Campbell Essential Biology Ch 4

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Light Microscope (LM)

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An optical instrument with lenses that refract (bend) visible light to magnify images and project them into a viewer's eye or onto photographic film.

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Magnification

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An increase in the apparent size of an object.

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Resolving Power

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A measure of the clarity of an image; the ability of an optical instrument to show two objects as separate.

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Scanning Electron Microscope (SEM)

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A microscope that uses an electron beam to study the surface architecture of a cell or other specimen.

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Transmission Electron Microscope (TEM)

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A microscope that uses an electron beam to study the internal structure of thinly sectioned specimens.

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Prokaryotic Cells

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A type of cell lacking a nucleus and other organelles; found only in the domain of Bacteria and Archaea.

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Eukaryotic cells

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A type of cell that has a membrane enclosed nucleus and other membrane enclosed organelles. All organisms except bacteria and archaea are composed of eukaryotic cells.

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Plasma Membrane

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The thin layer of lipids and proteins that sets a cell off from its surroundings and acts as a selective barrier to the passage of ions and molecules into and out of the cell; consists of a phospholipid bilayer in which proteins are embedded.

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Ribosomes

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A cellular structure consisting of RNA and protein organized into two subunits and functioning as the site of protein synthesis in the cytoplasm. The subunits are constructed in the nucleolus.

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Nucleus

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1) An atom's central core, containing protons and neutrons. 2) Th e genetic control center of a eukaryotic cell.

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Cytoplasm

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Everything inside a eukaryotic cell between the plasma membrane and the nucleus; consists of a semifluid medium and organelles; can also refer to the interior of a prokaryotic cell.

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Phospholipids

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A molecule that is a constituent of the inner bilayer of biological membranes, having a hydrophilic head and a hydrophobic tail.

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Phospholipid bilayer

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A double layer of phopholipid molecules (each molecule consisting of a phosphate group bonded to two fatty acids) that is the primary component of all cellular membranes.

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Fluid Mosaic

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A description of membrane structure, depicting a cellular membrane as a mosaic of diverse protein molecules embedded in a fluid bilayer made of phopholipid molecules.

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Extracellular Matrix

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A substance in which the cells of an animal tissue are embedded; consists of protein and polysaccharides.

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Cell Junctions

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A structure that connects animal cells to one another in a tissue

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Nuclear Envelope

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A double membrane, perforated with pores, that encloses the nucleus and separates it from the rest of the eukaryotic cell.

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Chromatin

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The combination of DNA and proteins that constitutes chromosomes; often used to refer to the diffuse, very extended form taken by the chromosomes when a eukaryotic cell is not dividing.

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Chromosome

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A gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of a prokaryotic cell. Each one consists of one very long threadlike DNA molecule and associated proteins.

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Nucleolus

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A structure within the nucleus of a eukaryotic cell where ribosomal RNA is made and assembled with proteins to make ribosomal subunits; consists of parts of the chrpmatin DNA, RNA transcribed from the DNA, and proteins imported from the cytoplasm.

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Endomembrane System

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A network of organelles that partitions the cytoplasm of eukaryotic cells into functional compartments. Some of the organelles are structurally connected to each other, whereas others are structurally separate bu functionally connected by the traffic of vesicles between them.

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Edoplasmic Reticulum (ER)

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An extensive membranous network in a eukaryotic cell, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.

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Rough ER

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A network of interconnected membranous sacs in a eukaryotic cell's cytoplasm. Its membranes are studded with ribosomes that make membrane proteins and secretory proteins. It constructs membrane from phospholipids and proteins.

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Transport Vesicles

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A tiny membranous sphere in a cell's cytoplasm carrying molecules produced by the cell. The vesicle buds from the ER or Golgi apparatus and eventually fuses with another organelle or the plasma membrane, releasing its contents.

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Smooth ER

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A network of interconnected membanous tubules ina eukaryotic cell's cytoplasm. Lacks ribosomes. Enzymes embedded in the membrane function in the synthesis of certain kinds of molecules, such as lipids.

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Golgi Apparatus

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An organelle in eukaryotic cells consisting of stacks of membranous sacs that modify, store, and ship products of the endoplasmic reticulum.

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Lysosome

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A digestive organelle in eukaryotic cells, contains enzymes that digest the cell's food and wastes.

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Food Vacuoles

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1) A tiny sac in a eukaryotic cell's cytoplasm that engulfs nutrients. 2) The simplest type of digestive compartment.

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Vacuole

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A membrane-enclosed sac, part of the endomembrane system of a eukaryotic cell, having diverse functions.

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Central Vacuole

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A membrane-enclosed sac occupying most of the interior of a mature plant cell, having diverse roles in reproduction, growth, and development.

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Chloroplasts

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An organelle found in plants and photosyntheitc protists. enclosed by two concentric membranes, a chloroplast absorbs sunlight and uses it to power the synthesis of organic food molecules (sugars).

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Stroma

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A thick fluid enclosed by the inner membrane of a chloroplast. Sugars are made in the stroma by the enzymes of the Calvin Cycle.

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Grana/Granum

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A stack of hollow disks formed of thylakoid membrane in a chloroplast. The sites where light energy is trapped by chlorophyll and converted to chemical energy during the light reactions of photosynthesis.

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Mitochondira

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An organelle in eukaryotic cells where cellular respiration occurs. Enclosed by two concentric membranes it is where most of the cell's ATP is made.

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Matrix

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The thick fluid contained within the inner membrane of the mitochondria.

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Cristae/Crista

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A fold of the inner membrane of a mitochondrion. Enzyme molecules embedded in it make ATP.

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Microtubules

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The thickest of the three main kinds of fibers making up the cytoskeleton of a eukaryotic cell; a straight, hollow tube made of globular proteins called tubulins. Form the basis of the structure and movement of cilia and flagella.

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Cytoskeleton

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A meshwork of fine fibers in the cytoplasm of a eukaryotic cell; includes microfilaments, intermediate filaments, and microtubules.

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Flagella/Flagellum

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A long appendage that propels protists through the water and moves fluids across the surface of many tissue cells in animals. A cell may have one or more flagella.

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Cilia/Cilium

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The metabolic cycle that is fueled by acetyl CoA formed after glycolysis in cellular respiration. Chemical reactions in the cycle complete the metabolic breakdown of glucose molecules to carbon dioxide. The cycle occurs in the matrix of mitochondria and supplies most of the NADH molecules that carry energy to the electron transport chains. Also referred to as the Krebs cycle.

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Kinetic energy

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Energy of motion. Moving matter performs work by transferring its motion to other matter, such as leg muscles pushing bicycle pedals,

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Energy

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The capacity to perform work, or to move matter in a direction it would not move if left alone.

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Conservation of Energy

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The principle that energy can neither be created nor destroyed.

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Potential energy

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Stored energy; the energy that an oobject has due to its location and/or arrangement. Water behind a dam and chemical bonds both possess potential energy.

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Entropy

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A measure of disorder, or randomness. One form of disorder is heat, which is random molecular motion.

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Chemical energy

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Energy stored in the chemical bonds of molecules; a form of potential energy.

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Heat

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The amount of kinetic energy contained in the movement of the atoms and molecules in a body of matter. Heat is energy in its most random form.

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ATP - Adenosine Triphosphate

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A molecule composed of adenosine and three phosphate groups; the main energy source for cells.

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ADP - Adenosine Diphosphate

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A molecule composed of adenosine and two phosphate groups. The molecule ATP is made by combining these molecules. with a third phosphate in an energy-consuming reaction

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Calorie

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The amount of energy that raises the temperature of 1 g of water by 1*C.

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Metabolism

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The total of all the chemical reactions in an organism.

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Enzymes

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A protein that serves as a biological catalyst, changing the rate of a chemical reaction without itself being changed in the process.

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Activation Energy

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The amount of energy that reactants must absorb before a chemical reaction will start.

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Substrate

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1) A specific substance (reactant) on which an enzyme acts. Each enzyme recognizes only the specific substrate of the reaction it catalyzes. 2) A surface in or on which an organism lives.

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Active Site

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The part of an enzyme molecule where a substrate molecule attaches (by means of weak chemical bonds); typically, a pocket or groove on the enzyme's surface.

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Induced Fit

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The interaction between a substrate molecule and the active site of an enzyme, which changes shape slightly to embrace the substrate and catalyze the reaction

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Enzyme Inhibitors

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A chemical that interferes with an enzyme's activity by changing the enzyme's shape, either by plugging up the active site or binding to another site on the enzyme.

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Feedback Regulation

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A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway

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Transport Proteins

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A membrane protein that helps move substances across a cell membrane.

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Diffusion

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The spontaneous movement of particles of any kind down a concentration gradient; that is, movement of particles from where they are more concentrated to where they are less concentrated

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Passive Transport

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The diffusion of a substance across a biological membrane without any input of energy.

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Concentration Gradient

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An increase or decrease in the density of a chemical substance within a given region. Cells often maintain concentration gradients of hydrogen ions across their membranes. When a gradient exists, the ions or other chemical substances involved tend to move from where they are more concentrated to where they are less concentrated.

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Facilitated diffusion

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The passage of a substance across a biological membrane down its concentration gradient, aided by specific transport proteins.

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Hypertonic

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In comparing two solutions, referring to the one with the greater concentration of solutes.

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Hypotonic

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In comparing two solutions, referring to the one with the lower concentration of solutes.

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Osmosis

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The diffusion of water across a selectively permeable membrane

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Isotonic

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Having the same solute concentration as another solution.

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Osmoregulation

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The control of the gain or loss of water and dissolved solutes in an organism.

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Plasmolysis

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A phenomenon that occurs in plant cells in a hypertonic environment. The cell loses water and shrivels, and its plasma membrane pulls away from the cell wall, usually killing the cell.

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Exocytosis

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The movement of materials out of the cytoplasm of a cell via membranous vesicles or vacuoles.

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Endocytosis

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The movement of materials into the cytoplasm of a cell via vesicles or vacuoles.

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Pinocytosis

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Cellular "drinking"; a type of endocytosis in which the cell takes fluid and dissolved solutes into small membranous vesicles.

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Phagocytosis

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Cellular "eating"; a type of endocytosis whereby a cell engulfs large molecules, other cells, or particles into its cytoplasm.

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Receptor-mediated Endocytosis

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The movement of specific molecules into a cell by the inward budding of vesicles. The vesicles contain proteins with receptor sites specific to the molecules being taken in.

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Signal transduction pathway

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A series of molecular changes that converts a signal on a target cell's surface to a specific response inside the cell.