Active Transport Review

Using energy - Some cells require creation and maintenance of a concentration gradient, and others require materials too large for membrane proteins to enter or exit. -this will require the cell to use energy to accomplish these goals

Active Transport -the movement of materials against a concentration gradient -allows substances to move across the cell membrane from an area of low concentration to an area of high concentration -requires energy in the form of ATP

Active Transport -A considerable portion of the energy used by cells in their daily activities is devoted to providing the energy to keep active transport working. -The use of energy enables cells to concentrate substances in a particular location, even when the forces of diffusion might tend to move these substances in the opposite direction.

-The active transport of ions or small molecules across a cell membrane is generally carried out by transport proteins, ion pumps and molecular pumps that are found in the membrane itself. Active Transport

Ion pumps -Many cells use such proteins to move calcium, potassium, and sodium ions across cell membranes. Ex> a nerve cell needs a high concentration of sodium ions outside the cell and a high concentration of potassium ions in the cytoplasm

Ion pumps -The creation of a concentration gradient is needed to keep so much sodium in one place and so much potassium elsewhere. Energy will be need to do this. Molecular pumps move uncharged molecules in a similar way.

Molecular Transport -The transport of larger materials sometimes involves changes in the shape of the cell membrane.

Transport into and out of the cell 1. Exocytosis 2. Endocytosis

Exocytosis -movement of materials out of the cell -The membrane of the vesicle surrounding the material fuses with the cell membrane, forcing the contents out of the cell. -Vesicles are usually produced by the ER or Golgi Apparatus. -Hormones and neurotransmitters are released from the cell this way to their destinations.

Exocytosis

Exocytosis

Endocytosis -movement of materials into the cell -Endocytosis is the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane. -The pocket that results breaks loose from the outer portion of the cell membrane and forms a vesicle within the cytoplasm.

Endocytosis

Endocytosis -Large molecules, clumps of food, and even whole cells can be taken in by endocytosis. The vesicles can fuse with other vesicles containing digestive enzymes to break down the material. -Two examples of endocytosis are phagocytosis and pinocytosis.

Types of Endocytosis 1.Phagocytosis -the plasma membrane surrounds a large solid piece of material and brings it into the cell -In phagocytosis, extensions of cytoplasm surround a particle, package it in a vesicle, and engulf it. Engulfing material in this way requires a considerable amount of energy and, therefore, is a form of active transport. Ex>Amoebas use this method for taking in food.

Phagocytosis

Types of Endocytosis 2. Pinocytosis -In pinocytosis, cells take in liquid from the surrounding environment by forming tiny pockets along the cell membrane. -The pockets fill with liquid and pinch off to form vesicles within the cell.

Pinocytosis