How things get in and out of cells. Cell Transport How things get in and out of cells.

Cell Transport Cell Transport is the movement of needed materials INTO the cell and waste materials and cell secretions OUT of the cell In order for transport to occur, materials must cross the Cell Membrane.

Review: Cell Membrane The membrane helps to regulate passage of materials between the cell and environment. It prevents large proteins and lipids from entering, but allows simple sugars, oxygen, water and carbon dioxide to pass across. We say the membrane is selectively permeable or semi-permeable because it only allows select items to pass through.

Types of Cellular Transport Active Transport = movement of materials across the membrane using the cells own energy Passive Transport = movement of materials across the membrane NOT using the cells energy

Diffusion Diffusion is the movement of molecules from an area of HIGHER CONCENTRATION to an area of LOWER CONCENTRATIONS. Diffusion continues until molecules are evenly distributed and we call this a state of dynamic equilibrium.

Concentration Gradients A diffusing substance moves down a Concentration Gradient. A gradient is a measure of the difference in concentration of a substance in two regions. The greater the concentration gradient the faster the rate of diffusion.

Osmosis Movement of Water across the cell membrane from high to low concentration. When a cell is placed in a solution, the dissolved solutes diffuse across a membrane and water will osmose in the opposite direction

Types of Solution ISOTONIC Concentration of solutes (dissolved stuff) is equal on both sides of the cell This means equal amounts of water will move across the membrane Cell remains same size

Another type of solution HypOtonic Concentration of solutes is greater INSIDE the cell than outside More water outside cell, water will go into cell Cell will get larger and may burst

Yet one more type of solution… Hypertonic Concentration of solutes is greater OUTSIDE the cell than inside Water will leave the cell Cell will shrink and may die

Facilitated Diffusion Most Molecules cannot cross the Membrane by simple diffusion. In facilitated diffusion, proteins in the membrane called Carrier Proteins help materials across This is done without energy!

Active Transport Transport of materials across the membrane AGAINST the concentration gradient using the cells Energy. Requires the aide of carrier proteins to do this

Bulk Transport Some Molecules, such as complex proteins, are too large to cross the Cell Membrane These Substances cross the Membrane by BULK TRANSPORT. Two types of bulk transport: Endocytosis = going INto the cell Exocytosis = Exiting the cell

Endocytosis Cells need to bring in large materials 2 Types of Endocytosis: Pinocytosis “Cell Drinking” Cell brings in liquids Phagocytosis “Cell Eating” Cell brings in large “food” particles

Exocytosis is the opposite of Endocytosis. During Exocytosis, waste and cell products leave the cell. No special types of exocytosis, liquids and solids leave the cell through the same process

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