Cell Membrane & Passive Transport

1. Cell Membrane & Passive Transport Diffusion Facilitated Diffusion Osmosis

2. I. The Cell Membrane • Also known as a Plasma Membrane. • Semi-permeable membrane (picket fence) • Made of: • two layers of phospholipids. • Proteins • Carbohydrates • cholesterol

3. Cell Membrane Characteristics: • Controls what enters and leaves the cell. • Provides Structure and Support. • Allows the cell to maintain Homeostasis. • Phospholipid Bilayer: • Two layers of lipids, proteins and carbohydrate chains. • Phosphate- head faces outward, while the lipid tails face inward. (remember oil and water don’t mix) • Considered a fluid mosaic structure due to lots of different types of molecules that assemble to form a function

4. Structure: 1. Two Layers: a. Cholesterol found between the phospholipids. Creates a strong and flexible structure. b. The Bilayer is Selective (semi-permeable) and only allows certain molecules to pass through. 2. Integral (transport) proteins help in communication between cells. 3. Carbohydrate chains are attached to integral proteins found on the outside layer of the membrane. a. Carbohydrates act as chemical identifiers (name tags), that allow one cell to identify another.

6. Cell Membrane Types of proteins and Carbohydrates within cell membrane: • Protein channel - allows specific large molecules to enter or leave cell (facilitated diffusion). • Communication – cell to cell • Carbohydrate chains – chemical identifiers

7. Two concepts we have to know: B. Concentration gradient C. Dynamic EQUILIBRIUM

8. Simple Diffusion • Moving from a High (more particles) concentration to a Low (less particles) concentration. • Solutes do not require energy to move molecules in and out. • Impermeable membrane – “brick wall”, nothing enters or leaves. • Semi-permeable – (picket fence), some can get through. • To find an equilibrium, balance, between both sides. • To find homeostasis (same amount on both sides). High  low

9. Diffusion • Diffusion – High to low • Passive Transport-requires no energy

10. Facilitated Diffusion • The movement of molecules through a protein channel. • Can not move through the phospholipid Bilayer due to either being very large or has a polar charge. • Channel proteins move molecules across the membrane very fast and only allow specific types to enter or leave by them. • Does not require ATP energy.

11. Molecule move through the channel from a high to low concentration.

12. Facilitated Diffusion • Channel proteins act as pore. • Molecules will from through channel.

13. Osmosis: The diffusion of water across a semi-permeable membrane. Isotonic Solution – concentration of solutes is the same inside and outside the cell. Water flows in and out of the cell. Hypertonic Solution – Concentration of solute is higher outside the cell. Water moves out of the cell. Hypotonic Solution – Concentration of solute is higher inside the cell and water moves into the cell.

14. Plants wilt animal cell shrink-Plasmolysis Salt “Sucks” or dehydrates the water in plant cells- Turgur-Pressure Animal Cells would swell and burst

15. Discuss this picture What organ goes through the process of osmosis?

17. Osmosis Key terms: 1.Turgid – rigid, full, swollen ex: A plant standing up after watering. 2. Lyse – To break apart, burst or separate. Ex: popping a balloon, when filled with too much helium. 3. Shrink – to shrivel up. Dehydrate, To get smaller. Ex: a grape sitting in the sun turning into a raisin.

18. Active Transport • When solutes move against the concentration gradient and requires ATP (cell energy). • Low -> high concentrations • Transports small molecules or ions (polar) molecules through proteins called carrier proteins. • One specific type of active transport is the Sodium/Potassium Pump.

20. Lab over diffusion and osmosis • Egg osmosis video demonstration http://youtu.be/SSS3EtKAzYc

21. To make 300 mL of a 0.5M NaOH solution. Convert 300 mL = 0.3 L Measuring for Molar Solutions _________ ____________ __________ _________g__ concentration X volume desired X molecular weight = mass of solute desired (mol/L) (L) (g/mol) (g) • Molecular Weight ? • Moles are used to count molecules and atoms since they are too small to count individually. 1 mole equals the amount of molecules that gives a mass, in grams, equal to that substance’s molecular or formula weight. • The formula weight (FW or MW) can be determined using a periodic table or by looking at a chemical reagent bottle.

22. Determine the molecular weight of the solute The formula weight can be determined using a periodic table or by looking at a chemical reagent bottle For Molar Solutions you need the MW