Chapter 4 Flashcards
(48 cards)
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.