7-3 Movement through the Membrane The cell membrane is semipermeable - only certain molecules can get through Passive transport: no energy required 1. Diffusion: the movement of molecules from a region of high concentration to a region of low concentration

- continues until equilibrium is reached (equal concentrations on both sides of membrane)

- temperature affects diffusion: higher = faster - size of particles affects diffusion: smaller = faster

2. Osmosis: the diffusion of water. across a membrane from high water 2. Osmosis: the diffusion of water across a membrane from high water concentration to low water concentration 97% water 100% water Which way will the water move?

97% water 90% water Which way will the water move?

This solution is hypertonic - water diffuses out of the cell This solution is hypotonic - water diffuses into the cell

This solution is isotonic - no net change 95% water This solution is isotonic - no net change

3. Facilitated diffusion: uses protein channels to move molecules from high concentration to low concentration Active Transport: energy required 1. Carrier proteins may act as pumps -example: sodium-potassium pump a. Cells continually pump potassium ions into the cell, and sodium ions out

Important for muscle contraction and nerve impulse transmission K+

2. Endocytosis: materials move into cell

a. Pinocytosis: membrane encloses a. Pinocytosis: membrane encloses a fluid droplet and brings it inside the cell b. Phagocytosis: membrane encloses a large particle and brings it inside the cell

3. Exocytosis: materials move outside the cell - wastes and cell products may leave the cell this way

7-4 The Diversity of Cellular Life Unicellular organisms a cell is the entire organism Do everything you would expect from a living things prokaryotic include bacteria eukaryotic include algae

Multicellular Organisms that contain many cells Cells are specialized to perform particular functions within the organism Levels of organization Cells Tissues Organs Organ systems