INC CET / BSc Nursing Entrance Biology - Botany Syllabus

Name the three tissue systems in flowering plants.

Epidermal tissue system, ground tissue system, and vascular tissue system.

What is the function of the Casparian strip in the endodermis of roots?

It is a band of suberin in the radial and tangential walls of endodermal cells that blocks the apoplastic pathway, forcing water and minerals to pass through the cell membrane (symplast).

Differentiate between open and closed vascular bundles based on cambium.

Open vascular bundles have cambium between xylem and phloem (capable of secondary growth, seen in dicots); closed bundles lack cambium (no secondary growth, seen in monocots).

What are the two types of meristems based on position, and where is the apical meristem located?

Apical and lateral (and intercalary) meristems. Apical meristem is located at the tips of roots and shoots, responsible for primary growth (increase in length).

What is the role of the vascular cambium in dicot stems?

It produces secondary xylem (inward) and secondary phloem (outward), causing increase in girth (secondary growth).

What are annual rings (growth rings) in trees?

Concentric rings of secondary xylem formed due to the activity of cambium varying between spring wood (early wood) and autumn wood (late wood); used to estimate the age of a tree (dendrochronology).

What is the difference between water potential and osmotic potential?

Water potential (Ψw) is the potential energy of water; pure water has Ψw = 0. Osmotic (solute) potential (Ψs) is always negative due to dissolved solutes. Ψw = Ψs + Ψp (pressure potential).

State the relationship: water potential = solute potential + pressure potential.

Ψw = Ψs + Ψp, where Ψw = water potential, Ψs = solute (osmotic) potential (negative), and Ψp = pressure potential (usually positive).

What is the transpiration pull (cohesion-tension) theory of water ascent?

Transpiration from leaves creates a negative pressure (tension) that pulls a continuous water column up the xylem, held together by cohesion of water molecules and adhesion to xylem walls.

What is root pressure, and what is guttation?

Root pressure is the positive pressure developed in root xylem due to active mineral uptake that pushes water upward. Guttation is the loss of water as liquid droplets from leaf margins (hydathodes), caused by root pressure.

Differentiate apoplast and symplast pathways of water movement.

Apoplast: movement through cell walls and intercellular spaces (no membrane crossing). Symplast: movement through cytoplasm and plasmodesmata (connected protoplasts).

What is the pressure-flow (mass flow) hypothesis of phloem transport?

Sugars loaded at the source raise osmotic pressure, drawing in water and creating high pressure; at the sink sugars are unloaded, so the pressure gradient drives the bulk flow of sap from source to sink.

Write the overall balanced equation of photosynthesis.

6CO2 + 12H2O → (light, chlorophyll) C6H12O6 + 6O2 + 6H2O.

In photosynthesis, where do the light reactions and the dark reactions (Calvin cycle) occur?

Light reactions occur in the thylakoid membranes (grana); the dark reactions (Calvin cycle) occur in the stroma of the chloroplast.

What is the primary CO2 acceptor in the Calvin cycle and the first stable product?

The CO2 acceptor is RuBP (ribulose-1,5-bisphosphate); the first stable product is 3-PGA (3-phosphoglyceric acid), a 3-carbon compound.

Why is the C4 pathway more efficient in hot, dry climates, and what is the first CO2 fixation product?

C4 plants concentrate CO2 in bundle sheath cells, minimising photorespiration. The first product is oxaloacetic acid (OAA), a 4-carbon compound, formed in mesophyll cells via PEP carboxylase.

What is photorespiration, and which enzyme causes it?

Photorespiration is the wasteful oxygenation of RuBP under high O2/low CO2 conditions, producing phosphoglycolate without ATP or sugar gain. It is caused by RuBisCO acting as an oxygenase.

Name the products of the light reaction that are used in the Calvin cycle.

ATP and NADPH (assimilatory power); O2 is released as a by-product.

Write the overall equation of aerobic respiration of glucose.

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (38 ATP, theoretically).

Where do glycolysis, the Krebs cycle, and the electron transport chain occur in a cell?

Glycolysis: cytoplasm. Krebs cycle (TCA): mitochondrial matrix. Electron transport chain: inner mitochondrial membrane.

What is the net ATP, NADH, and pyruvate yield from one glucose molecule in glycolysis?

Net 2 ATP, 2 NADH, and 2 molecules of pyruvic acid (3-carbon).

What is the respiratory quotient (RQ), and what is its value when carbohydrates are the substrate?

RQ = volume of CO2 evolved / volume of O2 consumed. For carbohydrates, RQ = 1.

What is the role of NADH and FADH2 in oxidative phosphorylation?

They are reduced coenzymes that donate electrons to the electron transport chain; the energy released pumps protons to create a gradient used by ATP synthase to make ATP.

State the difference between vegetative growth and the role of auxins versus cytokinins.

Auxins promote cell elongation, apical dominance, and rooting; cytokinins promote cell division, delay senescence, and overcome apical dominance (promote lateral bud growth).

Which plant hormone promotes seed dormancy, stomatal closure, and is called the stress hormone?

Abscisic acid (ABA).

Which gaseous plant hormone promotes fruit ripening, senescence, and abscission?

Ethylene.

What is photoperiodism, and which plant part perceives the photoperiod?

Photoperiodism is the response of plants to the relative lengths of light and dark periods (e.g., flowering). The leaves perceive the photoperiod (involving the pigment phytochrome).

What is vernalisation?

The promotion of flowering by exposure of a plant (or seed) to a period of low temperature (cold treatment).

In the embryo sac of a typical angiosperm, what is the 7-celled, 8-nucleate organisation?

3 antipodal cells, 1 central cell with 2 polar nuclei, and the egg apparatus of 1 egg cell + 2 synergids — 8 nuclei in 7 cells.

What is parthenocarpy?

The development of fruit without fertilisation, producing seedless fruits (e.g., banana).

State Mendel's Law of Segregation.

During gamete formation, the two alleles of a gene separate (segregate) so that each gamete receives only one allele; alleles pair again at fertilisation.

State Mendel's Law of Independent Assortment and the dihybrid F2 phenotypic ratio.

Alleles of different genes assort independently of one another during gamete formation. The dihybrid F2 ratio is 9:3:3:1.

What is the monohybrid F2 phenotypic and genotypic ratio in Mendel's cross?

Phenotypic ratio 3:1 (dominant:recessive); genotypic ratio 1:2:1 (homozygous dominant : heterozygous : homozygous recessive).

Define incomplete dominance with an example.

When the heterozygote shows a phenotype intermediate between the two homozygotes, e.g., in Antirrhinum (snapdragon) Rr gives pink flowers between red (RR) and white (rr). F2 ratio is 1:2:1.

What is the chromosomal basis of sex determination in humans (XX-XY type)?

Females are XX (homogametic) and males are XY (heterogametic); sex of the offspring is determined by whether the sperm carries an X or a Y chromosome.

State Chargaff's rule for DNA base composition.

In double-stranded DNA, the amount of adenine equals thymine (A=T) and guanine equals cytosine (G=C); thus purines = pyrimidines (A+G = T+C).

What is the central dogma of molecular biology?

Genetic information flows from DNA → RNA (transcription) → protein (translation).

What is a codon, and how many codons are stop (termination) codons?

A codon is a triplet of nucleotides on mRNA coding for one amino acid (or stop signal). There are 3 stop codons: UAA, UAG, and UGA.

What is semiconservative DNA replication, as shown by Meselson and Stahl?

Each new DNA molecule consists of one parental (old) strand and one newly synthesised strand; the two parental strands are conserved one per daughter molecule.