ACTIVE TRANSPORT This lesson meets the following DoE Specific Curriculum Outcome for Biology 11: 314-1, 314-3, 314-8

ACTIVE TRANSPORT Active transport is the movement of particles across the cell membrane against the concentration gradient with the use of cellular energy and it includes endocytosis and exocytosis.

ACTIVE TRANSPORT In active transport, cellular energy is used to change the shape of a carrier protein so that required particles move from an area of low concentration to an area of high concentration. Unlike diffusion, particles go against the concentration gradient. It is analogous to rowing a boat upstream against the current (concentration gradient).

ACTIVE TRANSPORT Active transport plays a very important role in homeostasis. Many molecules needed by the cell cannot enter the cell through passive transport because they are too large. The cell must use energy to move these molecules across the plasma membrane. There are two types of active transport; endocytosis and exocytosis.

ENDOCYTOSIS Endocytosis is the process used to ingest materials and bring them inside the cell. Due to the fluidity of the plasma membrane it is able to fold around materials in the external environment and bring them inside within a small pouch called a vesicle. Once inside the cell these vesicles often fuse with a lysosome that contains the digestive enzymes needed to break down the ingested molecules.

ENDOCYTOSIS There are three types of endocytosis: 1.Phagocytosis 2.Pinocytosis 3.Receptor-aided endocytosis

PINOCYTOSIS Pinocytosis involves liquid droplets being engulfed by the cell. –The transport of solutes or fluids. –Ingesting liquid droplets. For example, the cells in your small intestine engulf fat droplets by pinocytosis.

PHAGOCYTOSIS Phagocytosis involves solid particles being engulfed by the cell. The transport of large particles, whole cells, or solids. Common in unicellular organisms. For example, your white blood cells engulf foreign microbes that invade your blood stream by phagocytosis.

RECEPTOR-AIDED ENDOCYTOSIS Protein receptors (in membrane) hook up with a specific molecule. Indentation in membrane forms and pinches off inside cell.

EXOCYTOSIS A reverse process of endocytosis to get rid of wastes (indigestible substances) or secrete hormones. The substance is enclosed in a vesicle (surrounded by a membrane) Fuses with cell membrane The fused membranes open to let material outside cell.

EXOCYTOSIS Exocytosis is the process used by cells to move large molecules to the external environment. These molecules are often waste products. Some molecules released by exocytosis are products that have been made by that cell and they are needed elsewhere in the organism. For example, our nerve cells produce transmitter chemicals that leave the cells by exocytosis.

EXOCYTOSIS