(a) Classify carbohydrates by giving suitable examples. Also, mention characteristics of each category. (20 marks) (b) Explain…

Carbohydrates. Carbohydrates are classified by hydrolytic complexity and monomer composition. Monosaccharides are single units; aldoses such as glucose and galactose contain an aldehyde group, while ketoses such as fructose contain a ketone group. They are generally soluble, sweet and metabolically active; glucose is a reducing sugar, and fructose can also reduce due to tautomerism. The reducing property depends on a free anomeric carbon: reducing sugars can donate electrons in Benedict’s or Fehling’s tests, while non-reducing sugars cannot. Disaccharides contain two monosaccharides: maltose (glucose–glucose) and lactose (galactose–glucose) are reducing, whereas sucrose (glucose–fructose) is non-reducing because both anomeric carbons are locked in the glycosidic bond. Oligosaccharides contain three to ten units, for example raffinose and stachyose in pulses, and often participate in cell-surface recognition. Polysaccharides are long chains; homopolysaccharides include starch from rice and wheat (amylose and amylopectin, storage), glycogen (animal storage), cellulose (β-1,4 glucose, structural) and chitin (N-acetylglucosamine, arthropod/fungal support). Heteropolysaccharides contain different monomers, such as hyaluronic acid, chondroitin sulphate and guar gum, a galactomannan used as a thickener. Their characteristics vary with linkage, branching and solubility, determining energy storage, structure or matrix function.

Haemoglobin and CO₂ transport. Haemoglobin is a tetramer with quaternary structure α₂β₂, 574 amino acids, each chain carrying one heme with Fe²⁺. A labelled diagram would show two α-chains and two β-chains, four heme groups, the central cavity and allosteric sites. Its four subunits bind oxygen cooperatively: initial binding shifts the molecule from tense to relaxed state, producing a sigmoid oxygen-dissociation curve. The Bohr effect describes how increased H⁺ and CO₂ in tissues shift the curve right, promoting oxygen release. CO₂ is transported mainly as bicarbonate (about 70%) formed in red cells by carbonic anhydrase, as carbamino-haemoglobin (about 20–25%) when CO₂ binds amino groups of globin, and about 7% dissolved in plasma. The Haldane effect, whereby deoxygenated haemoglobin binds H⁺ and CO₂ more readily, and the Bohr effect modulate CO₂/O₂ exchange; they are not separate transport forms. In lungs, oxygenation releases CO₂ for exhalation.

In vitro fertilization techniques. Conventional IVF involves controlled ovarian stimulation, oocyte retrieval, in-vitro fertilization with washed sperm, embryo culture and transfer to the uterus; it is used for tubal blockage, endometriosis or unexplained infertility. Stimulation protocols are individualized; embryo transfer is timed to the endometrial window. ICSI injects a single sperm into an oocyte, indicated in severe male-factor infertility or failed conventional IVF. GIFT transfers oocytes and sperm into the fallopian tube, where fertilization occurs in vivo; it is therefore an assisted reproductive technique rather than strict IVF, used in selected tubal-factor cases. ZIFT transfers an in-vitro-fertilized zygote into the fallopian tube, indicated when tubal function is present but IVF embryo transfer has failed. Frozen embryo transfer (FET) involves cryopreservation and later transfer of embryos, useful for endometrial receptivity, multiple cycles, or to reduce multiple pregnancy risk. In India, ICMR guidelines regulate consent, donor screening, age limits and ethical oversight, while the ART (Regulation) Bill, 2021 proposes licensing, registries and accountability. Success rates vary with age and aetiology; live-birth rates of about 20–35% per transfer are reported for women under 35 at major Indian centres such as AIIMS, CMC Vellore and Manipal, which also contribute to national ART data and guideline implementation. Ethical care requires informed consent, embryo-number limits and prevention of sex selection.

Thus, carbohydrate classification, haemoglobin biochemistry and IVF techniques together show how molecular structure underlies metabolism, gas exchange and reproductive intervention. In the Indian biomedical context, accurate biochemical understanding supports nutrition, anaesthesia and safe, regulated ART practice; this integration is important for clinical medicine, where carbohydrate disorders affect energy and immunity, haemoglobin variants affect oxygen delivery, and ART outcomes depend on molecular, cellular and regulatory safeguards.