Transcript Cells
Cells Chapter 3 Composite Cell • The three major parts of a human cell is a nucleus, cytoplasm, and cell membrane • Nucleus-houses the genetic material • Cytoplasm-surrounds the nucleus and contains all the other organelles • Cell Membrane-surrounds the cytoplasm and controls what goes in and out, also communicates with other cells • Organelles-specialized structures that perform specific functions which divide the labor of the cell http://images.protopage.com/view/721661/9om6i6botf38jm7zive0ddjpj.jpg Cell membrane • Regulates movement of substances in and out of cell • Molecules that are part of the membrane receive information from outside and transmit it inward in a process called signal transduction • Also, helps adhere to other cells (important in forming tissues) • It is selectively permeable because it only lets some substances in and out of the cell http://upload.wikimedia.org/wikipedia/commons/e/ee/CellMembraneDrawing.jpg Cell Membrane structure • Composed of lipids, proteins, and carbs • Mainly a phospholipid bilayer (two layers) • The surface is made up of water soluble phosphate heads (hydrophilic-water loving) and water-insoluble fatty acid tales make up the interior (hydrophobic-water hating) http://t1.gstatic.com/images?q=tbn:ANd9GcSRFknJcaIVMIHrcsa-2d6DUgwFPkxA-JqQ-NYQ2HbfY6Jz3W-8 • O, and CO2 (soluble in lipids) can pass through easily • Water soluble molecules like amino acids, sugars, proteins, nucleic acids, and many ions cannot readily pass through • Cholesterol is also imbedded in membrane and make it less soluble, also stabilizes the membrane http://www.dynamicscience.com.au/tester/solutions/biology/cell/cholesterol.jpg • Also has proteins which: – Are receptors (hormones, growth factors) – Transport molecules or ions – Support the cells interior – Hold carbohydrates for identification and signaling – Determine where cells move in the body http://img.sparknotes.com/figures/A/a981208a1abd542364d5a13c08702881/cellmembrane.gif Cytoplasm • Contains networks of membranes and organelles suspended in the cytosol (clear liquid) • Also, contains Cytoskeleton which is a framework of proteins • Many types of organelles in cytoplasm http://nursingcrib.com/wp-content/uploads/cell2.jpg?9d7bd4 Cell Nucleus • Houses the genetic material which directs all cell activities • Surrounded by the nuclear envelope which is a bilayer of phospholipids http://library.thinkquest.org/06aug/01942/plcells/thinkquest/nucleus.jpg