Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize nutrients from and .
The process takes place primarily in the chloroplasts, which contain the green pigment called chlorophyll to absorb light energy.
The leaf structure is adapted for photosynthesis: Palisade mesophyll cells are packed with chloroplasts, while the spongy mesophyll allows for gas exchange of and .
Stomata are small pores, mostly on the underside of the leaf, regulated by guard cells to control the entry of and the exit of and (transpiration).
Plants require mineral ions for healthy growth: Magnesium () is needed to make chlorophyll, and Nitrates () are required to produce amino acids and proteins.
The glucose () produced is often converted into starch for storage, which can be tested using Iodine solution (turns from brown to blue-black).
📐Formulae
💡Examples
Problem 1:
A plant is left in a sealed container with a high concentration of but is kept in total darkness. Will it produce starch?
Solution:
No, the plant will not produce starch.
Explanation:
Photosynthesis requires light energy to convert and into glucose (). Without light, the chemical reaction cannot occur, and therefore no glucose is made to be stored as starch.
Problem 2:
Explain what happens to a plant's growth if it is deprived of Magnesium () ions.
Solution:
The leaves will turn yellow (chlorosis) and growth will be stunted.
Explanation:
Magnesium is the central atom in the chlorophyll molecule. Without , the plant cannot synthesize enough chlorophyll to capture light energy for photosynthesis, leading to a lack of glucose for energy and growth.
Problem 3:
In an experiment, a leaf is boiled in ethanol and then treated with Iodine. The leaf turns blue-black. What does this indicate?
Solution:
It indicates the presence of starch.
Explanation:
Boiling in ethanol removes the chlorophyll so color changes are visible. The blue-black color is a positive result for the Iodine test, proving that the leaf has performed photosynthesis and stored the resulting glucose as starch.