The role of carbohydrates and vitamins, the functioning of liver and pancreas, drinking water standards and heavy metals, and radioactivity and its laws

Understanding the topic

This question covers nutrition, human physiology, water safety and nuclear science. A strong answer links structure with function and separates related concepts that are often mixed together. Part (c) requires categories of drinking-water quality rather than a random list of chemicals, while part (d) needs the mathematical laws of radioactive decay as well as a definition.

(a) What is role of Carbohydrates and Vitamins in the body? Discuss briefly.

Carbohydrates

Carbohydrates are sugars, starches and fibre composed mainly of carbon, hydrogen and oxygen. Their primary role is to provide energy. Digested carbohydrate is converted largely into glucose, which cells use to produce ATP. The brain and red blood cells rely heavily on glucose under ordinary conditions. Excess glucose can be stored as glycogen in the liver and muscles for later use; prolonged excess may be converted into fat.

Carbohydrates also spare protein from being used as fuel and help normal fat metabolism. Dietary fibre is not digested like starch, but it supports bowel movement, helps regulate blood glucose, contributes to satiety and provides substrate for beneficial gut microbes. Whole grains, pulses, fruit and vegetables provide carbohydrate together with fibre and micronutrients.

Vitamins

Vitamins are organic micronutrients needed in small quantities for normal metabolism, growth and maintenance. They do not supply energy directly. Many act as coenzymes: B vitamins assist energy metabolism, vitamin C supports collagen synthesis and antioxidant defence, and folate is essential for DNA formation. Fat-soluble vitamins have specialised roles: vitamin A supports vision and epithelial tissues, D regulates calcium and bone health, E protects cell membranes, and K is required for normal blood clotting.

Deficiency causes characteristic disorders, but excessive supplementation may also be harmful, particularly for fat-soluble vitamins that can accumulate in the body.

(b) Discuss the functioning of Liver and Pancreas.

Liver

The liver is the body’s largest internal gland and a central processing organ. Blood from the digestive tract reaches it through the hepatic portal vein, allowing absorbed nutrients and many chemicals to be processed before entering general circulation. The liver regulates blood glucose by storing glucose as glycogen and releasing or producing glucose when needed. It converts amino acids, forms urea from toxic ammonia, synthesises cholesterol and packages lipids.

It also produces plasma proteins, including albumin and several clotting factors. Liver cells modify medicines, alcohol and metabolic wastes so they can be eliminated. Kupffer cells help remove microbes and damaged blood cells. The liver produces bile, which carries waste products such as bilirubin and helps the small intestine digest and absorb fats. It also stores glycogen, iron and several vitamins.

Pancreas

The pancreas has exocrine and endocrine functions. Its exocrine cells release digestive enzymes into the small intestine. Amylase digests carbohydrates, lipase digests fats, and proteases digest proteins. Bicarbonate-rich fluid neutralises acidic material arriving from the stomach, creating a suitable environment for intestinal enzymes.

Its endocrine islets release hormones into the blood. Beta cells secrete insulin, which lowers blood glucose by promoting uptake and storage. Alpha cells secrete glucagon, which raises blood glucose by stimulating the liver. Together, these functions make the pancreas essential for digestion and glucose control.

(c) What are the standards of drinking water? How Heavy Metals in the water affect the living organisms?

Safe drinking water is judged through several linked standards rather than appearance alone.

• Microbiological quality: Water intended for drinking should not contain faecal indicator organisms such as E. coli in a 100 mL sample. Microbial contamination can cause diarrhoea, cholera, typhoid and other infections.
• Physical acceptability: Turbidity, colour, taste and odour should remain acceptable. High turbidity can shield microorganisms and reduce the effectiveness of disinfection.
• Chemical quality: Salts, nutrients, pesticides and toxic elements must remain within health-based national limits. As examples of widely used WHO guideline values, arsenic should not exceed 0.01 mg/L and lead should not exceed 0.01 mg/L. Local regulators may adopt different or more stringent standards.
• Radiological quality: Natural or artificial radionuclides should remain below screening and guidance levels established by the competent authority.

Heavy metals are persistent and cannot be destroyed biologically. Lead damages the nervous system, especially in children, and can impair learning, blood formation and kidney function. Arsenic exposure is associated with skin lesions, cardiovascular effects and increased cancer risk. Mercury can damage the brain and kidneys; methylmercury also biomagnifies in aquatic food chains. Cadmium accumulates in the kidneys and can weaken bones.

Plants and aquatic organisms may absorb these elements from contaminated water or sediment. Bioaccumulation in individuals and biomagnification through food webs can then expose fish, wildlife and humans even when the water concentration appears modest.

(d) What is radioactivity? Discuss the laws of radioactivity. Name two radioactive elements.

Radioactivity is the spontaneous transformation of an unstable atomic nucleus into a more stable state with the emission of particles or electromagnetic energy. The common emissions are alpha particles, beta particles and gamma rays. Individual nuclear decays are random, but a large sample follows precise statistical laws.

1. Exponential decay law: The number of undecayed nuclei decreases at a rate proportional to the number still present. If N₀ is the initial number, then N = N₀ exp(-λt), where λ is the decay constant.
2. Activity law: Activity is the number of decays per unit time and is given by A = λN. Its SI unit is the becquerel, equal to one decay per second.
3. Half-life relation: Half-life is the time required for half the original radioactive nuclei to decay. It is constant for a given radionuclide and is related to the decay constant by t½ = 0.693/λ.
4. Independence from ordinary conditions: Nuclear decay is generally unaffected by temperature, pressure, chemical combination or external physical state because it occurs within the nucleus.

Examples of naturally radioactive elements include uranium and radium. Uranium-238 undergoes a series of decays that eventually forms stable lead, while radium-226 decays principally by alpha emission to radon-222. Radioactivity is used in medicine, industry, research and age determination, but uncontrolled exposure can damage living tissue.