CCEA Double Award Science:
Biology - Unit 2 Notes
,Contents
Osmosis & Plant Transport - Page 3
The Circulatory System - Page 7
The Genome, Chromosomes, DNA & Genetics - Page 15
Reproduction, Fertility & Contraception - Page 35
Variation & Natural Selection - Page 45
Health, Disease, Defence Mechanisms & Treatments - Page 53
Image Rights - Page 62
,Osmosis & Plant
Transport
, Osmosis In Cells & Diffusion
Diffusion: Movement of a substance from an area of high concentration to an area of low
concentration.
Osmosis: The diffusion of water from a dilute solution to a more concentrated solution
through a selectively permeable membrane, until there is an equal amount of water molecules
in each area.
Animal Cells: When water moves into an animal cell, the cell increases in volume, stretching
the cell membrane until it splits & bursts. This is called lysis.
Plant Cells: When water enters a plant cell it increase the size of the vacuole which pushes the
cell membrane against the cell wall. The force of this increases the pressure in the cell making
it turgid. This turgor pressure prevents the cell from absorbing too much water & bursting. It
also keeps the plant upright.
Plasmolysis: When a plant cell loses too much water through osmosis, causing the cell’s
contents to shrink. This moves the cell membrane away from the cell wall.
Biology - Unit 2 Notes
,Contents
Osmosis & Plant Transport - Page 3
The Circulatory System - Page 7
The Genome, Chromosomes, DNA & Genetics - Page 15
Reproduction, Fertility & Contraception - Page 35
Variation & Natural Selection - Page 45
Health, Disease, Defence Mechanisms & Treatments - Page 53
Image Rights - Page 62
,Osmosis & Plant
Transport
, Osmosis In Cells & Diffusion
Diffusion: Movement of a substance from an area of high concentration to an area of low
concentration.
Osmosis: The diffusion of water from a dilute solution to a more concentrated solution
through a selectively permeable membrane, until there is an equal amount of water molecules
in each area.
Animal Cells: When water moves into an animal cell, the cell increases in volume, stretching
the cell membrane until it splits & bursts. This is called lysis.
Plant Cells: When water enters a plant cell it increase the size of the vacuole which pushes the
cell membrane against the cell wall. The force of this increases the pressure in the cell making
it turgid. This turgor pressure prevents the cell from absorbing too much water & bursting. It
also keeps the plant upright.
Plasmolysis: When a plant cell loses too much water through osmosis, causing the cell’s
contents to shrink. This moves the cell membrane away from the cell wall.
