the basic biological unit of living organisms, containing a nucleus and a variety of organelles enclosed by a limiting membrane
Generalized cells are round or spherical in shape and perform basic life functions. Cheek cells are generalized cells. They are flat, basically round, and protect the inside lining of the mouth.
a dense central body in most cells containing the genetic material of the cell
Nuclear envelope/ nuclear membrane
The double-layered membrane enclosing the nucleus of a eukaryotic cell. The nuclear envelope has pores that allow the passage of materials into and out of the nucleus.
An octagonal opening where the inner and outer membranes of the nuclear envelope are continuous.
any one of the small, dense structures composed largely of ribonucleic acid that are situated within the cytoplasm of cells. Nucleoli are essential in the formation of ribosomes that synthesize cell proteins.
A complex of nucleic acids and proteins in the cell nucleus that stains readily with basic dyes and condenses to form chromosomes during cell division.
barlike body of tightly coiled chromatin; visible during cell division
membrane that encloses cell contents; outer limiting membrane
the tiny projections on the free surfaces of some epithelial cells' increase surface area of absorbtion
an intercellular junction at which adjacent plasma membranes are joined tightly together by interlinked rows of integral membrane proteins, limiting or eliminating the intercellular passage of molecules.
tight intercellular junctions formed by apposed areas of thickened cell membrane; intermediate filaments of one cell link with those of an adjacent cell
regions of high and special ionic permeability between closely apposed cells. They are places at which cells exchange molecules of large size and provide an avenue by which developing cells can influence each other. Called also nexus.
the functional unit of a gap junction; the hexagonal array of membrane-spanning proteins around a central channel that connects with its counterpart in an adjacent cell to form the intercellular pore of the gap junction.
the substance of a cell other than that of the nucleus
an epithelial cell is shown joined to adjacent cells by the three common types of cell junctions; tight, desmosomes, and gap.
The fluid component of cytoplasm, excluding organelles and the insoluble, usually suspended, cytoplasmic components.
specialized structures in a cell that perform specific metabolic functions
a usually lifeless, often temporary, constituent in the cytoplasm of a cell.
the rodlike cytoplasmic organelles responsible for ATP generation
cytoplasmic organelles at which proteins are synthesized
endoplasmic reticulum (ER)
a membranous network of tubular or saclike channels in the cytoplasm of a cell
a small network, especially a protoplasmic network in cells.
is a protein which serves the function of moving other materials within an organism. Transport proteins are vital to the growth and life of all living things.
a smooth network without the ribosomes.
is an organelle found in most eukaryotic cells
the cellular process of elaborating and releasing a specific product; this activity may range from separating a specific substance of the blood to the elaboration of a new chemical substance.
organelles that originate from the golgi apparatus and contain strong digestive enzymes
any of the microbodies present in vertebrate animal cells, especially liver and kidney cells, which are rich in the enzymes peroxidase, catalase, d-amino acid oxidase, and, to a lesser extent, urate oxidase.
compounds with an unpaired electron, which makes them extremely reactive.
a conspicuous internal reinforcement in the cytoplasm of a cell, consisting of tonofibrils, filaments of the terminal web, and other microfilaments
a substance formed in a chemical process that is essential to formation of the end-product of the process.
any of the submicroscopic filaments composed chiefly of actin, found in the cytoplasmic matrix of almost all cells, often with the microtubules.
Slender, elongated anatomical channels in worms
a minute body found near the nucleus of the cell composed of microtubules; active in cell division
tiny, hairlike projections on cell surfaces that move in a wave like manner
long whiplike extensions of the cell membrane of some bacteria and sperm, serve to propel the cell
a homogenous mixture of two or more components
the substance present in the largest amount in a solution; or dissolving medium
the dissolved substance in a solution
the portion of the total body water with its dissolved solutes which are within the cell membranes.
fluid between the cells
a barrier allows some substances to pass through it while excluding others
membrane transport processes that do not require cellular energy ATP; eg., difusion, which is driven by kinetic energy.
net movement of a substance across a membrane against a concentration or electrical gradient; requires release and use of cellular energy.
the spreading of particles in a gas or solution with a movement towards uniform distribution of particles
a difference in the concentration of a substance on two sides of a permeable barrier
the unassisted diffusion of solutes through the plasma membrane (or any selectively permeable membrane)
the diffusion of a solvent through a membrane from a dilute solution into a more concentrated one.
provides passage for certain needed substances that are both lipid-insoluble and too large to pass through the membrane pores
the passage of a solvent and dissolved substances through a membrane or filter
difference in hydrostatic (fluid) pressure that drives filtration
net movement of a substance across a membrane against a concentration or electrical gradient; requires release and use of cellular energy
active transports that use ATP to energize its protein carriers
moves substances into or out of cells without their actually crossing the plasma membrane
the discharge from a cell of particles that are too large to diffuse through the wall; the opposite of endocytosis
the uptake by a cell of material from the environment by invagination of its plasma membrane; it includes both phagocytosis and pinocytosis.
the ingestion of solid particles by cells
the engulfing of extracellular fluid by cells
the main cellular mechanism for taking up specific target molecules
cell life cycle
the series of changes a cell goes through from the time it is formed until it divides.
the cell grows and carries on its usual metabolic activities
during which the cell reproduces with itself
division of the nucleous
the division of the cytoplasm
the first stage in cell reduplication in either meiosis or mitosis
either of two parallel, spiral filaments joined at the centromere which make up a chromosome.
small button like body
composed of microtubules
the second stage of cell division (mitosis or meiosis), in which the chromosomes, each consisting of two chromatids, are arranged in the equatorial plane of the spindle prior to separation.
the third stage of division of the nucleus in either meiosis or mitosis.
the last of the four stages of mitosis and of the two divisions of meiosis, in which the chromosomes arrive at the poles of the cell and the cytoplasm divides; in plants, the cell wall also forms.
the indentation of the cell's surface that begins the progression of cleavage, by which animal and some algal cells undergo cytokinesis, the final splitting of the membrane, in the process cell division.
biological units of heredity located in chromatin; transmits hereditary information
a substance formed by living ells that act as catalyst in bodily chemical reactions
RNA (ribonuleic acid)
the nucleic acid that contains ribose; acts in protein synthesis
transfer RNA molecules
small cloverleaf-shaped molecules
helps form the ribosome, where proteins are built
messenger RNA molecule (mRNA)
are long, single nucleotide strands that resemble half of a DNA molecule and carry the message containing instructions for protein synthesis from the DNA gene in the nucleus to the ribosomes in the cytoplasm
the synthesis of RNA using a DNA template catalyzed by RNA polymerase; the base sequences of the RNA and DNA are complementary.