Active Transport, Exocytosis and Endocytosis Chapter 3, Section 5 Of your textbook

Active Transport Moves substances AGAINST their concentration gradient From areas of low concentration to areas of high concentration From areas of low concentration to areas of high concentration

Active Transport Needs Energy Active transport is an “uphill” process (low  hi) – the opposite of passive transport Therefore, active transport requires energy from ATP

Active Transport & Membrane Proteins Active transport uses transport proteins, often called pumps, to move substances across the membrane These membrane proteins are integral proteins – they extend all the way through the membrane These membrane proteins are integral proteins – they extend all the way through the membrane They use ATP to pump molecules / ions against their concentration gradients They use ATP to pump molecules / ions against their concentration gradients

Transport Proteins Most transport proteins change shape when they bond with the target molecule(s). Some bond to only one type of molecule (= uniport) and move that molecule in one direction (animation) animation

Proton Pump The proton pump is an example of a uniport transport protein. This pump is found in the membranes of certain organelles. It moves protons (H+) into the organelle.

Transport Proteins Others bond to two types of molecules May move the molecules in the same direction (= symport) May move the molecules in the same direction (= symport) May move the molecules in opposite directions (= antiport) May move the molecules in opposite directions (= antiport) Symport animationanimation Antiport animationanimation

Sodium-Potassium Pump Sodium-Potassium Pump click on title for animation Sodium-Potassium Pump An example of an antiport transport protein. Moves three sodium ions (Na+) out of the cell for every two potassium ions (K+) it moves in Important for re-establishing “normal” conditions after a nerve impulse / action potential

Endocytosis Endocytosis click on title for animation on Endo/Exocytosis Endocytosis A method for bringing large molecules into a cell Molecules are engulfed by the cell membrane. A pocket is made around the substance to be taken in A pocket is made around the substance to be taken in The pocket breaks off inside the cell and forms a vesicle The pocket breaks off inside the cell and forms a vesicle The vesicle fuses with a lysosome or other organelle The vesicle fuses with a lysosome or other organelle Requires energy from ATP

Phagocytosis Phagocytosis click on title for animation Phagocytosis Type of endocytosis The cell membrane engulfs larger, solid particles Literally means “cell eating” Literally means “cell eating” Example: Amoeba take in / engulf their food through phagocytosis.

Phagocytosis In the human immune system, some white blood cells (called macrophages) engulf and destroy foreign material, such as bacteria, through phagocytosis

Pinocytosis Type of endocytosis The cell takes in fluid (which may also contain some dissolved substances) Literally means “cell-drinking” Literally means “cell-drinking” Example: Fluid may cross the membrane of a blood vessel through pinocytosis.

Exocytosis The opposite of endocytosis Substances are released by a cell through a vesicle that carries the unwanted substance and fuses with the membrane Once it fuses with the membrane, the vesicle releases the substance outside the cell

Exocytosis Neurotransmitters – chemical signals in your nervous system - are released from nerve cell to nerve cell in this manner When the Golgi apparatus modifies proteins and sends them out of the cell, it uses exocytosis.