A.2.2.2 Micronutrients and their role in energy transfer and tissue synthesis (HL) Notes

Micronutrients and their Roles

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.

Types of Micronutrients

Micronutrients can be broadly categorized into two main groups:

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.

General Functions of Micronutrients

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. Vitamin A is essential for maintaining the health of epithelial tissues (e.g., skin, mucous membranes), and Vitamin C is needed for collagen synthesis, aiding in the repair of tissues after injury.

Maintain Bodily Functions

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

Key Micronutrients and Their Roles

Iron

1. Iron is a crucial mineral involved in the transport of oxygen throughout the body. It is a key component of hemoglobin, a protein found in red blood cells, and myoglobin, a protein in muscle cells.
2. Iron binds to oxygen in the lungs, allowing hemoglobin 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 hemoglobin, forming oxyhemoglobin, and releases it at tissues where oxygen is needed.
2. In muscles, myoglobin also binds to oxygen and releases it during intense exercise.
   1. Hemoglobin: 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.
   1. Skeletal Muscle Contraction: Calcium enables the actin-myosin cross-bridge to form, allowing muscle fibers to contract and perform movements.
   2. Cardiac and Smooth Muscle: Calcium also helps regulate contraction in cardiac and smooth muscles, supporting heartbeat and digestive functions.

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

1. Sodium is predominantly found in extracellular fluid and is crucial for regulating blood pressure, nutrient absorption, and maintaining the balance of fluids in and out of cells.
2. It is also involved in nerve transmission and muscle function.
   1. Water Balance: Sodium helps retain water in the body and maintain normal blood pressure.
   2. Nerve Function: Sodium ions play a critical role in transmitting nerve impulses.

Potassium

1. Potassium is mainly located in intracellular fluid and works in balance with sodium to maintain proper nerve and muscle function.
2. It helps regulate fluid balance and is essential for muscle contraction and maintaining the electrical potential across cell membranes.
   1. Muscle Function: Potassium helps muscles contract, and it plays a role in maintaining normal heart rhythms.
   2. Electrical Potential: Potassium helps regulate the electrical charge across cell membranes, which is crucial for nerve signaling and muscle contractions.

Chloride

1. Chloride works alongside sodium to maintain fluid balance and plays a role in regulating the pH of the blood.
2. It also supports nerve function, similar to sodium and potassium.

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.

Examples of Water-Soluble Vitamins:

1. Vitamin C: Involved in collagen synthesis (important for skin, blood vessels, and connective tissues), acts as an antioxidant, and enhances iron absorption.
2. B Vitamins: A group of vitamins, including B1 (thiamine), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), B9 (folate), B12 (cobalamin), and pantothenic acid, which all have varying roles in metabolism, including converting food to energy, nerve function, and red blood cell production.

Fat-Soluble Vitamins