Membrane Transport There are many molecules on (peripheral), within (trans), and inside (intracellular) the cell membranes. These all aid in getting necessary molecules into and out of the cell. They also play a role in cell to cell communication. Most are proteins with or without carbohydrates or lipids attached

These structures make membrane Selectively permeable : The cell membrane acts like a wall around the cell but it does have pores that act like doors (see page 97) Some molecules are brought into the cell and it TAKES energy to do this. ACTIVE TRANSPORT Some molecules can flow through without costing the cell any energy. PASSIVE TRANSPORT

Passive Transport & examples Osmosis: The movement of water from High to low concentrations.Aquaporins for diffusion of water, Filtration: process that is driven by hydrostatic pressure (pressure from water) it drives particles in and out of cell Blood pressure forces fluid through gaps in capillary walls Water, salts, nutrients are transferred from blood to tissues. Diffusion of molecules from High to Low conc O 2 from the air to blood Facilitated diffusion: Uses carrier proteins but does not use energy.

Active Transport and examples Carrier Mediated Transport: TAKES energy to do this!!! Usually in the form of ATP This can pump a molecule AGAINST the gradient!!! Sodium/Potassium pump 3 Na out, 2K in Half your daily calories are used for this alone!!!!!! Why so important?? THIS PUMP: 1. Regulates cell volume 2. Provides secondary active transport via generating electricity to pump other things..kidney function or Sodium Glucose transport 3. Heat production(thyroid stimulates na/k pump production..raising heat 4. Maintenance of membrane potential(Imp. In nerve function)

Vesicular Transport: TAKES energy Endocytosis, exocytosis, phagocytosis, pinocytosis

Most important Pumps Sodium-potassium pumps(Na-K): this pump burns one ATP to push 3 Na + out of cell and 2 K + into the cell Sodium-glucose transport protein(SGLT): binds Na + and glucose outside of cell. Uses ATP and Na + gradient to push glucose into cell ATP synthetase: As Na + enters the cell ATP is made from ADP and P +

Diffusion Diffusion: the process of particles, nutrients, molecules, salts moving from high to low concentration to achieve a balance Concentration Gradient: when the concentration of a particle is higher in one area then another

Osmolality Osmolality is the amount of solute (stuff) in a solution. HYPO-tonic solution= has a LOW concentration of solute compared to that inside the cell High conc of water HYPER-tonic solution= has a HIGH concentration of solute compared to that inside the cell Low conc of water ISO-tonic solution= has equal conc of water is same as the cell.

Osmosis: the process of water moving from low solute(High Water) to high solute (Low Water)through a selectively permeable membrane Osmotic Pressure: the force that stops osmosis due to filtration.(the flow of water across the membrane due to it’s own weight = the flow of water due to osmosis Movement of water