Biomolecules | Classification of Biomolecules | Carbohydrates, Proteins, Lipids and Nucleic Acids

Teacher Issa Maria introduces biomolecules, defining them as substances produced by cells and living organisms. They have diverse sizes, structures, and functions, and are classified into four main groups: carbohydrates, lipids, nucleic acids, and proteins. All biomolecules are organic, meaning they contain carbon, which is highly versatile and forms strong covalent bonds essential for life. Biomolecules are formed by linking small subunits called monomers into larger polymers.

The video distinguishes between organic (containing carbon) and inorganic (no carbon) compounds, listing examples like minerals, water, and gases as inorganic, and biomolecules as organic. It further classifies biomolecules into micromolecules (small size, low molecular weight) and macromolecules (large, greater molecular weight). Micromolecules include sugars, amino acids, and nucleotides, while macromolecules encompass carbohydrates, lipids, proteins, and nucleic acids, which are large polymers assembled from smaller monomer subunits.

Carbohydrates, also known as saccharides or carbs, are derived from 'hydrate of carbon' (CH2O)n. They are a primary energy source, providing four calories per gram. The body breaks them down into glucose for brain and muscle energy. Functions include being the most abundant dietary energy source, instant energy, energy storage, intermediates in biosynthesis, nerve tissue regulation, and aiding in constipation prevention due to fiber content. Carbohydrates are classified into monosaccharides, disaccharides, and polysaccharides.

Monosaccharides (simple sugars) include glucose (dextrose), fructose (fruit sugar), and galactose (milk sugar). Disaccharides are formed from two monosaccharides, such as sucrose (table sugar = glucose + fructose) and lactose (milk sugar = galactose + glucose), and maltose (malt sugar = two glucose). Polysaccharides (complex carbohydrates or glycans) are polymers of numerous monosaccharide monomers. Common polysaccharides include starch (plant energy storage), glycogen (animal energy storage in liver and muscle), and cellulose (plant cell walls, indigestible by humans but aids digestion).

Proteins, or polypeptides, are large, complex molecules crucial for body structure, function, and regulation, performing most cellular work. They are polymers of amino acids, acting as structural materials in hair, nails, and connective tissues. Composed of carbon, hydrogen, oxygen, nitrogen, and sulfur, proteins function as enzymes, pigments, and hormones. They are the second most common molecules in the human body, making up 10-20% of cell mass, and are vital for structural support, speeding up chemical reactions, molecule transport, and fighting infection. Amino acids are the building blocks of proteins, categorized as essential (obtained from diet) and non-essential (synthesized by the body).

Lipids are a concentrated energy storage form, comprising about 3.5% of cell content, and are also found in hormones and cell membranes. They are organic substances insoluble in water (hydrophobic) but soluble in organic solvents. Composed of carbon, hydrogen, and oxygen, lipids repel water. Their functions include storing energy, forming waterproof barriers and biological membranes, acting as chemical messengers (steroid hormones), and protecting internal organs as insulating materials. Common lipids include fatty acids, triglycerides, steroids, and waxes.

Fatty acids are carboxylic acids with long chains, either saturated (lack carbon-to-carbon double bonds, solid at room temperature) or unsaturated (one or more double bonds, liquid at room temperature). Triglycerides (fats and oils) combine glycerol and three fatty acids; fats are solid (saturated) and from animals, while oils are liquid (unsaturated) and from plants. Steroids, like cholesterol, are vital hormones, though excessive levels can harm arteries. Waxes combine long-chain alcohol and fatty acid, providing water repellency and protection in plants, animals (fur/feathers), and examples include beeswax, lanolin, sebum, cerumen (earwax), plant wax, and paraffin wax.

Nucleic acids are the genetic material of the cell, composed of recurring monomeric units called nucleotides. They contain blueprints for making proteins and transmit genetic information to the next generation. Like proteins, nucleic acids are long chains of polymers made from simpler monomer units. Each nucleotide consists of three principal components: a five-carbon pentose sugar, a phosphate group, and a nitrogenous base. The two kinds of nucleic acids are DNA (deoxyribonucleic acid), found mainly in cell nuclei, coding for amino acid sequences in proteins, and RNA (ribonucleic acid), found throughout the cell, carrying out protein synthesis. Nucleic acids contain carbon, hydrogen, oxygen, nitrogen, and phosphorus.