Agenda 9/29
 Cell
Organelle QUIZ
 Pass back biomolecule quiz
– Discuss corrections and retakes for
those who failed to get to a 70 possibly.
 Notes:
The Cell Membrane and
Transport.
 Homework over the cell membrane
due next class.
The Cell Membrane
and Transport
Objective
 Identify,
investigate and explain
cellular processes
– Transport of molecules across the cell
membrane
Three names
 Phospholipid
bi-layer
 Cell membrane
 Plasma membrane
What does the cell membrane do?
Regulates what enters & leaves the
cell
 Provides protection
 Provides support


GOAL: HOMEOSTASIS
What does the cell membrane look
like?
How does the cell membrane
regulate what enters and leaves
the cell?

Semi-permeable – Lets some things in and
out of the cell, but not all things

Passive Transport – does NOT require energy

Active Transport – does require energy (ATP)
Passive Transport - Diffusion
Movement of particles (food) from
HIGH concentration to LOW
 Goal = equilibrium or balance of
molecules both inside & outside the
cell (HOMEOSTASIS)
 Molecules flow through the lipid bi
layer

What does diffusion look like?
Passive Transport – Facilitated
Diffusion
 For
molecules that are too big to
diffuse directly through the cell
membrane
What is Facilitated Diffusion?
 Membrane
proteins will allow some
molecules (like sugar) in or out of
the cell that are too big to easily
diffuse through the cell membrane.
 Still moving from a high
concentration to a low
concentration…
 NO ENERGY REQUIRED!
Every time a cell’s environment
changes…
Water is moving from a higher
concentration to a lower
concentration.
The name of this process is…
Osmosis
 The
diffusion of water.
 Just like the iodine diffused across
the dialysis membrane, water moved
across the egg’s membrane.
Objective
 Identify,
investigate and explain
cellular processes
– Transport of molecules across the cell
membrane
Active Transport
 Movement
across the cell membrane
from a LOW concentration to a HIGH
concentration.
 Requires energy (ATP)
 One type uses membrane proteins to
push large molecules across the semi
– permeable cell membrane.
What does Active Transport look
like?
Image from “The Virtual Cell Textbook”
http://www.ibiblio.org/virtualcell/textbook/chapter3/cmf1c.htm
Cell Transport: Moving Across the Cell
Membrane
Endocytosis, Exocytosis
endo: inside
Exo: outside
Cyto: cell

Help for the large: Both designed
to move a large substance
or a large amount of substance.

The cell membrane is flexible and can change shape to form a
pocket.

Both require energy (ATP)
Cell Transport: Moving Across the Cell
Membrane
Endocytosis
 The membrane folds inward, surrounds the material, and
then fuses together.
 The bubble created with
materials is called a vesicle.
 Materials are usually
transported to the lysosome.
Exocytosis
 Vesicle transported to cytoplasm, vesicle fuses with cell
membrane, and then releases its contents outside the cell
Objective
 Identify,
investigate and explain
cellular processes
– Transport of molecules across the cell
membrane
Osmosis and Tonicity

Tonicity refers to the total solute
concentration of the solution
outside the cell.
What are the three types of tonicity?
1)
2)
3)
Isotonic - equal
Hypotonic – lower; under
Hypertonic – higher, over
Isotonic

concentration of water (solvent) outside the cell
is the same as the concentration inside the cell.
What will happen to a cell placed in an
Isotonic solution?
 The
cell will have no net movement
of water and will stay the same size.
 Ex. Blood plasma has high
concentration of albumin molecules
to make it isotonic to tissues.
Hypotonic

concentration of water (solvent) outside the cell is
higher than the concentration inside the cell.
What will happen to a cell
placed in a Hypotonic solution?
 The
cell will gain water and swell.
 If
the cell bursts, then we call this
lysis. (Red blood cells = hemolysis)
 In
plant cells with rigid cell walls, this
creates turgor pressure.
Hypertonic

concentration of water (solvent) outside the
cell is lower than the concentration inside
the cell.
What will happen to a cell
placed in a Hypertonic solution?
 The
 In
cell will lose water and shrink.
plant cells, the central vacuole will
shrink and the plasma membrane
will pull away from the cell wall
causing the cytoplasm to shrink
called plasmolysis.
Review Tonicity



What will happen to a red blood cell in a hypertonic
solution?
What will happen to a red blood cell in an isotonic
solution?
What will happen to a red blood cell in a hypotonic
solution?
Eggs-periment
 The
egg without its shell is a cell
with a semi-permeable
membrane
Cell in Distilled Water
 What
will happen and WHY????
Cell in Corn Syrup
 What
will happen and WHY????
Objective
 Identify,
investigate and explain
cellular processes
– Transport of molecules across the cell
membrane