BELL RINGER How do you think materials, molecules, and particles are moved into and out of cells. List 3 different ways.

Section 2:

OBJECTIVES We will be able to describe the function of a selectively permeable membrane We will be able to explain the processes of diffusion and osmosis. We will be able to explain the difference between passive and active transport

Life Application: Cell membranes control the substances that enter and leave the cells in your body Salts, calcium, potassium Cell membrane is selectively permeable Selectively permeable – allows some things to enter or leave the cell while keeping other things outside or inside the cell. The way materials move through cells depends on the size of the molecule, the path taken through the membrane, and whether or not energy is used.

Cell Membrane 2 types of Transport Acts much like a window screen 2 types of Transport Passive – The movement of substances through the cell membrane without the input of energy (ATP) Active – when an input of energy is required to move materials through a cell membrane

Types of Passive Transport Diffusion – the movement of molecules from an area where there are more molecules to an area that has fewer molecules. High concentration to low concentration Equilibrium – molecules will continue to move until the molecules are equal on both sides of the membrane Osmosis – diffusion of H2O through a cell membrane (into or out of the cell) When a plant cell loses water, the cell membrane comes away from its cell wall and the plant cell becomes limp When a plant cell takes in water, the cell membranes press against their cell walls, causing the plant cells to become firm.

Facilitated Diffusion – When molecules are moved into the cell with the help of other molecules in the cell membrane. These other molecules are called TRANSPORT PROTEINS Transport proteins – are used to move substances into and out of the cell

Active Transport – uses energy to move materials through a cell membrane Also requires transport proteins to help, just like facilitated diffusion Molecules and particles that are too large to enter by active transport or passive transport can enter the cell when they are surrounded by the cell membrane by using VESICLES.

Vesicles – are transport and storage structures in a cell’s cytoplasm Endocytosis – process of taking substances into a cell by surrounding it with the cell membrane Ex. Some one-celled organisms take food in this way

Exocytosis – occurs when a vesicle’s membrane fuses with a cell’s membrane, and the vesicle’s contents are released Stomach cells use this process to release chemicals that help digest food.