•Sodium-Potassium pump

•Types of molecules transport

•Endocytosis & Exocytosis

• Transport proteins within the membrane must use energy (ATP) to move substances either to the inside or outside of the membrane.

• Active transport requires the cell to spend energy, usually in the form of ATP.

• Examples include transport of large molecules (non-lipid soluble) and the sodium-potassium pump.

WHAT IS ACTIVE TRANSPORT?

• Transport of molecules against a concentration gradient (from regions of low concentration to regions of high concentration) with the aid of proteins in the cell membrane and energy from ATP.

• The mechanism that uses ATP energy to reset the sodium and potassium ions after transmission of a nerve impulse.

SODIUM-POTASIUM PUMP:

• The sodium-potassium pump must break ATP down into ADP in order to pump sodium three ions outside the cell, while it pumps two potassium ions into the cell.

• The ATP phosphorylates (adds a phosphate to) the membrane protein as it binds to the sodium and breaks down, and it dephosphorylates the protein as it binds with the potassium.

• Cellular respiration must occur to add the phosphate back to ADP, thus restoring the ATP.

• In the case of active transport, the proteins are having to move against the concentration gradient.

• For example the sodium-potassium pump in nerve cells. Na+ is maintained at low concentrations inside the cell and K+ is at higher concentrations.

• The reverse is the case on the outside of the cell.

• When a nerve message is propagated, the ions pass across the membrane, thus sending the message.

• After the message has passed, the ions must be actively transported back to their "starting positions" across the membrane.

• To reset them you must pick each one up, again at an energy cost.

• Up to one-third of the ATP used by a resting animal is used to reset the Na-K pump.

Uniport transports one solute at a time.

Symport transports the solute and a cotransported solute at the same time in the same direction.

Antiport transports the solute in (or out) and the co-transported solute the opposite direction.

One goes in the other goes out or vice-versa.

• An active process of taking in something through a cell membrane, which uses energy (ATP).

• Is the case when a molecule causes the cell membrane to bulge inward, forming a vesicle.

• The opposite of endocytosis, is also an active process.

• Exocytosis moves material to the outside.  • A vesicle fuses with the plasma membrane and

discharges its contents outside.  • This allows cells to secrete molecules.• The incorporation of materials from outside the cell

by the formation of vesicles in the plasma membrane.

• The vesicles surround the material so the cell can engulf it.

• The fusion of vesicles to the plasma membrane adds membrane to the cell surface.

Phagocytosis refers to the process of

engulfing large particles.

• A vacuole is formed that contains the material that has been engulfed.

• Known as cell eating.

• Phagocytosis is the cellular process of engulfing solid particles by the cell membrane to form an internal phagosome, or "food vacuole.“

• The phagosome is usually delivered to the lysosome, an organelle involved in the breakdown of cellular components, which fuses with the phagosome.

• The contents are subsequently degraded and either released extracellularly via exocytosis, or released intracellularly to undergo further processing.

• Phagocytosis is involved in the acquisition of nutrients for some cells, and in the immune system it is a major mechanism used to remove pathogens and cell debris.

• Bacteria, dead tissue cells, and small mineral particles are all examples of objects that may be phagocytosed.

• Phagocytosis is a specific form of endocytosis involving the vesicular internalization of solid particles, such as bacteria.

• As in phagocytosis, a vesicle is formed which contains the molecules that were brought into the cell.

• Vacuoles and vesicles produced by phagocytosis and pinocytosis can fuse with lysosomes (lysosomes are vesicles that contain digestive enzymes).

• Phagocytosis and pinocytosis remove membrane from cell surface to form vacuoles that contain the engulfed material.

• Cell drinking. • Pinocytosis refers to engulfing macromolecules.• Occur when the external fluid is engulfed.

• In the process of pinocytosis the plasma membrane froms an invagination.

• What ever substance is found within the area of invagination is brought into the cell.

• In general this material will be dissolved in water and thus this process is also refered to as "cellular drinking" to indicate that liquids and material dissolved in liquids are ingested by the cell.

• This is opposed to the ingestion of large particulate material like bacteria or other cells or cell debris.

Proton pumps operate both within the inner mitochondrial membranes in the electron transport system of cellular respiration, and in chloroplast membranes during

photosynthesis.

In cotransport, one process (the Na-K pump), is coupled with movement of a

molecule of sugar (glucose) out of the cell, while allowing sodium to enter through the

protein.

• Receptors help to attach molecules to the membrane before taking them in.

• Macromolecules bind to receptors on the surface of the cell.

• Receptors with bound macromolecules aggregate in one area and are brought into the cell by endocytosis.

• The vesicle containing the macromolecules can release the macromolecules into the cell directly or they can be processed by chemicals contained within lysosomes after fusing with the lysosomes.

• The vesicle (and receptors) then returns to the cell surface.

• Receptor-mediated endocytosis occurs when the material to be transported binds to certain specific molecules in the membrane.

• Examples include the transport of insulin and cholesterol into animal cells.