The Cell Membrane

1. 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 ATP 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 • 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”

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 ATP • 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.