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Tamil Nadu HSE Second Year Botany study materials
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Tamil Nadu HSE Second Year Botany practice questions

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Question 1Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

In the Linnaean hierarchy used in Tamil Nadu HSE Botany, which taxonomic rank is placed immediately below Division (Phylum) and above Class?

  1. Order
  2. Family
  3. Subkingdom Correct answer.
  4. Genus

Explanation

The standard descending sequence is Kingdom, Subkingdom (Division/Phylum), Class, Order, Family, Genus and Species. Subkingdom therefore sits directly below Kingdom and above Division, not below Division. Class, Order and Family all come further down the hierarchy, after Division.

Question 2Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

Which set of characters is used to place a plant in Division Algae rather than in Bryophyta?

  1. Presence of chlorophyll b and starch as reserve food
  2. Absence of vascular tissue and presence of antheridia and archegonia
  3. Thalloid plant body without true roots, stems or leaves, and no multicellular jacket around sex organs Correct answer.
  4. Presence of a cellulose cell wall and a large central vacuole

Explanation

Algae are thallophytes: the plant body is thalloid with no true root, stem or leaf, and the sex organs are mostly unicellular or multicellular without a jacket of sterile cells. Bryophytes, though also non-vascular, have multicellular jacketed sex organs and a definite gametophyte with rhizoids. The other options describe features shared with many land plants or are too general to separate the divisions.

Question 3Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

The reserve food material in most brown algae (Phaeophyceae) is

  1. Laminarin and mannitol Correct answer.
  2. Glycogen
  3. Paramylon
  4. Floridean starch

Explanation

Brown algae store carbohydrate chiefly as laminarin, together with mannitol, and their cell walls contain cellulose and algin. Floridean starch belongs to red algae, paramylon to euglenoids, and glycogen is the typical storage product of fungi and animals.

Question 4Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

Which red alga is commercially exploited in India for the extraction of agar?

  1. Ulva
  2. Gracilaria Correct answer.
  3. Sargassum
  4. Chara

Explanation

Gracilaria is a red alga (Rhodophyceae) widely harvested in India as a source of agar, a phycocolloid used in culture media and food. Sargassum is a brown alga yielding algin, Ulva is a green alga, and Chara is a green alga used in laboratory studies of sex organs.

Question 5Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

In the life cycle of Chlamydomonas, the zygote is the only diploid structure and undergoes meiosis immediately. This type of life cycle is called

  1. Isomorphic alternation of generations
  2. Haplo-diplontic
  3. Haplontic Correct answer.
  4. Diplontic

Explanation

In a haplontic cycle the dominant plant is the haploid gametophyte and the zygote is the sole diploid stage, undergoing meiosis at germination. Diplontic cycles have a diploid plant with gametic meiosis, while haplo-diplontic cycles have two multicellular generations. Isomorphic alternation is a form of haplo-diplontic cycle with similar generations.

Question 6Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

Volvox is described as a colonial green alga because

  1. It is a single large cell with many nuclei
  2. It forms a hollow sphere of cells with a few reproductive cells and cytoplasmic strands Correct answer.
  3. Its cells are joined end to end in an unbranched filament
  4. It forms a flat sheet of cells held in a gelatinous matrix

Explanation

Volvox colonies are hollow spheres (coenobia) in which numerous biflagellate cells are connected by cytoplasmic strands, and only a few cells are set apart for reproduction. Filamentous forms such as Spirogyra and sheet-like forms such as Ulva do not match this description. A multinucleate single cell would describe forms like Vaucheria, not Volvox.

Question 7Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

The chief reserve food of fungi and the main component of their cell wall are, respectively,

  1. Oil and cellulose
  2. Glycogen and chitin Correct answer.
  3. Mannitol and chitin
  4. Starch and cellulose

Explanation

Fungal cells store food mainly as glycogen and their walls are built largely of chitin, with cellulose in some forms such as oomycetes. Starch and cellulose are typical of green plants, while mannitol is a storage alcohol found in brown algae. This combination of glycogen plus chitin is the standard fungal character used in classification.

Question 8Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

A fungus in which the hyphae lack cross walls and contain many nuclei is best described as

  1. Aseptate and coenocytic Correct answer.
  2. Septate and dikaryotic
  3. Pseudoparenchymatous
  4. Septate and monokaryotic

Explanation

Hyphae without cross walls are aseptate, and their multinucleate cytoplasm is termed coenocytic; this condition is typical of Mucor and Rhizopus. Septate hyphae have cross walls, and dikaryotic refers to paired nuclei per cell after plasmogamy. Pseudoparenchyma is a tissue-like mass of hyphae and says nothing about septation.

Question 9Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

In Puccinia graminis, the stage that produces basidiospores and the host on which it occurs are

  1. Basidial stage on Berberis
  2. Teleutospore stage on wheat
  3. Uredial stage on wheat
  4. Aecial stage on Berberis Correct answer.

Explanation

Puccinia is heteroecious: the diploid teleutospores on wheat germinate to form basidia, and the resulting basidiospores infect the alternate host Berberis, where pycnidia and aecia develop. The aecial stage therefore occurs on Berberis and gives rise to aeciospores that return to wheat. Uredia and telia both occur on wheat.

Question 10Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

The fruiting body of Agaricus is best described as

  1. A basidiocarp with gills bearing basidia Correct answer.
  2. An ascocarp bearing asci in a hymenium
  3. A perithecium with a pore
  4. A cleistothecium enclosing asci

Explanation

Agaricus is a basidiomycete whose fleshy fruiting body is a basidiocarp; the gills on its underside carry the hymenium of club-shaped basidia. Ascocarps, cleistothecia and perithecia are all ascomycete fruiting structures. The presence of basidia rather than asci is the decisive character here.

Question 11Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

Which statement correctly distinguishes the mycelium of Rhizopus from that of Penicillium?

  1. Both have septate hyphae but differ in mode of nutrition
  2. Both have aseptate hyphae but differ in reserve food
  3. Rhizopus has aseptate coenocytic hyphae, while Penicillium has septate hyphae Correct answer.
  4. Rhizopus has septate hyphae, while Penicillium has aseptate hyphae

Explanation

Rhizopus belongs to the Mucorales and has broad, aseptate, coenocytic hyphae, whereas Penicillium has narrow septate hyphae with perforated cross walls. Both are saprotrophic, so nutrition does not separate them. Septation of hyphae is thus the reliable distinction between these two genera.

Question 12Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

Yeast is placed among the Ascomycetes mainly because it

  1. Reproduces only by fragmentation of hyphae
  2. Produces basidiospores on a club-shaped basidium
  3. Bears motile zoospores in a sporangium
  4. Forms asci with ascospores after karyogamy Correct answer.

Explanation

Saccharomyces is a unicellular ascomycete that reproduces asexually by budding and sexually by forming asci containing ascospores after fusion of nuclei. Basidia are characteristic of Basidiomycetes, and zoospores occur in oomycetes and lower fungi. Fragmentation of hyphae is not the basis for its classification.

Question 13Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

The plant body of a liverwort such as Marchantia is

  1. A protonema bearing leafy gametophores
  2. A protocorm bearing rhizoids and leaves
  3. A thallus that is dorsiventral and dichotomously branched, with rhizoids and scales on the ventral side Correct answer.
  4. A leafy stem with spirally arranged leaves and a distinct midrib

Explanation

Marchantia has a dorsiventral, dichotomously branched thallus with air pores on the dorsal surface and rhizoids plus scales on the ventral side. Spirally arranged leaves with a midrib describe mosses, and a protonema with leafy gametophores is the moss gametophyte. A protocorm is the juvenile stage of lycopods such as Selaginella.

Question 14Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

Why are bryophytes described as amphibians of the plant kingdom?

  1. They live only in fresh water throughout life
  2. They need a film of water for the transfer of motile sperms to the archegonium Correct answer.
  3. They absorb water only through submerged roots
  4. They need water for the dehiscence of the capsule

Explanation

Bryophytes are terrestrial but depend on a film of water for the biflagellate sperms to swim to the archegonium and effect fertilisation. They have no true roots, and they are not permanently aquatic. Capsule dehiscence depends on drying, not on water. Hence the amphibious habit refers specifically to the water requirement for sexual reproduction.

Question 15Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

In the moss life cycle, the structure that is haploid and produces gametes is the

  1. Sporophyte bearing a capsule
  2. Leafy gametophore with antheridia and archegonia Correct answer.
  3. Seta and apophysis
  4. Protonema only

Explanation

The leafy green moss plant is the gametophyte and bears the sex organs, so it is haploid and produces gametes. The sporophyte, consisting of foot, seta and capsule, is diploid and produces spores by meiosis. The protonema is a juvenile gametophyte but is not the structure bearing gametes in the mature plant.

Question 16Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

Which feature of Sphagnum makes it economically important as peat?

  1. It fixes atmospheric nitrogen in its leaf cells
  2. It produces abundant spores used as a food supplement
  3. It has large dead hyaline cells that hold water and accumulate as peat Correct answer.
  4. It yields a red dye used in textile industries

Explanation

Sphagnum, the peat moss, has leaves with a network of living chlorophyllose cells and large dead hyaline cells that absorb and retain water. Slow decay of its remains in bogs produces peat, used as fuel and as packing material. Dye-yielding and nitrogen-fixing properties are not attributed to it in this context.

Question 17Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

In pteridophytes, the gametophyte is best described as

  1. An independent, photosynthetic prothallus bearing antheridia and archegonia Correct answer.
  2. A large leafy plant bearing sori on the underside
  3. A dependent structure retained within the sporangium
  4. A protonema that gives rise to leafy shoots

Explanation

The pteridophyte gametophyte is a small, free-living, photosynthetic prothallus that bears antheridia and archegonia on its lower surface. It is independent of the sporophyte, unlike the gametophytes of gymnosperms and angiosperms. The large leafy plant with sori is the sporophyte, and a protonema is a moss structure.

Question 18Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

In Selaginella, the structure that produces microspores and the structure that produces megaspores are, respectively,

  1. Microsporangium and megasporangium Correct answer.
  2. Antheridium and archegonium
  3. Microphyll and sporophyll
  4. Megasporangium and microsporangium

Explanation

Selaginella is heterosporous: microsporangia produce numerous microspores that develop into male gametophytes, while megasporangia produce few large megaspores that develop into female gametophytes. Antheridia and archegonia are gametophyte sex organs, and microphylls and sporophylls are leaves. The pairing of microsporangium with microspores is therefore the correct one.

Question 19Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

The stelar organisation in which a central pith is surrounded by a ring of separate vascular bundles is called

  1. Solenostele
  2. Protostele
  3. Siphonostele Correct answer.
  4. Dictyostele

Explanation

A siphonostele has a central pith enclosed by a cylinder of vascular tissue, and when that cylinder is broken into separate bundles it is described as a dissected siphonostele. A protostele is a solid core without pith, while a dictyostele is broken into overlapping leaf gaps. Solenostele is a siphonostele with scattered leaf gaps, not simply a ring of bundles.

Question 20Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

The sporophyte of Equisetum is easily recognised by

  1. A dorsiventral thallus with gemma cups
  2. Jointod stems with whorls of scaly leaves and a terminal strobilus Correct answer.
  3. A rhizome with circinate vernation and sori
  4. A short unbranched stem with a single apical sporangium

Explanation

Equisetum has jointed, ridged, hollow stems with whorls of small scale-like leaves at the nodes, and reproductive shoots end in a cone-like strobilus of sporangiophores. Gemma cups belong to Marchantia, a single apical sporangium to Psilotum-like forms, and circinate vernation with sori to ferns. These vegetative and reproductive features together identify Equisetum.

Question 21Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

In a fern such as Nephrolepis, the sorus is protected by an indusium and contains

  1. A single megasporangium producing one megaspore
  2. Many sporangia, each producing haploid spores by meiosis Correct answer.
  3. Many basidia, each producing four basidiospores
  4. Many antheridia, each producing biflagellate sperms

Explanation

A fern sorus is a cluster of leptosporangiate sporangia on the underside of the sporophyll, and each sporangium undergoes meiosis to form haploid spores. Antheridia belong to the prothallus, and megasporangia occur in heterosporous plants. Basidia are fungal structures and have no place in fern reproduction.

Question 22Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

The chief characteristics that separate gymnosperms from pteridophytes are

  1. Naked ovules borne on megasporophylls and seeds formed after fertilisation Correct answer.
  2. Dependence of the sporophyte on the gametophyte
  3. Presence of archegonia and multicellular sex organs
  4. Presence of chlorophyll and cellulose walls

Explanation

Gymnosperms bear ovules exposed on megasporophylls, and after fertilisation these develop into seeds, a feature absent in pteridophytes. Both groups share chlorophyll, cellulose walls and archegonia, so those characters cannot separate them. In gymnosperms the gametophyte is dependent on the sporophyte, which is the reverse of the option given.

Question 23Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

Cycas is described as dioecious because

  1. Male cones and megasporophylls bearing ovules are borne on separate plants Correct answer.
  2. It bears only male cones and reproduces apomictically
  3. Male and female cones are borne on the same plant
  4. It bears bisexual cones with both microsporophylls and megasporophylls

Explanation

In Cycas the male plant bears compact cones of microsporophylls, while the female plant bears a loose crown of megasporophylls with naked ovules, so the sexes are on separate plants. Bisexual cones and single-sex reproduction do not describe Cycas. The term dioecious therefore refers to the separation of male and female reproductive structures on different individuals.

Question 24Taxonomy and Plant Diversity (Algae, Fungi, Bryophytes, Pteridophytes, Gymnosperms)

Which combination correctly matches a gymnosperm with a distinctive feature of its reproductive structure?

  1. Gnetum: ovules are enclosed in an integument and the plant bears broad leaves
  2. Pinus: ovules borne directly on the upper surface of a megasporophyll without a cone
  3. Pinus: male and female cones are borne on the same tree Correct answer.
  4. Cycas: seeds are enclosed within a fleshy fruit

Explanation

Pinus is monoecious, bearing small male cones and larger female cones on the same tree, and its ovules sit on ovuliferous scales within the female cone. Cycas does not form fruits, and its ovules are borne on megasporophylls. Gnetum has broad leaves but its ovules are not enclosed in an ovary. The Pinus statement is the only accurate pairing.

Question 25Plant Kingdom Classification and Nomenclature

In the Linnaean hierarchy used for Tamil Nadu Higher Secondary Botany, which taxonomic rank is placed immediately above Class and immediately below Kingdom?

  1. Genus
  2. Division (Phylum) Correct answer.
  3. Order
  4. Family

Explanation

The standard sequence of ranks from the top is Kingdom, Division (Phylum), Class, Order, Family, Genus and Species. Division therefore sits directly between Kingdom and Class in this descending arrangement, and in botany the term division is preferred over phylum.

Question 26Plant Kingdom Classification and Nomenclature

Carolus Linnaeus introduced a system in which every species is designated by two Latinised words. What is this naming system called, and what is the second word known as?

  1. Autonymy; the basionym
  2. Polynomial nomenclature; the descriptor
  3. Trinomial nomenclature; the variety epithet
  4. Binomial nomenclature; the specific epithet Correct answer.

Explanation

Linnaeus proposed binomial nomenclature, where the first word is the genus name and the second is the specific epithet. Together they form the scientific name of a species, such as Mangifera indica, with the genus capitalised and the epithet in lower case.

Question 27Plant Kingdom Classification and Nomenclature

A student writes the name of the mango as 'Mangifera Indica'. Which statement describes the error in this written form?

  1. The specific epithet must begin with a small letter while the genus is capitalised Correct answer.
  2. Both words should be underlined twice instead of italicised
  3. The name should contain three words to be valid
  4. The genus name should be in lower case and the epithet capitalised

Explanation

Under the rules of binomial nomenclature the generic name is written with an initial capital letter and the specific epithet entirely in lower case. The correct form is Mangifera indica, usually printed in italics or underlined when handwritten.

Question 28Plant Kingdom Classification and Nomenclature

The type specimen that serves as the permanent reference for a species name is known as which of the following?

  1. Neotype
  2. Isotype
  3. Paratype
  4. Holotype Correct answer.

Explanation

A holotype is the single specimen designated by the author as the nomenclatural type of a new species. Other specimens such as paratypes and isotypes are auxiliary material, while a neotype is chosen later when the original type is lost.

Question 29Plant Kingdom Classification and Nomenclature

Which of the following groups is classified as a division under the algae in the plant kingdom?

  1. Phaeophyceae
  2. Bacillariophyceae
  3. Chlorophyceae
  4. Rhodophyta Correct answer.

Explanation

Rhodophyta is the division name for red algae, so it stands at the rank of division. Chlorophyceae, Phaeophyceae and Bacillariophyceae are class-level names for green, brown and diatom algae respectively.

Question 30Plant Kingdom Classification and Nomenclature

In the Bentham and Hooker system of classification, which group is placed last in the sequence of flowering plants?

  1. Monocotyledons Correct answer.
  2. Pteridophytes
  3. Dicotyledons
  4. Gymnosperms

Explanation

Bentham and Hooker arranged the seed plants with dicotyledons first and monocotyledons at the end of the sequence. Gymnosperms were placed before the angiosperms, and pteridophytes belong to a separate group outside seed plants.

Question 31Plant Kingdom Classification and Nomenclature

Which of the following pairs correctly matches a taxonomic category with an example from the plant kingdom?

  1. Species - Solanaceae
  2. Family - Solanaceae Correct answer.
  3. Family - Solanum
  4. Order - Fabaceae

Explanation

Solanaceae is a family name, recognised by its characteristic -aceae ending, and it contains genera such as Solanum. Genus names do not end in -aceae, and species names are binomials rather than family names.

Question 32Plant Kingdom Classification and Nomenclature

Which suffix is conventionally used for the name of a plant family under the International Code of Nomenclature?

  1. -eae
  2. -ales
  3. -aceae Correct answer.
  4. -phyta

Explanation

Family names in botany end in -aceae, for example Poaceae, Fabaceae and Solanaceae. The ending -ales denotes an order, -phyta denotes a division, and -eae is used for a tribe.

Question 33Plant Kingdom Classification and Nomenclature

A plant is described as having a thallus without true roots, stems or leaves, and it is placed in division Thallophyta. Which statement best justifies this placement?

  1. Its body is undifferentiated into true vegetative organs Correct answer.
  2. It possesses vascular tissue but no seeds
  3. It lacks chlorophyll and is therefore a fungus
  4. It bears flowers but no fruit

Explanation

Thallophytes are characterised by a thalloid body that is not differentiated into true root, stem and leaf. This simple organisation is the key feature used to place algae and similar forms in the division Thallophyta.

Question 34Plant Kingdom Classification and Nomenclature

Which of the following features is used to distinguish bryophytes from pteridophytes in the plant kingdom?

  1. Presence of cellulose cell walls
  2. Presence of a multicellular embryo
  3. Presence of a vascular system Correct answer.
  4. Presence of chlorophyll a

Explanation

Pteridophytes possess vascular tissue (xylem and phloem), whereas bryophytes lack a true vascular system. Both groups are embryophytes with chlorophyll a and cellulose walls, so vascular tissue is the distinguishing feature.

Question 35Plant Kingdom Classification and Nomenclature

In the classification of the plant kingdom, which group is described as having naked seeds borne on the surface of megasporophylls?

  1. Gymnosperms Correct answer.
  2. Pteridophytes
  3. Bryophytes
  4. Angiosperms

Explanation

Gymnosperms are seed plants in which the ovules and seeds are not enclosed within an ovary, so they lie exposed on the megasporophylls. Angiosperms enclose their seeds in a fruit, while bryophytes and pteridophytes do not produce seeds.

Question 36Plant Kingdom Classification and Nomenclature

Two specimens are compared: one has a dominant gametophyte and requires water for fertilisation; the other has a dominant sporophyte with a vascular system. Which pair of divisions do they most likely represent?

  1. Bryophyta and Pteridophyta Correct answer.
  2. Gymnospermae and Angiospermae
  3. Pteridophyta and Bryophyta
  4. Thallophyta and Bryophyta

Explanation

Bryophytes have a dominant gametophyte and depend on water for sperm to reach the egg. Pteridophytes have a dominant sporophyte with vascular tissue, though they still need water for fertilisation, which fits the second description best among the options.

Question 37Plant Kingdom Classification and Nomenclature

Which of the following statements about the International Code of Nomenclature for algae, fungi and plants is correct?

  1. A species may carry two accepted scientific names at the same time
  2. A name is valid only after publication in a recognised journal with a Latin description
  3. Common names take precedence over scientific names in formal publication
  4. Names are applied by priority, the earliest validly published name having precedence Correct answer.

Explanation

The principle of priority states that the earliest validly published name for a taxon is the correct one, subject to conservation provisions. This rule keeps nomenclature stable and prevents competing names being used for the same species.

Question 38Plant Kingdom Classification and Nomenclature

A herbarium sheet labels a specimen as 'Solanum nigrum L.' According to the rules of binomial nomenclature, what does the 'L.' after the species epithet indicate?

  1. The family to which the species belongs, Linnaeaceae
  2. The author who first described the species, Carolus Linnaeus Correct answer.
  3. The location where the specimen was collected, London
  4. The variety of the species, 'large'

Explanation

In binomial nomenclature, the abbreviated name after the species epithet is the author citation, indicating the person who validly published the name. 'L.' is the standard abbreviation for Carolus Linnaeus. This is not a taxonomic rank or collection detail.

Question 39Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

In a eukaryotic cell, which structure is bounded by a double membrane and contains its own circular DNA and 70S ribosomes?

  1. Lysosome
  2. Peroxisome
  3. Golgi apparatus
  4. Mitochondrion Correct answer.

Explanation

Mitochondria are semi-autonomous organelles enclosed by two membranes; the inner membrane is folded into cristae, and the matrix holds circular DNA plus 70S ribosomes, so they synthesise some of their own proteins. This endosymbiotic feature distinguishes them from single-membrane organelles such as lysosomes, peroxisomes and Golgi cisternae.

Question 40Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

The fluid mosaic model describes the plasma membrane as a bilayer in which protein molecules are

  1. replaced by cellulose microfibrils in the hydrophobic core
  2. embedded at various depths or attached to the surfaces of the lipid bilayer Correct answer.
  3. confined strictly to the inner cytoplasmic face of the bilayer
  4. arranged in a continuous layer on the outer surface only

Explanation

According to the fluid mosaic model, the lipid bilayer behaves like a fluid in which proteins float as a mosaic, some spanning the bilayer, some partly embedded and others lying on either surface. The lipids and proteins are not fixed in place, which gives the membrane its dynamic character.

Question 41Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

Which organelle carries out the final glycosylation, sorting and packaging of proteins before they are dispatched to their destinations?

  1. Golgi apparatus Correct answer.
  2. Nucleolus
  3. Smooth endoplasmic reticulum
  4. Rough endoplasmic reticulum

Explanation

The Golgi apparatus receives transport vesicles from the endoplasmic reticulum, modifies the cargo by glycosylation, sorts it and buds off vesicles addressed to the plasma membrane, lysosomes or secretion. The endoplasmic reticulum mainly performs early folding and initial glycosylation rather than final sorting.

Question 42Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

During which phase of mitosis do sister chromatids separate and move towards opposite poles of the cell?

  1. Prophase
  2. Metaphase
  3. Telophase
  4. Anaphase Correct answer.

Explanation

In anaphase the centromeres split, and the spindle fibres shorten to pull the sister chromatids, now individual chromosomes, towards opposite poles. This poleward movement is the defining event of anaphase and precedes the reformation of nuclei in telophase.

Question 43Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

Which of the following is present in a plant cell but absent in an animal cell?

  1. Rough endoplasmic reticulum
  2. Nuclear envelope
  3. Ribosome
  4. Cellulose cell wall Correct answer.

Explanation

A rigid cellulose cell wall lying outside the plasma membrane is a characteristic feature of plant cells and is not formed by animal cells. Ribosomes, nuclear envelopes and rough endoplasmic reticulum are common to both cell types.

Question 44Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

A cell in G1 phase contains 2C DNA content. What is the DNA content of the same cell after it completes the S phase?

  1. 2C
  2. 8C
  3. 4C Correct answer.
  4. 1C

Explanation

S phase is the synthetic phase in which each chromosome is replicated, so the DNA content doubles from 2C to 4C while the chromosome number stays the same. The cell then enters G2 with 4C DNA until mitosis distributes it to daughter cells.

Question 45Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

Which statement correctly distinguishes rough endoplasmic reticulum from smooth endoplasmic reticulum?

  1. Rough ER bears ribosomes and participates in protein synthesis, whereas smooth ER lacks ribosomes and is involved in lipid synthesis Correct answer.
  2. Rough ER occurs only in prokaryotes, whereas smooth ER occurs only in eukaryotes
  3. Rough ER is a double-membrane organelle, whereas smooth ER is single-membraned
  4. Rough ER lacks ribosomes and stores calcium, whereas smooth ER bears ribosomes and synthesises proteins

Explanation

Rough ER is studded with ribosomes and is the site of synthesis and folding of secretory and membrane proteins. Smooth ER is ribosome-free and functions in lipid and steroid synthesis, detoxification and calcium storage.

Question 46Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

A cell is treated with a drug that prevents the assembly of spindle microtubules. Which event of mitosis would be blocked most directly?

  1. Reformation of the nuclear envelope
  2. Condensation of chromatin into chromosomes
  3. Movement of chromatids to the poles Correct answer.
  4. Replication of DNA before mitosis

Explanation

The spindle is built from microtubules, and its fibres attach to kinetochores and pull chromatids to opposite poles during anaphase. Blocking microtubule assembly therefore prevents chromosome alignment and poleward movement, even though chromosome condensation and nuclear envelope changes proceed independently.

Question 47Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

In which part of the chloroplast does the Calvin cycle, including the fixation of carbon dioxide, take place?

  1. Intermembrane space
  2. Stroma Correct answer.
  3. Outer chloroplast membrane
  4. Thylakoid membrane

Explanation

The stroma is the enzyme-rich ground substance of the chloroplast in which the Calvin cycle enzymes, including RuBisCO, fix carbon dioxide into carbohydrate. The thylakoid membranes, by contrast, carry the light-dependent reactions.

Question 48Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

A root tip meristem cell has 14 chromosomes. How many chromosomes and chromatids respectively will each daughter cell receive at the end of mitosis?

  1. 28 chromosomes and 28 chromatids
  2. 7 chromosomes and 7 chromatids
  3. 14 chromosomes and 14 chromatids Correct answer.
  4. 14 chromosomes and 28 chromatids

Explanation

Mitosis is equational, so each daughter cell receives the same chromosome number as the parent, that is 14. After anaphase separates the sister chromatids, each daughter receives 14 single-chromatid chromosomes, so the chromatid count also equals 14.

Question 49Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

Which organelle is described as the cell's principal site of hydrolytic degradation of worn-out organelles and ingested material?

  1. Lysosome Correct answer.
  2. Ribosome
  3. Centriole
  4. Peroxisome

Explanation

Lysosomes are single-membrane vesicles rich in acid hydrolases that digest ingested particles and damaged organelles during autophagy. Their acidic interior is maintained by proton pumps, and the released monomers are recycled by the cell.

Question 50Cell Biology: Cell Structure, Organelles, Cell Cycle and Division

During which stage of meiosis does crossing over between non-sister chromatids of homologous chromosomes occur?

  1. Leptotene of prophase I
  2. Metaphase I
  3. Pachytene of prophase I Correct answer.
  4. Anaphase II

Explanation

Crossing over takes place at the pachytene stage of prophase I, when homologous chromosomes are paired as bivalents and non-sister chromatids exchange segments at chiasmata. The earlier zygotene stage establishes pairing, and the later diplotene stage reveals the chiasmata already formed.