Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Photosynthesis is the process by which plants synthesize carbohydrates from raw materials ( and ) using energy from light.
Chlorophyll is the green pigment found in chloroplasts that traps light energy and converts it into chemical energy for the formation of carbohydrates.
The products of photosynthesis are glucose () and oxygen (). Glucose is often converted into starch for storage, which is an insoluble polysaccharide.
Limiting factors are environmental variables that, when in short supply, restrict the rate of photosynthesis. Key limiting factors include light intensity, concentration, and temperature.
The leaf structure is specialized for gas exchange; stomata allow for the diffusion of into the leaf and out, while the spongy mesophyll provides a large surface area for gas exchange.
Mineral requirements: Magnesium ions () are essential for making chlorophyll, and Nitrate ions () are required for producing amino acids and proteins for growth.
📐Formulae
💡Examples
Problem 1:
A student tests a variegated leaf for the presence of starch using iodine solution. Describe the expected result for the white and green parts of the leaf.
Solution:
The green parts turn blue-black, while the white parts remain orange-brown.
Explanation:
The green parts contain chlorophyll which allows for photosynthesis to produce glucose (), which is then stored as starch. Iodine reacts with starch to form a blue-black complex. The white parts lack chlorophyll, meaning no photosynthesis occurs and no starch is present.
Problem 2:
Why does the rate of photosynthesis decrease when the temperature exceeds ?
Solution:
The rate decreases because the enzymes catalyzing the reaction become denatured.
Explanation:
Photosynthesis is an enzyme-controlled process. At high temperatures (), the specific 3D shape of the enzyme's active site changes, meaning the substrate ( and derivatives) can no longer fit, halting the production of .
Problem 3:
A plant is grown in a solution lacking Magnesium ions (). Describe the appearance of the plant and explain the cause.
Solution:
The plant will show yellowing of the leaves, a condition known as chlorosis.
Explanation:
Magnesium () is the central atom in the chlorophyll molecule. Without it, the plant cannot synthesize chlorophyll, leading to a loss of green pigment and a reduced ability to photosynthesize.