Learning Targets
“I Can . . .”
-Describe the structure of the cell membrane.
-Describe the function of protein channels and
protein pumps that span the cell membrane.
-Define “diffusion.”
-Predict the direction of movement of particles
across a membrane by diffusion.
-Define “osmosis.”
-Predict the direction of movement of water
through a membrane by osmosis.
The Cell Membrane
Characteristics of the Cell
Membrane
1. Recall that ALL cells
have cell membranes
2. The cell membrane
is a double-layered
sheet called a
phospholipid bilayer
Characteristics of the Cell
Membrane
Characteristics of the Cell
Membrane
“WATER LOVING”
“WATER FEARING”
Characteristics of the Cell
Membrane
Water on the
OUTSIDE
of the cell
Lipids in the
MIDDLE
of the cell
membrane
Water on the
INSIDE
Of the cell
Characteristics of the Cell
Membrane
3. The cell membrane regulates what enters
and leaves the cell and also protects and
supports the cell
Characteristics of the Cell
Membrane
4. Proteins and carbohydrates are also
found in and on the cell membrane
a. Proteins form channels and pumps
that help to move materials across the
membrane
b. Carbohydrates attach to these
proteins and act as chemical
identification cards so that individual
cells can recognize each other
Characteristics of the Cell
Membrane
5. Because there are so many molecules
that make up the cell membrane and
because these molecules move around
within the membrane, scientists describe
the membrane as a “fluid mosaic.”
a. Fluid = constantly moving
b. Mosaic = involving bits
and pieces of different
colors or materials
Movement Across the Cell
Membrane
1. Materials that move through the cell
membrane are not random because the cell
membrane is selectively permeable
Movement Across the Cell
Membrane
2. This means that some materials move
easily, on their own, while other materials
need the help of proteins
3. Some materials cannot move through the
membranes AT ALL
Movement Across the Cell
Membrane
Types of Passive Transport
1. Passive transport allows the cell to
maintain homeostasis in its liquid
environment.
2. Passive transport is the movement of
molecules from one side of the
membrane to the other
3. Because diffusion depends on the
random movement of molecules, no
additional energy is required in passive
transport
Types of Passive Transport
4. Diffusion
a. Particles (molecules) move from
areas of HIGH particle concentration to
areas of LOW particle concentration
*What is a “particle”?
Oxygen, Carbon Dioxide, Sugars,
Vinegar, Iodine, etc.
Types of Passive Transport
b. Example: Cup of water with particles
+ = particles
Types of Passive Transport
Types of Passive Transport
Types of Passive Transport
5. Facilitated Diffusion: passive transport
that utilizes the help of carrier proteins
embedded in the cell membrane
a. Osmosis is a type of facilitated
diffusion that makes use of carrier
proteins called aquaporins
b. During osmosis, water moves from
areas of LOW particle concentration to
areas of HIGH particle concentration
Types of Passive Transport
c. Example: Cup of water with particles
+ = particles
+
+
+ +
+
++
++
+ +
+
+
+
+
+
+
+
+
+
+ +
+ +
+ +
Learning Targets
“I Can…”
-Describe active transport.
-Describe the role of vesicles in the cell.
-Distinguish between endocytosis and
exocytosis.
Types of Active Transport
1. Active transport is the movement of
materials AGAINST the concentration
gradient.
2. Active transport requires energy.
a. Molecular Transport: small
molecules and ions are carried across
the membrane by proteins that act as
pumps
Types of Active Transport
1. Active transport is the movement of
materials AGAINST the concentration
gradient.
2. Active transport requires energy.
b. Bulk Transport: the transport of
large molecules or even solid clumps of
materials using vesicles
• Endocytosis
• Exocytosis
References
http://www.stolaf.edu/people/giannini/biologi
cal%20anamations.html
http://www.youtube.com/watch?v=wO1yq6Y
TJDI