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 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 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 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 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 _______________.