Lipids - Structure + Function Of Phospholipids

Question 1

How is the structure of phospholipids different to the structure of triglycerides?

Answer 1

One of the 3 fatty acids is replaced by a phosphate molecule

Question 2

How are phospholipids made?

Answer 2

A condensation reaction between the hydroxyl groups on phosphoric acid and glycerol

This creates a phosphate ester bond and forms a molecule of water

Question 3

What is the head of the phospholipid?

Answer 3

The phosphate group

And

Glycerol molecule

Question 4

What is the tail of the phospholipid?

Answer 4

The fatty acid chains

Question 5

What happens when a phospholipid is surrounded by water?

4

Answer 5

The hydrogen ions dissociate from the phosphoric acid

This forms a phosphate group which has a negative charge

The negative charge means the phospholipid head is hydrophilic

However the fatty acid tails are non-polar and not charged and are therefore hydrophobic

Question 6

What is a hydrophilic molecule?

Answer 6

A molecule that is attracted to water due to having a charge

Question 7

What is a hydrophobic molecule?

Answer 7

A molecule that is repelled by water due to not having a charge

Question 8

What unique behaviour do the hydrophilic + hydrophobic ends of the phospholipid cause to happen in water?

(3)

Answer 8

Phospholipids may form:

A layer on the surface of the water

A monolayer of phospholipids called a micelles

A bilayer

Question 9

Which side attracts the water?
Which repels?

The hydrophilic (head)
The hydrophobic (tail)

Answer 9

The hydrophilic (head) = attracts water

The hydrophobic (tail) = repels water

Question 10

Why is the phospholipid bilayer an integral part of?

Answer 10

All membranes in a cell

Question 11

What is the structure of the phospholipid bilayer?

Answer 11

The hydrophilic heads form 2 rows on the outside while the hydrophobic tails are sheltered in the middle

The phospholipids can move past each other which keeps the membrane fluid

Question 12

How does the membrane stay stable?

Answer 12

The hydrophobic tails of the phospholipid bilayer will never be exposed in the water, keeping the membrane stable

Question 13

What important roles does the structure of the phospholipid bilayer allow the cell membrane to carry out?

(2)

Answer 13

Control of substances in and out

Electrical insulation

Question 14

What environment is the middle area of the phospholipid bilayer?

Answer 14

A non-aqueous environment

Question 15

What does the non-aqueous environment of the middle area of phospholipid bilayer create?

Answer 15

It creates a barrier to charge molecules which are dissolved in water

Question 16

What molecules can easily pass through the membrane?

Answer 16

Small, non-polar molecules like oxygen and carbon dioxide

Question 17

Some small non-polar molecules can pass through the membrane.

What does this make the membrane?

Answer 17

Partially permeable

Question 18

What does the partially permeable membrane allow?

2

Answer 18

Allows its to control what enters and leaves the cell

Allows it to act as an electrical insulator

Question 19

Why does the partially permeable membrane insulate against charge?

Answer 19

It insulates against charge because charged ions can’t pass through the phospholipid bilayer