Plasma Membrane

Question 1

Describe the structure of a phsopholipid

Answer 1

It is made of a phosphate group, 1 glycerol molecule and 2 fatty acids. It’s head is hydrophilic and it faces outwards whereas the hydrophilic tails face inwards

Question 2

What is the function of a phospholipid

Answer 2

It forms a barrier to water soluble substances but allows fat substances to travel through it ( controls what goes in and out the cell)

Question 3

What is the function of cholesterol

Answer 3

It provides the membrane with stability by binding to the hydrophobic tails of the phospholipids and help’s maintain the membrane’s fluidity

Question 4

What is the function of a carrier protein

Answer 4

It controls what enters and leaves the cell by allowing for larger molecules to diffuse through the membrane . It is ills involved in cell signalling

Question 5

What is the function of a channel protein

Answer 5

They transport substances through diffusion. It let’s charged and polar molecules to enter the cell. It is also used in cell signalling

Question 6

What is the function of a glycoprotein

Answer 6

It stabilises the membrane forming hydrogen bonds with water molecules. It also acts as a receptor cell allowing responses to hormones and drugs . Also used for cell signalling

Question 7

What is the function of a glycolipid

Answer 7

It stabilises the membrane by forming hydrogen bonds with water molecules . Most importantly it is used for self recognition (recognising what’s foreign )

Question 8

What are the 2 factors that affect membrane permeability

Answer 8

Solvents and temperature

Question 9

How does solvents affect membrane permeability

Answer 9

Solvents like alcohol dissolve lipids in the cell membrane which causes the membrane to lose its structure (breaks down the phospholipid bilayer )

Question 10

How does having a temp below 0 degrees Celsius affect the cell membranes permeability

Answer 10

There is a low kinetic energy reducing the cells fluidity which stops molecules from passing through the phospholipids as they aren’t moving as much
Ice crystals can form and can disrupt the arrangement of molecules due to thawing

Question 11

How does a high temperature affect the membranes permeability

Answer 11

There is an increase in kinetic energy which increases fluidity causing the membrane to lose its shape

Question 12

What happens to the cell membrane when the temperature reacts 45 degrees Celsius

Answer 12

The phospholipids melt and the proteins denature
Water expands putting pressure on the membrane to burst