| Term | Definition |
|---|
| element | substance that can't be broken down into simpler chemical substances. |
| atom | smallest particle of an element that has the characteristic of that element, basic building block of all matter. |
| nucleus | positively charged center of an atom composed of neutrons and positively charged protons and surrounded by a cloud of negatively charged electrons. |
| isotope | atoms of the same element that have different numbers of neutrons in the nucleus. |
| compound | substance composed of atoms of two or more different elements that are chemically combined. |
| covalent bond | chemical bond formed when two atoms combine by sharing electrons. |
| molecule | group of atoms held together by covalent bonds. |
| ion | atom or group of atoms that gain or lose electrons. |
| ionic bond | chemical bond formed by the attractive forces between two ions of opposite charge. |
| metabolism | all of the chemical reactions that occur within an organism. |
| mixture | combination of substances in which individual components do not combine chemically and retain their own properties. |
| solution | mixture in which one or more substances ( solutes) are distributed evenly in another substance (solvent). |
| pH | measure of how acidic or basic a solution is. |
| acid | any substance that forms hydrogen ions in water and has a pH below. |
| base | any substance that forms hydroxide ions in water and has a pH above. |
| cell | basic unit of all organisms. |
| compound light microscope | instrument that uses visible light and a series of lenses to magnify objects in steps. |
| cell theory | the theory that all organisms are composed of cells, the cell is the basic unit of organization of organisms, all cells come from preexisting cells. |
| electron microscope | instrument that uses a beam of electrons instead of natural light to magnify structures up too 500 000 times actual size. |
| prokaryote | unicellular organisms, such as bacteria, composed of prokaryotic cells. |
| eukaryote | unicellular or multicellular organisms, such as yeast, plants, and animals, composed of eukaryotic cells,which contain a true nucleus and membrane-bound organelles. |
| organelle | membrane bound structures within eukaryotic cells. |
| nucleus | positively charged center of an atom composed of neutrons an positively charged protons, and surrounded by a cloud of negatively charged electrons. |
| osmosis | diffusion of water across a selectively permeable membrane depending on the concentration of solutes on either side of the membrane. |
| isotonic solution | in cells, solution in which the concentration of dissolved substance in the solution is the same as the concentration of dissolved substances inside a cell. |
| hypotonic solution | in cells, solution in which the concentration of dissolved substances is lower in the solution outside the cell than the concentration inside the cell. |
| hypertonic solution | in cells, solution in which the concentration of dissolved substances outside the cell is higher than the concentration inside the cell. |
| passive transport | movement of particles across cell membranes by diffusion or osmosis. |
| active transport | energy-expending process by which cells transport materials across cell membrane against a concentration gradient. |
| endocytosis | active transport process where a cell engulfs materials with a portion of the cell's plasma membrane and releases the contents inside of the cell. |
| exocytosis | active transport process by which materials are secreted or expelled from a cell. |
| ATP ( Adenosine triphosphate) | energy-storing molecule in cells composed of an adenosine molecule, a ribose sugar and three phosphate groups. |
| ADP (Adenosine diphosphate) | molecule formed from the breaking off of a phosphate group for ATP. |
| polar molecule | molecule with an unequal distribution of charge resulting in the molecule having a positive end and a negetive end. |
| hydrogen bond | weak chemical bond formed by the attraction of positively charged hydrogen atoms to other negatively charged atoms. |
| diffusion | net, random movement of particles from an area of higher concentration to an area of lower concentration, eventually resulting in even distribution. |
| dynamic equilibrium | result of diffusion where their is continuous movemnent of particles with no overall change in concentration |
| isomer | compounds with the same simple formula but different three-dimensional structures resulting in different physical and chemical properties. |
| polymer | large molecule formed when smaller molecules bond together. |
| carbohydrate | organic compound used by cells to store and release energy. |
| lipid | organic compounds commonly called fats and oils. |
| protein | large, complex polymer essencial to all life composed of carbon, hydrogen, oxygen, nitrogen, and usualy sulfur |
| amino acid | basic building blocks of protein molecules. |
| peptide bond | covalent bond formed between amino acids |
| enzyme | type of protein found in all living things that increases the rate of chemical reactions. |
| nucleic acid | complex macromolecules, such as RNA and DNA, that store genetic information in cells in the form of a code. |
| nucleotide | subunits of nucleic acid formed from a simple sugar, a phosphate group, and a nitrogen base. |
| plasma membrane | serves as boundary between the cell and its enviorment |
| homeostasis | organisms regulation of its internal enviornment to maintain conditions suitable for survival |
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