Diffusion! Hot Water Cold Water

Equilibrium When the concentration of solute is equal throughout a solution.

Concentration Gradient A concentration gradient is a difference in concentration across a space. Going “down” the concentration gradient means moving from an area of high concentration to low High Concentration Low Concentration “down” the gradient 

How your cells get O2 and get rid of CO2

Diffusion: why flatworms are flat ! Since they have no respiratory system, planarians like this have a flattened body plan to allow for fast diffusion of oxygen and carbon dioxide to all their cells.

Osmosis: The diffusion of water across a semi-permeable membrane

Things always move from areas of higher concentration to lower concentration spontaneously (passively)

Effects of Osmosis can be serious for a cell! Hypotonic Hypertonic Isotonic Water out Of cell No net change Water into cell

SOLUTE SUCKS! Water moves to where there is more solute.

Hypo Hypo Hippo

How cells cope

Osmosis & Plants

Plant Cells & Osmosis Plasmolysis

Hypotonic environment Causes turgor pressure. Plant is healthy. Hypertonic environment Causes wilting. Plant is unhealthy. Plasmolysis

One Last Time

Facilitated Diffusion Membrane Proteins Solutes too big Or too polar To diffuse normally

Wrap Up / Key Ideas Diffusion: The movement of solute molecules down a concentration gradient. Small molecules (e.g. H2O, O2, CO2) cross the cell membrane via diffusion Osmosis: The diffusion of water across a semi-permeable membrane. Facilitated Diffusion: The diffusion of large and/or polar molecules across the cell membrane through proteins. Passive Transport: Movement of material into or out of a cell without the use of energy by the cell. Concentration gradient: A difference in solute concentration across a space.

You Need Energy to Go Up a Concentration Gradient! Fresh water out Salt water at high pressure Selective membrane prevents large solutes and ions from passing through. They become MORE concentrated

Passive Transport Definition: Type 1 Type 3 Type 2 DIFFUSION OSMOSIS The process of substances passing through the cell membrane WITHOUT ANY INPUT OF ENERGY BY THE CELL. Passive Transport Type 1 Type 3 Type 2 DIFFUSION OSMOSIS FACILITATED DIFFUSION Definition: Solute molecules move from an area of high concentra-tion to an area of low conc. Powered by the random motion of molecules. Key Term: Equilibrium Definition: Cell uses carrier proteins in membrane to allow the diffusion of molecules that can’t pass through membrane alone. Hypertonic: Solute conc. Bigr outside. H2O out Definition: Diffusion of water from an area of high H2O conc. (low solute conc.) to low (high solute conc.) Required for Ions (charged molecules) Isotonic: Solute conc. = Inside & out. No net H2O change. And Hypotonic: Solute conc. Lower outside. H2O in. Hypo-Hippo Large Molecules