PinkMonkey Online Study Guide-Biology
CHAPTER 4 : PHOTOSYNTHESIS
Energy is needed for existence as well as maintenance
of life. Solar radiation is the unending source of energy for all
forms of life on earth. However, living organisms can use only one
form of energy for various life activities i.e. the biologically
usable form of chemical energy. It is represented by the energy-rich
organic compound called ATP (adenosine tri-phosphate).
Photosynthesis is the only process in which the solar energy
is trapped and converted into the chemical energy ATP. This process
is described as photophosphorylation. This energy is stored
in food molecules as food energy. In respiration, organic food is
oxidized and the food energy is released as free energy and is made
available for various cellular activities. In cells, the ATP molecules
act as energy mediators.
Organisms which can synthesize their own organic food
from simple inorganic nutrients are called autotrophs or producers.
These are mostly photosynthetic (e.g. green plants) which take
energy from light. A few are chemosynthetic (e.g. certain soil
bacteria) which obtain energy from chemicals.
Photosynthesis is the most important and essential
physiological process in green plants. This is because it is the primary
source of organic food and ATP energy for all forms of life. It utilizes
carbon dioxide and converts it into organic food (carbohydrates). It also
releases oxygen into the atmosphere. In fact, oxygenic photosynthesis
was responsible for converting the totally anaerobic atmosphere on
earth into the aerobic atmosphere that exists today.
Table of Contents
4. 2 Overall Equation of Photosynthesis
4.3 Primary Process of Photosynthesis
4.4 Secondary Processes of Photosynthesis (Biochemical Phase, Dark Reaction)
4.5 Diversity in Photosynthesis Pathway
4.6 Significance of Photosynthesis