
*Remember* - regulates what moves in and
out of the cell

Cells transport various molecules ( water,
ions, salts, carbohydrates, lipids, proteins,
etc) into and out of the cell

All living cells exist in a liquid environment

Even in the desert, cells of cacti and
scorpions are bathed in liquid
•Most important features of cell membrane is to regulate
movement of molecules

Homeostatsis must be achieved for cells to survive

Raw materials must be taken in

Waste must be removed

The human body is composed of about 100
trillion cells

Cells range from 1 um – 100 um, with few
exceptions

Small cells can exchange substances more
rapidly than larger cells
 Materials travel the same speed, no matter the size
of cell
 Materials entering a larger cell take longer to reach
the center
Calculate the SA and V for the following cubes:
1 m x 1m x 1m
2m x 2m x 2m
3m x 3m x 3m

In phospholipids bilayer – various proteins
allow for materials to move in an out of cell

Different types of proteins play a vital role in
life of cell

Marker proteins – attracted to a carbohydrate
on cell surface
 Helps other cells recognize their cell type – liver
cell, heart cell, etc.

Receptor proteins – recognize and bind to
specific substances ( ex: signal molecules outside of
cell)

Transport proteins – aid in the movement of
substances into and out of the cell
Characteristics
Definition
Diffusion
Examples
Non-examples

Selective permeability – ability of the cell to
determine what enters and leaves
 Membrane is a highly fluid double layer called the
phospholipid bilayer

Why does the cell membrane have to be
selective?

Head = hydrophilic = which means?

Tails = hydrophobic = which means?

Marker proteins = identify cells

Transport proteins = transport large particles
across membrane

Receptor proteins = capture signal molecules
and cause a change in cell behavior

Describe why an entire room can smell like a
candle burning even the smell was all
contained in a jar when purchased ?

In a solution, particles move constantly

Particles move from areas of high
concentrations  low concentrations =
Diffusion

Passive transport – materials move down
concentration gradient without the use of energy
2 Types:
Unassisted: ( diffusion)
Protein assisted: ( facilitated diffusion)


occurs only when materials are transported
across the membrane WITH energy
Active Transport
- Requires energy
-
-
The energy is
called ATP
(adenine
triphosphate )

Diffusion Simulation
 In the space provided: create a higher concentration of circle
in area 1 and a lower concentration in area 2. Draw an arrow
indicating how the molecules.
 Occurs until concentrations are equal on both sides
a.) State of equality is called equilibrium - That is
what your cells want

when materials are passing in each direction,
but not enough to upset the balance

diffusion of H2O molecules across the cell
membrane

Aquaporins – channels specific to water

---that just means more SALT than WATER
MOLECULES!

Hypo –

Hyper –

Iso -
a solution with a higher concentration of
dissolved particles than the inside of the cell
- AKA = LESS WATER in cell


a solution with a lower concentration of
dissolved particles than inside the cell – AKA
more water!!

a solution with the same concentration of
dissolved particles as the inside of the cell –
AKA same concentration of water

Tonic – dissolved particles, not the water
Type 1:
-Cell remains
normal size
- Equal amount of
water inside and
outside of cell

Type 2
-Cell shrinks
More water
outside of cell
than inside
-

Type 3:
-Cell Swells
- More water
inside cell
than in
solution
Diffusion
-Movement of
materials
(proteins, ATP,
carbohydrates,
etc)
-Two types:
Unassisted and
Assisted
(Facilitated
Diffusion)
Osmosis
-Movement of
WATER
-Still considered a
type of diffusion
but just with
WATER
Osmosis