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Water can enter the cell by diffusion through the cell membrane or through selective membrane channels called aquaporins, which greatly facilitate the flow of water. [1] It occurs in a hypotonic environment, where water moves into the cell by osmosis and causes its volume to increase to the point where the volume exceeds the membrane's capacity ...
Water is the medium of the oceans, the medium which carries all the substances and elements involved in the marine biogeochemical cycles. Water as found in nature almost always includes dissolved substances, so water has been described as the "universal solvent" for its ability to dissolve so many substances.
Phototaxis is called positive if the movement is in the direction of increasing light intensity and negative if the direction is opposite. [3] Two types of positive phototaxis are observed in prokaryotes. The first is called scotophobotaxis (from the word "scotophobia"), which is observed only under a microscope. This occurs when a bacterium ...
While movement of water and minerals through the xylem is driven by negative pressures (tension) most of the time, movement through the phloem is driven by positive hydrostatic pressures. This process is termed translocation, and is accomplished by a process called phloem loading and unloading.
The term photosynthesis is derived from the Greek phōs (φῶς, gleam) and sýnthesis (σύνθεσις, arranging together), [97] [98] [99] while another word that he designated was photosyntax, from sýntaxis (σύνταξις, configuration). Over time, the term photosynthesis came into common usage. Later discovery of anoxygenic ...
Chemiosmosis is the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient. An important example is the formation of adenosine triphosphate (ATP) by the movement of hydrogen ions (H +) across a membrane during cellular respiration or photosynthesis.
The electron transport chain of photosynthesis is often put in a diagram called the Z-scheme, because the redox diagram from P680 to P700 resembles the letter Z. [3] The final product of PSII is plastoquinol, a mobile electron carrier in the membrane. Plastoquinol transfers the electron from PSII to the proton pump, cytochrome b6f. The ultimate ...
The residence time of a reservoir within the hydrologic cycle is the average time a water molecule will spend in that reservoir (see table). It is a measure of the average age of the water in that reservoir. Groundwater can spend over 10,000 years beneath Earth's surface before leaving. [17] Particularly old groundwater is called fossil water ...