The lifetime of an intracellular signaling molecule must be short for the cell to be able to cause a change in the concentration of the signaling molecule in an efficient manner. PKA is more closely related to PKC than to PKG at the amino acid level. Components of intracellular signaling pathways can be small molecules, proteins or lipids. Second messengers can convey a signal via a change in their steady state level. Negative feedback systems play important roles in regulating cellular signaling.

Two students are working together on an experiment that measures the effect of different liquid fertilizers on the thickness of plants’ stems. which is most likely to result in the greatest amount of error in their scientific experiment? a.one student measures the plant stem widths by using calipers. the other student measures the widths of the same plant stems again by using a different pair of calipers. b.one student measures the plant stem widths by using calipers. the other student types the measurements as they are taken into a computer spreadsheet. c.one student weighs liquids for the experiment by using a calibrated scale. the other student weighs liquids for the experiment by using a different calibrated scale.