Unit 32: Medicine, Agriculture and Industry — Long Questions

Structure Penicillin is a powerful antibiotic used to treat many bacterial infections (respiratory infections like strep throat, pneumonia, scarlet fever, sinusitis; skin/soft-tissue infections like cellulitis and erysipelas). Its structure contains two core rings: a strained, four-membered beta-lactam ring and a five-membered thiazolidine ring, with various side chains (R groups) attached to them. The beta-lactam ring is the key reactive, strained part of the molecule and is crucial for antibiotic activity; it is also the site attacked by bacterial beta-lactamase enzymes, which can deactivate penicillin (a resistance mechanism).

Mechanism of Action Penicillin's structure closely resembles the amino acid sequence of the natural substrate of transpeptidase, the bacterial enzyme responsible for cross-linking and strengthening the cell wall (peptidoglycan). The transpeptidase enzyme mistakenly binds penicillin in place of its normal substrate; the strained beta-lactam ring then opens and forms a permanent covalent bond with the enzyme's active site, inactivating it irreversibly. Without functional transpeptidase, the bacteria cannot build a strong cell wall; they continue to grow but, lacking structural support, eventually burst and die due to osmotic pressure. Since human cells do not have cell walls, penicillin does not harm human cells, giving it selective toxicity against bacteria.

Genetic engineering in agriculture involves changing an organism's DNA by adding, removing, or modifying specific genes, used to create genetically modified (GM) crops with desired traits. The process: scientists identify a useful gene with a desired trait (e.g., pest resistance from a bacterium, or drought tolerance); this gene is isolated from the source organism and inserted into the target plant's genome using a gene gun or a carrier bacterium; the new gene is then expressed by the plant's cells, so the modified plant produces a new protein it could not make before, giving it the new trait.

Benefits GM crops can have improved resistance to pests and diseases, tolerance to herbicides, and enhanced nutritional value; this increases crop yields and reduces the need for certain pesticides. For example, Bt-Cotton produces its own pesticide, reducing the need for chemical sprays, and Golden Rice is engineered with beta-carotene to help prevent blindness in developing nations.

Risks There is a potential for GM genes to spread to wild plants (outcrossing); herbicide-resistant genes can jump from GM crops to wild weeds via cross-pollination, creating hard-to-kill "superweeds"; GM crops can also lead to pesticide/herbicide-resistant insects and weeds, and there are concerns about long-term effects on human health and biodiversity.

Role in Pakistan's economy The chemical industry is vital to Pakistan's economy, contributing significantly to GDP and providing jobs. It supports other major sectors: agriculture (through fertilizers), construction (through cement), and textiles (through dyes and synthetic fibres). Being an agrarian economy, Pakistan's food security depends on the chemical industry — local companies use natural gas to produce urea, reducing the national import bill by billions of dollars. Textiles account for over 50% of Pakistan's exports, and this industry is a massive consumer of caustic soda (for mercerizing cotton), synthetic dyes (for colour and fastness), and hydrogen peroxide (for bleaching fabrics). Due to infrastructure projects and urbanization, the cement industry has also become a leading exporter to neighbouring regions. Overall, using locally available raw materials reduces Pakistan's reliance on imports.

Main raw materials available in Pakistan: (1) Natural Gas — major source of methane (CH₄), used for fertilizers (urea) and petrochemicals, and as a source of hydrogen. (2) Rock Salt (Khewra Mines) — one of the world's largest rock salt deposits, source of NaCl for soda ash, caustic soda, and chlorine. (3) Limestone — abundant in the salt range and Sindh, source of CaCO₃ for the cement industry. (4) Gypsum — used in cement and plaster, and as a source of calcium and sulphur and a soil conditioner. (5) Chromite — found in Muslim Bagh, used in stainless steel and pigment production. (6) Crude Oil — refined to produce fuels and petrochemicals. (7) Sulphur — used to make sulphuric acid (H₂SO₄), a key industrial chemical. Air (nitrogen for fertilizers, oxygen for steel) and water (solvent, coolant, source of hydrogen) are also important general feedstocks.

Industrial chemical processes 1. Polymerisation: Small monomer molecules link up to form large polymer chains. Addition polymerisation forms polymers without losing any atoms (e.g., ethylene monomers forming polyethene). Condensation polymerisation releases a small molecule, usually water, as monomers join (e.g., monomers forming polyesters). Engro Polymer and Chemicals is the sole producer of PVC in Pakistan.
2. Refining and Reforming: Fractional distillation separates crude oil into fractions (gasoline, diesel, kerosene, etc.) based on boiling point. Catalytic reforming converts straight-chain hydrocarbons into branched hydrocarbons to raise the octane number of gasoline. Refineries like PARCO and Attock Refinery supply petrochemical feedstocks to the wider chemical industry.
3. Haber-Bosch Process: Ammonia (NH₃) is synthesized from nitrogen (N₂) and hydrogen (H₂) using an iron catalyst: N₂ + 3H₂ → 2NH₃. About 70% of ammonia produced is used directly for fertilizer manufacture. Engro Fertilizers and FFC use natural gas as feedstock to produce ammonia, which is converted to urea.
4. Contact Process: Sulphur dioxide (SO₂) is converted to sulphur trioxide (SO₃) using V₂O₅ or Pt catalyst, then to oleum, and finally to sulphuric acid (H₂SO₄) — the "King of Chemicals." Nimir Industrial Chemicals runs this process in Pakistan.
5. Solvay Process: Produces sodium carbonate (Na₂CO₃) from brine and limestone. Ammonia is added to brine, and CO₂ is passed through to form sodium bicarbonate (NaHCO₃) precipitate, which is heated to give Na₂CO₃; ammonia is regenerated using lime, with calcium chloride (CaCl₂) as a by-product. Lucky Core Industries (formerly ICI) produces soda ash for the glass, detergent, and paper industries.
6. Chlor-Alkali Process: Electrolysis of NaCl brine produces chlorine (Cl₂), caustic soda (NaOH), and hydrogen (H₂), commonly using membrane cell technology. Sitara Chemical Industries and Ittehad Chemicals supply the textile and water-treatment sectors.

Applications in Pakistan Petrochemical industry — produces plastics, synthetic rubber, and fibres from cracked crude oil, also lubricants and waxes. Cosmetics industry — uses surfactants (soaps), emulsifiers (creams), and preservatives, with pH-balanced formulations for skin. Cement industry — heats limestone and clay to 1500°C in a rotary kiln, then grinds the product with gypsum. Food industry — makes preservatives (e.g., sodium benzoate), hydrogenates oils into solid fats (margarine), uses leavening agents (baking soda), and fortifies foods (iodized salt, vitamin A in oil).

Important safety measures 1. Personal Protective Equipment (PPE): Workers should use gloves, goggles, helmets, lab coats, and protective shoes to avoid injuries from chemicals, heat, or harmful fumes.
2. Proper labeling, handling and storage: Chemicals must be properly labeled and stored according to their properties; flammable, toxic, or corrosive substances should be kept in suitable containers and separate storage areas to prevent leaks, spills, contamination, or dangerous reactions.
3. Emergency planning: Industries should have clear emergency plans for fires, chemical spills, gas leaks, or explosions, with emergency exits, fire extinguishers, first-aid kits, and spill control materials available, and workers trained on how to respond.
4. Ventilation: Good ventilation systems are needed to remove toxic gases, fumes, and dust, reducing the risk of breathing harmful substances.
5. Training and maintenance: Workers must receive proper safety training on handling hazardous materials and operating equipment; machines, pipelines, and storage tanks should be regularly inspected and maintained to detect faults early.

Verification Checklist ☐ Are all workers in hazardous areas wearing the required PPE (gloves, goggles, helmets, lab coats, protective shoes)?
☐ Are all chemical containers correctly labeled, and are flammable/toxic/corrosive substances stored separately?
☐ Is there a documented emergency response plan, and have workers been trained/drilled on it?
☐ Are emergency exits, fire extinguishers, first-aid kits, and spill-control materials present, accessible, and in date?
☐ Is the ventilation system operating correctly and checked on a regular schedule?
☐ Have all workers completed up-to-date safety training on hazardous materials and equipment operation?
☐ Are machines, pipelines, and storage tanks inspected and maintained on a regular schedule, with records kept?