I. Unifying themes that relate to all cells A. All cells share basic FUNCTIONS performed by physical STRUCTURES. The universality of these functions and structures is a strong argument for the unity of life. B. Each cell's specialization depends on its shape, size, and organelles. C. The life of a cell depends on the arrangement of its parts and their integrated activities. D. Linnaeus was one of the first to recognize that patterns of structure and development indicated rela- tionships between groups of organisms. E. The development of the electron microscope and the ultracentrifuge enabled biologists and chemists to see patterns within the structure and chemistry of cells and thus to develop generalizations regarding the relationships between and among cells and organisms. F. Chemists discovered that the chemistry of living organisms did not differ in principle from the chemi- stry of the inorganic world. Biochemistry was thus a complex and fascinating branch of chemistry as applied to living systems. II. Fundamental features of cellular organization A. Compartmentalization - a property which allows the "effective" size of an object to increase without unduly affecting the surface area to volume relation- ship (S2V3) 1. allows for increased surface area by subdividing sections of the cell 2. limits certain cell constituents to certain parts of cell (destructive hydrolytic enzymes) 3. makes it possible to concentrate substances in specific regions where specialized biochemical activities can occur B. Self Assembly - spontaneous arrangement of molecules into specific structures; requires no additional energy input and is often the result of chemical bonding; e.g. phospholipids into bilayers in mem- branes; proteins into tubules and filaments C. Repitition - cells from pre-existing cells; thus patterns of cellular organization are repeated from one generation to another D. An Inherent Genetic Program - embodied in cell's DNA each gene represents a segment of a DNA strand: DNA--->RNA--->polypeptides (proteins) is usual sequence; The program of an organism represents a plan for action - a blueprint which provides a set of instructions to be used under specific circumstances, in a sequence that may be triggered by the operation of the program itself E. Redundancy - represented by multiple copies of mole- cules' (e.g. enzymes); multiple copies of the genetic information; All body cells of the organism contain identical genetic information. Given the correct chemical signals and environmental conditions, the cell is capable of differentiation in several possible directions. III. Microscopes were developed in 16th and 17th century Europe. Robert Hooke discovered cells in cork. Other scientists concluded that all living things are made of cells and that living cells arise only from preexisting cells. Non scientists like Leeuwenhoek made important contributions. IV. The most fundamental differences in the living world are differences between prokaryotic and eukaryotic cells. A. The Kingdom Monera includes prokaryotes. 1. Prokaryotes lack a membrane-bound nucleus; the DNA is a naked strand in a region called the nucleoid. 2. Prokaryotes do not have other membrane-bound ORGANELLES. B. The other four kingdoms, Protista, Fungi, Plantae, and Animalia, are eukaryotic. 1. Like prokaryotes, eukaryotic cells are surrounded by a CELL MEMBRANE. 2. Eukaryotic cells have internal membranes that surround the nucleus and other internal structures. 3. Eukaryotes have a highly organized CYTOPLASM with an internal latticework, the CYTOSKELETON, that contri- butes to structure and movement within the cell. 4. In multicellular eukaryotes, cells may specialize for given tasks. 5. Common features of plant and animal cells include a NUCLEUS, MITOCHONDRIA, RIBOSOMES, ENDOPLASMIC RETIC- ULUM, GOLGI BODIES, MICROTUBULES, MICROFILAMENTS, and a PLASMA OR CELL MEMBRANE. a. Plant cells may be surrounded by a CELL WALL and may be largely filled by a storage organelle, the VACUOLE. b. Plant cells may contain CHLOROPLASTS, which carry out photosynthesis. c. Cellular specialization leads to specialization of tissues, organs, and organisms. V. Cells vary in size and number in organisms A. Most cells are small. Prokaryotes are the smallest cells. The largest animal cells include ostrich eggs and giraffe nerve cells. B. The surface-to-volume ratio (S/V) determines a cell's ability to exchange materials with its environment. A cell's shape affects it S/V. VI. All cells must perform certain tasks. A. The cytoplasm must be separated from its environment so appropriate internal conditions can be maintained. B. The cell must take in raw materials and expel wastes through the barrier that separates it from its environment. C. It must take in energy and convert it to a form useful for powering the cellular machinery. D. It must synthesize molecules and cell parts for repair growth and replacement (reproduction). E. It must coordinate and regulate its activities. VII. All eukaryotic cells have certain structures. A. The PLASMA OR CELL MEMBRANE separates the cell from its environment and controls the movement of substances into and out of the cell. 1. The membrane is a LIPID BILAYER composed of PHOSPHO- LIPID molecules with hydrophilic heads and hydro- phobic tails. It is SEMIPERMEABLE. 2. The membrane includes proteins that stabilize the lipid bilayer and acts as gates, pumps, markers, or signal receptors. 3. The membrane may fold inward to import materials (endocytosis) or outward to expel materials from the cell (exocytosis). B. The NUCLEUS is the largest organelle and contains the genetic material, DNA. 1. The genetic information passes from DNA to RNA to proteins, which carry out the work of the cell. 2. The NUCLEOPLASM of the nucleus is surrounded by a double-layer membrane, the NUCLEAR ENVELOPE OR MEMBRANE, which is perforated by pores. Each pore is a cluster of proteins that form a channel. 3. RIBOSOMAL RNA is formed in the dark-stained regions known as NUCLEOLI. After being exported to the cyto- plasm, this RNA forms RIBOSOMES, which build protein according to the genetic blueprints encoded in messenger RNA. C. The cytoskeleton is a 3-dimensional latticework com- posed of MICROFILAMENTS, MICROTUBULES, and INTER- MEDIATE FILAMENTS that maintain the cell's shape and move materials within the cell. D. A system of INTERNAL MEMBRANES is involved in the manufacture, storage, transport, and export of pro- teins and raw materials. 1. The ENDOPLASMIC RETICULUM (ER) is a series of mem- brane channels that may be studded on the outside with ribosomes (rough ER) for protein synthesis or without ribosomes (smooth ER) and involved in the synthesis of non-proteins such as lipids. 2. At the ends of the ER channels, membrane sacs (vesicles) pinch off and carry the products to their destination, which may be another membrane system, the GOLGI COMPLEX, which modifies and packages proteins, lipids, and other substances and exports most of them from the cell. 3. Lysosomes contain digestive enzymes that break down ingested food or, if broken open, digest the cellu- lar components. E. MITOCHONDRIA provide chemical fuel for cellular processes by converting the energy in carbon-contain- ing molecules into the energy of ATP molecules. This process is called AEROBIC RESPIRATION. F. Plastids harvest solar energy and produce and store food. 1. CHLOROPLASTS are the organelles of photosynthesis, converting solar energy into chemical energy in the form of carbon compounds. Chloroplasts contain CHLOROPHYLL and other light-absorbing pigments embedded in membranous sacs called THYLAKOIDS. 2. CHROMOPLASTS are plastids that store yellow, red, or orange energy-trapping pigments and give color to fruits and flowers. G. Many plant cells have a CENTRAL VACUOLE that contains water and various storage products. 1. This reduces the volume of cytoplasm and thus increases the cell's S/V ratio. 2. The pressure of the water in the vacuole keeps the cell inflated. A plant wilts when the vacuole pres- sure drops because of drought. H. Many protists that live in fresh water have a CONTRAC- TILE VACUOLE that collects and pumps out water that could otherwise build up and burst the cell. I. Organelles of movement include CILIA, FLAGELLA, and microfilaments and microtubules. 1. Cilia and flagella have the same internal structure, with 9 pairs of microtubules in a circle surrounding 2 inner microtubules. 2. Using ATP energy, the microtubules slide past one another, causing the structure to bend. J. The plasma membranes of most cells are surrounded by cell coverings that protect the delicate membrane. 1. An EXTRACELLULAR MATRIX, a meshwork of secreted molecules, protects many cells that live within multicellular organisms. 2. CELL WALLS are made largely of cellulose and surround plant cells. 3. Virtually all animal cells secrete a meshwork of molecules that surrounds them. These molecules are mostly fibrous proteins. COLLAGEN is the most common of the fibrous proteins.