Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Photosynthesis takes place in the green parts of the plant, primarily in the leaves within the mesophyll cells, which contain a high concentration of chloroplasts.
Chloroplasts are double-membrane-bound organelles. The internal space is divided into the membranous system (grana and stroma lamellae) and the fluid matrix called the stroma.
The membranous system (thylakoids/grana) is the site for light-harvesting and the 'Light Reaction', where light energy is converted into chemical energy in the form of and .
The stroma is the site for the 'Dark Reaction' (Light-independent reaction) or the Calvin Cycle, where is enzymatically reduced to form sugars ().
Chloroplasts align themselves within the mesophyll cells (usually along the walls) to optimize the absorption of incident light.
Photosynthetic pigments such as Chlorophyll , Chlorophyll , Xanthophylls, and Carotenoids are located in the thylakoid membranes of the grana.
📐Formulae
💡Examples
Problem 1:
During an experiment, a student observes that a plant is unable to synthesize sugar despite being provided with and light. Upon microscopic examination, the stroma of the chloroplast is found to be damaged. Explain why sugar synthesis is affected.
Solution:
The synthesis of sugar occurs in the stroma of the chloroplast through the Dark Reaction.
Explanation:
The stroma contains the enzymes (like RuBisCO) necessary for the Calvin Cycle. While the light-harvesting occurs in the thylakoids, the actual fixation of into requires the enzymatic environment of the stroma. If the stroma is damaged, the chemical energy ( and ) produced in the grana cannot be utilized to form glucose.
Problem 2:
Which part of the chloroplast is responsible for the photolysis of and where is the resulting released?
Solution:
The photolysis of occurs on the inner side of the thylakoid membrane.
Explanation:
The Oxygen Evolving Complex (OEC) associated with Photosystem II () is located on the lumen side of the thylakoid membrane. Here, is split into protons (), electrons (), and oxygen (). The then diffuses out of the chloroplast.