The document summarizes key aspects of the cell membrane. It discusses how the cell membrane is made of phospholipids and proteins arranged in a fluid mosaic structure. It selectively controls what passes in and out of cells through diffusion, channels, and pumps that may require energy. Water movement across the membrane occurs through osmosis, with cell regulation to prevent bursting or shrinking due to gaining or losing too much water from their surroundings.
6. Membrane is a collage of proteins & other molecules embedded in the fluid matrix of the lipid bilayer Extracellular fluid Cholesterol Cytoplasm Phospholipids Glycolipid Transmembrane proteins Filaments of cytoskeleton Peripheral protein Glycoprotein
7.
8.
9. Why are proteins the perfect molecule to build structures in the cell membrane?
10. Classes of amino acids What do these amino acids have in common? nonpolar & hydrophobic
11. Classes of amino acids What do these amino acids have in common? polar & hydrophilic I like the polar ones the best !
12.
13. Examples proton pump channel in photosynthetic bacteria water channel in bacteria function through conformational change = shape change NH 2 H + COOH Cytoplasm Retinal chromophore Nonpolar (hydrophobic) -helices in the cell membrane H + Porin monomer -pleated sheets Bacterial outer membrane
14. Many Functions of Membrane Proteins Outside Plasma membrane Inside Transporter Cell surface receptor Enzyme activity Cell surface identity marker Attachment to the cytoskeleton Cell adhesion
29. Endocytosis phagocytosis pinocytosis receptor-mediated endocytosis fuse with lysosome for digestion non-specific process triggered by molecular signal
30. The Special Case of Water Movement of water across the cell membrane
31.
32.
33.
34.
35.
36.
37.
38.
39. Osmosis… Cell (compared to beaker) hypertonic or hypotonic Beaker (compared to cell) hypertonic or hypotonic Which way does the water flow? in or out of cell .05 M .03 M
The carbohydrates are not inserted into the membrane -- they are too hydrophilic for that. They are attached to embedded proteins -- glycoproteins.
Signal transduction - transmitting a signal from outside the cell to the cell nucleus, like receiving a hormone which triggers a receptor on the inside of the cell that then signals to the nucleus that a protein must be made.
The four human blood groups (A, B, AB, and O) differ in the external carbohydrates on red blood cells.
Movement from high concentration of that substance to low concentration of that substance .
Donuts! Each transport protein is specific as to the substances that it will translocate (move). For example, the glucose transport protein in the liver will carry glucose from the blood to the cytoplasm, but not fructose, its structural isomer. Some transport proteins have a hydrophilic channel that certain molecules or ions can use as a tunnel through the membrane -- simply provide corridors allowing a specific molecule or ion to cross the membrane. These channel proteins allow fast transport. For example, water channel proteins, aquaporins , facilitate massive amounts of diffusion.
Some transport proteins do not provide channels but appear to actually translocate the solute-binding site and solute across the membrane as the protein changes shape. These shape changes could be triggered by the binding and release of the transported molecule. This is model for active transport.
Plants: nitrate & phosphate pumps in roots. Why? Nitrate for amino acids Phosphate for DNA & membranes Not coincidentally these are the main constituents of fertilizer Supplying these nutrients to plants Replenishing the soil since plants are depleting it