Lipids, Triglycerides And Phospholipids

Question 1

What 3 elements do lipids always contain?

Answer 1

-carbon
-hydrogen
-oxygen

Question 2

Is the proportion of oxygen to carbon and hydrogen smaller than in carbohydrates?

Answer 2

Yes

Question 3

Are lipids soluble?

Answer 3

In water - no
In organic solvents such as alcohols and acetone - yes

Question 4

What are the main groups of lipids?

Answer 4

Triglycerides

Question 5

What make up triglycerides?

Answer 5

3 fatty acids and one glycerol molecule

Question 6

What do phospholipids in the membrane contribute to?

Answer 6

The flexibility of membranes and the transfer of lipid-soluble substances across them

Question 7

What are the 4 roles of lipids?

Answer 7

1) source of energy - when oxidised release more energy than carbs and release valuable water
2) waterproofing - insoluble in water
3) insulation - fats are poor conductors of heat so retain heat
4) protection - stores around delicate organs

Question 8

What forms in a condensation reaction between each fatty acid and the glycerol molecule?

Answer 8

An ester bond

Question 9

If the fatty acid has no Double bonds, what is it?

Answer 9

Saturated

Question 10

If the fatty acid has one double bond, what is it?

Answer 10

Mono-unsaturated

Question 11

If the fatty acid has more than one double bond, what is it called?

Answer 11

Polyunsaturated

Question 12

Why are triglycerides an excellent source of energy?

Answer 12

They have a high ratio of energy-storing carbon-hydrogen bonds to carbon atoms

Question 13

Why do lipids have the property of being a good storage molecule since it can be stored in a small volume?

Answer 13

They have a low mass to energy ratio so lots of energy can be stored in a small mass

Question 14

Why don’t triglycerides affect the water potential in cells/ osmosis?

Answer 14

They are large and non-polar so are insoluble in water

Question 15

How do triglycerides provide an important source of water?

Answer 15

They have a high ratio of hydrogen to oxygen atoms and release water when oxidised

Question 16

What is a phospholipid’s structure?

Answer 16

One fatty acid is replaced by a phosphate molecule

Question 17

If fatty acids repel water, do phosphate molecules attract or repel it?

Answer 17

Attract water - hydrophilic

Question 18

Which part of a phospholipid is hydrophobic/hydrophilic?

Answer 18

-hydrophobic tail
-hydrophilic head

Question 19

Are phospholipids polar?

Answer 19

Yes

Question 20

What 3 uses do phospholipids have?

Answer 20

1) in aqueous environment form phospholipid bilayer which forms a hydrophobic barrier
2) hydrophilic heads hold at the cell membrane
3) form glycolipids by combining with carbohydrates

Question 21

What is the test for lipids called?

Answer 21

The “emulsion test”.

Question 22

What solution is added to the test solution ??

Answer 22

Ethanol

Question 23

What indicates the presence of a lipid?

Answer 23

A milky-white cloudy EMULSION

Question 24

What forms the cloudy colour in the white emulsion?

Answer 24

any lipid in the sample is dispersed in the water and light refracts off these oil droplets to water droplets and make it seem cloudy

Question 25

What is the function of the hydrophilic head?

Answer 25

When placed in water, they position themselves so they are as close to the water as possible
Ensures only water and not fat is interacted with