Q631. During the light-dependent reactions of photosynthesis, oxygen gas is released as a byproduct of:
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Q632. Tiny pores on the surface of plant leaves that facilitate gas exchange are called:
Explanation
Stomata are microscopic pores located primarily on the undersides of plant leaves. They are surrounded by specialized guard cells that regulate their opening and closing. These openings are essential for gas exchange, allowing carbon dioxide to enter for photosynthesis and oxygen to exit. However, they also facilitate transpiration, the loss of water vapor from the plant into the surrounding environment.
Q633. Aerobic respiration differs from anaerobic respiration in that it:
Explanation
Aerobic respiration is a high-efficiency metabolic process that completely breaks down glucose to produce energy, and it strictly requires the presence of oxygen. In contrast, anaerobic respiration occurs in the absence of oxygen and is much less efficient, producing far less ATP per glucose molecule. Aerobic respiration results in carbon dioxide and water, while anaerobic processes produce lactic acid or ethanol.
Q634. The universal energy currency molecule generated during cellular respiration is:
Explanation
Adenosine Triphosphate, commonly known as ATP, is the universal energy currency for all living cells. It stores chemical energy in high-energy phosphate bonds that can be easily broken to power various cellular processes, including muscle contraction, active transport, and chemical synthesis. ATP is continuously generated during cellular respiration and consumed during metabolic work, maintaining the life-sustaining activities of the organism.
Q635. Which of the following processes is common to both aerobic and anaerobic respiration?
Explanation
Glycolysis is the initial stage of glucose metabolism and is common to both aerobic and anaerobic respiration. This metabolic pathway occurs in the cytoplasm and does not require oxygen to function. It involves the breakdown of one glucose molecule into two molecules of pyruvate, producing a small net gain of ATP and providing the necessary precursors for subsequent metabolic stages.
Q636. Consider the following factors affecting the rate of photosynthesis:
I. Light intensity
II. Carbon dioxide concentration
III. Temperature
IV. Availability of water
V. Atmospheric nitrogen concentration
Which of the above statement(s) identify the primary limiting factors for photosynthesis?
I. Light intensity
II. Carbon dioxide concentration
III. Temperature
IV. Availability of water
V. Atmospheric nitrogen concentration
Which of the above statement(s) identify the primary limiting factors for photosynthesis?
Explanation
Several environmental factors directly influence the rate of photosynthesis. Light intensity provides the energy, carbon dioxide concentration supplies the raw material, and temperature affects the activity of the enzymes involved. Water availability is also crucial, as it is a reactant and maintains plant health. Atmospheric nitrogen, while abundant, is not a direct reactant or primary limiting factor for photosynthesis.
Q637. Muscle cramps in human bodies during heavy exercise are caused by the accumulation of:
Explanation
During intense physical exercise, the demand for energy may exceed the oxygen supply to the muscles. This leads to anaerobic respiration, where glucose is partially broken down into lactic acid instead of being completely oxidized. The accumulation of lactic acid in the muscle tissues causes a drop in pH, leading to fatigue and the painful involuntary contractions commonly known as muscle cramps.
Q638. The Respiratory Quotient (R.Q.) is defined as the ratio of:
Explanation
The Respiratory Quotient, or R.Q., is a dimensionless number used in biological calculations to determine the type of fuel being metabolized by an organism. It is calculated as the ratio of the volume of carbon dioxide evolved to the volume of oxygen consumed during respiration. The R.Q. value varies depending on whether carbohydrates, fats, or proteins are being used for energy.
Q639. Organisms that synthesize their own food from simple inorganic substances using light or chemical energy are called:
Explanation
Autotrophs are organisms capable of producing their own organic nutrients from simple inorganic substances. Most autotrophs, such as green plants and algae, use light energy through photosynthesis. Others, known as chemoautotrophs, utilize chemical energy from inorganic reactions. These primary producers form the foundation of almost all food chains, providing the essential energy source for all other life forms in the ecosystem.
Q640. Human beings ingest complex solid organic food which is then digested and absorbed. This type of nutrition is termed:
Explanation
Human beings exhibit holozoic nutrition, a complex process that involves several distinct stages. First, solid or liquid organic food is ingested. This is followed by digestion, where complex molecules are broken down into simpler ones. These nutrients are then absorbed into the bloodstream and assimilated by the cells for energy and growth. Finally, the undigested waste material is eliminated.Answer key for these questions
| Q | Correct answer |
|---|---|
| 631 | (c) The photolysis of water molecules |
| 632 | (a) Stomata |
| 633 | (d) Strictly requires the presence of oxygen |
| 634 | (b) ATP (Adenosine Triphosphate) |
| 635 | (c) Glycolysis |
| 636 | (a) I, II, III and IV |
| 637 | (a) Lactic acid |
| 638 | (b) Carbon dioxide evolved to oxygen consumed |
| 639 | (b) Autotrophs |
| 640 | (a) Holozoic |
Frequently asked questions
How many RAS Prelims practice MCQs are there on RAS Prelims?
This page has 9654 practice MCQs on the RAS Prelims syllabus. Each has the correct answer, and most have an explanation.
How should I practise MCQs for RAS Prelims?
Attempt each question first, then open the answer and read the explanation. Practise one chapter at a time, note the facts you got wrong and revise them. Repeat the chapter after a few days.
Are these actual RAS Prelims past-paper questions?
No. These are practice questions written for the RAS Prelims syllabus. They follow the pattern the exam uses: factual questions, statement-based questions, match-the-list and assertion-reason.