Osmosis and Diffusion
Standard
 SB1. Students will analyze the nature of the
relationships between structures and functions in
living cells.
 d. Explain the impact of water on life processes (i.e.,
osmosis, diffusion)
Essential Question
How important is water?
Why is water important?
 Uses:
 Solvent
 Delivery mechanism
 Dissolves essential vitamins and nutrients
from food and delivers them to cells
 Used to flush out toxins, regulate body
temperature and help our metabolism.
How do Nutrients get in our cells?
 Cell membrane
 Selectively permeable
 chooses what goes in an out
 Water flows freely by
diffusion
 Two ways to get in
 Passive transport
 Active transport
 Passive Transport
 Two types
 Diffusion
 Facilitated diffusion
 Diffusion
 Go with the flow!
 Spread of molecules from high
concentrations to low
concentrations
 Osmosis
 Diffusion of water
 Salt draws water
towards it
 Facilitated diffusion
 For bigger molecules
 Carrier proteins help them pass
thru
Solution Gradients
Isotonic Solutions
If the concentration of solute (salt) is equal on both
sides
Hypotonic Solutions
there are less solute (salt) molecules outside the cell,
since salt sucks, water will move into the cell.
Hypertonic Solutions
there are more solute (salt) molecules outside the cell, which
causes the water to be sucked in that direction.
How do Nutrients get in our cells?
 Active Transport
 Go against the flow
 Move from low
concentration to high
concentration
 Requires energy (ATP)
 Proteins and pumps
 Move molecules across
the cell membrane
 Ex: Ca-calcium and Kpotassium
 Endocytosis
 Method of active transport
 Cell takes in large molecules
by engulfing them
 Ex: phagocytosis is how
amoebas eat
 Exocytosis
 Method of active transport
 Cell gets rid of stuff the way
 Ex: vesicles from the Golgi
apparatus