KCET Biology - Botany Syllabus

Compare the structure of a plant cell wall: primary vs secondary wall and the middle lamella.

Middle lamella: calcium pectate, cements adjacent cells. Primary wall: thin, capable of growth, formed first. Secondary wall: thick, formed inward after growth stops (more cellulose/lignin).

Describe the structure of a chloroplast: stroma, grana, and thylakoids.

Double-membraned organelle; stroma is the matrix containing enzymes, DNA, 70S ribosomes (site of dark reactions); grana are stacks of thylakoids (membranous sacs holding chlorophyll, site of light reactions).

What is the function of the nucleolus and what does it lack?

Nucleolus is the site of rRNA synthesis and ribosome subunit assembly; it is not membrane-bound (no membrane around it).

Differentiate rough and smooth endoplasmic reticulum by structure and function.

RER: bears ribosomes, synthesises and processes proteins. SER: lacks ribosomes, synthesises lipids/steroids and is involved in detoxification.

Name the four major classes of biomolecules and their basic building blocks.

Carbohydrates (monosaccharides), proteins (amino acids), lipids (fatty acids + glycerol), and nucleic acids (nucleotides).

What bond links amino acids in a protein and monosaccharides in a polysaccharide?

Amino acids: peptide bond (between –COOH and –NH2). Monosaccharides: glycosidic bond.

Describe the four levels of protein structure.

Primary: linear amino acid sequence. Secondary: local folding (alpha-helix, beta-pleated sheet). Tertiary: 3D folding of whole chain. Quaternary: assembly of two or more polypeptide subunits.

Define enzyme, and explain competitive inhibition with the example of malonate.

Enzyme: a biocatalyst (usually protein) lowering activation energy. Competitive inhibition: an inhibitor structurally similar to the substrate binds the active site, e.g., malonate competes with succinate for succinate dehydrogenase.

What are the four phases of interphase and which are the major checkpoints?

G1, S (DNA synthesis), G2, plus quiescent G0. Major checkpoints: G1/S (restriction point) and G2/M; also the spindle assembly (M) checkpoint.

Name the four stages of mitosis (M phase) in order and the key event of each.

Prophase (chromosomes condense, spindle forms), metaphase (chromosomes align at metaphase plate), anaphase (sister chromatids separate to poles), telophase (nuclear envelopes reform, chromosomes decondense).

What is the key difference between mitosis and meiosis in terms of products?

Mitosis: one division → two genetically identical diploid cells. Meiosis: two divisions → four genetically distinct haploid cells, providing variation and halving chromosome number.

What occurs during pachytene of prophase I, and what is the crossover structure called?

Crossing over (recombination) occurs between non-sister chromatids of homologous chromosomes; the structure where exchange occurs is the chiasma (recombination nodule mediates it).

Define water potential and state the water potential of pure water.

Water potential (Ψw) is the potential energy of water; water moves from higher to lower Ψw. Pure water at standard conditions has Ψw = 0; it equals solute potential (Ψs) + pressure potential (Ψp).

Differentiate apoplast and symplast pathways of water movement.

Apoplast: water moves through cell walls and intercellular spaces (no membranes crossed). Symplast: water moves through cytoplasm and plasmodesmata (membrane crossed at entry).

What is the root pressure and transpiration pull theory of ascent of sap?

Root pressure: positive pressure pushing water up (minor, seen as guttation). Transpiration pull (cohesion-tension theory): transpiration creates tension pulling a continuous water column up xylem via cohesion and adhesion (major mechanism).

What is the Pressure Flow (Münch) hypothesis of phloem translocation?

Sugars loaded at source raise solute concentration, drawing in water (high pressure); pressure pushes sap to the sink where sugars are unloaded and water exits, completing the gradient-driven flow.

Distinguish macronutrients and micronutrients in plants with examples.

Macronutrients (needed in large amounts >10 mmol/kg): C, H, O, N, P, K, Ca, Mg, S. Micronutrients (trace): Fe, Mn, Zn, Cu, B, Mo, Cl, Ni.

What are the criteria for an element to be considered essential for plants?

(1) Absolutely necessary for normal growth and reproduction; (2) requirement is specific and not replaceable by another element; (3) directly involved in plant metabolism.

Name the symbiotic and free-living nitrogen-fixing organisms and the key enzyme.

Symbiotic: Rhizobium (legume roots), Frankia. Free-living: Azotobacter, Clostridium, Anabaena, Nostoc. Enzyme: nitrogenase (requires anaerobic conditions; leghaemoglobin protects it in nodules).

Write the overall balanced equation for photosynthesis.

6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O (in light, with chlorophyll). Simplified: 6CO2 + 6H2O → C6H12O6 + 6O2.

What are the products of the light reaction that are used in the dark reaction?

ATP and NADPH (assimilatory power), produced via the light reactions, are used in the Calvin cycle to fix CO2; O2 is released as a by-product of water splitting.

Name the primary CO2 acceptor and first stable product in C3 and C4 plants.

C3: acceptor RuBP, first product 3-PGA (3-carbon). C4: acceptor PEP (in mesophyll), first product oxaloacetic acid/OAA (4-carbon).

What is photorespiration and why does it not occur in C4 plants?

Photorespiration: RuBisCO fixes O2 instead of CO2 (oxygenation of RuBP), wasting energy with no sugar/ATP gain. C4 plants concentrate CO2 in bundle sheath cells (Kranz anatomy), so RuBisCO sees high CO2 and avoids it.

State the net ATP yield from glycolysis, and where it occurs.

Glycolysis occurs in the cytoplasm; net gain is 2 ATP (and 2 NADH) per glucose, producing 2 pyruvate molecules.

How many ATP are generated by aerobic respiration of one glucose molecule (theoretical)?

Approximately 36–38 ATP (commonly given as 38) from complete aerobic oxidation: glycolysis + link reaction + Krebs cycle + oxidative phosphorylation.

Define respiratory quotient (RQ) and give its value for carbohydrates, fats and proteins.

RQ = volume of CO2 released / volume of O2 consumed. Carbohydrates = 1; fats < 1 (~0.7); proteins ~0.9; organic acids > 1.

Name the plant growth promoters and inhibitors among the five major PGRs.

Promoters: auxins, gibberellins, cytokinins. Inhibitors (stress hormones): abscisic acid (ABA) and ethylene (ethylene has dual roles but inhibits growth/promotes senescence).

Which hormone causes apical dominance, and which promotes cell division and delays senescence?

Auxin causes apical dominance (suppresses lateral buds). Cytokinin promotes cell division and delays leaf senescence (Richmond-Lang effect).

What is photoperiodism and name the three categories of plants based on it?

Photoperiodism is the response of flowering to relative day/night length. Categories: short-day plants, long-day plants, and day-neutral plants. The hormone-like signal involves florigen, perceived by leaves via phytochrome.

Define apomixis and polyembryony.

Apomixis: production of seeds without fertilisation (asexual reproduction mimicking sexual seed formation). Polyembryony: occurrence of more than one embryo in a single seed (e.g., Citrus).

Describe the structure of a typical anatropous ovule.

Inverted ovule attached by funicle; has nucellus enclosed by integuments leaving a micropyle, the embryo sac (female gametophyte) inside, hilum where funicle joins, and chalaza at the base; micropyle lies near the funicle.

What is the 7-celled, 8-nucleate structure of the mature embryo sac (Polygonum type)?

3 cells at micropylar end (egg + 2 synergids = egg apparatus), 3 antipodal cells at chalazal end, and 1 large central cell with 2 polar nuclei — total 8 nuclei in 7 cells.

State Mendel's Law of Segregation and Law of Independent Assortment.

Law of Segregation: the two alleles of a gene separate during gamete formation, each gamete getting one. Law of Independent Assortment: alleles of different genes assort independently of one another during gamete formation.

What is the phenotypic ratio of a Mendelian dihybrid cross F2 generation?

9:3:3:1 (e.g., round yellow : round green : wrinkled yellow : wrinkled green).

Define incomplete dominance and codominance with one example each.

Incomplete dominance: heterozygote shows an intermediate phenotype (e.g., pink flowers in Snapdragon/Mirabilis, Rr). Codominance: both alleles fully expressed in heterozygote (e.g., AB blood group, IA IB).

What experiment established DNA as the genetic material, and who performed the bacteriophage version?

Hershey and Chase (1952) used radioactively labelled bacteriophages (32P for DNA, 35S for protein) to show DNA, not protein, enters the bacterium and directs reproduction. Earlier, Avery, MacLeod and McCarty refined Griffith's transformation experiment.

State the Chargaff's rule and the base-pairing in DNA.

Chargaff's rule: in DNA, A = T and G = C (purines = pyrimidines). Pairing: adenine with thymine (2 H-bonds), guanine with cytosine (3 H-bonds).

Define the central dogma of molecular biology.

Genetic information flows DNA → RNA → protein (replication, transcription, translation). Reverse transcription (RNA → DNA) is an exception in retroviruses.

What are the three features of the genetic code (degeneracy, etc.)?

The code is triplet, nearly universal, non-overlapping, comma-less, degenerate (most amino acids coded by more than one codon), and has start (AUG) and stop (UAA, UAG, UGA) codons; it is read in a fixed reading frame.

What is the role of the lac operon's repressor and inducer?

In the lac operon, the i-gene makes a repressor protein that binds the operator and blocks transcription; lactose (allolactose, the inducer) binds the repressor, inactivating it, so RNA polymerase transcribes z, y, a genes (negative regulation).

Differentiate inbreeding and outbreeding in animal/plant improvement.

Inbreeding: mating of closely related individuals — increases homozygosity, fixes desirable traits but may cause inbreeding depression. Outbreeding: mating of unrelated individuals — increases vigour (heterosis) and variability.

What is single cell protein (SCP) and give an example organism?

SCP is protein-rich biomass obtained from microbes used as an alternative protein source (food/feed), e.g., Spirulina, Methylophilus methylotrophus, mushrooms (mycoprotein).

Define biofortification and give one example crop.

Biofortification: breeding crops with higher levels of vitamins, minerals, proteins or healthier fats to improve public nutrition, e.g., iron-rich rice, Vitamin A-enriched carrots/spinach, protein-rich maize.

What is the difference between somatic hybridisation and micropropagation?

Somatic hybridisation: fusion of protoplasts from two different plants to form a hybrid (somatic hybrid, e.g., pomato). Micropropagation: producing many plantlets through tissue culture, giving genetically identical somaclones.

Define ecological niche and habitat.

Habitat: the physical place/environment where an organism lives. Niche: the functional role and total set of conditions/resources an organism uses (its 'profession') in the ecosystem.

Write the logistic (Verhulst-Pearl) population growth equation and name 'K'.

dN/dt = rN[(K − N)/K], where r = intrinsic rate of increase, N = population size, K = carrying capacity (maximum population the environment can sustain); gives a sigmoid (S-shaped) curve.

Differentiate mutualism, commensalism and amensalism in population interactions.

Mutualism: both species benefit (+/+). Commensalism: one benefits, other unaffected (+/0). Amensalism: one is harmed, other unaffected (−/0).

Name the trophic levels in a grazing food chain and the energy transfer law involved.

Producers (T1) → primary consumers/herbivores (T2) → secondary consumers (T3) → tertiary consumers (T4). Energy transfer follows the 10 percent law (Lindeman): only ~10% passes to the next trophic level.

Define ecological pyramids and state which pyramid is always upright.

Graphical representation of trophic structure (number, biomass, or energy). The pyramid of energy is always upright (energy decreases at each level); pyramids of number and biomass can be inverted.

Distinguish primary and secondary ecological succession.

Primary succession: begins on bare, lifeless areas with no prior soil (e.g., bare rock, new lava); pioneer species are usually lichens — slow. Secondary succession: occurs where a community was destroyed but soil remains (e.g., abandoned farmland) — faster.

What are the three levels of biodiversity?

Genetic diversity (variation within a species), species diversity (variety of species in a region/community), and ecological/ecosystem diversity (variety of habitats, communities and ecological processes).

State the species-area relationship equation given by Alexander von Humboldt.

On a log scale: log S = log C + Z log A, where S = species richness, A = area, C = Y-intercept, Z = slope (regression coefficient, typically 0.1–0.2 for small areas, steeper 0.6–1.2 for large continents).

Differentiate in-situ and ex-situ conservation with examples.

In-situ: protecting species in their natural habitat (national parks, sanctuaries, biosphere reserves, biodiversity hotspots). Ex-situ: protecting outside natural habitat (zoos, botanical gardens, seed banks, cryopreservation).

Name the 'Evil Quartet' — the four major causes of biodiversity loss.

Habitat loss and fragmentation, over-exploitation, alien (invasive) species invasions, and co-extinctions.

What are the two core techniques that form the foundation of modern biotechnology?

Genetic engineering (recombinant DNA technology — altering and transferring genes), and maintenance of sterile (contamination-free) microbial process control for large-scale growth of organisms/cells.

What is the role of restriction enzymes and DNA ligase in rDNA technology?

Restriction endonucleases cut DNA at specific palindromic recognition sites (creating sticky ends). DNA ligase joins DNA fragments (e.g., insert into vector) by sealing the phosphodiester backbone.

Name the three steps of a PCR cycle and the enzyme used.

Denaturation (~94°C, strands separate), annealing (~55°C, primers bind), extension (~72°C, synthesis). Enzyme: thermostable Taq polymerase (from Thermus aquaticus).

What is Bt cotton and how does the Bt toxin work?

Bt cotton carries cry genes from Bacillus thuringiensis producing an inactive protoxin (crystal). In the insect's alkaline gut it is solubilised and activated, binding to midgut epithelium, creating pores that cause cell swelling, lysis and insect death.

What is RNA interference (RNAi) and its application against nematodes?

RNAi is silencing of a specific mRNA by complementary double-stranded RNA. In tobacco, introducing nematode-specific genes producing dsRNA via host (RNAi) silences the parasite's mRNA, killing Meloidogyne incognita and protecting the plant.

What is Golden Rice and what trait was engineered into it?

Golden Rice is a genetically engineered rice variety enriched with provitamin A (beta-carotene) in the grain to combat Vitamin A deficiency; the carotene gives it a golden colour.