Sept 22nd: Osmolarity, Tonicity, and Membrane Carriers

What two things do we need to know to calc. a fluid’s osmolarity?

• Conc. of solution

• Type of Substance

What is tonicity

ability of a solution to cause osmosis across the membrane

Isotonic has the — osmolarity as body fluids

same

Hypertonic has — osmolarity than body fluids

more

Hypotonic has — osmolarity than body fluids

less

membrane channel vs facilitated diff.

membrane channel

→small, hydrophilic

→ fairly selective

no conformational change

facilitated diff.

→ large, hydrophilic

→ VERY selective

→ conformational change

What is Endocytosis

engulfing a substance from outside the cell

What is exocytosis

process of vesicles fusing with the plasma membrane to release contents outside the cell

What is local communication? What do they use

• communication w/ nearby cells via direct communication

• cells use gap junctions are made up using connexons

What is paracrine signaling

cell releases chemical messenger that activates nearby cells

What is Autocrine signaling

cell releases chemical messenger that activates its own receptor and stimulates itself