A&P 1 Lab - Diffusion and Osmosis

plasma membrane

• separates the interior of the cell from its exterior

• regulates the passage of material in and out of the cell

• phospholipids

• structure/function → maintain homeostasis

phospholipids

• polar (hydrophilic) head region

  • polarity → membrane interact with water found in outside environment

• non polar (hydrophobic) tail region

  • face inwards → center of membrane impermeable to water

• arranged in two layers (phospholipid bilayer)

selectively permeable

some material (water and small non polar charged particles) can freely enter and leave the cell by passing between phospholipid molecules

proteins embedded in membrane

facilitate passage of other substances (polar molecules and ions) by creating channels, carriers and receptors

Passive transport

requires no energy because the movement of molecules follows a concentration gradient

active transport

utilizes energy in the form of ATP to move substances against a concentration gradient

solvent

substance (usually a liquid) that dissolves another substance to form a solution

solute

substance that dissolves in a liquid, gas or solid to form a solution

concentration gradient

the gradual difference in the concentration of a dissolved substance between two areas

equilibrium

state of balance or stability where opposing forces, influences or actions cancel each other out.

chem: a point where the forward reaction and reverse reaction happen at the same exact rate

bio: a stable internal state, often linked to homeostasis, where an organism regulates itself against outside changes

diffusion rate

how fast particles move from an area of high concentration to an area of low concentration

factors that affect the rate of diffusion

• molecular weight

• concentration gradient

• temperature

• membrane surface area

• permeability

diffusion

• the natural movement of a solute down a concentration gradient

• passive process

• spontaneously continues until equilibrium is achieved

diffusion examples in body

• gas exchange during respiration

• nutrients through blood vessels and into the cells of the body

cell survival

diffusion to quicklyl move nutrients and waste products across the plasma membrane

osmosis

• diffusion of water across a selectively permeable membrane

• water moves from an area of low solute concentration (high water concentration) to an area of high solute concentration (low water concentration) until equilibrium is reached

• when solute cannot move across a concentration gradient due to a barrier

hypotonic

• lyse → burst

• water rushing into a cell causing it to swell and burst

isotonic

• equal concentration to the cell

• no net gain or loss of water

hypertonic

• high solute concentration water leaves the cell

• crenate → shrink

• 
  

selectively permeable vs semi permeable

selectively permeable - regulates based on chemical properties and energy often using specialized transport proteins

semipermeable - regulates based on physical properties (size), blocks larger solutes