1. Membrane Structure

2. 1. Fat Soluble Molecules Examples: Fatty acids Passive Diffusion
Oxygen & carbon dioxide
Alcohol & nicotine

3. 2. Water Moves by OSMOSIS through protein lined pores
Called AQUAPORINS
Some water will passively diffuse (leak) through the membrane

4. 3. Transport by Carrier Molecules
A. FACILITATED TRANSPORT
Also called passive transport
Glucose & amino acids move in this way
They are LIPID INSOLUBLE (need a carrier protein)
Carrier proteins are reusable
Very specific

5. B. ACTIVE TRANSPORT
Moves molecules against a concentration gradient
Examples:
Iodine collects in thyroid gland
Glucose is completely absorbed by lining of intestine
Need carrier proteins and ATP ENERGY!!
Active transport cells high in mitochondria

6. C. SODIUM POTASSIUM PUMP
Also needs carrier proteins and ATP
Protein carrier changes shape to fit Na+, then K+
3 Na+ move OUT of the cell; 2 K+ move IN

7. Cell Size
Individual cells maintain a HIGH surface area to volume ratio

8. Example… Surface Area 6 units2 24 units2 Volume 1 unit3 8 units3 RATIO
Cell A (1x1x1)
Cell B (2x2x2)
Surface Area
6 units2
24 units2
Volume
1 unit3
8 units3
RATIO
6:1
HIGH ratio!
3:1
LOWER ratio

9. WHY does cell size seek to optimize this ratio?
Cells with a large volume require more nutrients, oxygen, etc AND produce more wastes
Membranes are limited to moving material in or out of the cell at a maximum rate
More membrane = better ability to move materials in/out of cell!

10. Membrane Structure
Group Activity: Your group will be assigned a fact about cell membranes and the tasks they accomplish. Your job is to explain HOW a cell carries out your task and provide the class with a basic diagram and a short description.

11. FACT: The concentration of water at the beginning of the large intestine is higher than at the end of the organ. However, the fatty part of the membrane is hydrophobic.
EXPLANATION

12. FACT: Virtually all glucose and amino acids in the foods you eat and digest are absorbed by the bloodstream.
EXPLANATION

13. FACT: Using electrical probes, scientists have determined that the part of a nerve cell at rest has a high Na+ concentration outside and high K+ concentration inside. When firing, Na+ and K+ trade places.
EXPLANATION

14. FACT: Cl- passively diffuses across membranes, yet it can’t move through lipids.
EXPLANATION

15. FACT: Fatty acids and glycerol move freely across membranes.
EXPLANATION

16. FACT: Hormones have specific target cells.
EXPLANATION

17. FACT: White blood cells such as macrophages engulf whole viruses.
EXPLANATION

18. FACT: Your immune system can recognize foreign antigens.
EXPLANATION

19. FACT: Glucose passes across membranes many times faster than fructose.
EXPLANATION

20. FACT: Cancer cells have lost “contact inhibition” and will grow into a mass.
EXPLANATION

21. FACT: Cells can communicate with their neighbours.
EXPLANATION

22. FACT: At the beginning of the filtration process, lots of glucose has left the blood and joined the potential urine. Kidney cells use up ATP when ensuring that your urine contains no glucose.
EXPLANATION