lipids

Question 1

what do lipids contain

Answer 1

large amounts of C and H and smaller amounts of O

Question 2

what are the 3 most important lipids

Answer 2

triglycerides (fats and oils), phospholipids and steroids

Question 3

are lipids soluble or insoluble in water

Answer 3

insoluble as they’re not polar

Question 4

are lipids a polymer

Answer 4

not polymer, but are made of different components.
is a macromolecule.

Question 5

structure of triglycerides

Answer 5

• 1 molecule of glycerol and 3 fatty acids
• contain C, H + O
• macromolecules

Question 6

what are the functions of triglycerides (5 functions)

Answer 6

• energy source = broken down in respiration to release energy + generate ATP
• energy store = stored without affecting the water potential of cell as triglycerides are insoluble in water
• insulation = lipids around the nerve cells act as an electrical insulator
• buoyancy = fat is less dense than water so used by aquatic mammals to stay afloat.
  -protection = fat around organs act as a shock absorber

Question 7

what is glycerol made up of

Answer 7

3 carbon atoms, each with a hydroxyl group attached and hydrogen atoms occupying the remaining positions.

Question 8

what does a single fatty acid molecule contain

Answer 8

an acid group (COOH) attached to a hydrocarbon chain.
the hydrocarbon chain can be 2-20 carbons long.

Question 9

what is a saturated fatty acid

Answer 9

every carbon atom in the chain is joined by a single bond (c-c)

Question 10

what is an unsaturated fatty acid

Answer 10

at least one double bond between the carbon atoms (c=c)

Question 11

what is a polyunsaturated fatty acid

Answer 11

contains many double bonds between the carbon atoms

Question 12

what is the bond between glycerol and fatty acid chains called

Answer 12

an ester bond - formed in esterification ( a type of condensation reaction).

Question 13

what do most phospholipids contain

Answer 13

• a diglyceride
• a phosphate group
• a simple organic molecule such as chlorine

Question 14

is the number of carbon atoms a fatty acid usually has even or odd

Answer 14

an even number

Question 15

where are phospholipids found

Answer 15

main component in cell surface membranes in both eukaryotic and prokaryotic cells.

Question 16

what is the structure of phospholipids

Answer 16

they have fatty acid tails, that are hydrophobic, and a phosphate head, that is hydrophilic, attached to a glycerol molecule.
there are only 2 fatty acids bonded to a glycerol molecule as one has been replaced by a phosphate ion (head).

Question 17

why are phospholipids amphipathic (having both hydrophilic and hydrophobic parts)

Answer 17

they have both hydrophobic and hydrophilic parts.
resulting in the molecules forming bilayers / monolayers in water.

Question 18

what type of molecule are phospholipids

Answer 18

macromolecules

Question 19

why is a bilayer formed with phospholipids

Answer 19

when in water, the phosphate group has a negative charge (polar) which attracts to the water. whereas, the fatty acid tails are non-polar and therefore repelled by the water.
forming a layer on the surface of the water with heads in the water and tails sticking up out of the water

Question 20

what is the structure of the bilayer

Answer 20

2 rows of phospholipids - hydrophobic tails pointing inwards and hydrophilic heads pointing outwards.

Question 21

what do phospholipids form other than bilayers

Answer 21

micelles - tiny balls with tails tucked inside and the heads pointing into the water.

Question 22

what is created when a phospholipid bilayer forms due to the presence of hydrophobic fatty acid tails

Answer 22

a hydrophobic core - acts as a barrier to water-soluble molecules.

Question 23

is the phosphate head soluble or insoluble in water

Answer 23

soluble - polar
(hydrophilic)

Question 24

are the fatty acid tails soluble or insoluble in water

Answer 24

insoluble - non-polar
(hydrophobic)

Question 25

where is cholesterol found

Answer 25

cell membrane of eukaryotic cells.
fits in between phospholipids.

Question 26

what is the structure of cholesterol

Answer 26

made from 4 carbon based rings and a hydrocarbon tail.
the ring has a polar hydroxyl (OH) group.
have hydrophobic and hydrophilic regions - allowing them to exist in the bilayer of the membrane.

Question 27

where are molecules of cholesterol synthesised (made)

Answer 27

in the liver + transported via the blood

Question 28

what does cholesterol affect in the cell membrane

Answer 28

the fluidity and permeability of the cell membrane
- disrupts the close-packing of phospholipids, increasing the rigidity of the membrane (makes it less flexible).
- acts as a barrier = prevents water soluble substances from diffusing across the membrane.

Question 29

what are molecules of cholesterol used to produce

Answer 29

steroid -based hormones = oestrogen, testosterone and progesterone

Question 30

what component does a phospholipid contain that is absent in a triglyceride

Answer 30

phospate group

Question 31

how many ester bonds do fatty acids and glycerol contain

Answer 31

3

Question 32

when does an ester bond form

Answer 32

when a hydroxyl (OH) group from the glycerol bonds with the carboxyl (COOH) group of the fatty acid

Question 33

what is the reaction that breaks ester bonds during the breakdown of the triglyceride molecule

Answer 33

hydrolysis reaction - 3 water molecules are taken in the reverse reaction to the condensation.

Question 34

what reaction is an ester bond

Answer 34

condensation

Question 35

what joins together during esterifiction

Answer 35

3 fatty acid molecules and 1 glycerol molecule to form a triglyceride.