WEEK TWO VOCABULARY Actin-­‐ globular protein that forms microfilaments. Active Transport-­‐ when moving a substance requires energy input. Used to move against gradients. Uses specific transport proteins. Amphipathic-­‐ containing both hydrophilic and hydrophobic regions. Cell Wall-­‐ a layer external to the plasma membrane that provides protection and support to plants, prokaryotes, fungi, and some protists. Different organisms use different polysaccharides to make up the structure of cell walls. Plants use cellulose, fungi use chitin, and bacteria use peptidoglycan. Centriole-­‐ centrosome contains two centrioles; microtubule triplets. Centrosome-­‐ structure in cytoplasm that functions as a microtubule organizing center during cell division. Channel Protein-­‐ transmembrane proteins that allow certain materials to pass through the membrane Chloroplast-­‐ plant (and protist) organelle. Converts carbon dioxide and water into organic compounds. It uses sunlight to drive forward this reaction. Chromosomes-­‐ structure carrying genetic material in nucleus of eukaryotes. Chromosome consists of DNA with its associated proteins. Bacterial chromosome is often composed of a circular DNA molecule. Cilia-­‐ short cellular appendage composed of microtubules. Can be used for movement or for sensory/signaling. Concentration Gradient-­‐ area where density of a substance increases or decreases Cotransport-­‐ coupling of favorable and unfavorable transport against a gradient Cytoplasm-­‐ gel like substance between the plasma membrane and the nucleus. Contains organelles. Cytoskeleton-­‐ includes microtubules, microfilaments, and intermediate filaments in the cytoplasm. Used for a variety of functions including support, transport, and signaling. Cytosol-­‐ the fluid part of the cytoplasm. Desmosome-­‐ type of intracellular junction in animal cells. They are analogous to rivets. Diffusion-­‐ spontaneous movement of substance down its concentration gradient. Moves from high concentration to low concentration. Electrochemical Gradient-­‐ diffusion gradient of an ion; includes concentration difference of ion and electrical potential (membrane potential) Endocytosis-­‐ when cells take in molecules by forming new vesicles from plasma membrane Endosymbiont Theory -­‐ theory that eukaryotic organelles evolved from symbiotic relationships between separate singled celled organisms Eukaryotes-­‐ refers to organisms with cells that include a membrane enclosed nucleus and membrane enclosed organelles. Eukaryotes belong to the domain Eukarya Exocytosis-­‐ method of removing molecules from cell; molecules are placed in vesicles and then the vesicles fuse with the plasma membrane; the molecules that were in the vesicles are excreted Extracellular matrix-­‐ substance in which animal tissue cells are located. Constructed for proteins and polysaccharides. Flagella-­‐ cellular appendage for movement. Gap Junction-­‐ type of intercellular junction in animal cells. Allows cells to exchange materials. Glycolipids-­‐ lipid with a carbohydrate covalently attached Glycoproteins-­‐ a protein with at least one carbohydrate attached Golgi Apparatus-­‐ eukaryotic organelle consisting of membrane sacs. Used to modify the endoplasmic reticulum and to produce carbohydrates. Hypertonic-­‐ between two solutions, the hypertonic solution is the one with higher solute concentration. If a cell is placed in a hypertonic solution, water will leave the cell. Hypotonic-­‐ between two solutions, the hypotonic solution is the one with lower solute concentration. If a cell is placed in hypotonic solution, water will enter the cell. Integral Proteins-­‐ proteins permanently attached to membrane; includes all transmembrane proteins Intermediate Filament-­‐ cytoskeleton component; intermediate because they are in between microtubules and microfilaments in size. Isotonic-­‐ when two solutions have same solute concentration; no effect on water movement Ligand-­‐ molecule that specifically binds to another Lysosome-­‐ a membrane sac containing hydrolytic enzymes. Found in cytoplasm of eukaryotes and some protists. Membrane Potential-­‐ charge difference between cell's internal cytosol and the surrounding environment. Microfilament-­‐ thinnest filament of cytoskeleton. Composed of actin. Works together with myosin to cause cell contraction. Microtubules-­‐ hollow rods that help make up the cytoskeleton. Made of tubulin. Also found in cilia and flagella. Mitochondria-­‐ eukaryotic organelle used for cellular respiration. Motor proteins-­‐ class of protein that produces movement in a cell. Myosin-­‐ protein filament that works with actin filaments as a motor protein; causes cell contraction Nuclear envelope-­‐ eukaryotic double membrane that encloses nucleus. Separates nucleus from cytoplasm. Nucleoid-­‐ DNA dense region in a prokaryote Osmosis-­‐ diffusion of water across a selectively permeable membrane Osmotic/Solute Potential-­‐ component of water potential; measures effect of solutes on the direction of water movement Passive Transport-­‐ transport of a substance across a membrane that requires no energy input Peripheral Proteins-­‐ protein loosely attached to membrane or to integral protein; not attached to membrane Peroxisome-­‐an organelle containing enzymes that produce/degrade hydrogen peroxide (H2O2). Used for catabolism. Phagocytosis-­‐ type of endocytosis in which cell ingests large particles/substances. Used by many cells including immune cells in animals. Pinocytosis-­‐ type of endocytosis. Cell ingests extracellular fluid and its solutes. Plasma Membrane-­‐ selective barrier that acts as boundary of cell Plasmodesmata-­‐ open channel in plant cell wall that connects cytosol of adjacent cells Plasmolysis-­‐ Occurs in cells with cell walls when cell loses water to hypertonic environment; cell shrivels and membrane moves away from cell wall Plastids-­‐ family of closely related organelles. These include chloroplasts, chromoplasts, and leucoplasts. Plastids are used in photosynthetic organisms such as plants. Pressure Potential-­‐ component of water potential; physical pressure on solution. Prokaryotes-­‐ single celled organisms that lack membrane enclosed nucleus and membrane enclosed organelles. Include the domains archaea and bacteria. Receptor Mediated Endocytosis-­‐ variation of endocytosis that involves the use of specific binding proteins in the plasma membrane for specific molecules or particles, and clathrin-­‐coated pits that become clathrin-­‐
coated vesicles Receptor Proteins-­‐ accepts signals and initiates responses. Ribosomes-­‐ a molecular machine consisting of rRNA and proteins; consist of a large and small subunit; used for protein synthesis (translation) Rough Endoplasmic Reticulum-­‐ part of ER that has ribosomes Selective Permeability-­‐ regulatory property of biological membranes. Allows some substances to pass and prevents others from passing. Smooth Endoplasmic Reticulum-­‐ part of ER that has no ribosomes Tension-­‐ a force that stretches something tight; in the context of cytoskeletons, tension refers to forces applied to cells that stretch the cytoskeletal filaments Tight Junction-­‐ type of intercellular junction in animal cells. Prevents leaks. Vacuoles-­‐ a vesicle that generally acts as storage; the materials they can contain and their functions can be widely varied. Vesicles-­‐ a membrane sac in the cytoplasm. Water Potential-­‐ the physical property that predicts the direction water will move; determined by solute concentrations and pressure.