Nutrients are chemical substances obtained from food and used in the body to provide energy, structural materials, and regulating agents to support growth, maintenance, and repair. The study of nutrition rests heavily on biochemistry, because every physiological process relies on chemical bonds breaking and forming. The major nutrient classes—carbohydrates, lipids, proteins, vitamins, minerals, and water—are composed of specific arrangements of elements, primarily carbon, hydrogen, oxygen, and nitrogen. Understanding these atomic structures helps nurses explain why the body processes different foods in distinct ways, especially when caring for patients with metabolic disorders common in Nigerian clinical practice, such as diabetes mellitus and protein-energy malnutrition.
Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen, generally with a hydrogen to oxygen ratio of 2:1, matching the formula $C_n(H_2O)_n$. They are classified based on their molecular complexity into three main groups:
Lipids are a diverse group of hydrophobic organic compounds containing carbon, hydrogen, and oxygen, though they have a much lower proportion of oxygen than carbohydrates. The most common dietary lipids are triglycerides, which consist of one glycerol molecule chemically bound to three fatty acid chains via ester bonds.
Fatty acids differ by their hydrocarbon chain length and saturation level:
Proteins are large, complex polymers built from smaller monomer units called amino acids. Every standard amino acid shares a common central carbon atom bonded to a hydrogen atom, an amino group ($NH_2$), a carboxyl group ($COOH$), and a variable side chain known as the R-group. This unique R-group determines the specific chemical behavior and polarity of each amino acid.
During protein synthesis, amino acids link together through covalent peptide bonds formed via condensation reactions between the carboxyl group of one amino acid and the amino group of the next. The resulting chain folds into intricate primary, secondary, tertiary, and quaternary structures essential for enzyme function, tissue repair, and immune defense.
Vitamins are organic compounds required in tiny amounts for normal metabolic functioning, growth, and development. Unlike carbohydrates and lipids, they do not provide energy directly, but many act as coenzymes that facilitate biochemical reactions. They are divided into two main groups based on their chemical solubility:
Minerals are inorganic chemical elements derived from the earth and water, absorbed by plants and consumed by animals. Unlike organic nutrients, they cannot be synthesized by living organisms and retain their elemental chemical identity during digestion. They are categorized into macrominerals, such as calcium, phosphorus, sodium, and potassium, which are needed in larger amounts for skeletal structure and fluid balance, and trace minerals, such as iron, zinc, iodine, and copper, which function primarily as co-factors for enzymes and hormones. Nurses monitor mineral balances closely, as imbalances in electrolytes like sodium and potassium rapidly disrupt cardiac and neurological functions.
Water is the most abundant and critical chemical compound in the human body, serving as the universal solvent for metabolic reactions. Chemically, a water molecule consists of two hydrogen atoms covalently bonded to one oxygen atom, forming a polar structure with a slight positive charge near the hydrogens and a slight negative charge near the oxygen. This polarity allows water to form hydrogen bonds, giving it high heat capacity, excellent lubricating properties, and the ability to dissolve polar and ionic substances easily. Maintaining proper fluid and electrolyte balance is vital for vascular volume, temperature regulation, and waste elimination in all clinical care settings.