-1A: lipids

Question 1

what are the two kinds of lipids?

Answer 1

-triglycerides
-phospholipids

Question 2

what do triglycerides and phospholipids have in common?

Answer 2

a molecule of glycerol

Question 3

what does a phospholipid contain instead of the 3rd fatty acid tail?

Answer 3

a phosphate group

Question 4

how are triglycerides formed?

Answer 4

-one molecule of glycerol + 3 fatty acids
-condensation reactions + removal of 3 molecules of water
-ester bonds formed

Question 5

because triglycerides are formed via condensation reactions, what does this mean is released?

Answer 5

3 molecules of water

Question 6

what are the properties of triglycerides?

Answer 6

-energy storage
-act as a metabolic water source
-doesn’t affect water potential + osmosis
-low mass

Question 7

energy storage?

Answer 7

due to large ratio of energy storing carbon-hydrogen bonds compared to carbon atoms, lots of energy can be stored

Question 8

metabolic water source?

Answer 8

-due to high ratio of hydrogen to oxygen atoms
-if triglycerides are oxidised (broken down) water is released, useful for animals that live in the desert e.g. camels

Question 9

doesn’t affect water potential/osmosis?

Answer 9

large + hydrophobic molecules -> insoluble in water

Question 10

low mass?

Answer 10

a large amount can be stored without increasing mass + preventing movement

Question 11

what are fatty acids?

Answer 11

-R groups
-as number of carbons in fatty acid chain can vary = variable group

Question 12

state and explain what are the two types of fatty acids

Answer 12

-saturated: hydrocarbon tail only has single bonds between carbons
-unsaturated: hydrocarbon tail consists of at least one double bond between carbons

Question 13

properties of phospholipids?

Answer 13

-hydrophilic head
-polar

Question 14

hydrophilic head (water loving)?

Answer 14

-attracts water due to negatively charged oxygen in phosphate group
-as phosphate group is charged + repels other fats
-fatty acid chains = hydrophobic tails to repel water + can mix with other fats

Question 15

polar?

Answer 15

-due to two oppositely charged regions
-when placed in water, they position themselves so tails face inwards due to them being repelled from water + heads being exposed to water on the outside
-forms phospholipid bilayer membrane used in plasma membranes around cells

Question 16

what is the test for lipids?

Answer 16

emulsion test

Question 17

describe test for lipids

Answer 17

-dissolve/mix sample in ethanol
-add distilled water + shake
-positive result: white milky emulsion (more lipid, more noticeable colour should be)

Question 18

the scientists expressed their results as percentage of lipid in plasma membrane by mass, explain how they would find these values

Answer 18

-divide mass of each lipid by total mass of all lipids
-multiply answer by 100

Question 19

triglycerides have a hydrophobic tail, explain how this is important for their function

Answer 19

-hydrophobic tails force them to clump together in the cytoplasm as insoluble droplets
-means they can be stored in cells as a source of energy without affecting cells water potential