lipids-biological molecules

Question 1

examples

Answer 1

-triglycerides, phospholipids, sterols

Question 2

how are triglycerides synthesised?

Answer 2

-by the formation of an ester bond between each fatty acid and glycerol molecule

Question 3

how is an ester bond formed between glycerol and fatty acid

Answer 3

-by a condensation reaction (water molecules are released)

Question 4

how is an ester bond broken

Answer 4

-by a hydrolysis reaction (water molecules used up)

Question 5

diff between a saturated and unsaturated fatty acid

Answer 5

-unsaturated have a carbon double bond= causes the chain to kink

Question 6

general formula for saturated fatty acid

Answer 6

CnH(2n+2)

Question 7

main use of triglycerides, phospholipids and cholesterol

Answer 7

• T, mainly used as energy storage molecules in animals and plants
• P, make up phospholipid bilayer in a cell membranes of all eukaryotes and prokaryotes
• C, in eukaryotic cells, strengthens the cell membrane by interacting with the phospholipid bilayer

Question 8

uses of adaptations in triglycerides

Answer 8

• long hydrocarbon tails of the fatty acids contains lots of chemical energy= lots of energy is released when they are broken down
• theyre insoluble= dont cause water to enter the cells by osmosis which would make them swell
• fatty tails are hydrophobic and shield themselves from water with their glycerol heads

Question 9

roles of phospholipids

Answer 9

• make up the phospholipid bilayer

- do not allow water-soluble substances e.g ions to pass through due to their tails being hydrophobic

Question 10

uses of adaptations in cholesterol

Answer 10

• has a small size and flattened shape-allows cholesterol to fit in between the phospholipid molecules in the membrane
• they bind to the hydrophobic tails of the phospholipids , causing them to pack more closely together. This helps the membrane less fluid and more rigid

Question 11

role of cholesterol

Answer 11

• makes membrane less fluid
• used to make vit D
• used in liver to produce bile

Question 12

Contains only carbon, hydrogen and oxygen

Answer 12

triglyceride and cholesterol

Question 13

insoluble in water

Answer 13

-triglyceride, phospholipid, cholesterol

Question 14

contains glycerol

Answer 14

triglyceride and phospholipids

Question 15

contains ester bonds

Answer 15

triglyceride and phospholipid

Question 16

important in membrane structure

Answer 16

phospholipids and cholesterol

Question 17

contains fatty acids

Answer 17

triglycerides and phospholipids

Question 18

Describe how to do the emulsion test for lipids and how a positive result would be identified

Answer 18

mix with / add , ethanol / alcohol , and water ;

(goes) cloudy

Question 19

State two roles of cholesterol in living organisms

Answer 19

regulates fluidity of / stabilises / AW, membranes / phospholipid bilayer ;
(converted to) steroid / named steroid, hormone(s) ;
waterproofing the skin ;
making Vitamin D ;
making bile (salts) ;

Question 20

Identify one way in which the molecular structure of cholesterol is similar to the molecular
structure of a carbohydrate.

Answer 20

contains C and H and O ;
has, OH / hydroxyl, groups ;
hex / 6-membered, ring

Question 21

Cholesterol is transported in the blood within molecules of low-density lipoprotein (LDL).
Name two molecules that combine with cholesterol to form LDLs

Answer 21

(saturated) lipids / fats / triglycerides ;

protein / polypeptide