Biomolecules connects chemistry to the living state and is one of the most concept-dense NEET Biology chapters. It is also highly predictable: monomer–polymer bonds, enzyme terms (apoenzyme, cofactor, holoenzyme), nucleotide vs nucleoside, Chargaff's rule, and ATP-metabolism questions appear in nearly every NEET paper. A clear conceptual map of this chapter converts directly into marks.
Living cells are composed of water, inorganic ions, and organic biomolecules. The major organic classes are carbohydrates, lipids, proteins, and nucleic acids. Carbon, hydrogen, oxygen, and nitrogen dominate the elemental composition of living matter.
Small molecules like sugars, amino acids, fatty acids, and nucleotides are called micromolecules, whereas proteins, nucleic acids, and polysaccharides are macromolecules (also called polymers).
When biological tissue is ground in trichloroacetic acid, the filtrate contains the acid-soluble pool (micromolecules such as glucose, amino acids, ATP, and vitamins), while the residue is the acid-insoluble fraction (macromolecules such as proteins, DNA, RNA, and polysaccharides).
Carbohydrates are aldoses or ketoses made of C, H, and O in the approximate ratio 1:2:1. They are classified as:
Lipids are not polymers in the strict sense. Triglycerides (fats/oils) consist of glycerol + 3 fatty acids via ester bonds. Phospholipids form the bilayer of cell membranes. Steroids (including cholesterol and hormones) and waxes are also lipids.
Proteins are polymers of amino acids joined by peptide bonds (formed between carboxyl group of one amino acid and amino group of the next, releasing water). There are 20 standard amino acids.
Protein structure is organised at four levels:
Enzymes are mostly proteins (exception: ribozymes = RNA catalysts). They lower activation energy without being consumed. Key terms:
Enzyme activity is affected by temperature (optimum ~37 °C in humans), pH, substrate concentration, and inhibitors (competitive vs non-competitive).
DNA and RNA are polymers of nucleotides. Each nucleotide = a nitrogenous base + a pentose sugar + a phosphate group.
DNA base pairing: A = T (2 hydrogen bonds), G ≡ C (3 hydrogen bonds). Adjacent nucleotides are connected by phosphodiester bonds.
Types of RNA and functions:
Metabolism is the sum total of all chemical reactions in the cell. It has two components:
ATP (adenosine triphosphate) is the universal immediate energy currency of the cell. Energy is stored in high-energy phosphate bonds. Electron carriers NADH and FADH₂ transfer reducing power during respiration.
The living state is a continuous state of chemical flux — steady-state reactions maintain order. A dead cell still has the same molecules for a while, but reactions stop because ATP is no longer regenerated.
Use this section after the first reading. It connects facts into mechanisms, comparisons, and NEET-style decision rules.
Most NEET biomolecule questions can be solved by matching monomer, polymer, and bond. Monosaccharides form polysaccharides through glycosidic bonds. Amino acids form proteins through peptide bonds. Nucleotides form nucleic acids through phosphodiester bonds. Fatty acids attach to glycerol by ester bonds.
Enzymes lower activation energy and are not consumed. Apoenzyme is the protein part alone, cofactor is the non-protein helper, and holoenzyme is the active complete enzyme. Competitive inhibitors compete with substrate at the active site, so increasing substrate concentration can reduce their effect. Non-competitive inhibitors bind elsewhere and change enzyme function.
Use this process after reading the notes. It turns NCERT lines into exam-ready recall, diagrams, and MCQ decisions.
Memory mistake: make a two-column comparison table.
Diagram mistake: redraw the labelled structure from memory.
Process mistake: rewrite the sequence with arrows.
Assertion-reason mistake: check truth of each statement first, then relation.
Practice these before starting MCQs. They are designed to lock core concepts with minimum theory load.
Peptide bond.
Nucleoside = base + sugar; nucleotide = base + sugar + phosphate.
Proteins.
No, lipids are not true polymers with repeating monomers.
Double-stranded DNA, where A = T and G = C.
Chapter note placement for Biomolecules.
Test your understanding of Biomolecules with focused sectional tests and a full-length NEET-style module test. Each chapter now runs 5 practice tests of 25 questions each, and every question has a 90-second timer — matching real NEET exam pacing.
5 chapter tests covering cell chemistry, carbohydrates and lipids, proteins and enzymes, nucleic acids, and metabolism — 25 NEET-style MCQs each.
Open Session TestsOne mixed module test on Biomolecules with 125 timed questions, answer review, and subtopic accuracy tracking.
Open Full MockInline banner shown in the practice section — high-intent placement for test-prep and coaching campaigns.
Move straight from chapter-wise questions into a subject test, then loop back into weaker areas instead of ending the session here.