B M 2 : Lipids

Question 1

what are triglycerides made of

Answer 1

• one molecule of glycerol

- 3 fatty acids attached to it

Question 2

fatty acids tails made of?

Answer 2

• fatty acids have long tails made of hydrocarbons
• tails are hydrophobic
• tails make lipids insoluble in water

Question 3

all fatty acids have same basic structure, what is it?

Answer 3

O=C-R
/
HO

C= carbon atom links fatty acid to glycerol
R= variable R group hydrocarbon tail

Question 4

whats one thing that varies in the different fatty acids?

Answer 4

hydrocarbon tail

Question 5

what reaction forms triglycerides?

Answer 5

Condensation reactions

Question 6

what bond forms between a fatty acid joining to a glycerol molecule?

Answer 6

Ester bond

Question 7

what is released when an ester bond is formed?

Answer 7

A water molecule (as it’s a condensation reaction)

Question 8

how many times does a glycerol molecule join to a fatty acid to produce a triglyceride?

Answer 8

3 times

Question 9

what are the two types of fatty acid?

Answer 9

Saturated or unsaturated

Question 10

what causes the difference between saturated and unsaturated?

Answer 10

The hydrocarbon tails (R group)

Question 11

structure of saturated fatty acids?

Answer 11

• Don’t have any double bonds between their carbon atoms

- fatty acid is saturated with hydrogen

Question 12

structure of unsaturated fatty acids?

Answer 12

• have at least one double bond between carbon atoms

- causes chain to kink

Question 13

what are the lipids found in cell membranes?

Answer 13

phospholipids

Question 14

whats the difference between phospholipids an triglycerides?

Answer 14

• similar except one fatty acid molecule is replaced with a phosphate group

Question 15

which parts of phospholipids are hydrophobic and hydrophilic

Answer 15

hydrophobic = fatty acid tails 
hydrophilic = phosphate group

Question 16

what does the structure of lipids relate to?

Answer 16

Their functions

Question 17

what are triglycerides mainly used as?

Answer 17

energy storage molecules

Question 18

1 reason why triglycerides are good as energy storage molecules?

Answer 18

• long hydrocarbon tails of fatty acids contain lots of chemical energy when they’re broken down
• because of this lipids contain twice as much energy per gram as carbhydrates

Question 19

another reason why triglycerides are good as energy storage molecules?

Answer 19

• insoluble, so don’t affect water potential of the cell and cause water to enter the cell by osmosis
• triglycerides clump together as insoluble droplets in cells because fatty acid tails are hydrophobic = tails face inwards. shielding themselves from water with their glycerol heads

Question 20

what do phospholipids make up?

Answer 20

the bilayer of cell membranes

Question 21

1 reason why phospholipids are good as a bilayer?

Answer 21

• heads hydrophilic and tails hydrophobic, so form a double layer with their heads facing out towards the water on either side

Question 22

another reason why phospholipids are good as a bilayer?

Answer 22

center of bilayer is hydrophobic, so water-soluble substances can’t easily pass through it - membrane acts as a barrier to those substances

Question 23

what test can test for lipids?

Answer 23

Emulsion test

Question 24

how to perform the emulsion test

Answer 24

1) shake substance with ethanol so it dissolves, the pour solution into water
2) any lipid will show up as a milky solution
3) the more lipid there is the more noticeable the milky colour will be