Interactions Between Cells and Their Environment

Body Fluids

67% water within cells, 33% in extracellular compartment

Tissue Fluid

80% of extracellular compartment, connects intracellular compartment with blood plasma

Active Transport

Requires ATP to move molecules from low to high concentration, often called pumps

Polarized Molecules

Charged ions that can pass through ion channels in the plasma membrane

Solution

Consists of solvent (water) and solute (molecules dissolved in water)

Osmosis

Diffusion of water across a membrane

Carrier-mediated

Facilitated diffusion (Passive), active transport (Active)

Secondary Active Transport

Energy acquired by moving sodium back into the cell, considered active transport

Extracellular Environment

Everything located outside the cells

Osmotic Pressure

Force surrounding a cell required to stop osmosis

Hypertonic

Higher osmolarity than plasma, water moves out of the cell causing shrinkage

Primary Active Transport

Hydrolysis of ATP directly responsible for carrier protein function

Hypotonic

Lower osmolarity than plasma, water moves into the cell causing swelling

Diffusion Rate

Measured by number of diffusing particles per unit of time

Passive Transport

Molecules move from higher to lower concentration without using energy

Active Transport

Molecules move from lower to higher concentration using ATP and carrier pumps

Tonicity

Osmolarity of a solution relative to the osmolarity of a cell

Countertransport or Antiport

Other molecule moved with sodium in the opposite direction

Cotransport or Symport

Other molecule moved with sodium in the same direction

Facilitated Diffusion

Passive transport powered by random movement of molecules, requires specific carrier proteins

Exocytosis

Process of releasing bulk molecules

Phagocytosis

Process of taking in bulk molecules

Endocytosis

Process of taking in bulk molecules (pintocytosis, receptor-mediated)

Na+/K+ Pump

Pumps 3 Na+ out of the cell and 2 K+ into the cell using ATP

Diffusion

Random motion of molecules from high to low concentration

Isotonic

Same osmolarity in both environments, no net movement of water

Plasma Membrane Permeability

Selective permeability of plasma membrane

Noncarrier-mediated (Passive)

Simple diffusion of lipid-soluble molecules, ions through channels, water (osmosis)

Diffusion Through the Plasma Membrane

Simple diffusion of nonpolar molecules, ions and water through channels, facilitated diffusion

Osmolarity

Unit of concentration that gives the total molarity of all solutes in a solution