Photosynthesis When a plant grows, the atoms used come from carbon dioxide in th
ID: 50788 • Letter: P
Question
Photosynthesis
When a plant grows, the atoms used come from carbon dioxide in the air and water. Plants are able to accomplish this through the process of photosynthesis, cellular respiration and biosynthesis of macromolecules.
Briefly explain the light-dependent reactions of photosynthesis: where does this take place, what are the reactants and what is produced?
Briefly explain the light-independent reactions of photosynthesis: where does this take place, what are the reactants and what is produced? How do plants store excess product from these reactions?
Where does the energy come from that allow plants to synthesize the necessary biological macromolecules that allow it to grow? Hint: It is NOT from sunlight. Explain your answer.
Explanation / Answer
Based on the given data,
The process in which green plants absorb radiant energy from sun and it will be converted to chemical energy is called photosynthesis. Green plants synthesize carbohydrates from atmospheric carbon dioxide (CO2) and water (H2O) in presence of chlorophyll (cl) and sunlight (hv).
The radiant energy from sun is converted to chemical energy some of this energy is stored in the chemical bonds of carbohydrate. The reaction can be written as follows:
Now, the chemical energy from carbohydrates is released by respiration process and this released energy supports the metabolism of living organisms. The chloroplast is involved in both light dependent and light-independent reactions stages of photosynthesis. The light-dependent reactions occur in thylakoid, while the light-independent reactions occur in stroma of the chloroplast.
The light reaction takes place in the thylakoid discs. Thylakoids are the component of the photosynthetic organelles, the chloroplasts. The thylakoid membrane of the chloroplast is the site where light dependent reactions occur. The thylakoid contains the chlorophyll pigments, which are divided into photosystems I and II. They absorb incident photons in their antenna complexes, and this photon energy is directed to the reaction center chlorophylls of the photosystems.
The light energy is converted into chemical energy, in the form of ATP (adenosine triphosphate) and NADPH (Nicotinamide adenine dinucleotide phosphate). The formed ATP and NADPH are used in light independent reactions to synthesize glucose by reducing carbon dioxide. The products of this reaction are carbohydrates (glucose) and other organic molecules necessary for cell function and metabolism.
The photosynthetic efficiency is the fraction of light energy converted into chemical energy during the process of photosynthesis. The value of the photosynthetic efficiency is dependent on how light energy is defined – it depends on light absorbed and the kind of light used. Utilizing one molecule of carbon dioxide (CO2) requires the energy of 8 photons. The Gibbs free energy for converting a mole of CO2 to glucose is 114 kcal, whereas eight moles of photons of wavelength 600 nm contains 381 kcal, giving a nominal efficiency of 30%.