NEET Biology: Cell: The Unit of Life questions with solutions

Q1. Plant cells are rigid due to the presence of

1. Cell membrane
2. Cell wall
3. cytoskeleton
4. chloroplasts E. Centrioles

Answer: Cell wall

Plant cells are rigid because the cell wall surrounds the cell and provides structural support and shape. The cell membrane is flexible, while chloroplasts and centrioles do not give rigidity.

Q2. In prokaryotes, the genetic material is

1. linear DNA with histones
2. circular DNA with histones
3. linear DNA without histones
4. circular DNA without histones

Answer: circular DNA without histones

Prokaryotes generally have a circular chromosome, unlike the linear chromosomes common in eukaryotes. They also do not have histones in the same way eukaryotic DNA does, so the best choice is circular DNA without histones.

Q3. According of fluid mosaic model, plasma membrane is composed of

1. phospholipids and oligosaccharides
2. phospholipids and hemicellulose
3. phospholipids and integral proteins
4. phospholipids, extrinsic proteins and intrinsic proteins

Answer: phospholipids, extrinsic proteins and intrinsic proteins

The fluid mosaic model describes the plasma membrane as a phospholipid bilayer containing proteins. These proteins include intrinsic (integral) proteins embedded in the bilayer and extrinsic (peripheral) proteins attached to its surface.

Q4. Cellulose, the most important constituent of plant cell wall is made of

1. unbranched chain of glucose molecules linked by α-1, 4 glycosidic bond
2. branched chain of glucose molecules linked by β-1, 4 glycosidic bond in straight chain and α-1, 6 glycosidic bond at the site of branching
3. unbranched chain of glucose molecules linked by β-1, 4 glycosidic bond
4. branched chain of glucose molecules linked by α-1, 6 glycosidic bond at the site of branching

Answer: unbranched chain of glucose molecules linked by β-1, 4 glycosidic bond

Cellulose is a structural polysaccharide made of glucose units joined by β-1,4 glycosidic bonds, producing long straight chains. These chains pack tightly and form strong fibers, which is ideal for plant cell walls.

Q5. Poisons like cyanide inhibit Na⁺ efflux and K⁺ influx during cellular transport. This inhibitory effect is reversed by an injection of ATP. This demonstrates that

1. ATP is the carrier protein in the transport system.
2. energy for Na⁺ – K⁺ exchange pump comes from ATP.
3. ATP is hydrolysed by ATP to release energy.
4. Na⁺ – K⁺ exchange pump operates in the cell.

Answer: energy for Na⁺ – K⁺ exchange pump comes from ATP.

Cyanide blocks ATP production, so active transport of Na⁺ and K⁺ stops. When ATP is injected and the transport resumes, it shows the pump depends on ATP-derived energy to work.

Q6. The association of histone H1 with a nucleosome indicates:

1. DNA replication is occurring.
2. The DNA is condensed into a Chromatin Fibre.
3. The DNA double helix is exposed.
4. Transcription is occurring.

Answer: The DNA is condensed into a Chromatin Fibre.

Histone H1 binds to the linker DNA between nucleosomes and promotes tighter folding of chromatin. Its association is a sign that DNA is in a more condensed chromatin fibre state, not exposed for transcription or replication.

Q7. A complex of ribosomes attached to a single strand of RNA is known as

1. Polysome
2. Polymer
3. Polypeptide
4. Okazaki fragment

Answer: Polysome

A polysome (polyribosome) is a cluster of ribosomes simultaneously attached to and translating a single mRNA molecule. This arrangement allows rapid production of many copies of the same protein.

Q8. One function of the telomeres in a chromosome is to

1. identify the correct number of the homologous pair of chromosomes
2. help two chromatids to move towards poles
3. "seal" the ends of chromosomes
4. start RNA synthesis

Answer: "seal" the ends of chromosomes

Telomeres are repetitive DNA sequences at chromosome ends that protect them from degradation and end-to-end fusion. Their role is to cap or “seal” the ends, not to guide pairing, movement, or transcription initiation.

Q9. Protein synthesis occurs

1. on ribosomes present in cytosol as well as in mitochondria
2. only on ribosomes attached to the nuclear envelope and endoplasmic reticulum
3. only on the ribosomes present in cytosol
4. on ribosomes present in the nucleolus as well as cytoplasm

Answer: on ribosomes present in cytosol as well as in mitochondria

Protein synthesis happens on ribosomes, and ribosomes are found in the cytosol and inside mitochondria. Mitochondria have their own genetic system and can translate some proteins independently.

Q10. Which of the following structures is not found in a prokaryotic cell?

1. Ribosome
2. Mesosome
3. Plasma membrane
4. Nuclear envelope

Answer: Nuclear envelope

Prokaryotic cells lack membrane-bound organelles, including a nucleus. Therefore, they do not have a nuclear envelope, while ribosomes, plasma membrane, and mesosome are associated with prokaryotes.

Q11. In eubacteria, a cellular component that resembles eukaryotic cells is:

1. Plasma membrane
2. Nucleus
3. Ribosomes
4. Cell wall

Answer: Plasma membrane

Eubacteria are prokaryotes, so they do not have a nucleus, but they do have a plasma membrane like eukaryotic cells. The plasma membrane is a universal cell boundary that controls what enters and leaves the cell.

Q12. Genophore/bacterial genome or nucleoid is made of

1. histones and nonhistones
2. RNA and histones
3. a single double stranded DNA
4. a single stranded DNA

Answer: a single double stranded DNA

The bacterial genophore (nucleoid chromosome) is generally a single circular double-stranded DNA molecule. Bacteria do not package their genome with true histones like eukaryotes, and their genetic material is not RNA or single-stranded DNA.

Q13. Genetic information in Paramecium is contained in:

1. micronucleus
2. macronucleus
3. both micronucleus and macronucleus
4. mitochondria

Answer: both micronucleus and macronucleus

Paramecium contains two types of nuclei: the micronucleus and the macronucleus. The micronucleus carries hereditary genetic material, while the macronucleus also contains DNA and controls the cell’s everyday activities, so genetic information is present in both.

Q14. The hereditary material present in the bacterium Escherichia coli is

1. single stranded DNA
2. deoxyribose sugar
3. double stranded DNA
4. single stranded RNA

Answer: double stranded DNA

Escherichia coli is a bacterium, and bacteria store their hereditary information mainly in a circular chromosome made of double-stranded DNA. Single-stranded RNA is typical of some viruses, and deoxyribose is only a sugar component, not the full genetic material.

Q15. In prokaryotes nucleoid consist of double stranded circular DNA without histone protein.

1. These are archaebacteria which can tolerate high temperature.
2. Transfer of genetic information from one bacterium to another by physical contact is called conjugation while if it takes place by some other medium like virus than it is called transduction.
3. In (E.coli) double stranded DNA is present.
4. E. coli is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms. Most types of E. coli are harmless and even help keep your digestive tract healthy. But some strains can cause diarrhea if you eat contaminated food or drink fouled water.

Answer: In (E.coli) double stranded DNA is present.

The nucleoid in prokaryotes contains a double-stranded circular DNA molecule, and E. coli is a prokaryote. So the statement that double-stranded DNA is present in E. coli correctly matches the given fact.

Q16. Which one of the following living organisms completely lacks a cell wall?

1. Cyanobacteria
2. Sea-fan (Gorgonia)
3. Saccharomyces
4. Blue-green algae

Answer: Sea-fan (Gorgonia)

Sea-fan (Gorgonia) is an animal (a cnidarian), and animal cells do not have cell walls. Cyanobacteria and blue-green algae are prokaryotic/algal forms with walls, and Saccharomyces is a fungus with a chitinous cell wall.

Q17. Match the following cell structure with its characteristic feature:

1. Tight junctions - Cement neighbouring cells together to form sheet.
2. Adhering junctions - Transmit information through chemical to another cells.
3. Gap junctions - Establish a barrier to prevent leakage of fluid across epithelial cells.
4. Synaptic junctions - Cytoplasmic channels to facilitate communication between adjacent cells.

Answer: Tight junctions - Cement neighbouring cells together to form sheet.

Tight junctions form a continuous seal between neighboring epithelial cells, helping them act as a sheet and preventing leakage between cells. The other options describe different junction types: gap junctions allow direct communication, adhering junctions provide mechanical attachment, and synaptic junctions transmit signals.

Q18. A student wishes to study the cell structure under a light microscope having 10X eyepiece and 45X objective. He should illuminate the object by which one of the following colours of light so as to get the best possible resolution?

1. Blue
2. Green
3. Yellow
4. Red

Answer: Blue

A light microscope’s resolving power increases when the illumination wavelength is smaller. Among the given colors, blue light has the shortest wavelength, so it gives the best resolution.

Q19. Names of Schleiden and Schwann are associated with

1. protoplasm as the physical basis of life
2. cell theory
3. theory of cell lineage
4. nucleus functions as control centre of cell

Answer: cell theory

Schleiden studied plants and Schwann studied animals, and together they proposed that all living organisms are made of cells. This is the basis of cell theory.

Q20. Which is correct about cell theory in view of current status of our knowledge about cell structure?

1. It needs modification due to discovery of subcellular structures like chloroplasts and mitochondria
2. Modified cell theory means that all living beings are composed of cells capable of reproducing
3. Cell theory does not hold good because all living beings (e.g., viruses) do not have cellular organisation
4. Cell theory means that all living objects consist of cells whether or not capable of reproducing

Answer: Modified cell theory means that all living beings are composed of cells capable of reproducing

The modified cell theory updates the classical idea by recognizing that living organisms are made of cells and that cells arise from pre-existing cells through reproduction. This matches the modern understanding of cell structure and function.