Chapter 6 Interactions Between Cells And The Extracellular Environment

Just certain substances can go through

Facilitated diffusion Active transport through a membrane = requires ATP and can be primary and secondary

Diffusion (passive transport) Osmosis

Movement of solute along its concentration gradient (for simple and facilitated diffusion) - from regions of higher concentration to region of lower concentration

Movement of molecules from one location to another

Carrier-mediated Is assisted by another molecule

Movement in both direction but the net diffusion follows the concentration gradient until the gradient no longer exist = equalibrium

• Concentration difference • Membrane permeability • Temperature • Mass of the solute molecule • Surface area of the membrane • Medium through which solute must pass • Distance

Right through the membrane Non-polar substances diffuse easily Small polar molecules can diffuse easily

Channels are proteins Channels selectively allow certain substances to pass Can be open or gated Electrochemical gradient must exist

In order to maintain homeostasis and perform physiological functions

Osmosis

Channel proteins that allow water to pass through

Pressure require to prevent the flow of water - region with higher solute concentration

67% ICF 33% ECF: 20% blood plasma 80% ISF

Solvent + solute

The effect of a solution on osmotic movement of water

equal osmotic pressure inside and outside the cell

higher osmotic pressure in the external solution

lower osmotic pressure in the external solution

faciliated diffusion active transport endothelial transport endocytosis exocytosis

diffusion along the concentration gradient; assisted by another molecule passive transport - doesn´t require ATP

• Transport of solute against its concentration gradient 2. Requires ATP Primary transport - in membrane integrated pump Secondary transport - Ion concentration gradient is used as the energy source to move a second solute;

3 Na+ out and 2 K+ in = inside of cell more negative