The deficiency of which one of the following vitamins causes delayed clotting of blood and haemorrhaging ?

1. Basics of Human Nutrition: Macro and Micronutrients (basic)

Hello! Let’s start our journey into human nutrition by understanding the very foundation of how our bodies fuel themselves. At its core, nutrition is the process by which an organism takes in and utilizes food substances to maintain life, growth, and health. These substances are called nutrients. Depending on the quantity our body requires and the functions they perform, we categorize these into two main groups: Macronutrients and Micronutrients.

Macronutrients are the "big hitters" that our bodies need in large quantities every day. They provide the bulk of our energy (calories) and act as the structural building blocks for our cells. This group includes Carbohydrates (our primary fuel), Proteins (essential for growth, repair, and gaining strength), and Fats (important for energy storage and hormone production). For instance, common staples like milk, curd, and cheese are rich sources of proteins and fats that help in optimal development Science-Class VII, Adolescence: A Stage of Growth and Change, p.79. In the context of plant life, you might see macronutrients like Nitrogen, Phosphorus, and Potassium discussed, but for humans, the focus is on the organic compounds that drive our metabolism Indian Economy, Nitin Singhania, Agriculture, p.302.

On the other hand, Micronutrients consist of Vitamins and Minerals. Although we only need them in minute amounts—often measured in milligrams or micrograms—their impact is massive. They act as essential "cogs" in the body's machinery, enabling chemical reactions to occur. For example, Iron is a critical mineral needed for the formation of blood, found in foods like spinach and kidney beans Science-Class VII, Adolescence: A Stage of Growth and Change, p.79. A deficiency in these small-scale nutrients can lead to significant health challenges, a concern often highlighted in studies regarding rural diets and food security Economics, Class IX, Food Security in India, p.54.

Feature	Macronutrients	Micronutrients
Required Amount	Large quantities (Grams)	Small quantities (Milligrams/Micrograms)
Primary Function	Energy production and structural growth	Regulating metabolism and biochemical processes
Components	Carbohydrates, Proteins, Fats	Vitamins and Minerals

Sources: Science-Class VII, Adolescence: A Stage of Growth and Change, p.79; Indian Economy, Nitin Singhania, Agriculture, p.302; Economics, Class IX, Food Security in India, p.54

2. Vitamins: Solubility and Storage (basic)

Vitamins are essential micronutrients that the human body generally cannot synthesize on its own, meaning they must be obtained through our diet Science-Class VII . NCERT(Revised ed 2025), Adolescence: A Stage of Growth and Change, p.80. To understand how our body manages these nutrients, we look at their solubility—whether they dissolve in water or fats. This single chemical property determines how the vitamin is absorbed, how it travels through the bloodstream, and, most importantly, whether the body can store it for later use.

Fat-soluble vitamins (A, D, E, and K) behave much like dietary fats. In the digestive system, they require bile salts (secreted by the liver) to be broken down into smaller globules for efficient absorption in the small intestine Science, class X (NCERT 2025 ed.), Life Processes, p.86. Once absorbed, these vitamins are stored in the liver and adipose (fatty) tissues. Because the body has a "storage tank" for them, we do not necessarily need to consume them every single day. However, this also means that taking excessive amounts can lead to toxic buildup, a condition known as hypervitaminosis.

In contrast, water-soluble vitamins (B-complex and C) dissolve easily in watery fluids. Just as sugar particles occupy the spaces between water particles Science, Class VIII . NCERT(Revised ed 2025), Particulate Nature of Matter, p.108, these vitamins circulate freely in the blood. Unlike fat-soluble vitamins, the body generally cannot store water-soluble vitamins in significant amounts. Any excess is typically filtered by the kidneys and excreted in urine. This is why a regular, daily intake of B and C vitamins is crucial for health. A notable exception is Vitamin B12, which, despite being water-soluble, can be stored in the liver for several years.

Feature	Fat-Soluble (A, D, E, K)	Water-Soluble (B-complex, C)
Storage	Stored in liver and fat tissues	Generally not stored (excreted)
Absorption	Requires bile and dietary fats	Absorbed directly into the blood
Frequency	Periodic intake (weekly/monthly)	Frequent intake (daily)

Sources: Science-Class VII . NCERT(Revised ed 2025), Adolescence: A Stage of Growth and Change, p.80; Science, class X (NCERT 2025 ed.), Life Processes, p.86; Science, Class VIII . NCERT(Revised ed 2025), Particulate Nature of Matter, p.108

3. Composition of Blood and Formed Elements (intermediate)

In complex multicellular organisms, simple diffusion is insufficient to meet the needs of all cells because most cells are not in direct contact with the environment Science, Class X (NCERT 2025 ed.), Life Processes, p.80. To solve this, the body uses blood, a specialized fluid connective tissue that acts as a transport highway. Blood is composed of two main parts: a liquid matrix called plasma and the cellular components known as formed elements suspended within it Science, Class X (NCERT 2025 ed.), Life Processes, p.91. Plasma makes up about 55% of blood volume and is primarily water. It is the medium responsible for transporting food (nutrients), carbon dioxide, and nitrogenous wastes in dissolved form Science, Class X (NCERT 2025 ed.), Life Processes, p.91. The formed elements consist of three types of cells with highly specialized functions:

• Red Blood Cells (RBCs): These contain hemoglobin and are the primary carriers of oxygen throughout the body.
• White Blood Cells (WBCs): These function as the body's primary defense mechanism against infections.
• Platelets: These are cell fragments that circulate in the body to plug leaks by helping to clot blood at points of injury, preventing excessive blood loss Science, Class X (NCERT 2025 ed.), Life Processes, p.94.

For the blood to function effectively as a repair system, specific nutrients are required. For example, the clotting process initiated by platelets relies on Vitamin K, which is essential for the synthesis of specific coagulation factors (II, VII, IX, and X). Without these nutrients, even if platelets are present, the chemical 'glue' needed to seal a wound won't form, leading to a risk of hemorrhaging. This highlights why the circulatory system is not just about movement, but also about the integrity of the network Science-Class VII, NCERT(Revised ed 2025), Life Processes in Animals, p.133.

Blood Component	Primary Form/State	Main Transport Function
Plasma	Liquid Medium	CO₂, Nutrients, Wastes
RBCs	Cellular	Oxygen (O₂)
Platelets	Cell Fragments	Clotting/Repair

Sources: Science, Class X (NCERT 2025 ed.), Life Processes, p.80, 91, 94; Science-Class VII, NCERT(Revised ed 2025), Life Processes in Animals, p.133

4. Role of Essential Minerals in Physiology (intermediate)

To understand human health, we must look beyond the organic molecules like carbohydrates and proteins to the inorganic world of minerals. While they make up only a small fraction of our body weight, minerals are the 'spark plugs' of our physiology. They are categorized into Macrominerals (needed in larger amounts like Calcium and Magnesium) and Trace Minerals (needed in tiny amounts like Iron and Zinc). These elements do not provide energy themselves but act as essential cofactors that allow enzymes to function and muscles to move.

Take Iron, for instance. It is perhaps the most critical trace mineral for energy metabolism because it forms the core of hemoglobin, the protein in red blood cells that carries oxygen from the lungs to the rest of the body. Without sufficient iron, the body cannot produce enough healthy oxygen-carrying red blood cells, leading to anemia. This is a significant health concern globally, particularly among adolescents and pregnant women, as their growing bodies have higher demands for blood production Science-Class VII, Adolescence: A Stage of Growth and Change, p.80. Managing iron deficiency often involves dietary intake of green leafy vegetables, jaggery, and meat, or through government-supported supplementation programs.

Another powerhouse is Calcium. While we often associate it solely with bone density, its physiological role is much broader. Calcium is a vital 'messenger' in the body; it is required for the contraction and expansion of muscles, including the heart Science, Class VIII, Exploring Forces, p.67. Furthermore, when an injury occurs, calcium works alongside platelets to initiate the clotting cascade, effectively 'plugging' leaks in the circulatory system Science, class X (NCERT 2025 ed.), Life Processes, p.94. This illustrates how minerals integrate with cellular components to maintain homeostasis.

Mineral	Primary Physiological Role	Deficiency Impact
Iron	Oxygen transport (Hemoglobin)	Anemia, fatigue, impaired growth
Calcium	Bone structure, muscle contraction, blood clotting	Osteoporosis, muscle cramps, poor clotting
Sodium & Potassium	Nerve impulse transmission and fluid balance	Confusion, muscle weakness, heart arrhythmias
Iodine	Synthesis of thyroid hormones	Goiter, impaired mental development

Sources: Science-Class VII . NCERT(Revised ed 2025), Adolescence: A Stage of Growth and Change, p.80; Science ,Class VIII . NCERT(Revised ed 2025), Exploring Forces, p.67; Science , class X (NCERT 2025 ed.), Life Processes, p.94

5. The Human Digestive System and Gut Microbiota (intermediate)

The human digestive system is far more than just a tube for processing food; it is a complex biological refinery. After the stomach churns food into a semi-liquid state, it enters the small intestine, which is the primary site for the complete digestion of carbohydrates, proteins, and fats. Here, secretions like bile from the liver play a dual role: they neutralize the acidity of food coming from the stomach and emulsify fats into tiny globules, significantly increasing the efficiency of digestive enzymes Science, class X (NCERT 2025 ed.), Life Processes, p.86. Interestingly, the length of the small intestine varies across species; for instance, carnivores have shorter intestines because meat is easier to digest compared to fiber-heavy plant matter Science, class X (NCERT 2025 ed.), Life Processes, p.86.

Once nutrients are absorbed in the small intestine, the remaining undigested material moves into the large intestine. Though shorter in length (about 1.5 meters), it is called "large" because of its wider diameter Science-Class VII, NCERT(Revised ed 2025), Life Processes in Animals, p.126. This region is home to a massive colony of microorganisms known as the gut microbiota. These bacteria, including species like Escherichia coli, live in a symbiotic relationship with us. They break down complex substances that our own enzymes cannot handle, particularly dietary fiber, and in return, they produce essential nutrients that our bodies can then absorb Science-Class VII, NCERT(Revised ed 2025), Life Processes in Animals, p.127.

One of the most critical functions of these gut bacteria is the synthesis of Vitamin K and several B-complex vitamins. While most vitamins must be obtained directly from our diet, our internal microbial "factory" ensures a steady supply of Vitamin K, which is indispensable for blood coagulation. To maintain this delicate microbial balance, consuming fermented foods like curd, buttermilk, and pickles is highly beneficial, as they replenish healthy bacteria and support overall well-being Science-Class VII, NCERT(Revised ed 2025), Life Processes in Animals, p.127.

Sources: Science, class X (NCERT 2025 ed.), Life Processes, p.86; Science-Class VII, NCERT(Revised ed 2025), Life Processes in Animals, p.126; Science-Class VII, NCERT(Revised ed 2025), Life Processes in Animals, p.127

6. Mechanism of Blood Coagulation (Clotting) (exam-level)

To understand blood coagulation, think of it as a two-stage emergency repair system. When a blood vessel is injured, the first responders are platelet cells. These specialized cells circulate in the blood and immediately move to the site of injury to 'plug' the leak Science, class X (NCERT 2025 ed.), Life Processes, p.94. However, a simple plug is often too weak to withstand blood pressure. The second stage is the clotting cascade, a sophisticated biochemical chain reaction that transforms liquid blood into a solid gel-like clot using proteins called clotting factors. At the heart of this cascade is Vitamin K. It acts as a critical cofactor in the liver for the synthesis of four major clotting factors: Prothrombin (Factor II), and Factors VII, IX, and X. Vitamin K modifies these proteins so they can effectively bind to Calcium ions (Ca²⁺), which acts as the 'glue' that allows these factors to adhere to the injured vessel's surface. The final result of this cascade is the conversion of soluble fibrinogen into a mesh of insoluble fibrin threads, which traps red blood cells and stabilizes the platelet plug. A deficiency in Vitamin K disrupts this entire process. Without it, the liver produces 'empty' clotting factors that cannot bind calcium or participate in the cascade. This leads to a dangerous condition known as haemorrhaging (excessive bleeding), as the blood loses its ability to clot. This is particularly vital in newborns, who are often born with low Vitamin K levels and require a supplement to prevent Vitamin K Deficiency Bleeding (VKDB).

Nutrient	Role in Clotting/Blood Health	Deficiency Symptom
Vitamin K	Synthesis of Prothrombin and Factors VII, IX, X	Delayed clotting, spontaneous haemorrhage
Calcium (Ca²⁺)	Essential ion for factor activation and binding	Impaired cascade progression
Vitamin C	Collagen synthesis for vessel strength	Scurvy and bleeding gums (weak capillaries)

Sources: Science, class X (NCERT 2025 ed.), Life Processes, p.94

7. Vitamin K: Functions and Deficiency Disorders (exam-level)

Vitamin K is a vital fat-soluble nutrient that serves as the body’s primary regulator for blood coagulation (clotting). While we often learn that platelets are the cellular components that circulate and plug leaks in our blood vessels Science, Class X, p.94, Vitamin K is the essential chemical "switch" that activates the proteins required for this process. It acts as a cofactor for an enzyme that modifies specific proteins, allowing them to bind with Calcium (Ca²⁺). This binding is a prerequisite for the clotting cascade to function correctly.

Specifically, Vitamin K is responsible for the synthesis of four major clotting factors in the liver: Factors II (Prothrombin), VII, IX, and X. Without Vitamin K, these proteins are produced in an inactive form, rendering the body's "pumping system" vulnerable to leaks that cannot be easily plugged Science, Class X, p.94. This is distinct from blood issues like anemia, which are often caused by deficiencies in Iron or Vitamin B12 Science-Class VII, p.80.

A deficiency in Vitamin K leads to a clinical condition known as haemorrhaging (excessive or spontaneous bleeding). Because the blood fails to clot in a timely manner, even minor injuries can become dangerous. This is particularly critical in newborns, who are born with low Vitamin K stores and a sterile gut (lacking the bacteria that normally synthesize Vitamin K2), leading to a high risk of Vitamin K Deficiency Bleeding (VKDB). For this reason, newborns are routinely given a Vitamin K supplement at birth.

Nutrient	Primary Blood Function	Deficiency Disorder
Vitamin K	Synthesis of Clotting Factors	Hemorrhage (delayed clotting)
Iron	Hemoglobin synthesis	Anemia (reduced oxygen transport)
Vitamin C	Collagen synthesis / Capillary strength	Scurvy (bleeding gums)

Sources: Science, Class X, Life Processes, p.94; Science-Class VII, Adolescence: A Stage of Growth and Change, p.80

8. Solving the Original PYQ (exam-level)

This question is a classic application of your recent study on Micronutrients and Human Physiology. To solve this, you must bridge the gap between biological chemistry and clinical symptoms. You’ve learned that certain vitamins act as essential cofactors for enzymes. In this specific case, the building blocks come together around the "coagulation cascade"—a complex series of steps your body takes to stop bleeding. As noted in StatPearls: Vitamin K Deficiency, the synthesis of clotting factors II, VII, IX, and X is entirely dependent on a specific fat-soluble vitamin that facilitates their carboxylation, enabling them to bind calcium and function correctly.

When you approach this question, follow the logic of physiological function. If the body cannot clot blood, the primary "glue" or proteins responsible must be inactive. Vitamin K is the correct answer because it is the specific catalyst that allows these proteins to form a stable clot. Without it, even minor injuries lead to haemorrhaging. Think of Vitamin K as the "Koagulation" vitamin (using the German spelling as a mnemonic). This is why, as highlighted in Healthdirect Australia, newborns are often given a Vitamin K shot immediately—to prevent Haemorrhagic Disease of the Newborn before their gut bacteria can start producing it naturally.

To avoid UPSC’s common traps, you must distinguish between clotting and tissue integrity. Vitamin C is a frequent distractor because its deficiency causes bleeding gums (scurvy); however, StatPearls: Vitamin C Deficiency explains this is due to weak collagen in blood vessel walls, not a failure in the clotting cascade itself. Similarly, Vitamin A is primarily linked to night vision and epithelial health, while Vitamin E acts as an antioxidant protecting cell membranes. While a lack of Vitamin E can cause red blood cell breakage, it does not directly impair the clotting mechanism. Mastery of these distinctions ensures you won't be swayed by options that share superficial symptoms like "bleeding."