Almost all life on Earth ultimately depends upon the Sun for its energy. The process of photosynthesis converts the Sun’s energy to sugars which living things may use as an energy source. These sugars are converted to a form living things can use by a process called respiration.
Thousands of chemical reactions occur in living things. These reactions are aided by compounds called enzymes. Enzymes and some other kinds of molecules have specific shapes which allow them to function.
The energy for life comes primarily from the Sun. Photosynthesis is the major way the energy of the Sun is converted to sugars which provide for the energy needs of living systems.
Plants and many microorganisms use solar energy to combine the inorganic molecules carbon dioxide and water into energy-rich organic compounds such as glucose sugar and release oxygen to the environment.
A Representation of Photosynthesis
The overall process of photosynthesis in a plant or algal cell is shown in the graphic below. Plants use use water and the energy provided by sunlight to combine carbon dioxide into glucose sugar with oxygen being released as a waste product.
chloroplasts: organelles that carry on photosynthesis in green plant cells
chlorophylls: the variety of green pigments within the chloroplasts
While chlorophyll is the chief pigment responsible for photosynthesis in green plants, many plants contain other colored pigments as well. These chlorophyll and colored pigments may be separated according to their various chemical charges by a technique known as chromatography. In this technique, a mixture of plant pigments is separated by placing a drop or two of pigment on a special paper called chromatography paper which is dipped in a chemical allowing the different plant pigments to move based on their charges. A picture of a completed chromatography may be viewed in the graphic at the right.
Homeostasis by Plants
Maintenance of Water
Plants need to regulate water loss and carbon dioxide intake for photosynthesis and other life activities
when plants do not keep enough water in their cells, they wilt and die
Stomate: a microscopic hole in a plant leaf which allows gases to enter and leave and water vapor to leave as well. Stomata is the plural of stomate.
Guard cells: open and close the stomate. The ability of the guard cell to close during periods of limited water availability for the plant allows the plant to maintain water homeostasis