The energy from sunlight comes in the form of photons, and this energy is used in the light dependent reactions of photosynthesis. The first function carried out by the photons in energizing electrons in the chlorophyll. The energized electron travels through the electron transport chain and subsequent steps are carried out to utilize this energy to form ATP.
Hmmm let me think.........
Water has some unusual properties due to its hydrogen bonds. One property is cohesion, the tendency for water molecules to stick together. The cohesive forces between water molecules are responsible for the phenomenon known as surface tension.
The phospholipid bilayer has two hydrophilic surfaces: the extracellular and the intracellular surfaces. These two layers sandwiches a major layer of lipids or fat. Because of this nature of the lipid bilayer, water-soluble or <em>hydrophilic</em> hormones cannot enter the cell membrane. They have to rely on the mechanisms of receptors.
One can find transmembrane proteins embedded across the whole length of the lipid bilayer. One of the functions of these proteins is to serve as the link for hormones such as the ones given above. When the water-soluble hormones attach to one of these receptors, the receptor will be activated and send down a signal to the intracellular environment; these signals will then travel down towards their target site and eventually activate whatever it is the hormone was made for. One example of these transmembrane proteins are <em>G-coupled proteins; </em>examples of signals that cascade down the cell are cylic AMP and cyclic GMP.
