Fluid mosaic model

Question 1

Describe the position of phospholipids within the cell membrane

Answer 1

They form a belayer, with one sheet of phospholipids opposite another. The tails of the phospholipids both point towards each other whereas the phosphate heads both point outwards.

Question 2

Why do phospholipids arrange themselves as a Bilayer with their tails pointing inwards and phosphate heads pointing outwards?

Answer 2

The heads are hydrophilic, meaning they are polar and will interact with water (in the cytoplasm or in the surrounding cells) whereas the hydrophobic tails are non-polar meaning they will not interact with water and therefore face inwards.

Question 3

What are the two different types of protein found in the cell membrane?

Answer 3

Intrinsic and extrinsic proteins

Question 4

What are the functions of extrinsic proteins?

Answer 4

They provide structural support (interact with water and form hydrogen bonds), they act as antigens for cell recognition and act as receptor/binding sites for hormone attachment.

Question 5

What are the functions of intrinsic proteins?

Answer 5

Some of them are carriers - they can transport water-soluble substances across and others allow for the active transport of small charged ions by forming channels.

Question 6

Why is it called the fluid mosaic model

Answer 6

The individual phospholipid molecules can move within the membrane relative to one another and the proteins imbedded in the bilayer vary in shape, size and pattern.

Question 7

Describe how hormones interact with the cell membrane

Answer 7

Hormones such as adrenaline are insoluble in lipids and so cannot diffuse through the membrane into the cell, instead they bond to extrinsic proteins which influences the behaviour of the cells.

Question 8

What else is found in the membrane of animal cells and what is its function?

Answer 8

Cholesterol and it is used for making the membrane more rigid and stable

Question 9

What else I found in the outer layer of the membrane and what is this membrane called?

Answer 9

Glycoproteins and glycolipids are found in the outer layer of the membrane and the carbohydrate layer around the membrane is called the glycocalyx.

Question 10

How thick is the cell membrane?

Answer 10

7 nanometres

Question 11

What are glycoproteins and lipoproteins made up of?

Answer 11

Glycoprotein - protein bonded to carbohydrate

Lipoprotein - protein bonded to lipid