IB Sports, exercise and health science A.2.2.3 Micronutrients and Their Roles in the Body Notes

Micronutrients enable energy transfer and tissue synthesis

1. Unlike macronutrients (such as proteins, fats, and carbohydrates), micronutrients do not provide energy (calories) but are crucial for numerous metabolic processes.
2. Micronutrients are required in small amounts. Despite being needed in smaller quantities, they are vital for good health.
3. These nutrients facilitate critical functions such as immune defense, cell function, and energy metabolism.

Micronutrients are divided into vitamins and minerals

Vitamins

1. Fat-soluble vitamins: These are stored in the body's fat and liver. Examples include vitamins A, D, E, and K.
2. Water-soluble vitamins: These are not stored in the body and are excreted in urine. Examples include vitamin C and the B-vitamins (B1, B2, B3, B6, B12, folate, etc.).

Minerals

1. Major minerals: Required in larger amounts, including calcium, phosphorus, magnesium, sodium, potassium, and chloride.
2. Trace minerals: Required in smaller amounts but still crucial for health, including iron, zinc, copper, iodine, and selenium.

Micronutrients enable energy transfer, tissue maintenance, and regulation

Facilitate Energy Transfer

1. Micronutrients, particularly B vitamins, are essential for converting food into usable energy.
2. They act as coenzymes in metabolic pathways such as glycolysis, the citric acid cycle, and oxidative phosphorylation.

Support Tissue Synthesis and Maintenance

1. Vitamins like Vitamin A and C, as well as minerals such as calcium, are involved in tissue growth and repair.
2. Different vitamins support tissue growth and repair (for example collagen synthesis and epithelial health), but specific vitamin functions are not assessed.

Maintain Bodily Functions

1. Micronutrients regulate various body functions, including immune response, bone health, blood clotting, and fluid balance.

Key Micronutrients and Their Roles

Iron

1. Body iron distribution: About 66% of the body's iron sits inside haemoglobin in red blood cells. Most of the rest is in myoglobin inside muscle fibres.
2. Iron is a crucial mineral involved in the transport of oxygen throughout the body. It is a key component of haemoglobin, a protein found in red blood cells, and myoglobin, a protein in muscle cells.
3. Iron binds to oxygen in the lungs, allowing haemoglobin to transport it to tissues, and myoglobin stores oxygen in muscles, releasing it during physical activity.

Iron in Hemoglobin and Myoglobin

1. Iron binds to oxygen in haemoglobin, forming oxyhaemoglobin, and releases it at tissues where oxygen is needed.
2. In muscles, myoglobin also binds to oxygen and releases it during intense exercise.
   1. Haemoglobin: Carries oxygen to body tissues and returns carbon dioxide to the lungs.
   2. Myoglobin: Provides a reserve of oxygen for muscle contractions.

Calcium

Role in Bone and Connective Tissue

1. Calcium is a major mineral component of bones and teeth.
2. It plays a vital role in bone formation and maintenance, providing structural strength.
3. Calcium is continuously deposited and withdrawn from bones to maintain bone density.
4. Calcium contributes to the rigidity and strength of bones and teeth.
5. It also helps in maintaining bone density, reducing the risk of fractures.

Muscle Contraction

1. Calcium is involved in muscle contraction.
2. It is released from the sarcoplasmic reticulum in muscle cells when a nerve impulse triggers a contraction.
3. Calcium ions bind to proteins on the actin filaments in muscles, facilitating the sliding of actin and myosin, which leads to muscle contraction.

Other Functions

1. Calcium also plays a role in nerve impulse transmission, enzyme activation, and regulating the permeability of cell membranes.
2. It is integral in maintaining proper cellular function.

Deficiency Impact

1. A lack of calcium can result in conditions such as osteoporosis, characterized by weak, brittle bones that are more prone to fractures.
2. It may also cause muscle cramps, nervous system dysfunction, and impaired muscle contractions.

Sodium and Potassium

Sodium and potassium are electrolytes essential for nerve impulse transmission, muscle contraction, and maintaining the electrical potential across cell membranes.

Sodium

1. Sodium (Na⁺): The dominant cation of extracellular fluid (blood plasma and interstitial fluid).
2. Functions: Supports nerve transmission, muscle contraction, blood pressure regulation, and absorption of glucose and other nutrients in the gut.
3. Loss in sweat: Athletes lose sodium in sweat, which is why sports drinks for long endurance events contain some salt.

Potassium

1. Potassium (K⁺): The dominant cation of intracellular fluid.
2. Functions: Vital for maintaining the electrical potential across cell membranes, which allows nerves to send impulses and muscle fibres to fire.
3. Low potassium: Can cause muscle cramps during prolonged exercise.

Why the Sodium-Potassium Balance Matters

1. The gradient: A sharp Na⁺ (extracellular) vs K⁺ (intracellular) concentration difference across the cell membrane is the foundation of every nerve impulse and muscle contraction.
2. Active transport: The Na⁺/K⁺-ATPase pump uses ATP to move 3 Na⁺ out and 2 K⁺ in per cycle, continuously maintaining the gradient.
3. Symptoms of disruption: Heavy sweating, severe dehydration, hyponatraemia, or hypernatraemia disturb the gradient. Nerves misfire and muscles cramp or fail.

Vitamins and Their Role in Metabolism

1. Vitamins are essential organic compounds that the body requires in small quantities to support a variety of functions, including tissue synthesis, growth, immune function, and energy metabolism.
2. Unlike macronutrients (carbohydrates, proteins, and fats), vitamins do not provide energy directly, but they are crucial for enabling biochemical reactions that facilitate the utilization of energy from food.

Water-Soluble Vitamins

1. Water-soluble vitamins dissolve easily in water and are not stored in the body, meaning they must be consumed regularly in the diet.
2. These vitamins are absorbed directly into the bloodstream during digestion and are excreted in the urine when in excess.
3. Because the body does not store these vitamins, toxicity is rare.
4. However, large doses can still lead to discomfort (e.g., gastrointestinal issues) or interfere with other metabolic processes.

Fat-Soluble Vitamins

1. Fat-soluble vitamins dissolve in fat and are stored in adipose tissue and the liver.
2. Because they are stored, excessive intake over time can lead to toxicity.
3. These vitamins are absorbed along with dietary fat in the intestines and transported through the lymphatic system before entering the bloodstream.