Lipids

Question 1

What are lipids NOT?

Answer 1

Polymers

Question 2

What are the characteristics of lipids?

Answer 2

-contain hydrogen, carbon and oxygen
-insoluble in water
-soluble in organic solvents

Question 3

What are the main groups of lipids called?

Answer 3

triglycerides and phospholipids

Question 4

What are the roles of lipids?

Answer 4

-source of energy
-waterproofing
-insulation
-protection
-cell membranes

Question 5

How are lipids a source of energy?

Answer 5

when oxidised, lipids provides x2 the energy as the same mass of carbohydrate and release valuable water

Question 6

How do lipids provide waterproofing?

Answer 6

Insoluble in water

Question 7

How do plants and insects use lipids as waterproofing?

Answer 7

waxy, lipid cuticles that conserve water

Question 8

How do mammals use lipids as waterproofing?

Answer 8

produce oily secretion from sebaceous glands in skin

Question 9

How do lipids act as insulation?

Answer 9

fats are slow conductors of heat and when stored below body surface, they help retain body heat

Question 10

How are lipids used in nerve cells?

Answer 10

In the myelin sheath as an electrical insulation

Question 11

How do lipids act as production?

Answer 11

fat often stored around delicate organs, e.g kidneys

Question 12

What state are fats at room temperature?

Answer 12

Solid

Question 13

What state are oils at room temperature?

Answer 13

Liquid

Question 14

How do lipids function in the cell membrane?

Answer 14

phospholipids contribute to flexibility and transfer of lipid-soluble substances

Question 15

What forms a triglyceride?

Answer 15

Three fatty acids and one glycerol molecule

Question 16

Where do bonds form in a condensation reaction for a triglyceride?

Answer 16

each fatty acid forms an ester bond with glycerol

Question 17

What bond is involved in triglycerides?

Answer 17

Ester

Question 18

What group do ALL fatty acids have?

Answer 18

-COOH

Question 19

What is a saturated fatty acid?

Answer 19

Fatty acid with no carbon-carbon double bond

Question 20

What makes a molecule saturated?

Answer 20

All carbon atoms linked to maximum possible number of hydrogen atoms
No double carbon-carbon bond

Question 21

What is an unsaturated fatty acid?

Answer 21

Fatty acid with a carbon-carbon double bond

Question 22

What happens to the fatty acid chain when it is unsaturated?

Answer 22

Kinks/Bends

Question 23

What are the properties of a triglyceride?

Answer 23

-high ratio of energy storing carbon hydrogen bonds to carbon atoms
-low mass to energy ratio
-large, non polar molecules: insoluble
-high ratio of hydrogen to oxygen atoms

Question 24

What is the importance of a high ratio of energy storing carbon hydrogen bonds to carbon atoms in a triglyceride?

Answer 24

good source of energy

Question 25

What is the importance of a low mass to energy ratio in triglycerides?

Answer 25

good storage molecule- more energy stored in small volume

Question 26

What is the importance of triglycerides being insoluble?

Answer 26

storage doesn’t affect water potential or draw in water by osmosis

Question 27

What is the importance of high ratio of oxygen to hydrogen atoms in triglycerides?

Answer 27

release water when oxidised: important source of water

Question 28

What is a phospholipid composed of?

Answer 28

two fatty acids glycerol molecule phosphate molecule

Question 29

What two parts are phospholipids divided into?

Answer 29

Hydrophilic head Hydrophobic tail

Question 30

What section of the phospholipid is hydrophilic?

Answer 30

phosphate molecules attract water

Question 31

What section of the phospholipid is hydrophobic?

Answer 31

fatty acid molecules repel water

Question 32

What does hydrophilic mean?

Answer 32

is attracted to water

Question 33

What does hydrophobic mean?

Answer 33

orients away from water

Question 34

How do polar phospholipid molecules position themselves in water?

Answer 34

hydrophilic heads are as close to water as possible and hydrophobic tail are as far away water as possible

Question 35

What are the properties of phospholipids?

Answer 35

-polar molecules -hydrophilic head -hydrophobic tail -can form glycolipids

Question 36

What is the importance of phospholipids being polar?

Answer 36

in aqueous environment phospholipid molecules form bilayer in cell surface membrane-hydrophobic barrier formed between inside and outside of cell

Question 37

What is the importance of glycolipids?

Answer 37

cell recognition

Question 38

How do we test for lipids?

Answer 38

-dry/grease free test tube -add 5cm ethanol to 2cm3 food sample -shake tube thoroughly -add 5cm3 water shake gently

Question 39

What indicates the presence of a lipid?

Answer 39

milky-white emulsion

Question 40

What do reagents are used to test for lipids?

Answer 40

Ethanol and water