NEET Biology Cell The Unit of Life MCQs Set 28

Answer: (a) Anton von Leeuwenhoek

Explanation:
1. Leeuwenhoek observed live cells with his simple microscope; Brown discovered the nucleus, Virchow proposed that new cells arise from pre-existing cells.

Teacher's Note:
1. Do not mix the first observer of live cells with the discoverer of the nucleus.
2. Revisit the NCERT diagram for this part.

Answer: (c) Nerve cell

Explanation:
1. Nerve cells can be over a metre long; the ostrich egg is the largest isolated single cell but not the longest.

Teacher's Note:
1. Largest and longest are different records.
2. Revisit the NCERT diagram for this part.

Answer: (c) Ribosome

Explanation:
1. Ribosomes have no membrane and are present in prokaryotes and eukaryotes; the others are bounded by membranes.

Teacher's Note:
1. Ribosomes and centrioles are non-membranous organelles.
2. Revisit the NCERT diagram for this part.

Answer: (d) Mycoplasma

Explanation:
1. Mycoplasma lacks a cell wall, which also makes it pleomorphic and the smallest living cell.

Teacher's Note:
1. Mycoplasma is the standard exception.
2. Revisit the NCERT diagram for this part.

Answer: (b) small circular DNA outside the genomic DNA, often giving antibiotic resistance

Explanation:
1. Plasmid DNA is extra-chromosomal and confers features such as antibiotic resistance; it is used as a vector in genetic engineering.

Teacher's Note:
1. Plasmids are not essential for normal growth but are useful in biotechnology.
2. Revisit the NCERT diagram for this part.

Answer: (d) an infolding of the plasma membrane that helps in cell wall formation, DNA replication and respiration

Explanation:
1. Mesosomes are membranous extensions that increase surface area and help in DNA replication and distribution to daughter cells.

Teacher's Note:
1. Mesosomes are characteristic of prokaryotes.
2. Revisit the NCERT diagram for this part.

Answer: (d) glycocalyx, cell wall, plasma membrane

Explanation:
1. The three layers are tightly bound, with the glycocalyx outermost (slime layer if loose, capsule if thick and tough).

Teacher's Note:
1. Order matters: outermost to innermost.
2. Revisit the NCERT diagram for this part.

Answer: (b) do not take part in motility; fimbriae help attach bacteria to surfaces

Explanation:
1. Pili are tubular protein structures (involved in conjugation) and fimbriae are bristle-like fibres for attachment; flagella are the motility organs.

Teacher's Note:
1. Motility = flagella only.
2. Revisit the NCERT diagram for this part.

Answer: (a) filament, hook and basal body

Explanation:
1. The filament is the longest part, extending outside the cell wall; the 9+2 pattern belongs to eukaryotic cilia and flagella.

Teacher's Note:
1. Bacterial and eukaryotic flagella differ in structure.
2. Revisit the NCERT diagram for this part.

Answer: (b) 70S, made of 50S and 30S subunits

Explanation:
1. Prokaryotic ribosomes are 70S (50S + 30S); eukaryotic cytoplasmic ribosomes are 80S (60S + 40S). Mitochondria and chloroplasts also contain 70S ribosomes.

Teacher's Note:
1. S is the Svedberg unit; sedimentation values do not add up simply.
2. Revisit the NCERT diagram for this part.

Answer: (d) reserve materials not bounded by any membrane, such as phosphate, cyanophycean and glycogen granules

Explanation:
1. Inclusion bodies lie free in the cytoplasm; gas vacuoles in blue-green algae and photosynthetic bacteria are also non-membranous inclusions.

Teacher's Note:
1. Prokaryotes lack membrane-bound organelles.
2. Revisit the NCERT diagram for this part.

Answer: (b) Singer and Nicolson (1972)

Explanation:
1. The model shows a quasi-fluid lipid bilayer with proteins floating in it, allowing lateral movement.

Teacher's Note:
1. Fluidity helps in endocytosis, secretion, cell growth and division.
2. Revisit the NCERT diagram for this part.

Answer: (d) 52 percent protein and 40 percent lipids

Explanation:
1. RBC membranes were the main material for early membrane studies because the cells lack a nucleus and organelles.

Teacher's Note:
1. Learn this ratio, it is asked directly.
2. Revisit the NCERT diagram for this part.

Answer: (c) active transport against a concentration gradient using energy

Explanation:
1. Active transport moves ions against their gradient and needs ATP.

Teacher's Note:
1. Compare with passive transport, which needs no energy.
2. Revisit the NCERT diagram for this part.

Answer: (a) calcium pectate

Explanation:
1. The middle lamella glues neighbouring cells together; the primary and secondary walls lie inside it.

Teacher's Note:
1. The middle lamella lies between the primary walls of adjacent cells.
2. Revisit the NCERT diagram for this part.

Answer: (b) Mitochondria

Explanation:
1. The endomembrane system includes ER, Golgi, lysosomes and vacuoles; mitochondria, chloroplasts and peroxisomes are excluded because their functions are not coordinated with the others.

Teacher's Note:
1. Endomembrane organelles are connected or exchange materials by vesicles.
2. Revisit the NCERT diagram for this part.

Answer: (b) studded with ribosomes and is active in protein synthesis and secretion

Explanation:
1. RER is continuous with the outer nuclear membrane; smooth ER lacks ribosomes and makes lipids and steroid hormones.

Teacher's Note:
1. RER is abundant in secretory cells such as pancreatic cells.
2. Revisit the NCERT diagram for this part.

Answer: (b) Camillo Golgi (1898)

Explanation:
1. Golgi observed the stained reticular structure in nerve cells; Palade described ribosomes.

Teacher's Note:
1. Do not mix up discoverers of organelles.
2. Revisit the NCERT diagram for this part.

Answer: (d) cis (forming) face

Explanation:
1. Vesicles from the ER fuse with the cis face and move to the trans face, where materials are packaged and released.

Teacher's Note:
1. Cis faces the ER, trans faces the cell membrane.
2. Revisit the NCERT diagram for this part.

Answer: (c) Golgi apparatus

Explanation:
1. Proteins from the ER are modified in the cisternae of the Golgi, which is an important site of formation of glycoproteins and glycolipids.

Teacher's Note:
1. The Golgi packages and modifies; the ER synthesises.
2. Revisit the NCERT diagram for this part.

Answer: (b) membrane-bound vesicles formed by the Golgi, rich in hydrolytic enzymes that are active at acidic pH

Explanation:
1. Lysosomal enzymes digest carbohydrates, proteins, lipids and nucleic acids; they are formed by the Golgi apparatus.

Teacher's Note:
1. Lysosomes are called suicide bags.
2. Revisit the NCERT diagram for this part.

Answer: (a) tonoplast

Explanation:
1. The tonoplast is a single membrane that transports ions against their gradient into the vacuole.

Teacher's Note:
1. Plant vacuoles can occupy up to 90 percent of the cell volume.
2. Revisit the NCERT diagram for this part.

Answer: (c) cristae

Explanation:
1. Cristae project into the matrix and increase the surface area for the enzymes of respiration.

Teacher's Note:
1. Grana belong to chloroplasts.
2. Revisit the NCERT diagram for this part.