Key Terms
- active transport
- the method of transporting material that requires energy
- cell wall
- a rigid cell covering made of cellulose in plants, peptidoglycan in bacteria, non-peptidoglycan compounds in Archaea, and chitin in fungi that protects the cell, provides structural support, and gives shape to the cell
- central vacuole
- a large plant cell organelle that acts as a storage compartment, water reservoir, and site of macromolecule degradation
- chloroplast
- a plant cell organelle that carries out photosynthesis
- chromatin
- protein-DNA complex that serves as the chromosomes' building material
- chromosome
- structure within the nucleus that comprises chromatin that contains DNA, the hereditary material
- cilium
- (plural: cilia) a 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
- concentration gradient
- an area of high concentration across from an area of low concentration
- cytoplasm
- the entire region between the plasma membrane and the nuclear envelope, consisting of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals
- cytoskeleton
- the network of protein fibers that collectively maintains the shape of the cell, secures some organelles in specific positions, allows cytoplasm and vesicles to move within the cell, and enables unicellular organisms to move
- cytosol
- the gel-like material of the cytoplasm in which cell structures are suspended
- desmosome
- a linkage between adjacent epithelial cells that forms when cadherins in the plasma membrane attach to intermediate filaments
- diffusion
- a passive process of transport of low-molecular weight material down its concentration gradient
- electrochemical gradient
- a gradient produced by the combined forces of the electrical gradient and the chemical gradient
- endocytosis
- a type of active transport that moves substances, including fluids and particles, into a cell
- endomembrane system
- the group of organelles and membranes in eukaryotic cells that work together to modify, package, and transport lipids and proteins
- endoplasmic reticulum (ER)
- a series of interconnected membranous structures within eukaryotic cells that collectively modify proteins and synthesize lipids
- eukaryotic cell
- a cell that has a membrane-bound nucleus and several other membrane-bound compartments or sacs
- exocytosis
- a process of passing material out of a cell
- extracellular matrix
- the material, primarily collagen, glycoproteins, and proteoglycans, secreted from animal cells that holds cells together as a tissue, allows cells to communicate with each other, and provides mechanical protection and anchoring for cells in the tissue
- facilitated transport
- a process by which material moves down a concentration gradient (from high to low concentration) using integral membrane proteins
- flagellum
- (plural: flagella) the long, hair-like structure that extends from the plasma membrane and is used to move the cell
- fluid mosaic model
- a model of the structure of the plasma membrane as a mosaic of components, including phospholipids, cholesterol, proteins, and glycolipids, resulting in a fluid rather than static character
- gap junction
- a channel between two adjacent animal cells that allows ions, nutrients, and other low-molecular weight substances to pass between the cells, enabling the cells to communicate
- Golgi apparatus
- a eukaryotic organelle made up of a series of stacked membranes that sorts, tags, and packages lipids and proteins for distribution
- hypertonic
- describes a solution in which extracellular fluid has higher osmolarity than the fluid inside the cell
- hypotonic
- describes a solution in which extracellular fluid has lower osmolarity than the fluid inside the cell
- isotonic
- describes a solution in which the extracellular fluid has the same osmolarity as the fluid inside the cell
- lysosome
- an 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
- microscope
- the instrument that magnifies an object
- mitochondria
- (singular: mitochondrion) the cellular organelles responsible for carrying out cellular respiration, resulting in the production of ATP, the cell’s main energy-carrying molecule
- nuclear envelope
- the double-membrane structure that constitutes the outermost portion of the nucleus
- nucleolus
- the darkly staining body within the nucleus that is responsible for assembling ribosomal subunits
- nucleus
- the cell organelle that houses the cell’s DNA and directs the synthesis of ribosomes and proteins
- organelle
- a membrane-bound compartment or sac within a cell
- osmolarity
- the total amount of substances dissolved in a specific amount of solution
- osmosis
- the transport of water through a semipermeable membrane from an area of high water concentration to an area of low water concentration across a membrane
- passive transport
- a method of transporting material that does not require energy
- peroxisome
- a small, round organelle that contains hydrogen peroxide, oxidizes fatty acids and amino acids, and detoxifies many poisons
- phagocytosis
- a process that takes particulate matter like macromolecules, cells, or cell fragments that the cell needs from the extracellular fluid; a variation of endocytosis
- pinocytosis
- a process that takes solutes that the cell needs from the extracellular fluid; a variation of endocytosis
- plasma membrane
- a phospholipid bilayer with embedded (integral) or attached (peripheral) proteins that separates the internal contents of the cell from its surrounding environment
- plasmodesma
- (plural: plasmodesmata) a channel that passes between the cell walls of adjacent plant cells, connects their cytoplasm, and allows materials to be transported from cell to cell
- prokaryotic cell
- a unicellular organism that lacks a nucleus or any other membrane-bound organelle
- receptor-mediated endocytosis
- a variant of endocytosis that involves the use of specific binding proteins in the plasma membrane for specific molecules or particles
- ribosome
- a cellular structure that carries out protein synthesis
- rough endoplasmic reticulum (RER)
- the region of the endoplasmic reticulum that is studded with ribosomes and engages in protein modification
- selectively permeable
- the characteristic of a membrane that allows some substances through but not others (also known as semipermeable)
- smooth endoplasmic reticulum (SER)
- the region of the endoplasmic reticulum that has few or no ribosomes on its cytoplasmic surface and synthesizes carbohydrates, lipids, and steroid hormones; detoxifies chemicals like pesticides, preservatives, medications, and environmental pollutants, and stores calcium ions
- solute
- a substance dissolved in another to form a solution
- tight junction
- a firm seal between two adjacent animal cells created by protein adherence
- tonicity
- the amount of solute in a solution.
- unified cell theory
- the 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
- vacuole
- a membrane-bound sac, somewhat larger than a vesicle, that functions in cellular storage and transport
- vesicle
- a 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