Across
- 3. A protein (or RNA molecule) that serves as a biological catalyst, changing the rate of a chemical reaction without itself being changed into a different molecule in the process.
- 7. The totality of an organism's chemical reactions.
- 8. The spontaneous tendency of a substance to move down its concentration gradient from where it is more concentrated to where it is less concentrated.
- 9. The passage of a substance through a specific transport protein across a biological membrane down its concentration gradient.
- 11. An increase or decrease in the density of a chemical substance in an area. Cells often maintain concentration gradients of ions across their membranes. When a gradient exists, substances tend to move from where they are more concentrated to where they are less concentrated.
- 14. The capacity to perform work, or to rearrange matter.
- 17. The amount of energy that reactants must absorb before a chemical reaction will start.
- 18. A solution having the same solute concentration as another solution, thus having no effect on passage of water in or out of the cell.
- 19. The movement of a substance across a biological membrane against its concentration gradient, aided by specific transport proteins and requiring input of energy (often as ATP).
- 21. Cellular uptake of molecules or particles via formation of new vesicles from the plasma membrane.
- 22. The movement of materials out of the cytoplasm of a cell by the fusion of vesicles with the plasma membrane.
- 23. The diffusion of water across a selectively permeable membrane.
Down
- 1. An energy-releasing chemical reaction in which the reactants contain more potential energy than the products. The reaction releases an amount of energy equal to the difference in potential energy between the reactants and the products.
- 2. The aerobic harvesting of energy from food molecules; the energy-releasing chemical breakdown of food molecules, such as glucose, and the storage of potential energy in a form that cells can use to perform work; involves glycolysis, the citric acid cycle, and oxidative phosphorylation (the electron transport chain and chemiosmosis).
- 4. (1) A specific substance (reactant) on which an enzyme acts. Each enzyme recognizes only the specific substrate or substrates of the reaction it catalyzes. (2) A surface in or on which an organism lives.
- 5. Method by which organisms regulate solute concentrations and balance the gain and loss of water.
- 6. A property of biological membranes that allows some substances to cross more easily than others and blocks the passage of other substances altogether.
- 10. The part of an enzyme molecule where a substrate molecule attaches (by means of weak chemical bonds); typically, a pocket or groove on the enzyme's surface.
- 12. An energy-requiring chemical reaction, which yields products with more potential energy than the reactants. The amount of energy stored in the products equals the difference between the potential energy in the reactants and that in the products.
- 13. In comparing two solutions, the one with the greater concentration of solutes; cells in such a solution will lose water to their surroundings.
- 15. In comparing two solutions, the one with the lower concentration of solutes; cells in such a solution will take up water from their surroundings.
- 16. The diffusion of a substance across a biological membrane, without any input of energy.
- 20. Cellular "drinking"; a type of endocytosis in which the cell takes fluid and dissolved solutes into small membranous vesicles.