biology help... i will give +10 to best answer. :0)?

Question

what happens when light is present and absent when cells reproduce ATP from nutrients in the environment
(i have a couple of ideas, but anything else will help... thanks)

Answer 1

Are you talking about photosynthetic cells? If you are, then the light drives the whole reaction. Light is absorbed by chlorophyll, which raises the energy level of an electron. As it decreases in energy, it hands off energy to various carrier molecules, and to ADP forming ATP. These carrier molecules and ATP then go on to convert CO2 into glucose for storage.

Some energy is lost in the creation of glucose, but it is a necessary process. Since the ATP/ADP ratio is used to regulate many cell processes, ADP levels need to be low in the cell, and it can't store large amounts of ATP.

If you're talking about an non-photosynthetic cell, then light will probably not have much of an effect. Light will impart some energy to the cell, but since there are no dedicated molecules to harness the energy in photons, most of the light will be converted to heat. Heat in a cell raises the overall energy level, and may make it a little easier for some reactions to occur, but the effect would be minimal. It would be the same as warming the cells by another method - they may increase their overall rate of metabolism, but there would be no direct effect from exposure to light.