Academic Biology Notes Diffusion and Osmosis Academic Biology Notes

Cell Boundaries Cell Membrane Provides protection and support Regulates what goes in and out of the cell Made of a lipid bi-layer

Cell Boundaries Cell Wall Present in Plant cells ONLY Provides support and protection for the cell Made of cellulose, a tough carbohydrate fiber

Diffusion Solution- a mixture of 2 or more substances Solute- the substance that is dissolved (ex. Salt) Concentration- the amount of solute in a solution

Diffusion Diffusion- particles move from an area of high concentration to an area of low concentration. (High  Low) Equilibrium- Concentration of solute = Concentration of solvent Diffusion does NOT require energy!

Types of Membranes Permeable- substance is able to diffuse across a membrane easily Impermeable- substances cannot pass through Selectively Permeable- some substances can pass across, while others cannot.

Osmosis Osmosis- the diffusion of water through a selectively permeable membrane Water moves from an area of high water concentration to low water concentration.

The Effects of Osmosis on Cells

The Effects of Osmosis on Cells Solution Animal Cell Plant Cell Isotonic Concentration of solutes is the same inside and outside of the cell Water goes in and out at an equal rate Water goes in and out at an equal rate. Hypertonic Concentration of solutes is higher outside of the cell. Water moves out of the cell. The cell shrinks. Hypotonic Concentration of solutes is lower outside of the cell. Water moves into the cell. The cell swells.

Facilitated Diffusion Cell membranes have protein channels that make it easy for certain molecules to pass through the membrane. Facilitated diffusion helps to diffuse molecules like glucose across the membrane. Does NOT require energy!

Active Transport Cells must SOMETIMES move materials in the opposite direction. Done by transport proteins (“pumps”) Requires energy

Types of Active Transport Endocytosis- the process of taking material into the cell by infoldings, or pockets, of the cell membrane. 1. Phagocytosis- “cell eating” 2. Pinocytosis- “cell drinking”

Types of Active Transport Exocytosis- Cells release large amounts of material from the cell.

Why is transport needed? To bring food and nutrients into the cell To maintain homeostasis To bring wastes out of the cell