2.1.2 Lipids

Question 1

what atoms are present in lipids

Answer 1

carbon, hydrogen and oxygen

Question 2

what makes lipids different to carbonhydrates

Answer 2

lipids contain a lower proportion of oxygen

Question 3

list 2 properties of lipids

Answer 3

non-polar molecules and hydrophobic (indoluble in water)

Question 4

name the two groups of lipids

Answer 4

triglycerides and phospholipids

Question 5

what do lipids play an important role in

Answer 5

energy yield, energy storage, insualtion and hormonal communication

Question 6

name the monomers that make up triglycerides

Answer 6

glycerol and fatty acids

Question 7

in what two ways can fatty acids vary

Answer 7

1.length of hydrocarbon chain
2.saturated or unsaturated

Question 8

what is the different between saturated and unsaturated fatty acids

Answer 8

saturated fatty acids have no double bonds (mainly found in animal fats)
unsaturated fatty acids have one or more double bonds, they are also less uniformly packed and have lower melting points (mainly found in vegetable oils)

Question 9

what are trans-fatty acids and why are they harmful

Answer 9

have H atoms on opposite sides of the double bond
they cannot form enzyme-substrate complexes and are linked to CHD

Question 10

describe the strcuture of a phospholipid

Answer 10

2 fatty acids and 1 phosphate ion bonded to 1 glycerol molecule

Question 11

what is the term used to describe phospholipds ad both hydrophobic and hydrophilic

Answer 11

amphipathic

Question 12

which parts of the fatty acid are polar and non-polar

Answer 12

head=polar (hydrophilic)
tail=non-polar (hydrophobic)

Question 13

what can phospholipids form due to its amphipathic nature

Answer 13

phospholipd bilayer in cell surface membranes

Question 14

where is the ester bond formed

Answer 14

between a hydroxyl group form the glycerol and the carboxyl group from the fatty acid

Question 15

what type of reaction forms an ester bond

Answer 15

condensation

Question 16

how many water molecules are released to form a triglyceride and phospholipid

Answer 16

3

Question 17

what is broken when you hydrolyse a lipid

Answer 17

ester bond

Question 18

list 5 functions of triglycerides

Answer 18

respiratory substrate
energy storage
thermal insulation
electrical insulation
buoyancy

Question 19

why are triglycerides a good form of energy storage

Answer 19

-they store more energy per gram than carbohydrates and proteins due to the lower proportion of oxygen, more energy stored in less space
-insoluble so they do not cause osmotic water uptake as they are hydrophobic
-fats have more carbon-carbon bonds/carbon-hydrogen bonds
-fatty acids are long carbon chains and can be broken down to release two acetyl groups, that enter krebs cycle

Question 20

where can triglycerides be used as insulation in the body

Answer 20

myelin sheath

Question 21

how do triglycerides help with buoyancy

Answer 21

low density fat tissue increases ability to float more easily

Question 22

if there are mainly saturated fatty acid tails the membrane wil be

Answer 22

less fluid

Question 23

what other lipid molecule can be found in the cell memebrane of eukaryotes

Answer 23

cholesterol

Question 24

what does cholesterol affect

Answer 24

fluidiy and permeability of cell membranes, and acts as a barrier

Question 25

describe the emulsion test for lipids

Answer 25

1. add ethanol to sample
   2.shake to mix
   3.add mixture to test tube of water

Question 26

describe the positive result of the emulsion test

Answer 26

milky emulsions

Question 27

explain how the structure of phospholipid moleucles allows for the formation of plasma membranes

Answer 27

phosphate ‘head’, is hydrophilic + bonds with water
2 fatty acid tails are hydrophobic
heads orientate towards water outside cell
tails orientate towards other fattyacids or tails orientate away fromwater, so a bilayer forms

Question 28

what is cholesterol also used to synthesis

Answer 28

steroid hormones and bile