Cells and Their Environment
Chapter 4
p 74-84
Homeostasis
• A biological balance
• Cells, tissues, organs, and organisms must
maintain a balance.
• Cells do so by controlling and regulating what gets
into and out of the cell.
Membrane Structure & Function
Transport
• Passive
• Active
• Transport that does
not require chemical
energy to occur
• ie: diffusion and
osmosis
• The movement of
any substance across
a cell membrane with
the use of chemical
energy
– ie: Na+/K+ pump
DIFFUSION
• Process by which
molecules spread from an
area of high concentration
to an area of low
concentration
• Concentration gradient:
a difference in the
concentration of a
substance
***Molecules are in
constant
motion
Osmosis
• Diffusion of water
through a membrane
from an area of high
concentration to an
area of low
concentration.
http://highered.mcgrawhill.com/sites/0072495855/student_vie
w0/chapter2/animation__how_osmosis
_works.html
HYPOTONIC
• Concentration of
solute molecules in
the environment
outside of the cell is
lower than that in
the cell.
• Water moves in
Red blood cell
Hypertonic
• Concentration of
solute molecules
outside the cell is
greater than that in the
cell
• Water moves out
Isotonic
Concentration of solute
molecules outside cell
and inside are equal.
**equilibrium
Think about it…
What happened if you eat salty foods?
Why do you gargle warm salt water if you
have a sore throat?
Why do athletes need to have electrolytes in
their drinks?
Grass wilts if you add too much
fertilizer…WHY?
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html
Requires Energy:
ex.: thyroid gland concentrates Iodine
glucose is completely absorbed by digestive
tract
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/a
nimation__phagocytosis.html
Exocytosis
• Ex. LDL cholesterol (bad cholesterol)
http://highered.mcgrawhill.com/olc/dl/120068/bio02.swf