1. The Cell Membrane Cell Biology standard 1a
Unit 2: Cells
Chapter 7-3
The Cell Membrane
Cell Biology standard 1a
Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.

2. Learning Goals: 1. Describe the job/function of the cell membrane
2. Explain what semi-permeable means.
3. Describe the structure of the cell membrane.
4. Describe the 3 types of movement across the cell membrane. Include whether energy is required and which direction the molecules move.

3. Cell Membrane Cell Membranes surround ALL cells!
It controls what enters/leaves the cell
SEMIPERMEABLE – means it allows some things through but not others

5. Structure Made up of a Phospholipid bilayer
Polar heads “love” water (hydrophilic)
Nonpolar tails “fear” water (hydrophobic)

6. Fluid Mosaic Model
“Fluid mosaic model” – describes the structure of the cell membrane.
Proteins float around in the membrane like icebergs in the ocean

7. Which of the following is NOT true about the cell membrane:
A. Surrounds all cells
B. Controls what enters and leaves the cell
C. Surrounds the nucleus
D. Is a phospholipid bilayer

8. The cell membrane is semipermeable. This means:
A. All things can pass through
B. Some things are let in or out but not everything
C. Everything is blocked
D. Only small molecules may pass through

9. Function (Job) Keeps things in or out
Molecules can enter/leave the cell 3 ways
1. Diffusion
2. Carrier-Facilitated (“helped”) diffusion
3. Active transport

10. 1. Diffusion No energy required
ATP
No energy required
Molecules move from area of high concentration to area of low concentration
Concentration = # of molecules in an area
Diffusion of water is called “osmosis”
X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X
X X X X X X X X X X X X X X X X X X X

11. 2. Carrier-Facilitated Diffusion (“helped diffusion”)
ATP
No energy required
Molecules “helped” across by proteins from high to low concentration

12. 3. Active Transport Energy required! ATP – the “battery” of the cell
Breaking a bond in ATP releases energy
Can “pump” molecules from low to high concentration building them up in the cell

14. The diffusion of water is called:
A Osmosis
B. Transfusion
C. Water transport
D. Active transport

15. In diffusion molecules move:
A. From low to high’ no energy
B. From low to high; needs energy
C. From high to low; no energy
D. From high to low; needs energy

16. In carrier facilitated diffusion molecules move:
A. From low to high’ no energy
B. From low to high; needs energy
C. From high to low with the help of a protein; no energy
D. From high to low; needs energy

17. In active transport molecules move:
A. From low to high’ no energy
B. From low to high; needs energy
C. From high to low; no energy
D. From high to low; needs energy

18. Learning Goals: 1. Describe the job/function of the cell membrane
2. Explain what semi-permeable means.
3. Draw and label the structure of the cell membrane.
4. Describe the 3 types of movement across the cell membrane. Include whether energy is required and which direction the molecules move.