Phospholipid bilayer

Question 1

A phospholipid bilayer is composed of two layers of phospholipids;

Answer 1

Their hydrophobic tails facing inwards and hydrophilic heads outwards

Question 2

Phospholipid bilayers can form compartments – the bilayer forming the cell surface membrane establishing the

Answer 2

boundary of each cell

Question 3

Internally, membrane-bound compartments formed from phospholipid bilayers provide the basic structure of organelles, allowing for

Answer 3

of processes within the cell

Question 4

An example of a membrane-bound organelle is the lysosome why do these need to be compartmentalized

Answer 4

These enzymes need to be kept compartmentalised otherwise they would breakdown most of the cellular components

Question 5

The phospholipid bilayers that make up cell membranes also contain proteins

The proteins can either be

Answer 5

intrinsic (or integral) or extrinsic (peripheral)

Question 6

Intrinsic proteins are

Answer 6

embedded in the membrane with their arrangement determined by their hydrophilic and hydrophobic regions

Question 7

Extrinsic proteins are

Answer 7

found on the outer or inner surface of the membrane

Question 8

The fluid mosaic model describes cell membranes as ‘fluid’ because:

Answer 8

The phospholipids and proteins can move around via diffusion constantly in motion

The phospholipids mainly move sideways, within their own layers

The many different types of proteins interspersed throughout the bilayer move about within it (a bit like icebergs in the sea) although some may be fixed in position

Question 9

The fluid mosaic model describes cell membranes as ‘mosaics’ because:

Answer 9

The scattered pattern produced by the proteins and phospholipids within the phospholipid bilayer looks somewhat like a mosaic when viewed from above

Question 10

You must know how to draw and label the fluid mosaic model, as well as ensure that you can describe why the membrane is called the fluid mosaic model.

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