Campbell Biology chapter 36 | Questions with 100% correct answers | Verified

hyllotaxy - the arrangement of leaves on a stem, is specific to each species. leaf area index - the ratio of total upper leaf surface of a plant divided by the surface area of land on which it grows self-pruning - Non-productive leaves in a crop or plant go through programmed cell death (apoptosis) and are shed to increase productivity of other leaves Passive transport - The movement of substances across a cell membrane without the use of energy by the cell - diffusion Active transport - transport of a substance (as a protein or drug) across a cell membrane against the concentration gradient transport proteins - A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane. Those involved in passive transport do not require energy. Proton pumps - Use energy from ATP to pump protons out of the cell. This results in a proton gradient with a higher proton concentration outside the cell than inside. The proton gradient across the membrane is a form of potential energy, and the flow back can be harnessed to do work. The inside of the cell also becomes negative in this process. Involved in active transport. membrane potential - The charge difference between a cell's cytoplasm and the extracellular fluid, due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances. cotransport - The coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient. Osmosis - net absorption or loss of water by a cell; diffusion of water