AIIMS Nursing (BSc) Entrance Biology - Botany Syllabus

What is the function of the rough endoplasmic reticulum versus the smooth ER?

Rough ER (with ribosomes) synthesizes proteins; smooth ER synthesizes lipids and steroids.

What is water potential and in which direction does water move?

Water potential (Ψw) is the potential energy of water; water always moves from a region of higher (less negative) to lower (more negative) water potential.

Write the water potential equation relating it to solute and pressure potential.

Ψw = Ψs + Ψp, where Ψs is solute (osmotic) potential and Ψp is pressure potential.

What is the difference between osmosis and diffusion?

Diffusion is the net movement of molecules from high to low concentration; osmosis is the diffusion of water across a semipermeable membrane down a water-potential gradient.

What is plasmolysis?

The shrinkage of the protoplast away from the cell wall when a cell is placed in a hypertonic solution, due to exosmosis.

What is the cohesion-tension theory of water ascent in plants?

Transpiration pull (tension) created at leaves, transmitted through continuous water columns held together by cohesion (water-water) and adhesion (water-walls), pulls water up the xylem.

What is guttation?

The loss of water in liquid form (droplets) from the margins/tips of leaves through hydathodes, mainly due to root pressure.

What are the two categories of essential mineral elements based on quantity required?

Macronutrients (required in large amounts, e.g., N, P, K, Ca, Mg, S) and micronutrients/trace elements (required in small amounts, e.g., Fe, Mn, Zn, Cu, B, Mo, Cl).

Which element is a constituent of chlorophyll and its deficiency causes interveinal chlorosis?

Magnesium (Mg).

What is biological nitrogen fixation and name the key enzyme involved?

The reduction of atmospheric N2 to ammonia by microorganisms; the enzyme is nitrogenase.

Write the overall balanced equation for photosynthesis.

6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O (in the presence of light and chlorophyll).

Where do the light reactions and the dark (Calvin cycle) reactions of photosynthesis occur?

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

What is the primary CO2 acceptor in the Calvin (C3) cycle and the first stable product?

Acceptor: RuBP (ribulose-1,5-bisphosphate); first stable product: 3-phosphoglyceric acid (3-PGA, a 3-carbon compound).

What is the first stable product in C4 plants and where does CO2 fixation begin?

Oxaloacetic acid (OAA, a 4-carbon compound), formed in mesophyll cells by PEP carboxylase fixing CO2 to PEP.

What is photorespiration and which enzyme is responsible?

The light-dependent uptake of O2 and release of CO2 due to RuBisCO acting as an oxygenase; it does not produce ATP or sugar (wasteful process).

Write the overall equation for aerobic respiration of glucose.

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

In which part of the cell do glycolysis and the Krebs cycle occur?

Glycolysis occurs in the cytoplasm; the Krebs cycle occurs in the mitochondrial matrix.

What is the respiratory quotient (RQ) and what is its value for carbohydrates?

RQ = volume of CO2 released / volume of O2 consumed; for carbohydrates RQ = 1.

How many net ATP molecules are produced in glycolysis per glucose?

Net 2 ATP (4 produced minus 2 used), plus 2 NADH.

What are the five major plant growth regulators (phytohormones)?

Auxins, gibberellins, cytokinins, ethylene, and abscisic acid (ABA).

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

Auxin promotes apical dominance; cytokinin promotes cell division and delays senescence.

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

Ethylene.

What is photoperiodism?

The response of plants to relative lengths of day and night (light/dark periods), affecting flowering; plants are classified as short-day, long-day, or day-neutral.

What is vernalization?

The promotion of flowering by exposure to low temperature for a certain period (cold treatment).

What are the parts of a typical anther and what is microsporogenesis?

A typical anther is dithecous and tetrasporangiate; microsporogenesis is the formation of haploid microspores (pollen) from diploid microspore mother cells via meiosis.

Describe the structure of a mature embryo sac in angiosperms (7-celled, 8-nucleate).

It has one egg apparatus (1 egg + 2 synergids), 3 antipodal cells, and 1 central cell with 2 polar nuclei = 7 cells, 8 nuclei.

What is apomixis?

The formation of seeds without fertilization (asexual reproduction mimicking sexual seed formation).

State Mendel's Law of Segregation.

The two alleles of a gene segregate (separate) from each other during gamete formation, so each gamete receives only one allele.

State Mendel's Law of Independent Assortment.

Alleles of different genes assort independently of one another during gamete formation (applies to genes on different chromosomes).

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

9:3:3:1.

In Watson and Crick's DNA model, which bases pair together and by how many hydrogen bonds?

Adenine pairs with Thymine (2 hydrogen bonds); Guanine pairs with Cytosine (3 hydrogen bonds).

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.

What is the central dogma of molecular biology?

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

What are the trophic levels in an ecosystem?

Producers (T1), primary consumers/herbivores (T2), secondary consumers/carnivores (T3), tertiary consumers (T4), and decomposers.

What is the 10 percent law of energy flow given by Lindeman?

Only about 10% of energy is transferred from one trophic level to the next; the rest is lost mainly as heat (metabolism).

Why is the pyramid of energy in an ecosystem always upright?

Because energy is lost at each successive trophic level (10% law), so available energy always decreases upward.

What is ecological succession, and distinguish primary from secondary succession?

Gradual, predictable change in species composition of an area over time. Primary succession starts on bare lifeless areas (no soil); secondary succession occurs where soil already exists after disturbance.

What are the levels of biodiversity?

Genetic diversity, species diversity, and ecological (ecosystem) diversity.

What is the difference between in-situ and ex-situ conservation?

In-situ: conservation in natural habitat (national parks, sanctuaries, biosphere reserves); ex-situ: conservation outside natural habitat (zoos, botanical gardens, seed banks).

Name the IUCN Red List category for a species at extremely high risk of extinction in the wild.

Critically Endangered (CR).

What is biotechnology and name its two core techniques.

The use of living organisms/their products for human benefit; core techniques are genetic engineering (recombinant DNA technology) and bioprocess engineering (maintaining sterile microbial/cell cultures).

What are restriction enzymes and why are they called 'molecular scissors'?

Endonucleases that cut DNA at specific recognition sequences; they cut DNA into fragments, hence 'molecular scissors'.

What is Bt cotton and how does it confer pest resistance?

Transgenic cotton carrying the cry gene from Bacillus thuringiensis; it produces Bt toxin (Cry protein) that kills bollworm pests.

What is RNA interference (RNAi) as used in pest-resistant plants?

A method of cellular defense that silences specific mRNA using complementary dsRNA; used in tobacco plants to protect against nematodes by silencing nematode genes.

What are Ti plasmids and their role in genetic engineering?

Tumour-inducing plasmids of Agrobacterium tumefaciens, used as cloning vectors to deliver desired genes into plant cells.