Living cells comprise crucial chemical substances including water and a wide variety of carbon-based organic compounds called biomolecules. Biomolecules are organic compounds that are produced by living organisms. These biomolecules primarily consist of carbon, hydrogen, oxygen, phosphorus and sulfur.
Biomolecules may be classified based on their weight into micromolecules and macromolecules. Micromolecules are low-weight molecules, such as monosaccharides, amino acids, nucleotides, fatty acids, etc. These micromolecules act as monomers that polymerise to form macromolecules. The macromolecules include carbohydrates, proteins, and nucleic acids.
Carbohydrates are polyhydroxy aldehydes (aldoses) or ketones (ketoses), or those compounds that upon hydrolysis yield aldoses or ketoses. Carbohydrates are further classified into −
Examples of monosaccharides include glucose (an aldohexose), fructose (an aldopentose), and galactose (an aldohexose).
The breakdown of simple sugars such as glucose is the primary source of energy which can be used to drive cellular reactions.
They also serve as precursors for the synthesis of other cellular material
Storage polysaccharides (glycogen and starch) can be broken down later on to serve the energy requirements of the cell
Structural polysaccharides (cellulose, peptidoglycan, etc) provide mechanical stability by forming structural components of the cells
Polysaccharides are involved in cell signalling activities
Carbohydrates also serve as an important dietary component
Proteins comprise repeating amino acid units, which are joined together via peptide linkages between the amino group of one and the carboxyl group of the other amino acid. 22 amino acids combine in different sequences to result in a wide variety of proteins.
The structure of a protein is described under the following four levels −
Primary structure − this is the amino acid sequence that makes the polypeptide molecule, specified by the genetic codes carried on the DNA.
Secondary structure − the localized spatial arrangement of the amino acids of the main chain of the polypeptide.
The most common secondary structures are −
Alpha-helices, formed when the polypeptide chain twists into a helical conformation via hydrogen bonds between the -CO and -NH groups, and
Beta-pleated sheets, formed when two or more segments of a polypeptide chain, or several polypeptide chains, line up side by side.
Tertiary structure − results from the interaction between the side chains of the polypeptides, causing the folding of the polypeptide chain globular domains.
Quaternary structure − refers to the arrangement of constituent polypeptide chains of multimeric proteins, which are held together by covalent and non-covalent bonds.
Structural proteins (keratin, collagen, etc.) provide the body and the cells support and shape
Catalytic proteins (aka enzymes) are imperative in all the biological reactions that occur in the cell
Regulation of metabolic processes as well.
Transport of material across cell membranes (e.g. aquaporins) and also across the body (e.g. haemoglobin)
Hormonal proteins transmit messages between cells and regulate metabolic processes
Defence proteins like immunoglobulins are imperative in protecting the body from pathogenic diseases
Contractile proteins (actin and myosin) facilitate muscle movement and also the movement across cells
Nucleic Acids are polymers of units called nucleotides. Hence they are also called polynucleotides.
Nucleic acids are of two kinds- the double-stranded molecule called the Deoxyribonucleic Acid (DNA) and, the single-stranded molecule known as the Ribonucleic Acid (RNA).
Each monomer in a DNA or RNA molecule contains −
A nitrogenous base (also known as a nucleobase), maybe a derivative of a purine (adenine and guanine) or a pyrimidine (cytosine, thymine and uracil)
A ribose sugar (deoxyribose in DNA, ribose in RNA)
A phosphate group
These monomeric nucleotides are joined to each other via phosphodiester linkages, forming polynucleotides.
DNA exists as a double helix molecule, comprised of two strands of polynucleotides that run antiparallel to each other. Contrastingly, the RNA is a single-stranded molecule
Nucleic acids carry genetic information that is encoded in the form of a triplet code, within the specific sequence of nucleotides in their structure. The genetic information is converted to the specific proteins which perform various metabolic functions in the body.
The nucleic acids are also used in conducting fingerprint analysis.
These are a group of diverse organic compounds that are insoluble in water. Their hydrophobicity is due to their structure- lipids predominantly contain hydrocarbon chains
Lipids may be of different types, depending upon their structural features −
Fatty acids − the simplest lipids, containing long chains of hydrocarbons (usually 12-24 C long). They may be unsaturated or saturated.
Triacylglycerols − triesters of three fatty acids and glycerol.
Phospholipids − an amphipathic lipid consisting of two hydrophobic) fatty acid tails and a hydrophilic “head”, esterified to a phosphate group.
Glycolipids − lipids containing saccharide groups, attached via glycosidic bonds
Lipoproteins − these are lipid-protein complexes, including LDL and HDL
Biomolecules are organic compounds found in living organisms and are of four types- carbohydrates, proteins, nucleic acids and lipids
Carbohydrates are polyhydroxy aldehyde or ketone molecules. They are classified as monosaccharides, disaccharides, or polysaccharides, based on the number of monomeric units
Proteins are polypeptide molecules of repeating units called amino acids. They serve as enzymes, hormones, immunoglobulins, and transporters, and also serve structural functions
Nucleic acids are polymers of nucleotides. They are of two kinds- DNA and RNA. They carry genetic information
Lipids are hydrophobic hydrocarbon molecules which serve as energy sources, hormones, structural components of biomembranes, etc.
Q1. Which are the simplest monosaccharides?
Ans. The simplest monosaccharides are trioses (3C sugars), like dihydroxyacetone and glyceraldehyde
Q2. What are some examples of heteropolysaccharides?
Ans. Chondroitin sulphate, keratan sulfate, heparin, hyaluronic acid, etc
Q3. Why doesn't RNA exist as a double helix?
Ans. RNA has ribose in its structure, which contains a hydroxyl group at the 2’ position. Hence, making a bond with another nucleotide would lead to steric hindrance and instability of the molecule.
Q4. What is the difference between fats and oils?
Ans. At room temperature, fats exist as solids and contain a high amount of saturated fatty acids, while oils exist as liquids at room temperature and contain more unsaturated fatty acids
Q5. Which protein is most abundant in mammals?
Ans. Collagen
Physics
Biology
Chemistry
Mathematics
Economics
Psychology
Environmental Science
Social Studies
Fashion Studies
English