lipids

Question 1

what are the two groups of lipid

Answer 1

triglycerides and phospholipids

Question 2

how are triglycerides formed

Answer 2

by the condensation of one molecule of glycerol and three molecules of fatty acid

Question 3

what bond is formed between a glycerol and a fatty acid

Answer 3

ester bond

Question 4

what is one of the fatty acids in a phospholipid substituted by

Answer 4

a phosphate-containing group

Question 5

biochemical test for lipids

Answer 5

(crush the sample if it is a solid)
dissolve the sample in ethanol
add it to cold water
result - if lipid is present, an emulsion is formed. if lipid is not present, no emulsion is formed

Question 6

what are triglycerides

Answer 6

long-term energy store in animals and plant seeds
- compared to carbs, fat stores more energy per gram
BUT more difficult to access as it takes more O2 to respire it and release its energy

Question 7

why are phospholipids considered to be both polar and non-polar

Answer 7

the phosphate group has a charge, the fatty acid/hydrocarbon tails do not

Question 8

functions of lipids

Answer 8

source of metabolic water
phospholipids - cell membrane
less dense - efficient storage of energy in seeds
waxy cuticle (waterproofing) on leaves to reduce water-loss
thermal insulation - sub-cutaneous fat (adipose tissue)
electrical insulation (neurones are surrounded by insulating myelin sheath)
bouyancy eg squaline that fills a shark’s liver
oils to protect and condition hair and skin produced by sebaceous glands

Question 9

what elements are present in lipids

Answer 9

carbon, hydrogen and oxygen

Question 10

triglyceride - energy storage

Answer 10

high ratio of carbon-hydrogen bonds to carbon-carbon bonds

Question 11

triglyceride - metabolic water source

Answer 11

high ratio of hydrogen to oxygen atoms

Question 12

triglycerides - insoluble

Answer 12

doesnt affect water potential due to triglycerides being hydrophobic

Question 13

phospholipid charge?

Answer 13

it is a polar molecule
hydrophilic head
hydrophobic fatty acid tails
form a bilayer

Question 14

saturated

Answer 14

only single bonds between the carbons within the hydrocarbon chain

Question 15

ester bond

Answer 15

the covalent bond formed by a condensation reaction between the -OH group of a carboxylic acid and the -OH group of an alcohol

Question 16

glycerol role

Answer 16

bonds to fatty acids/a phosphate group to form lipids/phospholipids

Question 17

COOH

Answer 17

carboxylic acid group

Question 18

two differences between a triglyceride and a phospholipid

Answer 18

triglycerides have 3 fatty acids and phospholipids have 2

phospholipids have a phosphate group in place of one fatty acid

Question 19

two properties of triglycerides that make them excellent storage compounds

Answer 19

insoluble

contains many bonds which release energy when broken

Question 20

state two advantages to a mammal of having fat in its tissues

Answer 20

insulation
buoyancy
protection of organs

Question 21

define the term hydrophobic as it relates to phospholipids

Answer 21

parts of the phospholipid repel water

Question 22

two parts of a phospholipid

Answer 22

phosphate group/head

fatty acid chain/ hydrocarbon chain

Question 23

what is a saturated fatty acid saturated with

Answer 23

hydrogen

Question 24

identify and explain the structural feature of saturated fats that causes them to be solid at room temperature

Answer 24

straight hydrocarbon chains in the fatty acids

so molecules pack closely together so they are less able to flow around eachother