Title Ex-2 Cell The unit of life Reviewed.pdf ✅

38 CELL THE UNIT OF LIFE EXERCISE – 2: Previous Year Competition Questions 1. The organelles that are included in the endomembrane system are: (NEET 2021) (a) Endoplasmic reticulum, Mitochondria, Ribosomes and Lysosomes (b) Endoplasmic reticulum, Golgi complex, Lysosomes and Vacuoles (c) Golgi complex, Mitochondria, Ribosomes and Lysosomes (d) Golgi complex, Endoplasmic reticulum, Mitochondria and Lysosomes Ans. (b) Sol. Endomembrane system is a system of closely coordinated, membrane bound organelles. For e.g., ER, golgi complex, lysosomes and vacuoles etc. So, the correct answer is option (b). 2. Match List-I with List-II. (NEET 2021) List-I List-II (A) Cristae (i) Primary constriction in chromosome (B) Thylakoids (ii) Disc-shaped sacs in Golgi apparatus (C) Centromere (iii) Infoldings in mitochondria (D) Cisternae (iv) Flattened membranous sacs in stroma of plastids Choose the correct answer from the options given below. (a) A-(iv), B-(iii), C-(ii), D-(i) (b) A-(i), B-(iv), C-(iii), D-(ii) (c) A-(iii), B-(iv), C-(i), D-(ii) (d) A-(ii), B-(iii), C-(iv), D-(i) Ans. (c) Sol. Cristae is the inner membrane of mitochondria, infolded variously. They are meant for increasing the physiologically active area of the inner membrane. The density of cristae indicatesthe intensity ofrespiration. Golgi apparatus consists of a stack of generally 4-8 membrane-bound cisternae. Cisternae are disc-shaped. Their membranes are smooth but of variable thickness. The cisternae are frequently curved to give a definite polarity to the Golgi apparatus. Thylakoids are membrane lined flattened sacs which run through-out the stroma or matrix of the chloroplast. Since they take part in photosynthesis; they are also called photosynthetic thylakoids. Thylakoids are thus the structural elements of the chloroplast. They generally run parallel but may show interconnections 3. Which is the important site of formation of glycoproteins and glycolipids in eukaryotic cells? (NEET 2020) (a) Polysomes (b) Endoplasmic reticulum (c) Peroxisomes (d) Golgi bodies Ans. (d) Sol. Golgi apparatus were discovered by Camillo golgi. The material synthesized by endoplasmic reticulum is transformed, modified, and packaged by golgi. They are the main site involved in formation of glycoproteins and glycolipids. It consists of a stack of generally 4-8 membrane-bound cisternae. 4. Which of the following statements is not correct? (NEET 2019) (a) Lysosomes have numerous hydrolytic enzymes. (b) The hydrolytic enzymes of lysosomes are active under acidic pH. (c) Lysosomes are membrane bound structures. (d) Lysosomes are formed by the process of packaging in the endoplasmic reticulum. Ans. (d) Sol. Lysosomes are single membrane bound small vesicle which contain hydrolytic enzymes. It has a compartment present, which is surrounded by a membrane for storing digestive enzymes that requires a low-pH environment. These hydrolytic enzymes can digest carbohydrate, proteins, nucleic acids and lipids. Nucleases, lipases, peptidases and proteases etc are the example of some hydrolytic enzymes
CELL THE UNIT OF LIFE 39 present in it. These organelles are not formed by the process of packaging in the endoplasmic reticulum. 5. The Golgi complex participates in (NEET 2018) (a) Respiration in bacteria (b) Formation of secretory vesicles (c) Fatty acid breakdown (d) Action of amino acid Ans. (b) Sol. The Golgi complex is a single membrane-bound cell organelle present in eukaryotic cells. It takes part in the formation of secretory vesicles. It also helps in the transportation of the materials within or outside the cells. 6. Which of the following is true for nucleolus? (NEET 2018) (a) It takes part in spindle formation (b) It is a membrane-bound structure (c) Larger nucleoli are present in dividing cells (d) It is a site for active ribosomal RNA synthesis Ans. (d) Sol. The nucleolus is the spherical structure present within the nucleoplasm. It is not membrane-bound and thus its content is continuous with nucleoplasm. It appears during cell division. Hence, the proteins of ribosomes are synthesised in the cytoplasm but diffused into the nucleus and reach the nucleolus. Here rRNA and ribosomal proteins are assembled to form ribosomes which move to the cytoplasm through nuclear pores. Thus, it provides a site for active ribosomal RNA synthesis. 7. Select the incorrect match: (NEET 2018) (a) Submetacentric chromosomes - L-shaped chromosomes (b) Allosomes - Sex chromosomes (c) Lamp brush chromosomes - Diplotene bivalents (d) Polytene chromosomes - Oocytes of amphibians Ans. (d) Sol. There are four types of chromosomes based on the position of the centromere. These are metacentric, submetacentric, acrocentric and telocentric. Submetacentric chromosomes are L-shaped as in those chromosomes one arm is short and the other arm is long. -Chromosomes are of two types- allosomes and autosomes. Allosomes are sex chromosomes. In humans, these are of two types, X and Y. -Lamb brush chromosomes are special types of chromosomes that are found in the immature eggs of many animals like amphibian oocytes but not in mammals. These are formed during the diplotene stage of meiotic prophase I. They are bivalent, i.e., made up of two conjugating homologues. Polytene chromosomes are giant chromosomes. They are commonly seen in two-winged flies. They result due to repeated rounds of DNA replication without any cell division. 8. Which of the following events does not occur in rough endoplasmic reticulum? (NEET 2018) (a) Cleavage of signal peptide (b) Protein glycosylation (c) Protein folding (d) Phospholipid synthesis Ans. (d) Sol. Rough endoplasmic reticulum (RER) is responsible for the synthesis of proteins. A single peptide is a short peptide that is present at the N-terminus of the newly synthesized proteins. It is cleaved by a single peptidase in RER and then enters the lumen of a rough endoplasmic reticulum. Protein glycosylation takes place in the lumen of the rough endoplasmic reticulum (RER). Protein folding takes place within the lumen of the endoplasmic reticulum. Smooth endoplasmic reticulum (SER) is involved in the synthesis of phospholipid and cholesterol. 9. Many ribosomes may associate with a single mRNA to form multiple copies of a polypeptide simultaneously. Such strings of ribosomes are termed as (NEET 2018) (a) Plastidome (b) Polyhedral bodies (c) Polysome (d) Nucleosome Ans. (c) Sol. A polysome is a single mRNA that is simultaneously being translated by many ribosomes. It results in the synthesis of multiple copies of a polypeptide. All the plastids of cells collectively are called plastidome. Polyhedral bodies are inclusion bodies that are associated with the replication of certain insect viruses. Nucleosome is a basic unit consisting of DNA wrapped around histone proteins.
40 CELL THE UNIT OF LIFE 10. Which of the following cell organelles is responsible for extracting energy from carbohydrates to form ATP (NEET 2017) (a) Lysosome (b) Ribosome (c) Chloroplast (d) Mitochondrion Ans. (d) Sol. Mitochondrion is the organelle that oxidizes the pyruvic acid (formed by the glycolysis of glucose) and produces energy in the form of ATP. It also stores energy. 11. Which of the following components provides sticky character to the bacterial cell? (NEET 2017) (a) Cell wall (b) Nuclear membrane (c) Plasma membrane (d) Glycocalyx Ans. (d) Sol. Glycocalyx may occur in the form of the loose sheath called Slime layer or thick, tough mucilage covering called a capsule. The capsule is responsible for giving gummy and sticky character to the cell wall. The capsule helps the bacteria to adhere to surfaces. 12. Mitochondria and chloroplast are (NEET 2016) (i) semi-autonomous organelles (ii) formed by division of pre-existing organelles and they contain DNA but lack protein synthesizing machinery Which one of the following options is correct? (a) Both (i) and (ii) are correct (b) (ii) is true but (i) is false (c) (i) is true but (ii) is false (d) Both (i) and (ii) are false Ans. (c) Sol. Mitochondria as well as chloroplasts are considered as semi-autonomous cell organelle thanks to the subsequent counts: Mitochondria have their own DNA which can replicate independently. The mitochondrial DNA produces its own mRNA, tRNA and rRNA. The organelles possess their own ribosomes, called mitoribosomes. The same applies to chloroplast as well. 13. Microtubules are the constituents of (NEET 2016) (a) Cilia, Flagella and Peroxisomes (b) Spindle fibres, Centrioles and Cilia (c) Centrioles, Spindle fibres and Chromatin (d) Centrosome, Nucleosome and Centrioles Ans. (b) Sol. The microtubules are found in the cytoplasmic matrix of all eukaryotic cells. They also occur in cilia, flagella, centrioles, basal bodies, and mitotic apparatus. Spindle fibres form the protein structure which helps in mitosis and meiosis. Centrioles are the two cylindrical structures of a cell organelle called the centrosome. Cilia and flagella are fine hair-like outgrowths of the membrane. While peroxisomes are the microbodies. So, the correct answer is 'Spindle fibers, centrioles, and cilia'. 14. A complex of ribosomes attached to a single strand of RNA is known (NEET 2016) (a) Polysome (b) Polymer (c) Polypeptide (d) Okazaki fragment Ans. (a) Sol. A complex of ribosomes attached to a single strand of RNA is known as Polysome. Polymers are large molecules composed of many monomer units. Polypeptide is a large linear polymer of amino acids bonded together by a peptide linkage. Okazaki fragments are small nucleic acid fragments formed by discontinuous replication of lagging strand during DNA replication and are later joined together by DNA ligase enzyme. 15. Which one of the following cell organelles is enclosed by a single membrane? (NEET 2016) (a) Mitochondria (b) Chloroplasts (c) Lysosomes (d) Nuclei Ans. (c) Sol. Mitochondrion is double membrane-bound organelle, wherein the inner membrane is present as infolding and forms cristae. Chloroplast is double membrane-bound organelle in which the inner membrane surrounds the alkaline stroma and thylakoid system.
CELL THE UNIT OF LIFE 41 Lysosomes are bound by a single layer of typical phospholipids. Nucleus is the double membrane-bound organelle of the eukaryotic cell. 16. Select the mismatch. (NEET 2016) (a) Gas vacuoles - Green bacteria (b) Large central vacuoles - Animal cells (c) Protists - Eukaryotes (d) Methanogens – Prokaryotes Ans. (b) Sol. Gas vacuoles are aggregates of gas vesicles and are found in green bacteria to impart buoyancy. The presence of large central vacuole is characteristic of plant cells while animal cells have multiple small vacuoles. Protists are diverse eukaryotic organisms and belong to third domain Eukarya. Methanogens are prokaryotic anaerobes that produce methane gas and belong to domain Archaea. 17. Select the wrong statement - (NEET 2016) (a) Bacterial cell wall is made up of peptidoglycan (b) Pili and fimbriae are mainly involved in motility of bacterial cells (c) Cyanobacteria lack flagellated cells (d) Mycoplasma is a wall-less microorganism Ans. (b) Sol. -The cell walls of bacteria are composed of a macromolecule, peptidoglycan which is a repeating framework of long glycan chains having alternate N- acetylglucosamine and N-acetylmuramic acid. -Pili and fimbriae are used for attachment rather than motility. Pili are long hair like tubular microfibres like structures present on the surface of bacteria and fimbriae are bristles like short fibres that occur on the surface of bacteria. -Cyanobacteria are motile or non-motile, non- flagellated organisms. -Mycoplasma is the smallest prokaryotic organism that lacks the cell wall but has rigid plasma membrane rich in sterols and lipoglycans. 18. A cell organelle containing hydrolytic enzymes is (NEET 2016) (a) Lysosome (b) Microsome (c) Ribosome (d) Mesosome Ans. (a) Sol. A cell organelle containing hydrolytic enzymes is lysosome. Lysosomes are membrane-bound organelles which contain acid hydrolases or digestive enzymes that digest excess or worn-out organelles, food particles, engulfed viruses or bacteria and macromolecules. 19. Which of the following structures is not found in a prokaryotic cell? (NEET 2015) (a) Plasma membrane (b) Nuclear envelope (c) Ribosome (d) Mesosome Ans. (b) Sol. Prokaryotic cells are unicellular organisms that lack membrane-bound organelles such as mitochondria, golgi complex. Prokaryotic cells are characterized by the absence of a membrane-bound true nucleus. The genetic material is not surrounded by a nuclear envelope. The genetic material without the nuclear envelope is called the nucleoid. Example of a prokaryotic cell is bacteria. Thus, the correct option is 'nuclear envelope'. 20. Which of the following are not membrane-bound? (NEET 2015) (a) Mesosomes (b) Vacuoles (c) Ribosomes (d) Lysosomes Ans. (c) Sol. Ribosomes are the protein factory of the cell. These are non-membranous organelle which attach an endoplasmic reticulum. Ribosomes are the site of protein synthesis. 21. Cellular organelles with membranes are (NEET 2015) (a) Lysosomes, Golgi apparatus and Mitochondria (b) Nuclei, ribosomes, and mitochondria (c) Chromosomes, Ribosomes and Endoplasmic Reticulum (d) Endoplasmic reticulum, Ribosomes and Nuclei Ans. (a)