Cellular Transport

• Cellular transport is the process of moving substances within the cell and moving substances into and out of the cell.

Diffusion

• Diffusion is the passive transport of particles from an area of high concentration to an area of low concentration.

Facilitated DiffusionFacilitated diffusion uses transport proteins to move ions and other small molecules across the plasma membrane.

• Channel proteins are water-filled transport proteins that open and close to allow substances to pass through.

• Carrier proteins are transport proteins that change shape to open and close as substances diffuse across the membrane.

Osmosis• Osmosis is the diffusion of water across

a membrane. Water passes through until dynamic equilibrium is achieved.

Isotonic Solutions

Isotonic solutions are those in which concentrations are equal on each side of the membrane. Water passes through in both directions at the same rate.

Hypotonic Solutions

• Hypotonic solutions are those in which the concentration of solutes outside the cell are lower than the concentration inside the cell. Water moves in at a higher rate than it moves out of the cell.

Hypertonic Solutions

• Hypertonic solutions are those in which the concentration of solutes outside the cell are higher than those inside the cell. Water moves out of the cell at a higher rate than it moves into the cell.

Active Transport

• Active transport happens when a substance is moved against a concentration gradient, from a low concentration to a higher concentration, with the help of carrier proteins called pumps.

Large Particle Transport

• Some substances are too large to move through the plasma membrane either via diffusion or protein channels. Cells have other ways to get these necessary particles through the membrane.

Endocytosis

• Endocytosis is the process by which a cell surrounds a substance in the outside environment, enclosing the substance in a portion of the plasma membrane, then pinching off to create a vesicle.

Exocytosis

• Exocytosis is the secretion of materials at the plasma membrane. Cells use this process to expel wastes and secrete substances, such as hormones, produced by the cell.

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