Q621. The primary distinguishing feature of a prokaryotic cell compared to a eukaryotic cell is the absence of:
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Q622. Which of the following structures is found in plant cells but strictly absent in animal cells?
Explanation
While both plant and animal cells share many organelles like mitochondria and the nucleus, plant cells have a rigid outer layer called the cell wall. Composed mainly of cellulose, this structure provides mechanical support and protection, helping the plant maintain its shape and withstand osmotic pressure. Animal cells lack a cell wall, possessing only a flexible plasma membrane as their outer boundary.
Q623. Mitochondria are often referred to as the "powerhouses" of the cell because they:
Explanation
Mitochondria are specialized organelles found in most eukaryotic cells and are responsible for aerobic cellular respiration. They convert the chemical energy from nutrients, such as glucose, into a form that the cell can easily use, known as adenosine triphosphate or ATP. This energy production is vital for all cellular activities, earning mitochondria the nickname "the powerhouses of the cell" in biology.
Q624. Consider the following cellular organelles and their functions:
I. Lysosomes - Intracellular digestion (suicide bags)
II. Ribosomes - Protein synthesis
III. Chloroplasts - Lipid synthesis
IV. Vacuoles - Storage of substances
Which of the above pair(s) is/are correctly matched?
I. Lysosomes - Intracellular digestion (suicide bags)
II. Ribosomes - Protein synthesis
III. Chloroplasts - Lipid synthesis
IV. Vacuoles - Storage of substances
Which of the above pair(s) is/are correctly matched?
Explanation
Most listed organelle functions are correct: lysosomes perform digestion, ribosomes synthesize proteins, and vacuoles store various substances. However, the statement about chloroplasts is wrong; their primary role is photosynthesis, the process of converting light energy into chemical energy. Lipid synthesis is actually performed by the smooth endoplasmic reticulum, not by chloroplasts, which are exclusive to plants and some algae.
Q625. The primary function of the Golgi apparatus in a eukaryotic cell is:
Explanation
The Golgi apparatus serves as the central shipping and receiving department of the eukaryotic cell. It receives proteins and lipids from the endoplasmic reticulum, modifies them chemically, and then sorts them into membrane-bound vesicles for delivery to specific destinations, such as the cell membrane or lysosomes. This processing is essential for ensuring that cellular products are functional and reach locations.
Q626. Rough Endoplasmic Reticulum (RER) appears "rough" under a microscope due to the presence of which attached structures?
Explanation
The Endoplasmic Reticulum is a network of membranes within the cell. The "rough" variety, or RER, is named for its bumpy appearance under an electron microscope, which is caused by the presence of numerous ribosomes attached to its outer surface. These ribosomes are actively involved in the synthesis of proteins that are destined for secretion or for use in the cell membrane.
Q627. Chromoplasts are a type of plastid primarily responsible for:
Explanation
Chromoplasts are specialized plastids found in certain plant tissues, such as the petals of flowers and the skins of ripening fruits. Unlike green chloroplasts, chromoplasts contain carotenoid pigments that produce yellow, orange, and red colors. These vibrant colors play a crucial biological role by attracting pollinators like bees and birds or animals that help in the dispersal of seeds and fruits.
Q628. The currently accepted model describing the structure of the cell membrane is known as the:
Explanation
The fluid mosaic model is the currently accepted description of the cell membrane’s structure. It depicts the membrane as a dynamic, flexible phospholipid bilayer in which various protein molecules are embedded or attached. This "mosaic" of proteins can move laterally within the "fluid" lipid layer, allowing the membrane to perform essential functions such as selective permeability, cell signaling, and structural support.
Q629. The primary role of chlorophyll in photosynthesis is to:
Explanation
Chlorophyll is a green pigment found within the chloroplasts of plants and algae. Its primary role in photosynthesis is to capture and absorb light energy, particularly from the blue and red wavelengths of the solar spectrum. This absorbed energy is then used to drive the chemical reactions that convert carbon dioxide and water into energy-rich glucose molecules while releasing oxygen gas.
Q630. Match the processes in List I with their site of occurrence in the cell in List II.
| Process/Stage | Site of occurrence in the cell |
|---|---|
| A. Glycolysis | i. Mitochondrial matrix |
| B. Krebs Cycle (Citric Acid Cycle) | ii. Cytoplasm |
| C. Light reaction of photosynthesis | iii. Stroma of chloroplast |
| D. Dark reaction (Calvin cycle) | iv. Thylakoids of chloroplast |
Explanation
Glycolysis occurs in the cytoplasm, while the Krebs cycle takes place in the mitochondrial matrix. In photosynthesis, the light-dependent reactions occur within the thylakoid membranes of the chloroplast, where light is captured. The light-independent dark reactions, or the Calvin cycle, take place in the surrounding stroma. These specific locations ensure that the necessary enzymes and substrates are concentrated for metabolic activity.Answer key for these questions
| Q | Correct answer |
|---|---|
| 621 | (a) A distinct, membrane-bound nucleus |
| 622 | (b) Cell wall |
| 623 | (b) Generate cellular energy in the form of ATP |
| 624 | (a) I, II and IV |
| 625 | (c) Modification, sorting, and packaging of proteins |
| 626 | (d) Ribosomes |
| 627 | (c) Imparting colors other than green to flowers and fruits |
| 628 | (b) Fluid mosaic model |
| 629 | (d) Absorb light energy |
| 630 | (a) A-ii, B-i, C-iv, D-iii |
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.