2.4 Cell Membranes
In fluid mosaic model, the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.
To Think About:
How does the structure of a phospholipid establish and maintain the internal environment of the cell? What role do phospholipids have in maintaining the internal environment of the cell? What role do proteins have in maintaining the internal environment of the cell? What is the structural framework of the Fluid Mosaic Model of cell membranes? How does the structure of cell membranes result in selective permeability? How do cell membranes separate the internal environment of the cell from the external environment? What is the direct consequence of membrane structure, as described by the fluid mosaic model? What type of molecules passes freely across the membrane? What type of substances moves across the membrane through embedded channels and transport proteins? What molecules pass through the membrane in small amounts? What type of boundaries do cell walls provide? What types of molecules are the cell walls of plants, prokaryotes, and fungi composed of?
Watch: AP Daily Video - Plasma Membranes
Answer the Following Questions:
- What is the function of the cell membrane?
- Why are phospholipids amphipathic?
- Where are peripheral proteins found?
- What type of embedded proteins span the cell membrane?
- Why do peripheral proteins have amino acids with hydrophilic side (R) groups but integral proteins have both hydrophobic and hydrophilic side (R) groups?
- List the six functions of transmembrane proteins.
- What does the “fluid mosaic model” mean?
- What is the role of cholesterol in cell membranes?
- Why are carbohydrates important in cell membranes? Where can these carbohydrates be found?
Watch: AP Daily Video - Membrane Permeability
Answer the Following Questions:
- Selective permeability is a direct consequence of____________________
- What types of molecules can pass freely through the cell membrane? Give some examples of these types of molecules.
- Large, polar (hydrophilic) molecules cannot move freely across the cell membrane. List and describe two types of transport proteins that help these large polar molecules cross the cell membrane.
- Can water pass through the cell membrane without a transport protein?
- What is the function of the cell wall?
- How do molecules cross the cell wall?
- How are plant, fungi, and prokaryotic cell walls different?
Supplementary Resources:
- Bozeman Science: Mr. Andersen’s “Cell Membranes” video
Hyperphysics: The Cell Membrane
