Free Forms and Functions of Plants MCQs with Answers

251. The product of light reaction travel from:

• A. Cristae to stroma
• B. Stroma to grana
• C. Grana to cristae
• D. Grana to stroma

Explanation: Photosynthesis occurs in 2 steps:1. Light-dependent reactions2. Light-independent reactionsLight-dependent reactions occur on the thylakoid membrane (stacks of thylakoids are called grana) and involve the production of ATP and NADPH using light energy. ATP and NADPH are required for the Calvin cycle (light-independent reactions) which occurs within the stroma of the chloroplast. The Calvin cycle makes use of ATP and NADPH (from light-dependent reactions) and CO2 to synthesize sugars (triose phosphates). Thus, the products of light-dependent reactions travel from the grana to the stroma.

252. Photo-respiration can generate:

• A. 4-ATP
• B. 36-ATP
• C. 32-ATP
• D. NO-ATP

Explanation: Photorespiration (also known as the C2 cycle) is a metabolic process in plants where the enzyme rubisco combines O2 with RuBP in the presence of light to form unwanted products. The process leads to the production of CO2. The rate of photorespiration increases at high light intensities. At high light intensities, the rate of photolysis of water and light-dependent reactions increases. This increases the rate of production of oxygen leading to an increase in [O2] : [CO2], thereby favoring the oxygenase activity of rubisco combining O2 with RuBP. Photorespiration causes the rate of photosynthesis to decrease as less RuBP is available for carbon fixation. Thus, it leads to a decrease in the rate of the Calvin cycle and hence the overall rate of photosynthesis. It wastes energy and decreases sugar synthesis. In the photorespiratory pathway, there is no synthesis of ATP or NADPH.

253. Dark reaction gets completed by the regeneration of:

• A. PGA
• B. PGAL
• C. RUBP
• D. RUBISCO

Explanation: In the third and final stage of the Calvin cycle i.e. regeneration of RuBP, 1 glyceraldehyde 3-phosphate molecule is used to create glucose or other organic compounds as it exits the cycle. The rest of the 5 glyceraldehyde 3-phosphate molecules are recycled to regenerate 3 molecules of RuBP to enable the Calvin cycle to continue.

254. Outer wall of guard cells is:

• A. Thin & elastic
• B. Thick & elastic
• C. Thin & non elastic
• D. Thick & non elastic

Explanation: Guard cells are pairs of specialized epidermal cells that work to control excessive water loss, closing on hot, dry, or windy days and opening when conditions are more favorable for gas exchange. The inner wall of a guard cell is thicker than the outer wall. When the guard cell is filled with water and it becomes turgid, the outer wall balloons outward, drawing the inner wall with it and causing the stomata to enlarge. The outer wall of guard cells is thin and elastic.

255. Select mineral that is considered as a macronutrient.

• A. Phosphorus
• B. Zinc
• C. Iron
• D. Iodine

Explanation: Calcium, sodium, magnesium, phosphorus and potassium are sometimes included as macronutrients because they are required in relatively large quantities compared with other vitamins and minerals.

256. All of the following are micronutrients except:

• A. Iron
• B. Copper
• C. Zinc
• D. Magnesium

Explanation: Magnesium (Mg2+) is an essential macronutrient of living cells and is the second most prevalent free divalent cation in plants. Mg2+ plays a role in several physiological processes that support plant growth and development.

257. The following elements H,N,P and Mg are included in:

• A. Macronutrients
• B. Micronutrients
• C. Trace elements
• D. Minor elements

Explanation: Hydrogen, magnesium, nitrogen, and phosphorus all are macronutrients. Macronutrients are the nutrients we need in larger quantities that provide us with energy: in other words, fat, protein, and carbohydrate. Micronutrients are mostly vitamins and minerals and are equally important but consumed in very small amounts

258. The guard cell of the stomata in Monocot is:

• A. Kidney shape
• B. Oval
• C. Rounded
• D. Dumbbell shaped

Explanation: The correct answer is dumbbell-shaped. Monocots have stomatal guard cells that are dumbbell-shaped, allowing for better regulation of gas exchange. This shape is better suited for monocots, which often grow in environments where water conservation is critical. In contrast, dicots usually have kidney-shaped guard cells, which are adapted to their specific environmental conditions. The other options, such as kidney, oval, and rounded shapes, do not accurately represent the typical guard cell shape found in monocots.

259. Photorespiration involved the following reaction which occurs in the sequence of:

• A. Glycolate --> Glycine, Glycine --> Serine + CO2, RuBP + O2 --> Glycolate
• B. RuBP + O2 --> Glycolate, Glycine --> Serine + CO2, Glycolate --> Glycine
• C. RuBP + O2 --> Glycolate, Glycolate --> Glycine, Glycine --> Serine + CO2
• D. Glycine --> Serine + CO2, RuBP + O2 --> Glycolate, Glycolate --> Glycine

Explanation: Photorespiration is a process in plants where RuBP (Ribulose Bisphosphate) reacts with oxygen, rather than carbon dioxide, leading to a series of reactions:1. RuBP + O2 --> Glycolate: RuBP oxygenation is the first step, producing glycolate.2. Glycolate --> Glycine: Glycolate is then converted to glycine.3. Glycine --> Serine + CO2: Finally, glycine is converted to serine with the release of CO2.Option C correctly follows this sequence. Options A, B, and D misrepresent the order of these reactions, either starting with or incorrectly placing the reactions, which makes them incorrect.

260. Pigment combination of a carotenoid is:

• A. Blue, green, brown, or red
• B. Orange, yellow, blue, or brown
• C. Yellow, orange, red, or brown
• D. Blue, red, orange, or brown

Explanation: Carotenoids are accessory pigments found in plants that include colors such as yellow, orange, red, and brown. They are crucial in photosynthesis because they absorb light energy and protect chlorophyll from photo-damage. The other options are incorrect as they include colors like blue and green, which are typically associated with chlorophyll pigments, not carotenoids.