Glossary of BIOLOGY Glencoe Sicence North Carolina Edition: Chaper 7 vocabulary

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define "Cell"
basic unit of all organisms; all living things are
composed of cells.
Define "compound light microscope"
instrument that uses light and a series of lenses to magnify objects in steps; can magnify an object up to 1500 times its original size.
Define "cell theory"
the theory that (1) all organisms are composed
of one or more cells, (2) the cell is the basic unit of
structure and organization of organisms, (3) all cells come
from preexisting cells.
Define "electron microscope"
instrument that uses a beam
of electrons instead of light to magnify structures up to
500 000 times actual size; allows scientists to view structures
within a cell.
Define "organelles"
membrane-bound structures with particular
functions within eukaryotic
Define "prokaryotes"
unicellular organisms, such as bacteria, each of which is composed of a prokaryotic cell. Prokaryotic cells lack internal membrane-bound structures.
Define "eukaryotes"
unicellular or multicellular organisms,
such as yeast, plants, and animals, composed of eukaryotic
cells, which contain a true nucleus and membrane-bound
Define "nucleus"
positively charged center of an
atom composed of neutrons and positively charged protons,
and surrounded by negatively charged electrons. (p. 174) in
eukaryotic cells, the central membrane-bound organelle that
manages cellular functions and contains DNA.
Define "plasma membrane"
flexible boundary between the
cell and its environment; allows materials such as water and
nutrients to enter and waste products to leave.
Define "selective permeability"
feature of the plasma
membrane that maintains homeostasis within a cell
by allowing some molecules into the cell while keeping
others out.
Define "phospholipids"
lipids with an attached phosphate group; plasma membranes are composed
of phospholipid bilayer with embedded proteins.
Define "fluid mosaic model"
structural model of the plasma
membrane where molecules are free to move sideways
within a lipid bilayer.
Define "transport proteins"
proteins that span the plasma
membrane creating a electively permeable membrane that regulates which molecules enter and leave a cell.
Define "chromatin"
long strands of DNA
found in the eukaryotic cell nucleus; condense to form
Define "nucleolus"
organelle in eukaryotic
cell nucleus that produces ribosomes.
Define "ribosomes"
nonmembrane-bound organelles in the
nucleus where proteins are assembled.
Define "cytoplasm"
clear, gelatinous fluid in cells that is the
site of numerous chemical reactions; in eukaryotic cells, it
suspends the cell’s organelles.
Define "endoplasmic reticulum (ER)"
organelle in eukaryotic
cells with a series of highly folded membranes
surrounded in cytoplasm; site of cellular chemical
reactions; can either be rough (with ribosomes) or smooth
(without ribosomes).
Define "Golgi apparatus"
organelle in eukaryotic
cells with a system of flattened tubular membranes; sorts and
packs proteins and sends them to their appropriate
Define "vacuole"
membrane-bound space in the cytoplasm of
cells used for the temporary storage of materials.
Define "lysosomes"
organelles that contain digestive
enzymes; digest excess or worn out organelles, food particles,
and engulfed viruses or bacteria.
Define "chloroplasts"
chlorophyll-containing organelles
found in the cells of green plants and some protists; capture
light energy and converted it to chemical energy.
Define "plastids"
group of plant organelles that are used for
storage of starches, lipids, or pigments.
Define "chlorophyll"
light-absorbing pigment in plants and
some protists that is required for photosynthesis; absorbs
most wavelengths of light except for green.
Define "mitochondria"
eukaryotic membrane-bound organelles
that transform energy stored in food molecules; has a
highly folded inner membrane that produces energy-storing
Define "cytoskeleton"
cellular framework found within the
cytoplasm composed of microtubules and microfilaments.
Define "microtubules"
thin, hollow cylinders made of protein
that provide structural support for eukaryotic cells.
Define "microfilaments"
thin, solid protein fibers that provide structural support for eukaryotic cells.
Define "cilia"
short, numerous, hairlike projections composed of pairs of microtubules; frequently aid in locomotion.
Define "flagella"
long projections composed of microtubules; found on some cell surfaces; they help propel cells and organisms by a whiplike motion.

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