Chapter 5 Section 1: Proteins and their cellular locations, after p. 185:
Topic Name: Molecular Probes Photo Gallery
Proteins are involved in nearly every cellular function. Enzymes catalyze biochemical reactions. Antibodies seek out and bind to infectious agents. Hormones and growth factors function as chemical messengers to communicate with other cells. For example, Epidermal Growth Factor (EGF) is a small soluble protein that travels to cells, binds to the surface of the cells and transmits a signal from the outside of the cells to the inside.
Go to this web site to look at an image of cells that have been treated with a fluorescent probe that labels EGF. There are six cells in this image.
1. Where in the cell is the EGF detected?
2. There is an EGF receptor that is present in these cells. EGF binds to this receptor to transmit its signal. Based on the information contained in this image, where in the cell is this EGF receptor located?
Other proteins provide a structural framework or support system (called the cytoskeleton) to the cell. Some of these cytoskeletal proteins function as molecular motors to generate movement within the cell (recall the discussion of actin and myosin in muscle cells in your text). In non-muscle cells, actin filaments also provide support and structure to the cell and are involved in the movement or migration of cells themselves. When do cells need to move? Certain cells migrate to sites of infection and cells migrate during embryonic development, as you will see in Chapter 6, Community.
Single molecules of the protein tubulin polymerize to form microtubules that, together with other proteins, are involved in the transport of proteins from one part of the cell to another and in the movement of chromosomes during cell division.