2.1.2 h-j Biological molecules - lipids

Question 1

Which elements are present in lipids?

Answer 1

C, H, O (P phospholipids)

Question 2

Define macromolecule

Answer 2

complex molecules with large MR

Question 3

What are the 3 lipid categories?

Answer 3

• Triglycerides
• Phospholipids
• Cholesterol

Question 4

Draw a labelled diagram showing the basic structure of a triglyceride

Answer 4

3 fatty acids joined to one glycerol
*structure drawn on flashcard

Question 5

What is the difference between saturated, monounsaturated and polyunsaturated fatty acids/glycerides?

Answer 5

• unsaturated fatty acids have kinks in the chain due to the double bonds ( 1 kink for mono, several kinks for poly)
• saturated have no kinnks as no c=c

Question 6

Why do saturated triglycerides tend to be solids (fats) at RT whereas unsaturated triglycerides tend to be liquid (oil)

Answer 6

• Saturated fatty acids can pack more tightly as there are no c=c so no kinks - therefore have higher MP
• unsaturated fatty acids cannot pack as closely together due to kinks so are more spread out so have lower MP

Question 7

What is the difference between triglycerides found in non-fish animals and those in plants and fish?

Answer 7

• plant and fish triglycerides are usually unsaturated (oils)
• animal fats are saturated (solid fats)

Question 8

Draw a labelled diagram showing the basic structure of a phospholipid

Answer 8

one phosphate group attached to a glycerol with 2 fatty acids
*drawn on flashcard

Question 9

What property does each end of the phospholipid have?

Answer 9

phospholipids have
- hydrophilic head
- hydrophobic fatty acid tails

Question 10

What is the difference between a triglyceride and a phospholipid?

Answer 10

phospholipids have a phosphate group in place of one of the fatty acids on a triglyceride

Question 11

Draw a diagram to show how a triglyceride is formed and broken down

Answer 11

*on flashcard
glycerol + 3 fatty acids —> triglyceride

glycerol - 3 carbon with 3 OH
fatty acids - COOH and R-group

Question 12

What is the bond that holds the building blocks of triglycerides together?

Answer 12

ester bond

Question 13

What is the name of the reaction that forms triglycerides and the reaction that breaks them apart

Answer 13

formed via condensation - + 3H20

broken via hydrolysis take - 3H20

Question 14

Explain how an ester bond is formed between glycerol and a fatty acid

Answer 14

via esterification
- reaction between hydroxyl of glycerol and carboxyl of fatty acid - giving off water

Question 15

What is the number of water molecules produced in the production of 1 triglyceride

Answer 15

3

Question 16

What are the products of digestion of a triglyceride (include partial digestion) and state what would happen to the pH of the solution and why

Answer 16

Produces fatty acids and glycerol
or partially only removes some of the fatty acids to produce a monoglyceride etc.

Due to fatty acids (which are acidic) pH would decrease

Question 17

What is the structure of sterols (cholesterol is a type of sterol)?

Answer 17

4 carbon ring structure with a OH group

Question 18

What are the 5 functions of triglycerides?

Answer 18

• energy store
• thermal insulation
• cushioning for internal organs
• buoyancy
• waterproofing

Question 19

What is the main function of phospholipids?

Answer 19

• membranes (phospholipid bilayer)

Question 20

What are the 2 functions of cholesterol?

Answer 20

• cell membranes
• hormones (made by adding different side group)

Question 21

What is the structure of triglycerides?

Answer 21

• long hydrocarbon fatty acid tails contain a lot of chemical energy - when broken down release 2x energy that carbohydrates would
• insoluble - water doesn’t enter the cells by osmosis - triglycerides bundle together in insoluble droplets (tails face inwards (hydrophobic)

Question 22

What is the structure of phospholipids?

Answer 22

• make the phospholipid bilayer - control what enters + leaves the cell
  1- phospholipid heads are hydrophilic and their tails are hydrophobic - form double layer with heads facing out towards water
  2- centre of bilayer hydrophobic - water soluble substances cant pass easily throught it - membrane acts as barrier

Question 23

What is the structure of cholesterol?

Answer 23

• small size
• flattened shape
  –> both allow cholesterol to fit in between the phospholipid molecules in the membrane
• cholesterol molecules bind to the hydrophobic tails of the phospholipids —> causes them to pack more closely togther - membrane less fluid+more rigid

Question 24

Why triglyceride store more energy per gram than carbohydrates?

Answer 24

they require more oxidation to be broken down into CO2 and O2
- release more energy although it takes longer

Question 25

How do phospholipids form a membrane?

Answer 25

phospholipid bilayer
- 2 layers with the hydrophobic fatty acid tails sandwiched on the inside and the hydrophilic heads on the outside

Question 26

How does the presence of cholesterol affect the properties of cell membranes?

Answer 26

cholesterol regulates membrane fluidity