Cell Structure & Function — Part 4: 40 MCQs with Explanations

Utricle (horizontal) and saccule (vertical) contain maculae with hair cells embedded in otolithic membrane that detect head position/gravity.

Thymus is primary lymphoid organ where T cells mature and undergo selection before migrating to secondary lymphoid tissues.

Microvilli (brush border) on intestinal epithelial cells increase absorptive surface area approximately 20-fold.

Anaphase: centromeres divide and sister chromatids (now daughter chromosomes) move toward opposite poles via spindle fibers.

Osmosis is the passive movement of water molecules from an area of lower solute concentration to an area of higher solute concentration across a semi-permeable membrane.

Mitochondria are the sites of aerobic respiration where ATP is generated through the Krebs cycle and oxidative phosphorylation.

In metaphase, chromosomes line up along the metaphase plate (equator) attached to spindle fibers from opposite poles.

Ribosomes (composed of rRNA and proteins) translate mRNA into polypeptide chains during protein synthesis.

O negative blood lacks A, B, and Rh antigens on red blood cells, minimizing transfusion reactions in recipients with different blood types.

Pepsin, secreted as pepsinogen by chief cells in the stomach, breaks down proteins into smaller peptides in acidic environment.

Human somatic (body) cells are diploid with 46 chromosomes (23 pairs: 22 autosomes + 1 sex chromosome pair). Gametes are haploid with 23 chromosomes.

Cell theory states that cell is the fundamental unit of structure and function in all living organisms.

Insulin facilitates glucose uptake by cells and glycogen synthesis in liver and muscles, decreasing blood glucose concentration.

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

Ribosomes (composed of rRNA and proteins) translate mRNA into polypeptide chains during protein synthesis.

Transcription produces mRNA complementary to DNA template strand in nucleus (eukaryotes) or cytoplasm (prokaryotes).

Down syndrome (trisomy 21) results from nondisjunction during meiosis, causing intellectual disability and characteristic physical features.

Hormone production is primarily endocrine system function. Skeletal system provides support, protection, movement (with muscles), mineral storage, and blood cell production.

Crossing over (exchange of genetic material between non-sister chromatids) occurs during pachytene substage of prophase I.

Active natural immunity develops when body produces antibodies and memory cells after natural infection.

Osmosis is passive movement of water from region of lower solute concentration to higher solute concentration across selectively permeable membrane.

Cellulose is a structural polysaccharide (polymer of glucose) in plant cell walls. Glucose is monosaccharide; sucrose and lactose are disaccharides.

Lymphatic system returns excess tissue fluid to bloodstream, transports absorbed fats via lacteals, and houses immune cells in lymph nodes.

Fruit ripening is primarily controlled by ethylene. Auxin promotes cell elongation, apical dominance, phototropism, and root formation.

Genetic variation arises from mutations (new alleles), crossing over (recombination during meiosis), and random fusion of gametes during fertilization.

During telophase, nuclear envelopes reassemble around separated chromosome sets, chromosomes decondense, and nucleoli reappear.

Insulin is produced by pancreatic beta cells; liver stores glycogen, produces bile, detoxifies substances, and synthesizes plasma proteins.

HIV is a retrovirus with single-stranded RNA genome that reverse transcribes into DNA upon infecting host cells.

Anther (part of stamen) contains microsporangia where meiosis produces microspores that develop into pollen grains (male gametophytes).

Pyruvate dehydrogenase complex in mitochondrial matrix converts pyruvate to acetyl CoA, producing NADH and CO₂ before Krebs cycle.

Cancer cells exhibit uncontrolled division, loss of contact inhibition, ability to invade other tissues (metastasis), and evasion of apoptosis.

Krebs cycle (citric acid cycle) occurs in mitochondrial matrix, producing NADH, FADH₂, ATP, and CO₂ from acetyl CoA.

Meiosis reduces chromosome number by half, producing four genetically distinct haploid gametes from one diploid parent cell.

DNA serves as long-term genetic storage; RNA functions include mRNA (genetic message), tRNA (amino acid delivery), rRNA (ribosome structure), and some RNAs have catalytic activity (ribozymes).

Stomata (pores surrounded by guard cells) are primary sites for transpiration and gas exchange; cuticle minimizes water loss.

Vaccination introduces antigens to stimulate body's own immune response, producing memory cells—active artificial immunity.

C4 plants (e.g., maize) have Kranz anatomy with bundle sheath cells containing chloroplasts where Calvin cycle occurs; mesophyll cells fix CO₂ into C4 acids.

Thyroid-stimulating hormone (TSH) from anterior pituitary stimulates thyroid follicular cells to synthesize and release T3 and T4.

Anaphase I: homologous chromosomes (each with two chromatids) separate and move to opposite poles; sister chromatids remain attached.

In prokaryotes, transcription and translation occur simultaneously in cytoplasm since no nuclear envelope separates them.

Percentage of water in brain cells is 85% .

In 1831, the presence of nucleus in the cells was reported by Robert Brown .

7 Secretions are products formed within cell on Golgi bodies .

Ribosomes are tiny Granules first studied in 1955 by Palade .

Mitosis is divided into Both a & b .

Ribosomes and DNA are also present in mitochondria .

Taking in liquid material into the cells is known as Pinocytosis .

Robert hooke is the correct answer to “Who discovered the living cell first time”. Items of this type are drawn from the Cell Structure & Function — Part 4 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

The arrangement of Organelles speaks of the division of labour within cell.

The heart is enclosed in a membrane called pericardium .

helper-T is the correct answer to “The major cell infected by the HIV is lymphocyte”. Items of this type are drawn from the Cell Structure & Function — Part 4 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Glucose is the correct answer to “Which is an organic compound found in most cells”. Items of this type are drawn from the Cell Structure & Function — Part 4 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

carbon, oxygen, hydrogen, nitrogen is the correct answer to “Which are the four most abundant elements in living cells”. Items of this type are drawn from the Cell Structure & Function — Part 4 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Concentration of water molecules inside and outside the cell is the correct answer to “Normally, in the process of osmosis, the net flow of water molecules into or out of the cell depends upon differences in the”. Items of this type are drawn from the Cell Structure & Function — Part 4 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Active transport is the correct answer to “Sodium ions are œpumped from a region of lower concentration to a region of higher concentration in the nerve cells of humans. This process is an example of”. Items of this type are drawn from the Cell Structure & Function — Part 4 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Protein and Lipids is the correct answer to “Most cell membranes are composed principally of”. Items of this type are drawn from the Cell Structure & Function — Part 4 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

A Tissue is the correct answer to “A structure formed by groups of similar cells organized into loose sheets or bundles performing similar functions is called as:”. Items of this type are drawn from the Cell Structure & Function — Part 4 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Dolly, the sheep was a highly successful clone from a somatic cell, reported back in 1996 .

Organelles are Sub-cellular structures .

Tissues is the correct answer to “A group of similar cells that perform a specific function is:”. Items of this type are drawn from the Cell Structure & Function — Part 4 syllabus of Pakistani competitive exams, where the fact is tested verbatim.