What Are Biomolecules? Carbohydrates, Proteins and Nucleic Acids
Chemistry · Biomolecules · NEET
Biomolecules are the carbon-based compounds that make up every living cell. The four main types you must know for NEET are carbohydrates (energy, made of sugar units), proteins (built from amino acids), nucleic acids (DNA and RNA, which carry genes), plus helpers like lipids and vitamins. Memory hook: "Cells Prefer Not Losing Vitamins" = Carbohydrate, Protein, Nucleic acid, Lipid, Vitamin.
The main biomolecules and the small building blocks they break down into: carbohydrates to monosaccharides, proteins to amino acids (joined by peptide bonds), and nucleic acids to nucleotides.
Your doubts, answered
What exactly is a biomolecule? Is it different from a normal molecule?
A biomolecule is just an organic (carbon-based) molecule that is made by, or found inside, a living body. It is not a special kind of atom. The difference is where it comes from and what job it does: biomolecules like glucose, insulin and DNA run life processes. So a biomolecule follows the same chemistry rules you already learned, it just works inside cells.
What are the four main types of biomolecules I need for NEET?
Carbohydrates (like glucose and starch, mainly for energy), Proteins (made of amino acids, they build tissue and act as enzymes), Nucleic acids (DNA and RNA, they store and pass on genetic information), and Lipids (fats, used for energy and cell membranes). NCERT also discusses Vitamins and hormones. For the exam, carbohydrates, proteins and nucleic acids get the most questions.
How do I tell carbohydrates, proteins and nucleic acids apart?
Look at the building block. Carbohydrates are built from sugar units (monosaccharides like glucose). Proteins are built from amino acids joined by peptide bonds. Nucleic acids are built from nucleotides (a base + a sugar + phosphate). Different building block means different biomolecule.
Are lipids, vitamins and hormones biomolecules too?
Yes. Lipids (fats and oils), vitamins and hormones are all biomolecules because they are organic molecules that living systems use. NCERT lists carbohydrates, proteins, nucleic acids, lipids, vitamins and hormones. But most NEET questions focus on carbohydrates, proteins and nucleic acids, so study those in the most depth.
Why is 'DNA to RNA to Protein' important? What is the central dogma?
The central dogma is the direction that genetic information flows: DNA makes RNA, and RNA makes protein (DNA to RNA to Protein). It links two biomolecules directly, nucleic acids control which proteins are built. NEET has asked this exact flow, so memorise the order and the direction.
⚠️ The NEET trap ✗ Amino acids in a protein are joined by glycosidic bonds (because sugars use glycosidic bonds too). ✓ Amino acids in a protein are joined by peptide bonds (an amide -CO-NH- linkage). Glycosidic bonds join sugar units in carbohydrates, not amino acids. 🧠 Match the bond to the biomolecule: Peptide = Protein, Glycosidic = carbohydrate (suGar), Phosphodiester = nucleic acid.
Real NEET questions
NEET 2016
In a protein molecule various amino acids are linked together by:
A · alpha-glycosidic bond
B · beta-glycosidic bond
C · Peptide bond ✓
D · Dative bond
Solution: A peptide bond is an amide linkage (-CO-NH-) formed when the -COOH of one amino acid joins the -NH2 of the next amino acid, losing one water molecule. This is the bond that links amino acids into proteins. Glycosidic bonds join sugar units in carbohydrates, and a dative (coordinate) bond is a shared electron pair donated by one atom, neither of these links amino acids. So the answer is C.
NEET 2016
The correct statement regarding RNA and DNA, respectively is:
A · The sugar in RNA is arabinose and in DNA is 2'-deoxyribose
B · The sugar in RNA is ribose and in DNA is 2'-deoxyribose ✓
C · The sugar in RNA is arabinose and in DNA is ribose
D · The sugar in RNA is 2'-deoxyribose and in DNA is arabinose
Solution: RNA and DNA are both nucleic acids, but their pentose sugar differs. RNA contains D-ribose, which has an -OH group at the C-2' position. DNA contains 2'-deoxyribose, where that C-2' -OH is replaced by -H (deoxy means 'missing one oxygen'). Arabinose is in neither. So option B is correct.
NEET 2016
The central dogma of molecular genetics states that the genetic information flows from:
A · Amino acids to Proteins to DNA
B · DNA to Carbohydrates to Proteins
C · DNA to RNA to Proteins ✓
D · DNA to RNA to Carbohydrates
Solution: The central dogma describes the one-way flow of genetic information between biomolecules. DNA is first transcribed into RNA, and that RNA is then translated into protein: DNA to RNA to Proteins. Carbohydrates carry no genetic information, so any option with carbohydrates is wrong. The answer is C.
Solved Biomolecules NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Biomolecules are organic, meaning they are built around carbon atoms. Carbohydrates, proteins, nucleic acids and lipids all have carbon skeletons. Water and mineral salts are inorganic and support life but are not counted as the main biomolecules.
Which biomolecule stores genetic information?
Nucleic acids do. DNA stores the genetic code, and RNA helps carry that code to make proteins. This is why the central dogma is written DNA to RNA to Protein.
What is the smallest unit of each biomolecule?
Carbohydrates break down to monosaccharides (like glucose). Proteins break down to amino acids. Nucleic acids break down to nucleotides. Lipids give fatty acids and glycerol.
Why are biomolecules important for NEET?
Biomolecules is a full NCERT chapter and NEET asks 1 to 2 direct questions from it almost every year, often on bond types, DNA vs RNA, and reducing sugars. The facts are memory-based and scoring, so it is high value for low effort.
