CH. 4 Cell Structure

unified cell theory

a biological concept that states that all organisms are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells

microscope

an instrument that magnifies an object

electron microscope

an instrument that magnifies an object using a beam of electrons passed and bent through a lens system to visualize a specimen

light microscope

an instrument that magnifies an object using a beam visible light passed and bent through a lens system to visualize a specimen

nucleus

cell organelle that houses the cell's DNA and directs the synthesis of ribosomes and proteins

eukaryote

cell that has a membrane-bound nucleus and several other membrane-boundcompartments or sacs

ribosome

cellular organelle that carries out protein synthesis

mitochondria (plural = mitochondrion)

cellular organelles responsible for carrying out cellular respiration, resulting in the production of ATP, the cell's main energy-carrying molecule

nucleoid

central part of a prokaryotic cell in which the chromosome is found

gap junction

channel between two adjacent animal cells that allow ions, nutrients, and low molecular weight substances to pass between cells, enabling the cells to communicate

plasmodesma (plural = plasmodesmata)

channel that passes between the cell walls of adjacent plant cells connects their cytoplasm, and allows materials to be transported from cell to cell

organelle

compartment or sac within a cell

intermediate filament

cytoskeletal component, composed of several intertwined strands of fibrous protein, that bears tension, supports cell-cell junctions and anchors cells to extracellular structures

nucleolus

darkly staining body within the nucleus that is responsible for assembling the subunits of the ribosomes

nuclear envelope

double-membrane structure that constitutes the outermost portion of the nucleus

cytoplasm

entire region between the plasma membrane and the nuclear envelope, consisting of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals

Golgi apparatus

eukaryotic organelle made up of a series of stacked membranes that sorts, tags, and packages lipids and proteins for distribution

tight junction

firm seal between two adjacent animal cells created by protein adherence

cytosol

gel-like material of the cytoplasm in which cell structures are suspended

chlorophyll

green pigment that captures the light energy that drives the light reactions of photosynthesis

endomembrane system

group of organelles and membranes in eukaryotic cells that work together modifying, packaging, and transporting lipids and proteins

central vacuole

large plant cell organelle that regulates the cell's storage compartment, holds water, and plays a significant role in cell growth as the site of macromolecule degradation

desmosome

linkages between adjacent epithelial cells that form when cadherins in the plasma membrane attach to intermediate filaments

flagella (flagellum)

long, hair-like structure that extends from the plasma membrane and is used to move the cell

extracellular matrix

material (primarily collagen, glycoproteins, and proteoglycans) secreted from animal cells that provides mechanical protection and anchoring for the cells in the tissue

vacuole

membrane-bound sac, somewhat larger than a vesicle, which functions in cellular storage and transport

microfilament

narrowest element of the cytoskeleton system; it provides rigidity and shape to the cell and enables cellular movements

cytoskeleton

network of protein fibers that collectively maintain the shape of the cell, secure some organelles in specific positions, allow cytoplasm and vesicles to move within the cell, and enable unicellular organisms to move independently

lysosome

organelle in an animal cell that functions as the cell's digestive component; it breaks down proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles

plasma membrane

phospholipid bilayer with embedded (integral) or attached (peripheral) proteins, and separates the internal content of the cell from its surrounding environment

chloroplast

plant cell organelle that carries out photosynthesis

chromatin

protein-DNA complex that serves as the building material of chromosomes

centrosome

region in animal cells made of two centrioles

smooth endoplasmic reticulum (SER)

region of the endoplasmic reticulum that has few or no ribosomes on its cytoplasmic surface and synthesizes carbohydrates, lipids, and steroid hormones; detoxifies certain chemicals (like pesticides, preservatives, medications, and environmental pollutants), and stores calcium ions

rough endoplasmic reticulum (RER)

region of the endoplasmic reticulum that is studded with ribosomes and engages in protein modification and phospholipid synthesis

cell wall

rigid cell covering made of cellulose that protects the cell, provides structural support, and gives shape to the cell

nucleoplasm

semi-solid fluid inside the nucleus that contains the chromatin and nucleolus

endoplasmic reticulum (ER)

series of interconnected membranous structures within eukaryotic cells that collectively modify proteins and synthesize lipids

cilia (cilium)

short, hair-like structure that extends from the plasma membrane in large numbers and is used to move an entire cell or move substances along the outer surface of the cell

vesicle

small, membrane-bound sac that functions in cellular storage and transport; its membrane is capable of fusing with the plasma membrane and the membranes of the endoplasmic reticulum and Golgi apparatus

peroxisome

small, round organelle that contains hydrogen peroxide, oxidizes fatty acids and amino acids, and detoxifies many poisons

chromosome

structure within the nucleus that is made up of chromatin that contains DNA, the hereditary material

prokaryote

unicellular organism that lacks a nucleus or any other membrane-bound organelle

microtubule

widest element of the cytoskeleton system; it helps the cell resist compression, provides a track along which vesicles move through the cell, pulls replicated chromosomes to opposite ends of a dividing cell, and is the structural element of centrioles, flagella, and cilia