Cell Membrane: Structure and Function
In or Out?
1. What are some things that can pass through a window screen?
2. What are some things that cannot pass through a window screen? Why is it important to keep these things from moving through the screen?
3. The cell is surrounded by a cell membrane, which regulates what enters and leaves the cell. Why is it important to regulate what moves into and out of a cell?
Interest Grabber
Outsideof cell
Insideof cell(cytoplasm)
Cellmembrane
Proteins
Proteinchannel Lipid bilayer
Carbohydratechains
Section 7-3
Figure 7-12 The Structure of the Cell Membrane
Cell Membrane
Function = controls what enters the cell and what leaves the cell
Made of a lipid bilayer Has proteins Has some carbohydrates, which
help with identification Is fluid (fluid mosaic model)
Diffusion
Def. of diffusion = Spreading of molecules in a given space.
What happens? -Substances move from an area
where there is more of them to an area where there is less of them
Diffusion
Def. of permeable = membrane that lets substances pass through it
Cell membrane is selectively permeable, which means that it lets some things in but does not let other things in
Substances keep moving till there is about equal amounts of them on both sides of the membrane
HighConcentration
LowConcentration
CellMembrane
Glucosemolecules
Proteinchannel
Section 7-3
Diffusion
Factors that Affect Diffusion
Amounts of substances involved
Temperature
Pressure
Stirring -speeds up the rate of diffusion
Diffusion
Diffusion Video
Osmosis Def. of osmosis = movement of
water from greater to lesser
Figure 8.11 Osmosis
Figure 8.12 The water balance of living cells
Osmosis
Water goes into a cell causing it to swell up and burst = plasmoptysis
Water leaves the cell causing it to shrink = plasmolysis
*Know the difference between plasmoptysis and plasmolysis!*
Osmosis
Some one-celled organisms have a contractile vacuole that pumps water out of a cell
In plants, as water goes into the cell, it builds up pressure that pushes against cell wall. This is called turgor pressure.
Contractile Vacuole
Osmosis
Osmosis Video
Passive Transport
NO ENERGY NEEDED!
Is the movement of small molecules in and out of a cell
Molecules go from greater to lesser (=with concentration gradient)
Examples: amino acids, fatty acids, glycerol, simple sugars (glucose)
Passive Transport
Passive Transport
Passive Transport Video
Active Transport
ENERGY NEEDED!
Molecules go from lesser to greater (=against concentration gradient)
This is when large molecules are pulled through the cell membrane by the use of ENERGY
Do not fully know how it works
Molecule tobe carried
Moleculebeing carried
Energy
Section 7-3
Figure 7-19 Active Transport
Active Transport
Active Transport Video
Endocytosis and Exocytosis
Def. of endocytosis = process by which cells take in large molecules from the outside
-ex. pinocytosis and phagocytosis
• Def. of exocytosis = process by which cells get rid of large molecules in the cell
Pinocytosis
Pinocytes are pockets on the cell membrane.
Large molecules fall into the pockets and get turned into food vacuoles inside the cell
Pinocytosis
Phagocytosis: Engulfing
This is when large molecules are surrounded and pulled into the cell
Examples: amoeba, white blood cells called phagocytes
This is the same method used by white blood cells to trap bacteria in our blood
Phagocytosis: Engulfing
Endocytosis and Exocytosis Video
Endocytosis and Exocytosis
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