1.2 Transport across cell membranes

Question 1

What is diffusion?

Answer 1

Diffusion is the movement of substances from an area of high concentration to an area of low concentration. As it is passive it does not require any energy.

Question 2

What will happen to an animal and a plant cell when they are placed in a solution of a lower water concentration than they contain?

Answer 2

animal cell - shrink

plant cell - plasmolysed

this will happen due to osmosis

Question 3

What is active transport?

Answer 3

The movement of a substance up (against) the concentration gradient. it requires membrane proteins and energy

Question 4

What is osmosis?

Answer 4

Osmosis is a “special case” of diffusion. Osmosis is the movement of water from an area of high water concentration to an area of low water concentration down the concentration gradient through a semi permeable membrane. As it is passive it does not require any energy

Question 5

What do membrane proteins acting as channels do?

Answer 5

Allow substances to enter or leave the cell

Question 6

State one characteristic of a cell membrane

Answer 6

it is selectively permeable

Question 7

Describe the structure of the cell membrane

Answer 7

The cell membrane is made up of a phospholipid bilayer. scattered around that bilayer are proteins that can be on either side of the bilayer or they can create a channel through the membrane.

Question 8

Give examples of molecules that diffuse across the cell membrane

Answer 8

carbon dioxide
oxygen
animo acids

Question 9

What will happen to an animal and a plant cell when they are placed in a solution of a higher water concentration than they contain?

Answer 9

animal cell - burst

plant cell - become turgid

this will happen due to osmosis

Question 10

What is passive transport?

Answer 10

Passive transport is the movement of molecules down a concentration gradient and it does not require any energy