actin filament -64
Each actin filament consist of two chains of globular actin monomers twisted about one another in a helical manner to form a long filament.
Def: Cytoskeletal filament of eukaryotic cells composed of the protein actin, also refers to the thin filaments of muscle cells. 64
adenosince triphosphate (ATP) - 62
Mitochondria (singular mitochondrion) break down carbohydrates to produce adenosine triphosphate (ATP) molecules.
Def: Nucleotide with three phosphate groups. The breakdown of ATP into ADP + P makes energy available for energy requiring processes in cells.
adhesion junction -67
In adhesion junctions, internal cytoplasmic plaques, firmly attached to the cytoskeleton within each cell, are joined by intercellular filaments (fig 4.23 a)
Def: Junction between cells in which the adjacent plasma membranes do not touch but are held together by intercellular filaments attached to button like thickenings. 67
The capsule is a protective layer of polysaccharides lying outside the cell wall.
Def: Gelatinous layer surrounding the cells of green algae and certain bacteria. 52
cell - 50
Cells are extremely diverse, but nearly all erquire a microscope to see them (fig. 4.1)
Def: Smallest unit that displays the properties of life; composed of cytoplasm surrounded by a plasma membrane. 2,50
cell theory -52
The concepts that all organisms are composed of cells, and that cells come only from preexisting cells, are the two central tenents of the cell theory.
Def: 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 reexisting cells. 52
cellular respiration -63
The complete breakdown of carbohydrates, which also involves the cytoplasm, is called cellular respiration because oxygen is needed and carbon dioxide is given off.
Def: Metabolic reactions that use the energy from carbohydrates, fatty acid, or amino acid breakdown to produce ATP molecules. 63
cell wall - 52,66
The cell wall
maintains the shape of the cell, even if the cytoplasm should happen to take up an abundance of water.
- All plant cells have cell wall.
- Def: Structure that surrounds a plant, protistan, fungal, or bacterial cell and maintains the cell's shape and rigidity. 52, 66
Centrioles are short cylinders with a 9 + 0 pattern of microtubule triplets -- that is nine sets of triplets occur in a ring,m and none are in the middle of the cylinder (fig 4.19)
Def: Cell organelle, existing in pairs, that occurs in the centrosome and may help organize a mitotic spindle for chromosome movement during animals cell division. 65
centrosome - 64
Microtubule assembly is controlled by the centrosome, a microtubule organizing center which lies near the nucleus.
Def: Central microtubule organizing center of cells. In animal cells, it contains two centrioles 64,117
Chloroplasts use solar energy to synthesize carbohydrates.
Def: Membrane-bounded organelle in algae and plants with chlorophyll-containing membranous thylakoids where photosynthesis take place. 62,87
The nucleus contains chromatin within a semifluid nucleoplasm. Chromatin looks grainy, but actually it is a network of strands.
Def: uNetwork of fibrils consisting of DNA and associated proteins observed within a nucleus that is not dividing. 58, 115
chromosome - 58
Just before the cell divides, the chromatin condenses and coils into rodlike structures called chromosomes.
Def: Structure consisting of DNA complexed with proteins that transmits genetic information from the previous generation of cells and organisms to the next generation. 58, 115
cilium - 65
In eukaryotes, cilia and flagella are hairlike projections that can move either stiffly, like an oar, or in an undulating fashion, like a whip.
Def: Plural, cilia, Short hairlike projection from the plasma membrane, occurring usually in larger numbers. 65
conjugation pili -53
Conjugation pili are rigid tubular structures used by bacteria to pass DNA from cell to cell.
Def: Tubular, rigid baterial structures that enable the transmission of DNA fron cell to cell.
The inner membrane is highly convoluted into folds called cristae that project into the matrix.
Def: Short, fingerlike projections formed by the folding of the inner membrane of mitochondria. 63
cytoplasm - 52
The plasma membrane encloses a semifluid substance called cytoplasm and the cell's genetic material.
Def: Contents of a cell between the nucleus (nucleoid region of bacteria) and the plasma membrane. 52
cytoskeleton - 57, 64
The cytoskeleton is a lattice of protein filaments and tubules that maintains the shape of the cell and assists in the movement of organelles.
The cytoskeleton is a network of interconnected protein filaments and tubules that extends from the nucleus to the plasma membrane in eukaryotic cells.
Def: Internal framework of the cell, consisting of microtubules, actin filaments, and intermediate filaments. 57, 64
endomembrane system - 60
The endomembrane system consists of the nuclear envelope, the membranes of the endoplasmic reticulum, the Golgi apparatus, and many small membranous sacs called vesicles.
Def: Collection of membranous structures involved in transport within the cell. 60
endoplasmic reticulum (ER) -59
Many ribosomes are attached to the endoplasmic reticulum (ER), an organelle composed of many saccules and channels.
Def: System of membranous saccules and channels in the cytoplasm, often with attached ribosomes. 59
eukaryotic cell - 52
The other type of cell, called the eukaryotic cell, has a nucleus that houses its DNA.
Def: Type of cell that has a membrane bounded nucleus and membranous organelles; found in organisms within the domain Eukarya. 52
extracellular matrix (ECM) -66
An extracellular matric (ECM) is a meshwork of fibrous proteins and polysaccarides in close association with the cell that produced them (fig. 4.22)
Def: Meshwork of polysaccharides and proteins that provides support for the animal cell and affects its behavior. 66
fimbriae - 53
Fimbriae are small, bristle-llike fibers that sprout from the cell surface. They don't have anything to do with mobility, but they do help bacteria attach to the surface, such as a tabletop, or even your skin!
Def: In bacteria (singular, fimbria) small bristlelike fibers on bacterial cell surface that enable bacteria to adhere to surfaces. 53, 522
flagellum - 53, 65
Some bacteria have flagella (singular, flagellum) which are tail-like appendages that allow bacteria to propel themselves.
In eukaryotes, cilia and flagella are hairlike projections that can move either stiffly, like an oar, or in an undulating fashion, like a whip.
Def: flagellum - plural, flagella. Long slender extension sued for locomotion by some bateria, protozoans and sperm. 53, 65, 274
gap junction - 67
A gap junction allows cells to communicate. A gap junction is formed when two identical plasma membrane channels join. (fig 4.23c)
Def: 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. 67
golgi apparatus -60
The Golgi apparatus, named for its discoverer, Camillo Golgi, consists of a stack of three to twenty slightly curved, flattened saccules resembling pancakes. The Golgi apparatus may be thought of as a transfer station. First, it receives transport vesicles sent to it by rough and smooth ER. Then molecules within the vesicles are modified as they move between saccules.
Def: Organelle consisting of saccules and vesicles that processes, packages and distributes molecules about or from the cell. 60
granum - 62
Chloroplasts has a membrane system. The large inner space is called stroma, contains a concentrated mixture of enzymes and thylakoids. The thylakoids are disclike sacs formed from the third membrane. A stack of thylakoids is called a granum.
Def: Plural, grana. Stack of chlorophyll-containing thylakoids in a chloroplast. 62, 87
Lysosomes are vesicles produced by the Golgi apparatus that digest molecules and even portions of the cell itself.
Def: Membrane bounded vesicle that contains hydrolytic enzymes for digesting macro molecules. 60
matrix - 63
Mitochondria . . . .The inner membrane encloses the matrix, which contains a highly concentrated mixture of enzymes that assists the breakdown of carbohydrates and other nutrient molecules.
Def: Unstructured semifluid substance that fills the space between cells in connective tissues or inside organelles. 63, 386
Microtubules are small, hollow cylinders composed of 13 long chains of tubulin dimers (two tubulin molecules at a time.).
Def: Small, cylindrical organelle composed of tubulin protein around an empty central core; present in the cytoplasm, centrioles, cilia, and flagella, 64
Mitochondria (singular, mitochondrion) break down carbohydrates to produce adenosine triphosphate (ATP) molecules.
Def: Membrane-bounded organelle in which ATP molecules are produced during the process of cellular respiration. 62
motor protein - 64
Motor proteins associated with the cytoskeleton are instrumental to allowing cellular movements. The major motor proteins include those called myosin, kinesin, and dynein.
Def: Proteins associated with the cytoskeleton that allows movement of transport vesicles and organelles. 64
nuclear envelope -59
The nucleus is separated from the cytoplasm by a double membrane known as the nuclear envelope.
Def: Double membrane that surrounds the nucleus in eukaryotic cells and is connected to the endoplasmic reticulum, has pores that allow substanced to pass between the nucleus and the cytoplasm.
nuclear pore -59
The nuclear envelope has nuclear pores of sufficient size (100 nm) to permit the passage of ribosomal subunits and mRNA out of the nucleus into the cytoplasm, and the passage of proteins from the cytoplasm into the nucleus.
Def: Opening in the nuclear envelope that permits the passage of proteins into the nucleus and ribosomal subunits out of the nucleus. 59
nucleoid - 52
The DNA of a bacterium is located in a single coiled chromosome that resides in a region called the nucleoid.
Def: Region of prokaryotic cells where DNA is located; it is NOT bounded by a nuclear envelope. 52, 274
nucleus - 56
Unlike prokaryotic cells, eukaryotic cells have a membrane-bounded nucleus that houses their DNA.
Def: Center of an atom, in which protons and neutrons are found; membrane-bounded organelle within a eukaryotic cell that contains chromosomes and controls the structure and function of the cell. 18,56
They are also compartmentalized and contain small structures called organelles that differ in structure and function. All the molecules necessary to perform a particular function are concentrated inside the organelle.
Def: Small, often membranous structure in the cytoplasm having a specific structure and function. 56
plasma membrane -54
The plasma membrane marks the boundary between the outside and inside of the cell.
Def: Membrane surrounding the cytoplasm that consists of a phospholipid bilayer with embedded proteins: functions to regulate the entrance and exit of molecules from a cell. 54
In a plant, living cells are connected by plasmodesmata (singular, plasmodesma), numberous narrows, membrane-lined channels that pass through the cell wall.
Def: In plants, cytoplasmic strands that extend through pores in the cell wall, and connect the cytoplasm of two adjacent cells. 66
In eukaryotic cells, some ribosomes occur freely within the cytoplasm, either singly or in groups called polyribosomes.
Def: String of ribosomes simultaneously translating regions of the same mRNA strand during protein synthesis. 59, 171
prokaryotic cell - 52
Prokaryotic cells are so named because they loack a membrane-bounded nucleus.
Def: Lacking a membrane-bounded nucleus and organelles the cell type within the domains Bacteria and Archaea. 52
The many proteins specified by bacterial DNA are synthesized on tiny particles called ribosomes.
Def: RNA and protein in two subunits; site of protein synthesis in the cytoplasm. 53, 167
rough ER -60
Rough ER is studded with ribosomes on the side of the membrane that faces the cytoplasm: therefore, rough ER is able to synthesize polypeptides.
Def: Membranous system of tubules, vesicles, and sacs in cells; has attached ribosomes. 60
Outgoing transport vesicles may return to the ER or proceed to the plasma membrane, where they discharge their contents during secretion.
Def: In the cell, release of a substance by exocytosis from a cell that may be a gland or part of a glad; in the urinary system, movement of certain molecules from blood into the distal tubule of a nephron so that they are added to urine. 60, 425
smooth ER -60
Smooth ER, which is continuous with rough ER, does not have attached ribosomes. Smooth ER synthesizes lipids such as phospholipids and steroids.
Def: Membranous system of tubules, vesciles, and sacs in edukaryotic cells, lacks attached ribosomes. 60
stroma - 62
chloroplasts . . .
The large inner space, called the stroma, contains a concentrated mixture of enzymes and thylakoids. The thylakoids are disclike sacs formed from the third membrane.
Def: Fluid within a chloroplast that contains enzymes involved in the synthesis of carbohydrates during photosynthesis. 62, 87
surface-area-volume ratio -51
If you were to cut a large cube into smaller cubes, the smaller cube would have alot more surface area per volume than the large cube. For example, a 4-cm cube has a surface-area-to -volume ratio of only 1.5:1, but a 1-cm cube has a surface-area-to-volume ratio of 6:1.
Def: Ratio of a cell's outside area to its internal volume. 51
thylakoid - 62
The thylakoids are disclike sacs formed from the third membrane.
Def: Flattened sac within a granum whole membrane contains chlorophill and where the light reactions of photosynthesis occur. 62, 87.
tight junction -67
Adjacent cells are even more closely joined by tight junctions, in which plasma membrane proteins actually attach to each other, producing a zipperlike fasteining (fig 4.23b)
Def: Junction between cells when adjacent plasma membrane proteins join to form a impermeable barrier. 67
transport vesicle - 57
The products are carried between the ES (endomembrane system)organelles by transport vesicles, small membranolus sacs that keep the products from entering the cytoplasm.
Def: Small membranous sacs that carry products between endomembrane system organelles and prevent the products from entering the cytoplasm. 57
vacuole - 61
Vacuoles, like vesicles, are membranous sacs, but vacuoles are larger than vesicles.
Def: 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. 61
vesicle - 60
The endomembrane system consists of the nuclear envelope, the membrane of the endoplasmic reticulum, the Golgi apparatus, and many small membranous sacs called vesicles.
Def: Small, membrane-bounded sac that stores substances within a cell. 60