Download Cell Membrane and Cell Wall

Cell Membrane and Cell Wall:
Structure and Function
What are you going to learn?
The molecular arrangement of the cell
membrane.
2. Components of the cell wall.
3. Understand how molecules pass through the cell
membrane.
4. Be able to determine what molecules can and
cannot pass through the membrane.
1.
Cell Membrane
1. Cell membranes are present in ALL cells. They
control the movement of substances into and out of
the cell.
2. A biological membrane, also called the plasma
membrane, that surrounds a cell and selectively
controls which substances can enter or leave the cell.
Components of the Cell Membrane
 The cell membrane is
made up a many
phospholipids.
 The phosphate head is
hydrophilic.
 The fatty lipid tails are
hydrophobic.
Activity
You will be given a handful of phospholipids. Knowing
that the body is approximately 70% water. Water is in
cells and between cells. How do you think the
membrane is arranged?
Use the phospholipids and arrange how you think it
might look.
Cell Membrane
Cell Membrane
 Regulates what enters and leaves the cell and also
provides protection and support
 Composition is a lipid bilayer, which gives it a
flexible structure and forms a strong barrier
between the cell and it’s surroundings.
 Phospholipids are arranged in this way because the
tails are hydrophobic (don’t like water)
Cell Membrane - Proteins
 In addition to lipids most cell membranes contain
proteins that are embedded, they form channels or
pumps that help materials across the membrane.
Cell Membrane - Carbohydrates
 Carbohydrates are attached to the proteins, many act
like chemical identification cards, allowing
individual cells to identify one another.
Cell Membrane
 There are so many molecules in the cell membrane
scientist call it a “mosaic” of different molecules.
(mosaic = a large structure made of many small structures)
Fluid Mosaic Model
Cell Wall
 The main function of the cell wall is to provide
support and protection for the cell.
 Made from firm fibers of complex carbohydrates
called cellulose.
 Humans can’t break cellulose down, that is why it is
considered roughage.
How do things cross cell boundaries?
Solutions
Solution: a liquid mixture in which the minor
component (the solute) is uniformly distributed
within the major component (the solvent)
ex. Sea water, soda, lemonade
Solute: What is being dissolved
ex. Salt, Sugar, lemon juice
Solvent: What is doing the dissolving
ex. Water
Passive Transport
Diffusion
 Movement of particles from an area of high
concentration to an area of low
concentration=diffusion (a type of passive transport)
Passive Transport
Diffusion
 Solute particle move toward equilibrium.
Passive Transport
Passive
 Because diffusion depends upon random particle
movements, substances diffuse across membranes
without needing ENERGY!!
Diffusion of Particles
What can pass through the
membrane by diffusion
What cannot pass through
by diffusion
 Small, uncharged
 Large molecules
molecules such as O2 and
CO2.
 Charged molecules
 Have to use protein
channels
 Ex. water and sucrose
(disaccharide)
Facilitated Diffusion
 Proteins embedded in the cell membrane help large
(glucose C6H12O6) and or charged molecules/ions
(H2O or Na+) through the membrane through a
channel.
Review Question
1. Explain why the cell membrane is arranged the way it is?
2. What is the purpose of the proteins and carbohydrates
embedded in the cell membrane?
3. Identify the solute and solvent from the following
solutions.
Sugar water
Lemon water
4. Explain diffusion, by using the word concentration in
your response.
5. How do terms passive transport, diffusion, and
facilitated diffusion relate?
Vocabulary
 Phospholipid
 Solute
 Hydrophobic
 Solvent
 Hydrophilic
 Solution
 Phospholipid bilayer
 Selectively permeable




membrane
Equilibrium
Concentration gradient
Passive transport
Facilitated diffusion
Please define these using
these notes or DE
interactive glossary on a
vocabulary wkst.