Download The Cell in Action

Cellular Processes
ACTIVE AND PASSIVE TRANSPORT
“Close that window! Do you want to let in all the
bugs???
 How do you prevent
unwanted things from
coming through a
window?
 What part of a cell does
the same thing?
Moving Cellular Materials
 Cells take in food, oxygen
and other substances
from their environments.
 They also release waste
materials into their
environments.
 What organelle works as
a gatekeeper to let
materials in and out of a
cell?
Cellular Processes: Active and Passive Transport
 Found in both plant and animal cells, the exchange
of materials between a cell and its environment takes
place in the cell membrane.
Small particles cross the cell
membrane by way of
ACTIVE TRANSPORT
AND
PASSIVE TRANSPORT
Active Transport
Active Transport
 The movement of
substances across the
cell membrane that
requires using energy
by the cell
 Endocytosis and
Exocytosis


Low concentration to high
concentration
Riding a bike up a hill!
Endocytosis
 The cell membrane
surrounds a particle and
encloses this particle in a
vesicle and brings the
particle into the cell
 “Into”cytosis
 A hug
 https://www.youtube.co
m/watch?v=4gLtk8Yc1Z
c
 Endocytosis
Exocytosis
 The cell membrane
encloses a particle in the
cell in a vesicle, then
moves to the surface,
fuses with the cell
membrane, and expels
the particle.
 “Exit”cytosis
 Shoving someone
 https://www.youtube.co
m/watch?v=U9pvm_4bHg
Passive Transport
 The movement of
substances across the cell
membrane without using
energy by the cell.
 Diffusion and Osmosis


High to low concentration
Coasting down a hill on
your bike
Diffusion is
the movement
of particles
from areas of
high density to
areas of lower
density.
When the
molecules are
evenly spread,
equilibrium
occurs.
To understand how materials move
in and out of a cell, you need to
know about diffusion….
Diffusion
occurs in ….
 Example of a diffusion in a solid:
 You put a metal spoon into hot tea or
coffee and the entire spoon is hot after a
few minutes.
Solids
 Example of diffusion in a liquid:
 Adding a more dense liquid (such as
corn syrup) to water
Liquids
Gasses
 Example of diffusion in a gas:
 Someone puts on too much Axe Body
Spray after PE. You can smell him
before AND after you see him
Osmosis is a
special example
of diffusion.
It is the
diffusion of
water through
a semipermeable
membrane .
Semi = partial
Permeable= go
through, cross
Osmosis
Osmosis
 Osmosis is the process by which water enters our
tissues.
 All of our cells are surrounded by a membrane that
selectively allows anything the cell needs, but
prevents unwanted molecules from entering.
 https://www.youtube.com/watch?v=9QCxTf0QfTo
 This works because the
How osmosis
works
membrane contains lots of tiny
holes that will let anything
smaller through but obviously will
stop big molecules from entering
the cell.
 Water is small enough to get
through and enters by diffusion.
 Water will enter until equilibrium
is achieved.
Osmosis
 If cells weren’t surrounded by water that contains few
dissolved substances, the water in the cells would diffuse
out of them.

Plants=wilting
 However, the dissolved substances (solutes), such as
salts, sugars, and other substances in the water that
surrounds cells, prevent this from happening.

Equilibrium

https://www.youtube.com/watch?v=qotIWgL7zFs
Hypertonic, Hypotonic and Isotonic
 A hypertonic solution is a solution(mixture) containing
more solute than solvent

A lot of salt (solute) dissolved in water (solvent)
 A hypotonic solution is a solution containing more
solvent than solute

Purified water --- almost no solute dissolved in the solvent (water)
 An isotonic solution is a solution where the solute and
solvent are equally distributed.

Cells normally want to remain in an isotonic solution, where the
concentration of liquid inside is the same as the concentration of the
liquid outside of it.

Equilibrium!