Transcript Cell Transport - Conackamack Middle School

Step into my elevator!
• When the elevator was
crowded, what did all the
people in the elevator want
to do? WHY?
• When one more person was
forced into the already
crowded elevator did they
find it was easy or
difficult to get in? WHY?
Just like people entering or exiting
an elevator, molecules move into or
out of cells. Sometimes easily,
sometimes with great effort.
Cell Transport
Pages 80-85
• There are two ways that molecules can
move through a cell membrane
1. Passive Transport
ex. Osmosis
ex. Diffusion
2.Active Transport
ex. Transport Proteins
ex. Engulfing
• Diffusion is the main method that small
molecules move across a membrane
• It’s the process by which molecules move
from an area of higher concentration to an
area of lower concentration.
• Example – perfume bottle
What Does Concentration Mean?
• Taste the liquid in the three cups.
• Which cup has a lower concentration of water in it?
(higher concentration of lemonade mix)?
• Which cup has a higher concentration of water
molecules in it (lower concentration of lemonade
mix)?
More
mix, less
water
molecules
Less mix,
more
water
molecules
Diffusion Across A Cell Membrane
OUTSIDE OF CELL
Cell
Membrane
INSIDE OF CELL
How do most small molecules move
across the cell membrane?
• The cell membrane that
surrounds the cell is
selectively permeable.
– Some substances can pass
through the membrane
while others cannot Ex.
the balloon with vanilla
• Cells must get needed
molecules in and expel
waste
Substances move in and out
through pores.
What causes Diffusion?
• Molecules are always
moving and bumping into
each other.
• The more molecules
there are the more
collisions there will be.
• Collisions will cause the
molecules to push away
from each other until,
over time, they will
spread out evenly.
– They meet a point of
equilibrium.
OSMOSIS
• Like oxygen, water passes easily into
and out of cells.
• Osmosis is the diffusion of water
molecule.
– Water moves from an area of higher
concentration to an area of lower
concentration.
• Cells cannot function without water,
so most cell processes depend on
osmosis.
Effects of Osmosis
Normal blood cell
at equilibrium.
Concentration of
water inside the
cell is the same
as outside.
Hypertonic blood
cell.
Concentration of
water inside the
cell is higher
than the
outside.Water
flows out of the
cell, shrinking it.
Hypotonic blood
cell.
Concentration of
water inside the
cell is lower than
the outside.
Water flows in
the cell, swelling
it.
ACTIVE TRANSPORT
• Diffusion and osmosis are forms of passive
transport.
– Movement of molecules without using cellular
energy
• What if cells need to take in molecules
that are found in a higher concentration?
– The cell has to move molecules in the opposite
direction.
– Cells can do this, but they need to use their own
energy
• Active transport is the movement of
molecules using cellular energy.
Methods of Active
Transport
1. Transport proteins –
proteins that pick up
molecules outside the
cell and carry them in
using energy. (ex.
calcium, potassium,
sodium)
2. Engulfing – Cell
membrane surrounds
the particle and forms
a vacuole around it.
The cell uses energy in
this process.
In PASSIVE transport molecules
(in this case, sugar) will move
from a more concentrated area
and will spread out to a less
concentrated area throughout
the beaker filled with water.
Molecules NATURALLY want to
move this way, so it does NOT
require energy to happen.
In ACTIVE transport
molecules will move from a
less concentrated area and
will be taken into a more
concentrated area. The cells
need lots of energy in order
to do this.