Chapter 3Cells: The Living UnitsI. Overview of the Cellular Basis of Life (pp. 65–66)A. The four concepts of the cell theory state (p. 65): 1. Cells are the basic structural and functional units of life. 2. The activity of an organism depends on the activities of its cells. 3. The biochemical activities of a cell are dictated by their organelles. 4. The continuity of life has a cellular basis. B. Characteristics of Cells (pp. 65–66; Figs. 3.1–3.2)1. Cells vary greatly in their size, shape, and function. 2. All cells are composed primarily of carbon, hydrogen, nitrogen, and oxygen. 3. All cells have the same basic parts and some common functions.4. A generalized human cell contains the plasma membrane, the cytoplasm, and the nucleus.II. The Plasma Membrane: Structure (pp. 67–69)A. The Fluid Mosaic Model (pp. 67–68; Figs. 3.3–3.4)1. The plasma membrane is composed of a double layer of phospholipids embedded with small amounts of cholesterol and proteins.2. The phospolipid bilayer is composed of two layers of phospholipids lying tail to tail, with their polar heads exposed to water inside and outside the cell.3. The inward-facing and outward-facing surfaces of the plasma membrane differ in the kinds and amounts of lipids they contain.a. Glycolipids are found only in the outer membrane.b. Lipid rafts are also found only in the outer membrane, and are assumed to functionin cell signaling.4. Integral proteins are firmly inserted into the plasma membrane. a. Most integral proteins are transmembrane proteins that span the entire width of the membrane and are involved with transport as channels or carriers.5. Peripheral proteins are not embedded in the plasma membrane, but attach to integral proteins or to phospolipids. a. Peripheral proteins may function as enzymes or in mechanical functions of the cell.6. The glycocalyx is the fuzzy, sticky, carbohydrate-rich area surrounding the cell.B. Specializations of the Plasma Membrane (p. 69; Fig. 3.5)1. Microvilli are fingerlike extensions of the plasma membrane that increase the surface area of the cell.2. Most body cells are bound together using glycolipids, specialized interlocking regions,or specialized membrane junctions.a. Tight junctions are a type of membrane junction in which integral proteins on adjacent cells fuse together to form an impermeable junction in order to prevent molecules from passing through the extracellular space between cells.b. Desmosomes are mechanical couplings that are scattered along the sides of adjoining cells that prevent their separation and reduce the chance of tearing whena tissue is stressed.c. Gap junctions are a communication junction between cells that allows substances to pass between adjacent cells.III. The Plasma Membrane: Functions (pp. 70–83)A. Membrane Transport (pp. 69–81; Tables 3.1–3.2; Figs. 3.6–3.14)1. The plasma membrane is a selectively permeable barrier, regulating how substances pass into and out of the cell. 2. Passive processes do not use energy and move substances down a concentration gradient.a. Diffusion is a process in which substances move directly through the plasma membrane from an area of higher concentration to an area of lower concentration.b. In facilitated diffusion substances are moved through the plasma membrane by binding to protein carriers in the membrane or by moving through channels.c. Osmosis is the diffusion of water through a selectively permeable membrane. d. Filtration is a pressure-driven process that forces water and solutes through a membrane or capillary wall. 3. Active processes use energy (ATP) to move substances across a membrane.a. Active transport uses solute pumps to move substances against a concentration gradient. The two kinds of active transport are primary active transport and secondary active transport.b. Vesicular transport is the means by which large particles, macromolecules, and fluids are transported across the plasma membrane, or within the cell.i. Exocytosis is a process used to move substances from inside the cell to the extracellular environment.c. Endocytosis, transcytosis, and vesicular traffiking are vesicular transport processes that move molecules using protein-coated vesicles.d. Clathrin-coated vesicles are the main route for endocytosis and transcytosis of bulk solids.e. Non-clathrin-coated vesicles, or caveolae, are inpocketings of the cell membrane that capture specific molecules in vesicles lined with caveolin, not clathrin.B. Generating and Maintaining a Resting Membrane Potential (pp. 81–83; Fig. 3.15)1. A membrane potential is a voltage across the cell membrane that occurs due to a separation of oppositely charged particles (ions).2. The resting membrane potential is a condition in which the inside of the cell membrane is negatively charged compared to the outside, and ranges in voltage from25 to 2100 millivolts.a. The resting membrane potential is determined mainly by the concentration gradient of potassium (K1).b. Active transport pumps ensure that passive ion movement does not lead to an electrochemical equilibrium across the membrane, thus maintaining the resting membrane potential.C. Cell-Environmental Interactions (pp. 83–84)1. Cells can interact directly with other cells, respond to extracellular chemicals, and interact with molecules that direct migration.2. Roles of Cell Adhesion Molecules a. Cell adhesion molecules (CAMs) are glycoproteins that play roles in embryonic development, wound repair, and immunity.3. Roles of Membrane Receptors (Fig. 3.16)a. Membrane receptors are integral proteins and glycoproteins that serve as binding sites.b. Some membrane receptors function in contact signaling, electrical signaling, and chemical signaling.4. Nitric oxide, consisting of one atom of oxygen and one atom of nitrogen, is the first known gas to act as a biological messenger.IV. The Cytoplasm (pp. 84–95)A. The cytoplasm is the cellular material between the cell membrane and the nucleus, and isthe site of most cellular activity (p. 84).1. There are three major elements of the cytoplasm: cytosol, cytoplasmic organelles, and cytoplasmic inclusions.B. Cytoplasmic Organelles (pp. 84–95; Table 3.3; Figs. 3.17–3.27)1. Mitochondria are sausage-shaped membranous organelles that are the power plants of the cell, producing most of its ATP.2. Ribosomes are small staining granules consisting of protein and ribosomal RNA that are the site of protein synthesis.3. The endoplasmic reticulum is an extensive