4. Lipids

Question 1

Give an example of a lipid?

Answer 1

Triglyceride.

Question 2

What is the structure of a triglyceride?

Answer 2

One molecule of glycerol with 3 fatty acids attached to it.

Question 3

What is the structure of a fatty acid molecule?

Answer 3

Long tails made of hydrocarbons.
The tails are hydrophobic (repel water) makes them insoluble in water.
All have the same basic structure but hydrocarbon tail varies.

Question 4

What is the basic structure of a fatty acid? diagram

Answer 4

Carbon atoms links fatty acid to glycerol.

Variable R group hydrocarbon tail.

Question 5

How is a triglyceride formed?

Answer 5

When a fatty acid joins to glycerol molecule.
Ester bond is formed, a molecule of water is releases - its a condensation reaction.
Process happens twice more to from triglycerides.

Question 6

Name the 2 kinds of fatty acid?

Answer 6

Saturated.
Unsaturated.
Difference is in their hydrocarbon tails - r group.

Question 7

What are saturated fatty acids?

Answer 7

Don’t have any double bonds between their carbon atoms.
Fatty acid is saturated with hydrogen - maximum saturation.

Form straight chains

Question 8

What are unsaturated fatty acids?

Answer 8

Have atleast one double bond between carbon atoms, causing chain to kink.

More double bonds the more it’s bent

Question 9

What are the lipids found in cell membranes called?

Answer 9

Phospholipids.

Question 10

What are phospholipids?

Answer 10

Similar to triglycerides except one of the fatty acid molecules is replaced by phosphate group.

Question 11

What is a phosphate group?

Answer 11

Its hydrophilic (attracts water).
The fatty acid tails are hydrophobic (repel water).
This is important in the cell.

Question 12

What are triglycerides mainly used for?

Answer 12

Energy storage.

Question 13

Why are triglycerides good for energy storage?

Answer 13

Long hydrocarbon tails of the fatty acids contain lots of chemical energy - lots of energy released when broken down.
They’re insoluble so don’t affect water potential of the cell and cause water to enter cells by osmosis.

Question 14

How much energy do lipids contain?

Answer 14

Twice as much energy per gram as carbohydrates.

Question 15

What do the triglycerides clump into?

Answer 15

A insoluble droplets in cells because the fatty acid tails are hydrophobic - tails face inwards, shielding them from the water with their glycerol heads.

Question 16

What do phospholipids make up?

Answer 16

The bilayer of cell membranes.

Cell membranes controls what enters and leaves the cell.

Question 17

Structure of phospholipids?

Answer 17

Heads are hydrophilic and tails ate hydrophobic so they form double later with heads facing out towards water.
Centre of bilayer is hydrophobic so water-soluble substances can’t pass through it easily.

Question 18

What is the emulsion test for lipids?

Answer 18

To find fat in a food use the emulsion test.
Shake the test substance with ethanol for 1 minute so it dissolves, then pour solution into water.
Lipid will show up as milky emulsion.
More lipid=more noticeable milky colour is.

Question 19

What are phospholipids made up of ?

Answer 19

1 glycerol

2 fatty acids

1 inorganic phosphate

Question 20

What TYPE of properties do phospholipids have ?

Answer 20

Amphiphillic

Question 21

What are the phospholipids droplets which exclude water, called ?

Answer 21

Micelle

And

Bilayers

Question 22

What elements do lipids contain ?

Answer 22

Carbon

Hydrogen

Oxygen

Question 23

Example of triglycerides

Answer 23

Fats - solid at room temp

Oils - liquid at room temp

Question 24

How many ester bonds form in triglycerides

Answer 24

3

After water is removed

Question 25

Hydrolysis of triglycerides

Answer 25

Add 3 molecules of water to break ester bond

This produces 3 fatty acid molecules and 1 glycerol molecule

Question 26

What does saturation refer to ?

Answer 26

Hydrogen

More “full of hydrogen” the hydrocarbon chain is the more saturated fatty acid is

Not fully saturated then doubly bonds form between carbon atoms

Question 27

What will a triglycerides with all saturated fatty acids forms ?

Answer 27

Fat

Solid

Question 28

Mono saturated fatty acid

Answer 28

1 carbon double bond

Question 29

What will triglycerides be with all unsaturated fatty acids?

Answer 29

Oil

Can’t compact as tight together