Transport across cell membranes

Question 1

Label the structures within a cell membrane

Answer 1

1. Protien
2. Phospholipids

Question 2

Explain why the cell membrane is selectively permeable

Answer 2

his means that some substances freely cross the cell membrane in or out of the cell, whilst other substances cannot.

Question 3

Explain why different concentrations of substances exist between cells and their environments

Answer 3

ince the cell membrane is selectively permeable, this means some substances can pass across whilst others cannot. This can create differences in concentrations of substances on one side of the membrane compared to another. This creates a CONCENTRATION GRADIENT.

Question 4

Describe passive transport

Answer 4

Passive transport involves the movement of molecules from HIGH concentration to a LOW concentration DOWN a concentration gradient. This process does NOT require energy.

Question 5

Describe Osmosis as an example of passive diffusion involving water

Answer 5

Osmosis is the movement of water from an area of high water concentration to an area of low water concentration down a water concentration gradient across a selectively permeable membrane.

Question 6

Describe and explain the effects on plant cells when placed in solutions of different water concentrations

Answer 6

1. Plant cells placed in lower water soloution = plasmolysed
2. Plant cell in equal water soloution = stay the same
3. Plant cell in higher water soloution = turgid

Question 7

Describe active transport

Answer 7

Active transport is the movement of molecules from an area of LOW concentration to an area of HIGH concentration against the concentration gradient.