Introduction to Cells Vocabulary
Cell - The smallest structural unit of an organism that is capable of independent functioning, consisting of one or more
nuclei, cytoplasm, and various organelles, all surrounded by a semipermeable cell membrane.
cell theory - Scientific theory that states:
1. All living organisms are composed of one or more cells.
2. Cells are the most basic unit for function and structure of all organisms.
3. All cells come from cells that already exist.
Nucleus – The largest of the membrane-bounded organelles which characterize eukaryotic cells; it is thought of as the
control center since it contains the bulk of the cell's genetic information in the form of deoxyribonucleic acid (DNA).
Nucleiod – Ring of DNA found in prokaryotes.
Unicellular – an organism made up of a single cell.
Prokaryote –unicellular organism lacking membrane bound nucleus and organelles. Bacteria are Prokaryotes.
Multicellular – an organism made up of more than one cell
Eukaryote - Any organism composed of one or more cells, each of which contains a clearly defined nucleus enclosed by a
membrane, along with organelles (small, self-contained, cellular parts that perform specific functions). The organelles
include mitochondria, chloroplasts, a Golgi apparatus, an endoplasmic reticulum, and lysosomes. All organisms except
bacteria are eukaryotes; bacteria are prokaryotes.
Tissue – A group of cells that together perform a function, and are similar in shape. There are four basic types of tissue:
muscle, nerve, epidermal, and connective.
Organ – a group of tissues that together perform closely related functions.
organ system -a group of organs that work together to perform a specific function.
Organelle – A differentiated structure within a eukaryotic cell, such as a mitochondrion, vacuole, or chloroplast, that
performs a specific function.
Cytoplasm – liquid or gel within a cell, found between the cell membrane and nuclear envelope. The organelles of a cell
are found in the cytoplasm. The nucleus does not contain cytoplasm.
nuclear envelope - The double-layered membrane enclosing the nucleus of a cell. Also called nuclear membrane.
Chromatin –Material visible within the nucleus; made up of nucleic acids and proteins. Stains readily with basic dyes and
condenses to form chromosomes during cell division.
Chromosome –thread-like structures within the nucleus containing Genetic information that is passes on from one
generation of cells to the next. Made up of long strands of DNA coiled around proteins.
Nucleolus – area of the nucleus responsible for making ribosomes. Appears as a dark staining dot within the nucleus of a
cell.
Ribosome - Tiny particle, the site of protein synthesis, that is present in large numbers in living cells. They can be found
free in the cytoplasm and attached to the endoplasmic reticulum. They are made up of protein and RNA.
endoplasmic reticulum -(ER)- membrane continuous with the nuclear envelope, responsible for the modification of
proteins. The rough RR has Ribosomes attached that synthesize the proteins to be modified. The smooth ER has no
ribosomes attached and is responsible for making phospholipids, steroids and helps in detoxification of the cell.
Golgi apparatus – membrane bound organelle that sorts, modifies and packages macromolecules such as proteins for
delivery to other parts of the cell.
Lysosome – membrane bound sacs of digestive enzymes, they break down materials taken into the cell from the outside,
as well as break down parts of the cell that are no longer functioning or needed.
Vacuole – a membrane bound organelle that can function to remove unwanted structural debris, isolate materials
that might be harmful to the cell, contain waste products, maintain an internal pH, storage or large molecules
such as starch, export unwanted substances from the cell, allow the cell to change shape. In plants it is
important in maintaining cell shape by increasing the cells internal pressure.
Mitochondria - a double membrane bound organelle that is responsible for cellular respiration. Mitochondria contain their
own DNA.
Chloroplast – a double organelle with a double membrane found in green plants and algae. The site of Photosynthesis.
Has a green color due to the pigment chlorophyll. Chloroplasts have their own DNA.
Cytoskeleton -A system of filaments found in the cytoplasm of cells and responsible for the maintenance of and changes
in cell shape, cell locomotion, movement of various elements in the cytoplasm, cell division, chromosome organization and
movement, and the adhesion of a cell to a surface or to other cells.
Microtubule –hollow tube like structures, made of protein, in the cytoplasm of eukaryotic cells, providing structural support
and assisting in cellular locomotion and transport.
Cilia -Short, hair like structures that are found on the outside of some cells. Capable of beating in unison, cilia perform a
variety of functions, including providing the means of locomotion for some protozoans, moving mammalian ova (eggs)
through oviducts, generating water currents to carry food and oxygen past the gills of clams, and cleaning debris from
mammalian respiratory systems.
Flagella –whip-like structure used for locomotion in single celled organisms and sex cells.
Pili - Many species of bacteria have pili (singular, pilus), small hairlike projections emerging from the outside cell surface. These
outgrowths assist the bacteria in attaching to other cells and surfaces, such as teeth, intestines, and rocks. Without pili, many
disease-causing bacteria lose their ability to infect because they're unable to attach to host tissue.
centriole -a barrel shaped microtubule structure found in most animal cells and algae. Centrioles are very important in the
cell division process.
cell membrane -The semi permeable membrane that encloses the cytoplasm of a cell. Also called plasma membrane.
Made up of a phospholipid bi-layer and proteins.
cell wall -The rigid outer covering of a typical plant cell, composed mainly of cellulose and lying outside the cell membrane.
Animal cells do not have cell walls. It is the cell walls that give plant stems and wood their stiffness.
Cellulose -A complex carbohydrate, (C6H10O5)n, that is composed of glucose units, forms the main constituent of the cell
wall in most plants, and is important in the manufacture of numerous products, such as paper, textiles, pharmaceuticals,
and explosives.
Chlorophyll -green pigments that are found in the chloroplasts of plants and in other photosynthetic organisms such as
cyanobacteria. (C55H72MgN4O5)
Compound microscope - A microscope consisting of an objective and an eyepiece at opposite ends of an adjustable tube.
electron microscope - A device for forming greatly magnified images of objects by means of electrons. Electron
Microscopes allow the visual examination of structures too small to be resolved with ordinary compound or light
microscopes.