Ch. 5 Cells

Plasma membrane

acts as barrier, regulates movement in/out of sale, cell communication

passive transport

no energy required, down concentration gradient,

active transport

requires energy, up concentration gradient

diffusion

• movement of ions/molecules using kinetic energy

• influenced by temp., and steepness

• molecules move through phospholipid bilayer (small, nonpolar)

facilitated diffusion

passive transport using membrane proteins, used for charged or polar molecules

channel-mediated diffusion

• ions move through protein channels, specific to ion type

• leak channels always open

• gated channel opes to stimulus

osmosis

Passive movement of WATER through semipermeable membrane

water transport methods

• Between phospholipids

• Through aquaporins (water channels)

permeable solutes

• pass through membrane

• oxygen for example

non-permeable solutes

• can’t pass through membrane

• ions, glucose, proteins

osmotic pressure

Pressure from water movement across membrane

hydrostatic pressure

pressure fluid exerts on container walls

tonicity

Ability of solution to change cell volume by osmosis

isotonic

equal solution inside/outside cell

hypotonic

lower solute outside the cell

hypertonic

high solute outside cell

sodium-potassium pump

pumps Na in and K out

secondary active transport

• Uses energy from another substance moving down gradient

• Usually depends on Na⁺ movement

vesicular transport

bulk transport using vesicles, requires energy

phagocytosis

engulfs large particles

pinocytosis

uptake of fluid drops

Resting Membrane Potential (RMP)

• Electrochemical gradient across membrane

• Essential for muscle and nerve function

conditions for RMP

unequal ion and charge distribution