Molecules Move
Figure 1. A section of a schematic of insulin-induced translocation of glucose transporter 4 . Insulin binding to its receptors initiates GLUT4-containing vesicles to fuse with the cell membrane. Modified from Wang et al. 2020. Fish in freshwater consistently gain water from the environment. This is because water follows the rules of physics and follows a gradient from high water to low water. There is more water in the freshwater pond than in the fish’s cells since the cells contain concentrations of other stuff, salts, proteins, etc. One way to envision this is to put percentage values on the solution. A freshwater pond might have 99.8% water and 0.2 percent other stuff, while fish blood and cells are about 99.1% water and 0.9 percent dissolved stuff, mainly salt (0.8%). Water, following a concentration gradient, high to low, flows faster from 99.8% to 99.1%. I mention that it flows faster in one direction because water, if not prev...