TEAS OSMOSIS, DIFFUSION, ACTIVE TRANSPORT

what is diffusion?

the passive movement of molecules from an area of HIGH concentration to an area of LOW concentration until equilibrium is reached

ex: oxygen moving into cells

characteristics of diffusion

• Passive process (does NOT require energy)

• Driven by the concentration gradient

• Occurs in gases and liquids

what are the two types of diffusion?

simple and facilitated diffusion

what is simple diffusion?

molecules move directly through the lipid bilayer (ex: oxygen or carbon dioxide moving in / out of cells)

what is facilitated diffusion?

molecules move through a protein channel / carrier (ex: glucose transport into cells via GLUT transporters)

what is osmosis?

the diffusion of water across a selectively permeable membrane from a region of LOW solute concentration to HIGH solute concentration

ex: water entering RBC’s

characteristics of osmosis?

• Passive process: no ATP required

• Water moves to balance solute concentrations

• Depends on tonicity of the solution

what are the 3 tonicity solutions?

isotonic, hypotonic, and hypertonic solution

what is isotonic solution?

 equal solute concentration inside and outside cell → water moves equally → cell stays the same

what is hypotonic solution?

lower solute outside → water moves into cell → cell swells, may burst (lysis)

what is hypertonic solution?

higher solution outside → water moves out of cell → cell shrinks (crenation)

what is active transport?

the movement of molecules across a cell membrane against their concentration gradient, requiring energy (ATP)

characteristics of active transport?

• Moves from LOW to HIGH concentration (opposite of diffusion)

• Requires carrier proteins / pumps

• Important for maintaining ion gradients and cell function

what is an important example of active transport?

the Sodium-Potassium pump (Na+ / K+)

how does the sodium-potassium pump maintain the correct balance of sodium and potassium inside and outside the cell?

1. Pumping 3 sodium ions (Na+) OUT of the cell

2. Pumping 2 potassium ions (K+) INTO the cell

3. Using 1 molecule of ATP to power the exchange

what is filtration?

the movement of water and solutes across a membrane due to hydrostatic pressure (force of fluid pushing)

ex:  blood pressure pushes water and small solutes into the nephron → kidney filtration

• Capillary exchange in tissues: nutrients and waste pass in and out of cells

what are the characteristics of filtration?

• Passive process: no ATP required

• Often occurs in capillaries and kidneys

• Driven by pressure gradients rather than concentration gradients