Cellular Boundaries
I. Cell Membrane
A. All cells are surrounded by a
thin, flexible barrier known as a
_______________.
B. The two main functions of
the cell membrane are:
1. to _______________ what
enters and leaves the cell and
2. to provide
_______________ and
_______________.
C. The composition of cell
membranes is a double-layered
sheet called a
_______________.
1. _______________ are
embedded in the lipid bilayer of
most cell membranes.
2. _______________ form
channels or pumps that help to
move materials across the cell
membrane.
Analogy time…
• A cell membrane is like a
___________ because
_________________________.
• Protein pumps are like the
_____________ in a ___________
because ________________.
3. _______________ are attached
to many proteins embedded on the
outside of the bilayer.
4. The carbohydrates allow
individual cells to
_______________ one another.
5. Because of the
many types of
molecules found in
cell membranes
many scientists
refer to them as a
_______________.
II. Cell Wall
A. Many cells also produce a
strong supporting layer around the
membrane known as a
_______________.
B. Plants, algae, fungi, and all
prokaryotes have
_______________.
C. Cell walls are located
_______________ of the cell
membrane.
D. The main function of the cell
wall is to provide _______________
and _______________ for the cell.
Analogy time (part 2)…
• Cell membranes are like
__________ while cell walls
are like ______________
because
_________________________
__________.
E. The cell walls of plants are
made of _______________.
Osmosis and Diffusion
I. Concentration
A. The _______________is the
amount of a substance dissolved
into water.
+
II. Diffusion
A. In a solution, particles are
constantly moving.
B. They collide with one another
and tend to spread out
_______________.
C. Particles move from an area of
high concentration to an area of
low concentration.
This process is known as
_______________.
D. A _______________ is a
difference between two
concentrations.
E. Diffusion is the movement of
particles _______________ the
concentration gradient.
F. When the
concentration of a
solute is the same
throughout a
system, the system
has reached
_______________.
Substances that diffuse across a
membrane do not require the cell
to use _______________.
Molecules that are too large or too
strongly charged cannot diffuse
across biological membranes.
If a substance is able to diffuse
across a membrane, the membrane
is said to be _______________ to it.
If a substance cannot diffuse across
a membrane, the membrane is said
to be _______________ to it.
_______________ means that
some substances can pass across
while others cannot.
Biological membranes are
selectively permeable.
Diffusion of water through a
selectively permeable membrane is
called _______________.
When two solutions have the same
concentration of solute they are
said to be _______________.
A solution that has a higher
concentration of solute is said to be
_______________.
A solution that has a lower
concentration of solute is said to be
_______________.