You're on the pilot episode of a new game show called "The Transport Factor." The host hands you three different amino acids, fo
ur different sugars, and two different ions. Then the host shouts, "How many different proteins does the cell need to move these molecules across the plasma membrane using facilitated transport?" Quickly, you correctly respond: _____.
These are called carrier proteins, and they have what it is called: solute-binding sites, that when saturated, they are considered "full".
Each different amino acid needs a separate carrier protein to move it across the plasma membrane, so that's 3, then the four different sugars need separate carriers as well, we add 4 more then, we have 7 so far, finally the 2 different ions use 2 more, plus the other 7, totals 9.
Homeostasis typically involves negative feedback loops that counteract changes of various properties from their target values, known as set points. In contrast to negative feedback loops, positive feedback loops amplify their initiating stimuli, in other words, they move the system away from its starting state.
