Molecular Biology - Photosynthesis

Photosynthesis is the process by which light energy is converted into chemical energy in the form of carbon compounds, primarily $C_6H_{12}O_6$.

The process consists of two main stages: the light-dependent reactions occurring in the thylakoid membranes and the light-independent reactions (Calvin cycle) occurring in the stroma.

Chlorophyll absorbs red and blue light most effectively and reflects green light, which is why most plants appear green.

Photolysis of water involves the splitting of $H_2O$ molecules to release electrons, $H^+$ ions, and $O_2$ gas: $2H_2O + ext{photons} ightarrow 4e^- + 4H^+ + O_2$.

The Light-Dependent Reactions produce $ATP$ and reduced $NADP$ ($NADPH$) which are essential for the subsequent Calvin cycle.

The Light-Independent Reactions involve the fixation of $CO_2$ by the enzyme Rubisco to form glycerate-3-phosphate ($GP$), which is then reduced to triose phosphate ($TP$) using $ATP$ and $NADPH$.

Limiting factors for the rate of photosynthesis include temperature, light intensity, and $CO_2$ concentration. As temperature increases, the rate increases until enzymes like Rubisco denature.

Chromatography can be used to separate photosynthetic pigments, calculated by the $R_f$ value (retention factor).