Lipids

Question 1

What are lipids?

Answer 1

• a group of substances that are soluble in alcohol rather than in water

Question 2

What is a macromolecule?

Answer 2

• very large organic molecule

- complex molecules with relatively large molecular mass

Question 3

What is a triglyceride?

Answer 3

1 molecule of glycerol attached to 3 fatty acids via ester bonds

Question 4

How are ester bonds formed?

Answer 4

in a condensation reaction where water is released

Question 5

What is esterification?

Answer 5

it is another name of a process in which triglycerides are formed

Question 6

Structure of triglyceride

Answer 6

look at notes

Question 7

What are saturated fatty acids?

Answer 7

• no double bonds between carbon atoms so a fatty acid is saturated with hydrogen

Question 8

What are unsaturated fatty acids?

Answer 8

• has a double bonds so fewer hydrogen atoms can be bonded to the molecule
• double bonds cause kinks in the chain

Question 9

Triglyceride properties/function

Answer 9

• mainly used as energy storage molecules
• good for storage as long hydrocarbon tails of fatty acids have lots of chemical energy so lots of energy can be released when they are broken down
• insoluble so doesn’t cause water to enter cells by osmosis which would make them swell. They bundle together forming insoluble droplets as hydrophobic tails face inwards shielding themselves from water with their glycerol heads

Question 10

Why do storage molecules need to be insoluble?

Answer 10

• otherwise they would dissolve and release whatever they were holding whenever they come in contact with water

Question 11

Phospholipid structure

Answer 11

look in notes

Question 12

What is a phospholipid?

Answer 12

1 molecule of glycerol with 2 fatty acids and 1 phosphate groups

Question 13

Phospholipid properties/function

Answer 13

• found in cell membranes
• makes a phospholipid bilayer where hydrophilic heads face out to water on both sides of membrane and the hydrophobic tails face inwards
• centre of bilayer is hydrophobic so water-soluble substances cant easily pass through hence membrane acts as a barrier to these substances

Question 14

What is cholesterol?

Answer 14

• a hydrocarbon ring structure attached to a hydrocarbon tail.
• ring structure has a polar hydroxyl (OH) group attached to it

Question 15

cholesterol structure

Answer 15

look in notes

Question 16

cholesterol properties/function

Answer 16

• helps strengthen membranes in eukaryotic cells by interacting with phospholipid bilayer
• small size and flattened shape so allows it to fit between the phospholipid molecules in membrane
• bind to hydrophobic tails of phospholipids causing them to pack more closely together. it helps to make membrane less fluid and more rigid.