Cell Structure & Function — Part 5: 40 MCQs with Explanations

ATP (adenosine triphosphate) stores and transfers energy for cellular processes through hydrolysis of its high-energy phosphate bonds.

Fungi have chitin in cell walls, absorptive heterotrophic nutrition (secrete enzymes externally), and unique reproductive structures distinguishing them from plants and animals.

O negative blood lacks A, B, and Rh antigens on RBC surface, minimizing risk of agglutination in recipients of any blood type.

Insulin facilitates glucose uptake by cells (especially muscle and adipose tissue) and promotes glycogen synthesis in liver and muscles.

In metaphase, chromosomes attached to spindle fibers from opposite poles align along the equatorial plane (metaphase plate) of the cell.

Prokaryotes lack a true nucleus; their single circular chromosome resides in the nucleoid region without a nuclear membrane.

Ribosomes (70S in prokaryotes, 80S in eukaryotes) translate mRNA codons into amino acid sequences during protein synthesis.

Humans have 46 chromosomes: 22 pairs of autosomes and 1 pair of sex chromosomes (XX in females, XY in males).

Insulin is secreted by beta cells of pancreatic islets of Langerhans. Liver stores glycogen, produces bile, detoxifies substances, and synthesizes plasma proteins.

Transcription occurs in nucleus (eukaryotes) or cytoplasm (prokaryotes), producing mRNA complementary to the template strand of DNA.

Hormone production is primarily an endocrine system function. Skeletal system provides structural support, protects organs, stores calcium/phosphate, and produces blood cells in red bone marrow.

Erythrocytes (red blood cells) contain hemoglobin which binds O₂ in lungs (forming oxyhemoglobin) and releases it in tissues.

Active natural immunity involves the body producing its own antibodies and memory cells after exposure to pathogen antigens during infection.

Prokaryotes have a single circular chromosome in nucleoid; eukaryotes have multiple linear chromosomes within a nuclear envelope.

Osmosis equalizes solute concentrations on both sides of membrane; water moves toward region of higher solute concentration.

Light-dependent reactions in thylakoid membranes produce ATP and NADPH using light energy; these power the Calvin cycle to fix CO₂ into sugars.

Thylakoid membranes contain photosystems I and II, electron transport chain components, and ATP synthase complexes for photophosphorylation.

Cellulose is a polymer of β-glucose units with β-1,4-glycosidic bonds; humans lack cellulase enzyme to digest it (dietary fiber).

tRNA has an anticodon that base-pairs with mRNA codon and carries the corresponding amino acid attached to its 3' end.

Fruit ripening is primarily controlled by ethylene. Auxin promotes cell elongation, apical dominance (inhibits lateral buds), phototropism, and adventitious root formation.

Leukocytes (white blood cells) include granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes) with various immune functions.

Telophase marks the end of nuclear division; cytokinesis (cytoplasmic division) typically follows to produce two daughter cells.

Insulin is produced by beta cells of pancreatic islets; liver responds to insulin by storing glucose as glycogen.

Anther contains four microsporangia where microsporocytes undergo meiosis to produce microspores that develop into pollen grains (male gametophytes).

Pyruvate dehydrogenase complex in mitochondrial matrix catalyzes: pyruvate + CoA + NAD⁺ → acetyl CoA + CO₂ + NADH + H⁺.

Metastasis involves cancer cells breaking away from primary tumor, entering blood/lymph vessels, and forming secondary tumors in other organs.

Phototropism: auxin accumulates on shaded side of shoot, causing greater cell elongation there and bending toward light (positive phototropism).

Krebs cycle enzymes are located in mitochondrial matrix; cycle oxidizes acetyl CoA to CO₂, producing NADH, FADH₂, and ATP (or GTP).

Meiosis I separates homologous chromosomes (reduction division); meiosis II separates sister chromatids, yielding four genetically distinct haploid gametes.

DNA serves as long-term genetic storage; RNA functions include mRNA (information carrier), tRNA (amino acid delivery), rRNA (catalytic and structural ribosome component), and regulatory RNAs.

Viruses are acellular particles with protein coat (capsid) surrounding nucleic acid core; some have lipid envelope. They replicate only inside host cells using host machinery.

Testosterone from Leydig cells of testes promotes growth of facial/body hair, deepening of voice, increased muscle mass, and sperm production.

Stomata (singular: stoma) are pores surrounded by two guard cells that regulate opening/closing; most abundant on lower leaf epidermis.

Vaccines contain antigens that stimulate the body's immune system to produce antibodies and memory cells without causing disease—active artificial immunity.

C4 plants have bundle sheath cells surrounding vascular bundles containing chloroplasts where Calvin cycle occurs; mesophyll cells fix CO₂ into C4 acids (e.g., oxaloacetate).

In prokaryotes, ribosomes can begin translating mRNA while it is still being transcribed because there is no nuclear envelope separating the processes.

ADH increases permeability of collecting ducts to water by inserting aquaporin channels into cell membranes, producing concentrated urine when dehydrated.

Growth hormone is secreted by anterior pituitary gland; skeletal system stores minerals, produces blood cells, provides leverage for movement, and protects organs.

Lysosomes contain hydrolytic enzymes (acid hydrolases) active at pH ~5; they digest phagocytosed material, worn-out organelles, and cellular debris.

Anaphase II resembles mitotic anaphase: centromeres divide and sister chromatids (now individual chromosomes) move to opposite poles.