1. C-Notes: Cell Membrane (Plasma Membrane)
Stnd: BI 1.a
C-Notes: Cell Membrane (Plasma Membrane)
12/2/13
SWBAT describe the functions of proteins in the cell membrane
Objective:

2. Why is the Plasma Membrane called the Fluid Mosaic Model?
FLUID- because individual phospholipids and proteins can move side-to-side within the layer, like it’s a liquid. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above.

3. What molecules can get through the cell membrane directly?
allow SOME materials but not all to pass through the membrane (Semi-Permeable) Fats and oils can pass directly through Movement In: -Food: (sugar, proteins, fats); salts, O2, and H2O Movement Out: Waste: ammonia; salts, CO2, H2) Products: proteins
lipid
inside cell
outside cell
salt
waste
sugar aa
H2O

4. How do cells build a barrier (Membrane) that keeps the watery contents of the cell separate from the watery environment?
Membrane is made out of a special kind of lipid (phospholipid) and is double layer (2 layers of phospholipids)
“attracted to water”
 FATS 
 LIPIDS 
Remember: oil & water don’t mix!!
phosphate
lipid
“repelled by water”
inside cell
outside cell

5. Ex: H2O channels, salt channels, sugar channels
How does other molecules get through the membrane?
The cell membrane makes Protein Channels “doors” through the membrane to allow these specific materials/substances in and out
Ex: H2O channels, salt channels, sugar channels
inside cell
H2O aa
sugar
salt
outside cell
waste

6. Channels are made of proteins
How do you build a semi-permeable cell membrane?
Channels are made of proteins
proteins both “like” water & “like” lipids
bi-lipid
membrane
protein channels in bi-lipid membrane

7. How do proteins function in the semi-permeable phospholipid bilayer?
- Act as doors in the membrane to
transport substances in and out of the cell.
-Cell recognition
-Enzymes to catalyze reactions
HIGH
LOW

8. Because molecules move from high to low concentration
Why do molecules move through membrane if you give them a channel?
Because molecules move from high to low concentration
Ex: Diffusion, Osmosis, passive transport, etc

9. By a process called Endocytosis 3 types of Endocytosis
How do larger molecules move into the cell?
By a process called Endocytosis
3 types of Endocytosis
Pinocytosis “Cell Drinking”
most common
Takes in dissolved molecules as a vesicles
2. Receptor-Mediated Endocytosis
some proteins have receptors on their surface to recognize and take in hormones, cholesterol, etc.
3. Phagocytosis “Cell Eating”
- Used to engulf (eat) large particles such as food, bacteria, etc. into vesicles.

10. copyright cmassengale
The Plasma Membrane
Pinocytosis
5/11/2019
Most common form of endocytosis.
Takes in dissolved molecules as a vesicle.
copyright cmassengale
G. Podgorski, Biol. 1010

11. copyright cmassengale
The Plasma Membrane
5/11/2019
Receptor-Mediated Endocytosis
Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc.
copyright cmassengale
G. Podgorski, Biol. 1010

12. copyright cmassengale
The Plasma Membrane
5/11/2019
Endocytosis – Phagocytosis
Used to engulf large particles such as food, bacteria, etc. into vesicles
Called “Cell Eating”
copyright cmassengale
G. Podgorski, Biol. 1010

13. How do Larger molecules move out of the cell?
A process called Exocytosis (opposite of endocytosis)
Large molecules that are manufactured (made) in the cell are released through the cell membrane.
Inside Cell
Cell environment