Muscle protein making up the thin filaments in a sarcomere; its movement shortens the sarcomere, yielding muscle contraction. Actin filaments play a role in the movement of the cell and its organelles.
Adenosine Triphosphate (ATP)
Nucleotide with three phosphate groups. The breakdown of ATP into ADP +P makes energy available for energy-requiring processes in cells.
Junction between cells in which the adjacent plasma membranes do not touch but are held together by intercellular filaments attached to buttonlike thickenings.
Programmed cell death involving a cascade of specific cellular events leading to the death and destruction of the cell.
Smallest unit that displays the properties of life; composed of cytoplasm surrounded by a plasma membrane.
One of the major theories of biology, which states that all organisms are made up of cells; cells are capable of self-reproduction and come only from preexisting cells.
Structure that surrounds a plant, protistan, fungal, or bacterial cell and maintains the cell's shape and rigidity.
Metabolic reactions that use the energy from carbohydrates, fatty acid, or amino acid breakdown to produce ATP molecules.
Cell organelle, existing in pairs, that occurs in the centrosome and may help organize a mitotic spindle for chromosome movement during animal cell division.
Central microtubule organizing center of cells. In animal cells, it contains two centrioles.
Membrane-bound organelle in algae and plants with chlorophyll-containing membranous thylakoids; where photosynthesis takes place.
Network of fibrils consisting of DNA and associated proteins observed within a nucleus that is not dividing.
Structure consisting of DNA complexed with proteins that transmit genetic information from the previous generation of cells and organisms to the next generation.
Contents of a cell between the nucleus (nucleoid) region of bacteria and he plasma membrane.
Internal framework of the cell, consisting of microtubules, actin filaments, and intermediate filaments.
Endoplasmic Reticulum (ER)
System of membranous saccules and channels in the cytoplasm, often with attached ribosomes.
Type of cell that has a membrane-bounded nucleus and membranous organelles; found in organisms within the domain Eukarya.
Meshwork of polysaccharides and proteins that provides support for an animal cell and affects its behavior.
In bacteria, small, bristle-like fibers on bacterial cell surface that enables bacteria to adhere to surfaces.
Junction between cells formed by the joining of two adjacent plasma membranes; it lends strength and allows ions, sugars, and small molecules to pass between cells.
Organelle consisting of saccules and vesicles that processes, packages, and distributes molecules about or form the cell.
Unstructured semifluid substance that fills the space between cells in connective tissues or inside organelles.
Small, cylindrical organelle composed of tubulin protein around an empty central core; present in the cytoplasm, centrioles, cilia, and flagella.
Membrane-bounded organelle in which ATP molecules are produced during the process of cellular respiration.
Double membrane that surrounds the nucleus in eukaryotic cells and is connected to the endoplasmic reticulum; has pores that allow substances to pass between the nucleus and the cytoplasm.
Opening in the nuclear envelope that permits the passage of proteins into the nucleus and ribosomal subunits out of the nucleus.
Membrane-bounded organelle within a eukaryotic cell that contains chromosomes and controls the structure and function of the cell.
Small, often membranous structure in the cytoplasm having a specific structure and function.
Membrane surrounding the cytoplasm that consists of a phospholipid bilayer with embedded proteins; functions to regulate the entrance and exit of molecules from cell.
In plants, cytoplasmic strands that extend through pores in the cell wall and connect the cytoplasm of two adjacent cells.
String of ribosomes simultaneously translating regions of the same mRNA strand during protein synthesis.
Lacking a membrane-bounded nucleus and organelles; the cell type within the domains Bacteria and Archaea
Rough ER (Endoplasmic Reticulum)
Membranous system of tubules, vesicles, and sacs in cells; has attached ribosomes.
In the cell, release of a substance by exocytosis from a cell that may be a gland or part of a gland; in the urinary system, movement of certain molecules from blood into the distal tubule of a nephron so that they are added to urine.
Smooth ER (Endoplasmic Reticulum)
Membranous system of tubules, vesicles, and sacs in eukaryotic cells; lacks attached ribosomes.
Fluid within a chloroplast that contains enzymes involved in the synthesis of carbohydrates during photosynthesis.
Flattened sac within a granum whose membrane contains chlorophyll and where the light reactions of photosynthesis occur.
Junction between cells when adjacent plasma membrane proteins join to form an impermeable barrier.
Membrane-bounded sac, larger than a vesicle; usually functions in storage and can contain a variety of substances. In plants, the central vacuole fills much of the interior of the cell.