Chapter 4 Flashcards
LIGHT MICROSCOPE (LM)
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.
CELL THEORY
The theory that all living things are composed of cells and that all cells come from other cells.
ELECTRON MICROSCOPE (EM)
A microscope that uses magnets to focus an electron beam through, or onto the surface of, a specimen. An electron microscope achieves a hundredfold greater resolution than a light microscope.
SCANNING ELECTRON MICROSCOPE (SEM)
A microscope that uses an electron beam to study the surface details of a cell or other specimens.
TRANSMISSION ELECTRON MICROSCOPE (TEM)
A microscope that uses an electron beam to study the internal structure of thinly sectioned specimens.
PLASMA MEMBRANE
The membrane at the boundary of every cell that acts as a selective barrier to the passage of ions and molecules into and out of the cell; consists of a phospholipid bilayer with embedded proteins.
PROKARYOTIC CELLS
cells that lack membrane-bound nuclei
EUKARYOTIC CELLS
anycellor organism that possesses a clearly definednucleus.
CYTOSOL
The semifluid portion of the cytoplasm.
CHROMOSOMES
A gene-carrying structure found in
RIBOSOMES
the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of a prokaryotic cell. A chromosome consists of one very long DNA molecule and associated proteins.
CYTOPLASM
The contents of 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.
NUCLEOID
A non–membrane-bounded region in a prokaryotic cell where the DNA is concentrated.
FLAGELLA
A long cellular appendage specialized for locomotion. The flagella of prokaryotes and eukaryotes differ in both structure and function. Like cilia, eukaryotic flagella have a “9 + 2” arrangement of microtubules covered by the cell’s plasma membrane.
ORGANELLES
a specialized part of a cell; analogous to an organ
CELLULAR METABOLISM
All the chemical activities of a cell.
NUCLEUS
(1) An atom’s central core, containing protons and neutrons. (2) The organelle of a eukaryotic cell that contains the genetic material in the form of chromosomes, made of chromatin.
CHROMATIN
The complex of DNA and proteins that makes up eukaryotic chromosomes; often used to refer to the diffuse, very extended form taken by chromosomes when a cell is not dividing.
NUCLEAR ENVELOPE
A double membrane that encloses the nucleus, perforated with pores that regulate traffic with the cytoplasm.
NUCLEOLUS
A structure within the nucleus where ribosomal RNA is made and assembled with proteins imported from the cytoplasm to make ribosomal subunits.
ENDOMEMBRANE SYSTEM
A network of membranes inside and sur- rounding a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles.
VESICLES
a small anatomically normal sac or bladderlike structure (especially one containing fluid)
ENDOPLASMIC RETICULUM (ER)
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. See also rough ER; smooth ER.
SMOOTH ENDOPLASMIC RETICULUM
That portion of the endoplasmic reticulum that lacks ribosomes.
ROUGH ENDOPLASMIC RETICULUM
That portion of the endoplasmic reticulum with ribosomes attached that make mem- brane proteins and secretory proteins.
GLYCOPROTEIN
A protein with one or more short chains of sugars attached to it.
TRANSPORT VESICLE
A small membranous sac in a eukaryotic cell’s cytoplasm carrying molecules produced by the cell. The vesicle buds from the endoplasmic reticulum or Golgi and eventually fuses with another organelle or the plasma membrane, releasing its contents.
GOLGI APPARATUS
An organelle in eukaryotic cells consisting of stacks of membranous sacs that modify, store, and ship products of the endoplasmic reticulum.
VACUOLES
a tiny cavity filled with fluid in the cytoplasm of a cell
CENTRAL VACUOLE
In a plant cell, a large membranous sac with diverse roles in growth and the storage of chemicals and wastes.
PEROXISOMES
a small organelle present in the cytoplasm of many cells, which contains the reducing enzyme catalase and usually some oxidases.
MITOCHONDRIA
an organelle containing enzymes responsible for producing energy
MITOCHONDRIAL MATRIX
The compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the citric acid cycle.
CHLOROPLASTS
plastid containing chlorophyll and other pigments; in plants that carry out photosynthesis
STROMA
The dense fluid within the chloroplast that sur- rounds the thylakoid membrane. Sugars are made in the stroma by the enzymes of the Calvin cycle.
THYLAKOIDS
A flattened membranous sac inside a chloroplast. Thylakoid membranes contain chlorophyll and the molecular complexes of the light reactions of photosynthesis. A stack of thylakoids is called a granum.
GRANUM
A stack of membrane-bounded thylakoids in a chloroplast. Grana are the sites where light energy is trapped by chlorophyll and converted to chemical energy during the light reactions of photosynthesis.
ENDOSYMBIONT THEORY
The theory that mitochondria and chloroplasts originated as prokaryotic cells engulfed by an ancestral eukaryotic cell. The engulfed cell and its host cell then evolved into a single organism.
CYTOSKELETON
A network of protein fibers in the cytoplasm of a eukaryotic cell; includes microfilaments, intermediate filaments, and microtubules.
MOTOR PROTEINS
a class of molecularmotorsthat can move along the cytoplasm of animal cells. They convert chemical energy into mechanical work by the hydrolysis of ATP.
MICROTUBULES
a microscopically small tubule
CENTROSOME
A structure found in animal cells from which microtubules originate and that is important during cell division. A centrosome has two centrioles.
INTERMEDIATE FILAMENTS
cytoskeletal components found in the cells of vertebrate animal species, and perhaps also in other animals, fungi, plants, and unicellular organisms. They are composed of a family of related proteins sharing common structural and sequence features.
MICRO FILAMENTS
filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton and are primarily composed of polymers of actin, but in cells are modified by and interact with numerous other proteins.
CILIA
A short cellular appendage specialized for loco- motion or moving fluid past the cell, formed from a core of nine outer doublet microtubules and two single microtubules (the “9 + 2” arrangement) covered by the cell’s plasma membrane.
EXTRA CELLULAR MATRIX (ECM)
a three-dimensional network ofextracellularmacromolecules, such as collagen, enzymes, and glycoproteins, that provide structural and biochemical support of surrounding cells.
INTEGRINS
proteins that function mechanically, by attaching the cell cytoskeleton to the extracellular matrix (ECM), and biochemically, by sensing whether adhesion has occurred
PLASMODESMATA
An open channel in a plant cell wall that connects the cytoplasm of adjacent cells.
