Answer 7

hydrogen gas, in the presence of a nickel catalyst is forced through the double bond of an unsaturated oil converting the unsaturated oil into a saturated solid fat

Question 8

explain plasticity

Answer 8

describes how soft, pliable and moveable a fat is at a given temperature, it is determined by the degree of saturation

Question 9

state the elemental composition of lipids

Answer 9

elemental composition - carbon, hydrogen, oxygen

Question 10

describe the chemical structure of a triglyceride

Answer 10

made up of 3 fatty acids and one glycerol molecule

Question 11

describe the structure and give one example of saturated fatty acids

Answer 11

-each carbon atom is fully saturated
-solid at room temperature
-no double bonds occur between the carbon atoms
-example - butyric acid in butter

Question 12

describe the structure and give one example of monounsaturated fatty acids

Answer 12

-each carbon atom is not fully saturated
-liquid at room temperature
-there is one double bond between the carbon atoms
-example - oleic acid in olive oil

Question 13

describe the chemical structure and give one example of polyunsaturated fatty acids

Answer 13

-each carbon atom is not fully saturated
-liquid at room temperature
-there is more than one double bond between the carbon atoms
-exmple - linoleic acid in nuts

Question 14

outline the significance of fatty acids in the diets(unsaturated)

Answer 14

generally good as they help reduce LDL and increase HDL

Question 15

outline the significance of fatty acids in the diet(saturated)

Answer 15

increases levels of LDL cholesterol and lower HDL cholesterol increasing the risk of CHD

Question 16

outline the significance of fatty acids in the diet(essential)

Answer 16

linoleic and arachidonic cannot be manufacture in the body so much be obtained from food

Question 17

name two different food sources of omega 3 fatty acids

Answer 17

-oliy fish e.g. sardines
-seeds

Question 18

explain smoke point

Answer 18

if lipids are heated to 200C(fats) or 250C(oils) they begin to decompose causing the glycerol to separate from the fatty acids. glycerol is then broken down into acrolein and produces a blue smoke or hair and an acid smell

Question 19

explain false point

Answer 19

extreme overheating of lipids to 310C(fats) and 325C(oils) causes a vapour to be emitted that can spontaneously ignite

Question 20

complete the following table in relation to the digestion of lipids

Answer 20

secretion - intestinal juice
enzyme - lipase
product - fatty acids and glycerol

Question 21

describe the structure of omega 3 fatty acids

Answer 21

have a double bond between the third and fourth carbon atoms along their hydrogen carbon chain

Question 22

explain low density lipoproteins (LDL)

Answer 22

in the blood cholesterol is bound to certain proteins forming lipoproteins, LDL harmful, thought to build up cholesterol in the arteries which causes damage to blood vessels and heart disease

Question 23

explain high density lipoproteins(HDL)

Answer 23

help to remove cholesterol from circulation and reduce the risk of heart disease