Transcript provide support and protection for the cell.

Continued 7-3 notes
Cell Membrane
• Regulates what enters and leaves
• Flexible structure
• Strong barrier
Lipid Bi- layer
• Water, oxygen, and carbon dioxide
flow freely through the lipid bi-layer
• Besides lipids the cell membrane also
contains
– Protein molecules: form channels and
pumps to help move material across the
cell membrane
– Carbohydrate molecules attached to
proteins…. act like ID cards, so cells can
identify each other
Cell Wall
• porous enough to allow water, oxygen,
carbon dioxide, and certain other
substances to pass through easily
• provide support and protection for
the cell.
• composed mostly of cellulose, a tough
carbohydrate fiber
Concentration
• The concentration of a solution is the
mass of solute in a given volume of
solution, or mass/volume.
• In this lab you need to make a
solution that is 90% water and 10%
sugar, and another that is 80% water
and 20% sugar.
• How will you do that?
Diffusion
• In a solution, particles move
constantly.
• They collide with one another and
tend to spread out randomly.
• The particles move from where it is
too crowded to an area where there
is more room… this is called diffusion
• EZ pass analogy:
Diffusion
– Tolls are up to $6 to
cross the tunnels into
NYC
– They are going to
raise it even higher,
during rush hour…
– If they don’t need
the money then why
would they do that?
Equilibrium
• The particles keep moving and
eventually both areas are
balanced….this is called equilibrium.
• Particles will continue to move back
and forth but because numbers are
equal, no change in concentration
Facilitated Diffusion
• Substances, that are too
large or have too strong of
a charge can still get across
the cell membrane• How? Proteins act as
tunnels or channels
• This is still diffusion
though, and does not
require the cell’s energy-
Example
• Red blood cells: have a protein
channel for glucose.
• Only glucose can pass through this
channel, and it can move through in
either direction.
• 100’s of different protein channels
have been found that allow particular
substances to cross different
membranes.
Active Transport
• Sometimes cells must move against
the concentration gradient– From areas of low concentration to
areas of high
– This requires the cell’s energy
– Done by transport proteins called
“pumps”
– Larger molecules can also be
transported across the membrane
by endocytosis and exocytosis
Active Transport Lab
• Background Information: Congo red
is a biological dye, that diffuses
easily into the cell, like water
• This diffusion does not require
energy
• You are using yeast cells, that I woke
up by adding water and sugar- they
are currently alive …
Lab Results
1. Macroscopically… which sample is darker?
2. Microscopically…. Which cells have absorbed
the dye?
3. Are the (not boiled) yeast cells alive?
4. Are the boiled yeast cells alive?
5. Which cells moved the dye via active
transport?
6. Of the cells that moved the dye…Did they
move the dye in or out?
7. If active transport was used to move the dye,
out via what mechanism did the dye get in?
Endocytosis
• Endocytosis is the process of taking material
into the cell by means of infoldings, or pockets,
of the cell membrane. The pocket that results
breaks loose from the outer portion of the cell
membrane and forms a vacuole within the
cytoplasm. Large molecules, clumps of food, and
even whole cells can be taken up in this way. Two
examples of endocytosis are phagocytosis (fagoh-sy-TOH-sis) and pinocytosis.
Phagocytosis
• Phagocytosis means “cell eating.” In
phagocytosis, extensions of cytoplasm
surround a particle and package it within a
food vacuole. The cell then engulfs it.
Amoebas use this method of taking in
food. Engulfing material in this way
requires a considerable amount of energy
and, therefore, is correctly considered a
form of active transport.
PINOCYTOSIS/
EXOCYTOSIS
• In a process similar to endocytosis, many
cells take up liquid from the surrounding
environment. Tiny pockets form along the
cell membrane, fill with liquid, and pinch off
to form vacuoles within the cell. This
process is known as pinocytosis.
• Many cells also release large amounts of
material from the cell, a process known as
exocytosis (ek-soh-sy-TOH-sis). During
exocytosis, the membrane of the vacuole
surrounding the material fuses with