The Cell in its Environment

The Cell in its Environment Mr. Fox 7th Grade Science

The Membrane • Remember, selectively permeable. • Substances that can move into an out of a cell do so by one of three methods: diffusion, osmosis, or active transport.

Diffusion • The movement of molecules from HIGH concentration  LOW Concentration • Requires NO ENERGY • Molecules are always moving, so they bump together and then tend to bump each other away. • Happens Naturally within Nature!

Diffusion

Osmosis • The diffusion of WATER from • Requires NO energy • Happens Naturally within nature! • Passive transport – transport of molecules without the need for energy! Ex: diffusion and osmosis HIGH concentration  LOW Concentration

Tonicity • Tonicity means, how water is going to move in or out of the cells. • Things in osmosis and diffusion want to reach equilibrium. • Equilibrium – a state in which molecules keep moving but they equal out in concentration

Isotonic • When water inside and outside the cell are at equilibrium. • NO NET MOVEMENT OF WATER! (but the water is still moving in and out of the cell)

Hypotonic • Concentration of water is higher outside of the cell so, water moves into the cell more than out of the cell. • NET MOVEMENT OF WATER INTO THE CELL

Hypertonic • Concentration of water is lower outside of the cell, water moves OUT of the cell more. • NET MOVEMENT OF WATER OUT OF THE CELL

Active Transport • The transport of materials across the cell membrane requiring energy. • Transport Proteins – ‘pick up’ molecules outside the cell, and bring them into the cell • Transport by Engulfing – transport of materials by the cell surrounding it’s food. Low Concentration  High Concentration

Why are cells so small? • The larger the cell the harder to move materials around as well as get rid of waste • Small size = efficient transport of materials

Homework • Page forty-four one through four

The Cell in its Environment