120 likes | 127 Vues
The Cell in its Environment. Mr. Fox 7 th 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
E N D
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!
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