Cell (Plasma) MembraneWhat is it made of?
Why is this a good material for a cell membrane?
Cell Membrane
• Phospholipid bilayer• Hydrophilic head• Hydrophobic tail
Cell Membrane
• Homeostasis – Steady state maintained by
the body • Selectively Permeable
– Regulates what can come in and out of the cell
Selectively Permeable (6.3) CANSmall Nonpolar
– (O2)
– (CO2) – WATER
CANNOT – Large (glucose)– Polar ( exception is water because its so
small) – Ion (charged)
Breathing
Proteins in the Cell Membrane
• “Fluid Mosaic Model” – Many proteins will help
transport molecules across the membrane
– Proteins drift freely
Membrane Proteins Embedded
1. Transport Proteins2. Cell Recognition
Proteins- sugars hang off proteins
3. Receptors Proteins- receive signals
4. Enzymes- proteins that make reactions happen
Cell Recognition Proteins
• Sugars hang off of proteins in the cell membrane
• Give us different blood types
Receptor Protein
Receptor Protein- is a cell membrane protein that receives a signal
Transport
Passive Transport: Diffusion
• Diffusion • The movement of particles
HIGH concentration to LOW concentration
Why? • Molecules are always in
random motion Ex. Perfume, food coloring, tea bag
Equilibrium- particles equally spread out
Osmosis Water ONLY!- Diffusion of water from HIGH to LOW
concentrationSolute: Substance in solution that is dissolved (ex. Sugar or Salt)
Solvent: Substance in solution that does the dissolving ( ex. Water)
Hypotonic Environment
Hypertonic Environment
Isotonic Environment
TONICITY
Isotonic
97% H2O
Diagram
Where is the most water?
Which way does water go?
Result?
Big words
Examples
97% H2O
Same
Inside and outside
Even, same concentration overall
“dynamic equilibrium” “homeostasis
contact lens solution, Gatorade
97% H20
HypotonicDiagram
Where is the most water?
Which way does water go?
Result?
Big words
Examples
97% H2O
Outside
Inside
Burst, get bigger; firm
“cytolysis”- to burst; “turgid”- get firm; “turgor pressure” :pressure inside plant cells to help stand upright
- Distilled water ( 100% Water) - Plants standing upright
92 % H20
HypertonicDiagram
Where is the most water?
Which way does water go?
Result?
Big words
Examples
80% Water
Inside
Outside
Smaller, shrink, go limp
“plasmolysis”- to wilt, shrivel, loss of pressure; “flaccid”- go limp
97% H20
Hypertonic Red Blood Cells
Check Yourself
Is the lettuce in a hypertonic isotonic hypotonic environment and why??
Poll
Passive Transport: Facilitated Diffusion
Facilitated Diffusion- diffusion across a
membrane through transport proteins
Ex. sugars, ions , alcohol
NO ENERGY: From HIGH to LOW concentration
Active Transport Movement of molecules across a membrane require energy• From LOW to HIGH concentrations!
Why? • To maintain a certain internal environment: • 1. Sodium Potassium Pump
Active Transport
Exocytosis & Endocytosis
1. Exocytosis - Removal of materials - Vesicle fuses with
membrane, forcing contents out
Active Transport 2. Endocytosis• process of taking in
materials by infolding of the cell membrane
• Pocket breaks and forms a vesicle in the cell • Ex.
• Pinocytosis: take in fluid
• Phagocytosis: Large particle/food• Amoeba
Concentration Gradient measurement of how the concentration of something changes from one place to another
B. Passive Transport: molecules go DOWN concentration gradient
from HIGH to LOW concentration
C. Active Transport: molecule go UP concentration gradient from
LOW to HIGH concentration
• Review Video of Transport
Elodea Plasmolysis
http://www.youtube.com/watch?v=2Th0PuORsWY
“Egg”citing “Eggs”periment Cell membrane
Egg Lab: Osmosis
Why does a plant like hypotonic but an animal does not?
• http://www.phschool.com/science/biology_place/labbench/lab1/watpot.html