KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

Cell membranes are composed of two phospholipid layers.

Cell membranes are composed of two phospholipid layers. The cell membrane has two major functions. cell membrane

Cell membranes are composed of two phospholipid layers. The cell membrane has two major functions. forms a boundary between inside and outside of the cell cell membrane outside cell inside cell

Cell membranes are composed of two phospholipid layers. The cell membrane has two major functions. forms a boundary between inside and outside of the cell controls passage of materials cell membrane outside cell inside cell

Cell membranes are composed of two phospholipid layers.

Cell membranes are composed of two phospholipid layers. The cell membrane is made of a phospholipid bilayer. cell membrane

Cell membranes are composed of two phospholipid layers. The cell membrane is made of a phospholipid bilayer. There are other molecules embedded in the membrane. cell membrane protein cholesterol carbohydrate chain protein channel

Cell membranes are composed of two phospholipid layers. The cell membrane is made of a phospholipid bilayer. There are other molecules embedded in the membrane. The fluid mosaic model describes the membrane. cell membrane protein cholesterol carbohydrate chain protein channel

Cell membranes are composed of two phospholipid layers.

Cell membranes are composed of two phospholipid layers. The cell membrane is selectively permeable. Some molecules can cross the membrane while others cannot.

Cell membranes are composed of two phospholipid layers. The cell membrane is selectively permeable. Some molecules can cross the membrane while others cannot.

Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors.

Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors. intracellular receptor

Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors. intracellular receptor membrane receptor

3.4 Diffusion and Osmosis KEY CONCEPT Materials move across membranes because of concentration differences.

3.4 Diffusion and Osmosis Passive transport does not require energy input from a cell. Molecules can move across the cell membrane through passive transport. There are two types of passive transport. diffusion osmosis

3.4 Diffusion and Osmosis Diffusion and osmosis are types of passive transport. Molecules diffuse down a concentration gradient.

3.4 Diffusion and Osmosis Diffusion and osmosis are types of passive transport. Osmosis is the diffusion of water molecules across a semipermeable membrane.

3.4 Diffusion and Osmosis Diffusion and osmosis are types of passive transport. There are three types of solutions. isotonic hypertonic hypotonic

3.4 Diffusion and Osmosis Some molecules can only diffuse through transport proteins. Some molecules cannot easily diffuse across the cell membrane. Facilitated diffusion is diffusion through transport proteins.