Cell

61. Movement of materials to different parts of cytoplasm and nucleus is g

Movement of materials to different parts of cytoplasm and nucleus is generally carried out by

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Ribosomes.
Mitochondria.
Lysosomes.
Endoplasmic reticulum.
This question was previously asked in
UPSC NDA-1 – 2021
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Movement of materials to different parts of cytoplasm and nucleus is generally carried out by the Endoplasmic reticulum.
The endoplasmic reticulum (ER) is a vast network of interconnected membranes extending throughout the cytoplasm of eukaryotic cells. It forms a continuous network with the outer membrane of the nuclear envelope, providing channels and pathways for the transport of molecules within the cell. Proteins synthesized on ribosomes attached to the rough ER are often transported within the ER lumen, and lipids synthesized in the smooth ER can also move through the ER network. The ER system is crucial for intracellular transport.
Ribosomes synthesize proteins but do not transport materials within the cell’s internal network. Mitochondria are involved in energy production. Lysosomes are involved in degradation and recycling. While vesicles budding from the ER and Golgi are involved in transport to other organelles or outside the cell, the basic network for internal movement of materials through the cytoplasm and towards the nucleus is largely provided by the ER.

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62. Which one of the following organelles of mammalian cell is rich in hyd

Which one of the following organelles of mammalian cell is rich in hydrolytic enzymes ?

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Mitochondria
Ribosomes
Lysosome
Nucleus
This question was previously asked in
UPSC NDA-1 – 2019
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Lysosomes are the organelles of mammalian cells that are rich in hydrolytic enzymes.
Lysosomes contain enzymes like proteases, lipases, nucleases, and glycosidases, which work optimally in an acidic environment (pH ~4.5-5.0).
These enzymes are responsible for breaking down waste materials, cellular debris, excess organelles, and ingested pathogens through processes like phagocytosis and autophagy. Mitochondria are involved in energy production, ribosomes in protein synthesis, and the nucleus contains genetic material.

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63. Which one of the following cell organelles does NOT possess its own ge

Which one of the following cell organelles does NOT possess its own genetic material encoding proteins ?

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Ribosome
Nucleus
Mitochondria
Chloroplast
This question was previously asked in
UPSC NDA-1 – 2019
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The correct answer is A) Ribosome.
Cell organelles like the nucleus, mitochondria, and chloroplasts contain their own DNA which encodes some of their proteins. Ribosomes are composed of ribosomal RNA (rRNA) and proteins, but they do not possess their own DNA. The genes for ribosomal RNA are located in the nuclear DNA, and ribosomal proteins are synthesized in the cytoplasm based on mRNA transcribed from nuclear DNA.
Mitochondria and chloroplasts are believed to have originated from endosymbiotic bacteria, which is why they retained their own circular DNA and protein synthesis machinery (including ribosomes distinct from cytoplasmic ribosomes). The nucleus contains the vast majority of a eukaryotic cell’s genetic material in the form of linear DNA chromosomes. Ribosomes are responsible for protein synthesis, translating mRNA into protein sequences, but they do not carry the genetic code for their own proteins or rRNA in a dedicated genome within the organelle itself.

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64. Which one of the following cell organelles does NOT possess nucleic ac

Which one of the following cell organelles does NOT possess nucleic acid ?

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Nucleolus
Chloroplast
Ribosome
Plasma Membrane
This question was previously asked in
UPSC NDA-1 – 2019
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The correct option is D, Plasma Membrane. The plasma membrane is primarily composed of a lipid bilayer and proteins and does not contain nucleic acids (DNA or RNA).
– Nucleolus is found within the nucleus and contains ribosomal RNA (rRNA) and proteins involved in ribosome synthesis.
– Chloroplasts are organelles found in plant cells and possess their own circular DNA, as well as RNA.
– Ribosomes are complexes of ribosomal RNA (rRNA) and proteins, responsible for protein synthesis. They contain nucleic acid (RNA).
Other organelles that contain nucleic acids (DNA) include the nucleus (main repository of DNA) and mitochondria (possess their own circular DNA).

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65. Who among the following first discovered cell ?

Who among the following first discovered cell ?

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Robert Brown
Robert Hooke
Leeuwenhoek
Rudolf Virchow
This question was previously asked in
UPSC NDA-1 – 2018
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Robert Hooke was the first person to observe and describe cells.
In 1665, Robert Hooke published his book “Micrographia”, where he described his observations using a microscope. He examined a thin slice of cork and observed small, box-like compartments, which he called “cells” because they reminded him of the rooms (cells) in a monastery.
Robert Brown discovered the nucleus in plant cells in 1831. Antonie van Leeuwenhoek, a contemporary of Hooke, made significant improvements to microscopes and was the first to observe living cells, including bacteria and protozoa, which he called “animalcules”. Rudolf Virchow is known for his contribution to cell theory with the principle “omnis cellula e cellula”.

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66. Which one of the following is an organelle that is NOT found in prokar

Which one of the following is an organelle that is NOT found in prokaryotic cells?

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Cell wall
Mitochondria
Plasma membrane
Ribosome
This question was previously asked in
UPSC NDA-1 – 2018
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The correct answer is B) Mitochondria.
Prokaryotic cells (like bacteria and archaea) are structurally simpler than eukaryotic cells. A key difference is the absence of membrane-bound organelles in prokaryotes.
A) Cell wall: Many prokaryotes have a cell wall (though different in composition from eukaryotic cell walls like those in plants or fungi).
B) Mitochondria: Mitochondria are membrane-bound organelles responsible for cellular respiration and ATP production in eukaryotic cells. They are *not* found in prokaryotic cells. In prokaryotes, respiration occurs in the cytoplasm and across the cell membrane.
C) Plasma membrane: The plasma membrane (cell membrane) surrounds the cytoplasm and is present in *all* cells, both prokaryotic and eukaryotic.
D) Ribosome: Ribosomes are responsible for protein synthesis and are found in the cytoplasm of *all* cells, both prokaryotic and eukaryotic (though prokaryotic ribosomes are 70S, and eukaryotic ribosomes are 80S).
Besides mitochondria, other membrane-bound organelles like the nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, and chloroplasts are also absent in prokaryotic cells. Their genetic material (DNA) is typically a single, circular chromosome located in a region called the nucleoid, without a nuclear membrane.

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67. Cell wall of any fungus is different from plants in having

Cell wall of any fungus is different from plants in having

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cellulose
chitin
cholesterol
glycogen
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UPSC NDA-1 – 2017
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Plant cell walls are primarily composed of cellulose, a polysaccharide. The cell walls of fungi, however, are primarily composed of chitin, a nitrogen-containing polysaccharide also found in the exoskeletons of insects and crustaceans. This difference in cell wall composition is a key characteristic distinguishing fungi from plants.
Fungal cell walls contain chitin, whereas plant cell walls contain cellulose.
The presence of chitin in fungal cell walls is targeted by some antifungal drugs, making it an important difference from human cells which lack cell walls. Glycogen is a common storage carbohydrate in both fungi and animals, not a cell wall component. Cholesterol is a lipid found in animal cell membranes, not plant or fungal cell walls.

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68. Which of the following statements about DNA is/are correct ? 1. DNA

Which of the following statements about DNA is/are correct ?

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  • 1. DNA is the hereditary material of all living organisms.
  • 2. All segments of DNA code for synthesis of proteins.
  • 3. Nuclear DNA is double helical with two nucleotide chains which run anti-parallel.
  • 4. DNA is also found in mitochondria.

Select the correct answer using the code given below :

1, 2 and 3 only
3 and 4 only
1, 3 and 4 only
4 only
This question was previously asked in
UPSC NDA-1 – 2016
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Let’s evaluate each statement:
1. DNA is the hereditary material of all living organisms. This is incorrect. While DNA is the hereditary material for most organisms (bacteria, archaea, eukaryotes), some viruses use RNA as their genetic material.
2. All segments of DNA code for synthesis of proteins. This is incorrect. Large portions of DNA in eukaryotic genomes are non-coding. This includes regulatory sequences, introns (non-coding regions within genes), repetitive DNA, telomeres, etc.
3. Nuclear DNA is double helical with two nucleotide chains which run anti-parallel. This is correct. The Watson-Crick model describes DNA as a double helix where the two polynucleotide strands are complementary and run in opposite directions (5′ to 3′ and 3′ to 5′).
4. DNA is also found in mitochondria. This is correct. Mitochondria (and chloroplasts in plants) contain their own circular DNA (mtDNA), which is distinct from the nuclear DNA.
Based on the analysis, statements 3 and 4 are correct.
– DNA is the primary genetic material, but not universal (some viruses use RNA).
– Not all DNA sequences are protein-coding.
– Nuclear DNA is a double helix with anti-parallel strands.
– Extranuclear DNA exists in organelles like mitochondria and chloroplasts.
Mitochondrial DNA (mtDNA) is typically circular and much smaller than nuclear DNA. It encodes some proteins involved in cellular respiration, as well as ribosomal RNAs and transfer RNAs used within the mitochondrion. Due to its maternal inheritance pattern in many species, mtDNA is useful in tracing evolutionary lineages.

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69. Which one of the following is the smallest unit showing the properties

Which one of the following is the smallest unit showing the properties of life such as capacity for metabolism, response to the environment, growth and reproduction ?

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Gene
Chromosome
Nucleus
Cell
This question was previously asked in
UPSC NDA-1 – 2015
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The cell is considered the fundamental structural and functional unit of life. It is the smallest unit that exhibits all the basic properties of life, including metabolism, response to stimuli, growth, and reproduction (at the cellular level, via division). Genes, chromosomes, and the nucleus are components within a cell and cannot independently perform all life processes.
Understanding the concept of the cell as the basic unit of life.
Genes are units of heredity made of DNA. Chromosomes are structures containing coiled DNA, carrying genetic information. The nucleus is an organelle containing the cell’s genetic material in eukaryotes. All these components work within the framework of a cell to carry out life functions.

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70. All life forms contain “molecules of life”. These are

All life forms contain “molecules of life”. These are

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Carbohydrates
Proteins
Nucleic acids
All of the above
This question was previously asked in
UPSC NDA-1 – 2015
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The correct answer is All of the above. Carbohydrates, Proteins, and Nucleic acids (DNA and RNA) are fundamental classes of organic macromolecules essential for all known forms of life.
These three types of molecules play crucial roles: Carbohydrates are primary energy sources and structural components; Proteins perform a vast array of functions including enzymes, structural support, and transport; Nucleic acids carry genetic information (DNA) and are involved in protein synthesis (RNA). Lipids are also often considered a fourth major class of biomolecules.
These macromolecules are built from smaller repeating units (monomers): carbohydrates from monosaccharides, proteins from amino acids, and nucleic acids from nucleotides. Their presence and interactions are fundamental to cellular structure and function.

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