Notes

The human body comprises roughly 30 trillion cells that collectively perform the essential functions of life. The cells can perform these life-sustaining tasks with the help of several organic molecules. These organic molecules are referred to as biomolecules. there are four types of biomolecules and their functions.

Four Major Types of Biomolecules
1. Carbohydrates - Carbohydrates are a vital part of a healthy diet. They provide the energy required to do work.

Types of Carbohydrates and Their Functions
1. Monosaccharides - are colorless, crystalline solids that are completely soluble in water.[1] They are involved in generating energy for the body.
2. Disaccharides -
3. Polysaccharides -

2. Proteins - Proteins are essential components of organisms. It participates in almost every process within cells. It is involved in the processes of DNA replication, cell signaling, catalyzing metabolic reactions, construction of cell and tissue structures, and transportation of molecules from one place to another. Proteins are categorized into four groups depending on their structural organization.

Primary structure - It is formed by the formation of a peptide bond between amino acids.
Secondary structure - It is a folded structure within a polypeptide that’s due to the formation of hydrogen bonds between amide hydrogen and the carbonyl oxygen of the peptide backbone.
Tertiary structure - It is a three-dimensional conformation that’s formed due to the interaction between R-groups or side chains of the amino acids that make up the proteins.[1] Bonds that contribute to the formation of this structure include hydrophobic interaction, electrostatic interactions, hydrogen bonds, and Van der Waals forces of interaction.
Quaternary structure - The quaternary structures may occur between identical or different polypeptide chains. The bonds involved in the formation of these structures include hydrophobic bonds, electrostatic bonds, hydrogen bonds, and covalent cross-links.

Functions of Proteins
1. Structural proteins - These proteins are fibrous proteins that are tough and insoluble in water. They form the structural component of connective tissues, bones, tendons, cartilages, nails, hairs, and horns. Examples of structural proteins are collagen, elastin, and keratin.

2. Enzymes - These are globular conjugated proteins that are also known as biological catalysts. They catalyze metabolic reactions by reducing the activation energy that increases the rate of the reaction.

3. Hormones - They play critical roles in regulating the physiological processes of the body, these processes include reproduction, growth and development, electrolyte balance, sleep, etc. Some examples of these hormones are growth hormone (GH) and follicle-stimulating hormone (FSH).

4. Respiratory pigments - These are globular protein pigments that are usually soluble in water. Examples include myoglobin which provides oxygen to the working muscles and hemoglobin which transfers blood to all the tissues and organs through the blood.

5. Transport proteins - These are structural components of the cell membrane. They form channels in the plasma membrane to transfer selective molecules inside the cells. Some of them also form components of blood and lymph in animals.

6. Motor proteins - These proteins are involved in the contraction and relaxation of the muscle (muscle movement). It includes actin, myosin, kinesin, and dynein.

7. Storage proteins - These proteins are the storage reserve of amino acids and metal ions in cells. They are present in eggs, seeds, and pulses. Examples of storage proteins include ferritin, ovalbumin, and casein.

8. Toxins - These proteins are generally produced by bacteria. They include diphtheria toxin, Pseudomonas exotoxin, and ribosome-inactivating proteins. They help bacteria to attack and kill their host organism by creating cytotoxicity.

3. Nucleic Acids - Nucleic acids are macromolecules present in cells and viruses, and they are involved in the storage and transfer of genetic information.

Types of Nucleic Acids and Their Functions
1. Deoxyribonucleic acids (DNA) - DNA is the genetic material that stores all the information required to be transferred to the progeny and specifies the biological development of all living organisms and viruses.

2. Ribonucleic acids (RNA) - RNA is present in all living cells and has different roles in different organisms. It acts as genetic material in some viruses and has enzymatic activity in other organisms. Three types of RNA are present among organisms: rRNA, mRNA - MESSENGER, and tRNA - TRANSFER. All three have essential roles in the development and maintenance of life and are involved in the transfer of genetic information for protein synthesis. RNA exists in both single-stranded and double-stranded forms, with the double-helical structure of RNA being present in the A form.

4. Lipids - Lipids are hydrophobic and structurally composed of hydrocarbons, and are involved in membrane structure and energy storage.

Classes of Lipids and Their Functions
1. Fatty acids - These are the simplest forms of lipids. They are composed of hydrocarbon chains of 4-36 carbons and one acidic group. They can be linear or branched. Moreover, fatty acids are the building blocks of other types of lipids.

2. Waxes - These are esters of fatty acids and long-chain alcohols. They are composed of hydrocarbon chains of 14-36 carbons. They are synthesized by many plants and animals. However, the best-known wax is bee wax which is composed of an ester of palmitic acid with triacontanol alcohol.

3. Phospholipids - These are composed of fatty acids, an attachment platform for fatty acids, a phosphate, and an alcohol attached to phosphate. They are part of the cell membrane of the organisms.

4. Glycolipids - These are lipids containing saccharide groups. They are constituents of the cell membrane and are involved in signal transductions.

5. Steroids - These are complex derivatives of triterpenes. For example, cholesterol is a constituent of the cell membrane and acts as a precursor for the biosynthesis of steroid hormones and bile acids.

6. Eicosanoids - They arise from the 20 carbons of polyunsaturated fatty acids. They perform several functions. For example, prostaglandins stimulate uterine contraction and lower blood pressure, leukotrienes are involved in chemotaxis and inflammation, and thromboxanes act as vasoconstrictors and stimulate platelet aggregation.

Therefore, biomolecules are essential for life, allowing organisms to grow, sustain themselves, and reproduce.