-
actin filament
cytoskeletal filaments of eukaryotic cells composed of the protein actin; also refers to the thin filaments of muscle cells.
-
active site
region on the surface of an enzyme where the substrate binds and where the reaction occurs
-
active transport
use of a plasma membrane carrier protein and energy to move a substance into or out of a cell from lower to higher concentration
-
-
anaerobic
growing or metabolizing in the absence of oxygen
-
cell theory
one of the major theories of biology; states that all organisms are made up of cells and cells come only from preexisting cells.
-
cellular respiration
metabolic reactions that use the energy primarily from carbohydrates but also from fatty acid or amino acid breakdown to produce ATP molecules
-
centrosome
central microtubule organizing center of cells. in animal cells, it contains centrioles.
-
chromatin
network of fine threads in the nucleus composed of DNA and proteins.
-
chromosome
chromatin condensed into a compact structure
-
cilium
short, hair-like projection from the plasma membrane, occurring usually in large numbers.
-
citric acid cycle
cycle of reactions in mitochondria that begins with citric acid; it breaks down an acetyl group as CO2, ATP, NADH, and FADH2 are given off; also called the Krebs cycle.
-
coenzyme
nonprotein organic molecule that aids the action of the enzyme to which it is loosely bound
-
cytoplasm
contents of a cell between the nucleus and the plasma membrane that contains the organelles
-
cytoskeleton
internal framework of the cell, consisting of microtubules, actin filaments, and intermediate filaments.
-
diffusion
movement of molecules or ions from a region of higher to lower concentration; it requires no energy and stops when the distribution is equal.
-
electron transport chain
passage of electrons along a series of membrane-bound carrier molecules from a higher to lower energy level; the energy released is used for the synthesis of ATP.
-
endomembrane system
a collection of membranous structures involved in transport within the cell
-
endoplasmic reticulum (ER)
system of membranous saccules and channels in the cytoplasm, often with attached ribosomes.
-
eukaryotic cell
type of cell that has a membrane-bound nucleus and membranous organelles
-
facilitated transport
use of a plasma membrane carrier to move a substance into or out of a cell from higher to lower concentration; no energy required.
-
fermentation
anaerobic breakdown of glucose that results in a gain of two ATP and end products such as alcohol and lactate.
-
flagellum
slender, long extension that propels a cell through a fluid medium
-
fluid-mosaic model
model for the plasma membrane based on the changing location and pattern of protein molecules in a fluid phospholipid bilayer
-
glycolysis
anaerobic breakdown of glucose that results in a gain of two ATP molecules
-
golgi apparatus
organelle, consisting of saccules and vesicles, that processes, packages, and distributes molecules about or from the cell
-
intermediate filament
rope-like assemblies of fibrous polypeptides in the cytoskeleton that provide support and strength to cells; so called because they are intermediate in size between actin filaments and microtubules.
-
lysosome
membrane-bound vesicle that contains hydrolytic enzymes for digesting macromolecules
-
metabolism
all of the chemical reactions that occur in a cell
-
microtubule
small cylindrical structure that contains 13 rows of the protein tubulin around an empty central core; present in the cytoplasm, centrioles, cilia, and flagella.
-
mitochondrion
membrane-bound organelle in which ATP molecules are produced during the process of cellular respiration
-
NAD+ (nicotinamide adenine dinucleotide)
coenzyme that functions as a carrier of electrons and hydrogen ions, especially in cellular respiration.
-
nuclear envelope
double membrane that surrounds the nucleus and is connected to the endoplasmic reticulum; has pores that allow substances to pass between the nucleus and the cytoplasm.
-
nuclear pore
opening in the nuclear envelope that permits the passage of proteins into the nucleus and ribosomal subunits out of the nucleus
-
nucleolus
dark-staining, spherical body in the cell nucleus that produces ribosomal subunits.
-
nucleoplasm
semifluid medium of the nucleus, containing chromatin
-
nucleus
membrane-bounded organelle that contains chromosomes and controls the structure and function of the cell
-
organelle
small membranous structure in the cytoplasm having a specific structure and function
-
osmosis
diffusion of water through a selectively permeable membrane
-
osmotic pressure
measure of the tendency of water to move across a selectively permeable membrane; visible as an increase in liquid on the side of the membrane with higher solute concentration
-
phagocytosis
process by which amoeboid-type cells engulf large substances, forming an intracellular vacuole
-
plasma membrane
membrane surrounding the cytoplasm that consists of a phospholipid bilayer with embedded proteins; functions to regulate the entrance and exit of molecules from the cell
-
polyribosome
string of ribosomes simultaneously translating regions of the same mRNA strand during protein synthesis
-
product
substance that forms as a result of a reaction
-
prokaryotic cell
type of cell that lacks a membrane-bounded nucleus and organelles
-
reactant
substance that participates in a reaction
-
ribosome
RNA and protein in two subunits; site of protein synthesis in the cytoplasm
-
selectively permeable
having degrees of permeability; the cell is impermeable to some substances and allows others to pass through at varying rates.
-
substrate
reactant in a reaction controlled by an enzyme
-
tonicity
osmolarity of a solution compared with that of a cell. if the solution is isotonic to the cell, there is no net movement of water; if the solution is hypotonic, the cell gains water; and if the solution is hypertonic, the cell loses water
-
vesicle
small, membrane-bounded sac that stores substances within a cell
|
|