Diffusion and Osmosis

The main function of the cell membrane is to:

maintain homeostasis within the cell by controlling what enters and exits

Homeostasis

a state of relatively constant internal physical and chemical conditions

If no energy is used by the cell in transporting materials it is called

passive transport

Molecules in living organisms are in _______ motion.

constant

Diffusion

A type of passive transport where molecules move from an area of higher concentration to lower concentration

The difference in concentrations of a substance across an area

gradient

When does a space reach equilibrium?

When the concentration of a substance is the same on both sides of a cell membrane

Define permeable

allowing liquids or gases to pass through

selectively permeable

the ability to choose what goes in and out of a material

osmosis

diffusion of water across a semi permeable membrane, moving from high to low water concentration

One way osmosis is different from diffusion

molecule

list one way osmosis is the same as diffusion

molecules move from higher to lower concentration

what is a solution composed of?

two or more compounds

The NET direction of osmosis depends on the relative concentrations of ______ on the two sides of the membrane

solute

hypotonic

low concentration of solute relative to water

hypertonic

high concentration of solute relative to water

isotonic

equal concentration of solute to water

hypo, hyper, and iso refer to the relative _____ concentration of two solutions

solute

how do unicellular organisms rid themselves of excess water that enters via osmosis?

they use contractile vacuoles to pump out fluid

when water diffuses into a plant cell and builds up firm pressure, that is called

osmotic pressure

in a hypertonic environment, water leaves the cell through osmosis. What happens to the cell?

the cell shrinks and shrivels up

A cell that cannot compensate for solute concentration changes

Red blood cells can’t compensate for solute concentration changes, and therefore may burst or shrink

Cytolysis

the destruction or breaking down of cells

Passive or Active: Osmosis and diffusion

Passive

Facilitated Diffusion

when protein channels assist in diffusion of a material that could not pass through the cell membrane

is facilitated diffusion active or passive?

passive because it doesn’t require energy

movement from lower to higher concentration

active transport

three types of active transport

protein pumps, endocytosis and exocytosis

Endocytosis

movement of materials to the inside of the cell

Exocytosid

release of materials from the cell

Pinocytosis vs Phagocytosis

Both are endocytosis, but phago deals with large solids while pino deals with small liquids

Two properties of facilitated diffusion

1- involves transfer proteins

2- specificity to certain molecules