Photosynthesis: Process, Light Absorption, Limiting Factors

Photosynthesis Fundamentals

Photosynthesis: Carbon Compound Production

• Living organisms require complex carbon compounds to carry out life processes and build the structures in their cells.
• Photosynthesis involves the conversion of light energy into chemical energy (carbohydrates, lipids, proteins, and nucleic acids).
• Chloroplasts absorb light energy from the sun and convert this energy into chemical energy (glucose) to be used by the organisms for energy.

Visible Light Spectrum and Wavelengths

• Light from the sun is composed of a range of wavelengths.
• The visible spectrum is the portion of the electromagnetic spectrum that is visible to or can be detected by the human eye.
• Electromagnetic radiation in this range of wavelengths (380 to 750 nm) is called visible light.
• All these wavelengths together form white light, with violet and blue colors having shorter wavelengths (more energy) and red colors having longer wavelengths (less energy).

Chlorophyll's Light Absorption and Reflection

• Sunlight is a mixture of different wavelengths of visible light, which we see as colors.
• The two main colors of light that are absorbed by chlorophyll are red and blue light.
• The main color that is reflected is green light, which is why most leaves look green.

Oxygen Production via Water Photolysis

• Photolysis is one of the first and most important steps in the light-dependent reactions of photosynthesis.
• Two water (H₂O) molecules are split by photons of light to produce 4 e^- + 4H⁺ + O₂.

Energy Requirements for Carbon Compound Synthesis

• Plants convert inorganic CO₂ into organic carbohydrates through the process of photosynthesis.
• Carbon dioxide + Water → CH₂O (carbohydrates) + Oxygen
• Energy is required for this reaction to occur.
• Light energy from the sun is used and converted into chemical energy.
• The reactions are generally endothermic.

Limiting Factors of Photosynthesis Rate

• Light intensity, CO₂ concentration, and temperature can all be limiting factors for the rate of photosynthesis.
• If any of these factors is below their optimal level, they can be limiting; however, only one of these factors can be limiting at one time.
• This is usually the factor that is the furthest away from its optimal level.
• This is the only factor that can increase the rate of photosynthesis.
• As this factor gets closer to its optimal level, the limiting factor can change to one of the other factors.