Cell Biology Questions and Answers Graded A

Cell Biology Questions and Answers Graded A Theory of Endosymbiosis Eukaryotic cells emerged when mitochondria and chloroplasts, once free-living prokaryotes, took up permanent residence inside other larger cells, about 1.5 billion years ago. Eukaryotic Cell A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with eukaryotic cells (protists, plants, fungi, and animals) are called eukaryotes. Prokaryotic Cell A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles; found only in the domains Bacteria and Archaea. Nucleolus Found inside the nucleus and produces ribosomes Ribosomes Makes proteins Peroxisomes Organelles in both plants and animals that break down peroxide, a toxic byproduct of cell respiration Nucleus Contains DNA Smooth Endoplasmic Reticulum An endomembrane system where lipids are synthesized, calcium levels are regulated, and toxic substances are broken down. Golgi Apparatus A system of membranes that modifies and packages proteins for export by the cell Lysosomes An organelle containing digestive enzymes Mitochondria An organelle in eukaryotic cells that serves as the site of cellular respiration; uses oxygen to break down organic molecules and synthesize ATP Nuclear Envelope A double membrane that surrounds the nucleus in the cell Chromatin DNA and protein that makes up chromosomes Rough Endoplasmic Reticulum An endomembrane system covered with ribosomes where many proteins for transport are assembled. Apoptosis Programmed cell death Vacuoles Stores food, water, wastes, and other materials Chloroplast An organelle found in plant and algae cells where photosynthesis occurs Cytoskeleton A network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement Microtubules A hollow rod of the protein tubulin in the cytoplasm of all eukaryote cells that make up cilia, flagella, spindle fibers, and other cytoskeletal structures of cells Microfilaments Long, thin fibers that function in the movement and support of the cell Cleavage Furrow The first sign of cleavage in an animal cell; a shallow groove in the cell surface near the old metaphase plate. Cell Wall A rigid layer of nonliving material that surrounds the cells of plants and some other organisms. Cellulose Carbohydrate component of plant cell walls. Plasma Membrane A selectively-permeable phospholipid bilayer forming the boundary of the cells Phospholipid Bilayer A double layer of phospholipids that makes up plasma and organelle membranes. Peripheral Protein The proteins of a membrane that are not embedded in the lipid bilayer; they are appendages loosely bound to the surface of the membrane. Integral Protein Integrated into the Phospholipid bilayer, they form membrane channels that regulate the passage of specific ions through the membrane. Phagocytosis A type of endocytosis in which a cell engulfs large particles or whole cells Pinocytosis A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes. Active Transport Energy-requiring process that moves material across a cell membrane against a concentration difference Diffusion Movement of molecules from an area of higher concentration to an area of lower concentration. Facilitated Diffusion Movement of specific molecules across cell membranes through protein channels Osmosis Diffusion of water through a selectively permeable membrane Passive Transport Movement of substances through a cell membrane without the use of cellular energy; includes diffusion, osmosis, and facilitated diffusion. Solvent In a solution, the substance in which the solute dissolves. Solute A substance that is dissolved in a solution. Hypertonic In comparing two solutions, referring to the one with a greater solute concentration. Hypotonic In comparing two solutions, referring to the one with a lower solute concentration. Isotonic Having the same solute concentration as another solution. Osmotic Potential The tendency of water to move across a permeable membrane into a solution Water Potential The physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure. Turgid swollen as from a fluid; bloated Plasmolysis This happens when a cell shrinks inside its cell wall while the cell wall remains intact. Aquaporins A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane Endocytosis A process in which a cell engulfs extracellular material through an inward folding of its plasma membrane. Exocytosis A process in which a cell releases substances to the extracellular environment by fusing a vesicular membrane with the plasma membrane, separating the membrane at the point of fusion and allowing the substance to be released. Vesicle Small membrane-bound sac that functions in moving products into, out of, and within a cell. Tight Junctions Membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid Desmosomes Join two cells at a single point, attach directly to the cytoskeleton of each cell. Found in tissues that normally experience a lot of stress due to sliding. Gap Junctions In animal cells, pores formed from connected membrane proteins that allow molecules to pass directly from cell to cell. Plasmodesmata An open channel in the cell walls of plant cells allowing for connections between the cytoplasm of adjacent cells Signal Transduction Pathway The process by which a signal on a cell's surface is converted into a specific cellular response. Centrioles Cell organelle that aids in cell division in animal cells only Centrosomes Microtubule-organizing centers that help to form and organize the mitotic spindle during mitosis Cilia Hairlike projections that extend from the plasma membrane and are used for locomotion Flagella A long, whip-like filament that helps in cell motility. Many bacteria are flagellated, and sperm are flagellated. Contractile Vacuoles Specialized organelles in single-celled organisms that collect and pump excess water out of the cell. Selectively Permeable a property of cell membranes that allows some substances to pass through, while others cannot Cholesterol A lipid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids.