Biomolecules Class 11 Notes Biology Chapter 9 - CBSE

Chapter : 9

What Are Biomolecules ?

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    (Organic molecule produced in living cell)

    • Molecular Weight < 1000 Daltons
    • Polysaccharide , protein , nucleic acid, lipid
    • Molecular Weight > 1000 Daltons
    • Monosaccharide , Amino acids, nucleotides

    Average composition of cells

    Component % of the total cellular mass
    Water 70-90
    Proteins 10-15
    Carbohydrates 3
    Lipids 2
    Nucleic acids 5-7
    Ions 1


    It is large, complex molecule that play very important role in our body.

    Types Of Proteins


    (made up of only amino acids)


    Long, Coiled and Thread like

    • Collagen
      • Most abundant protein in animal body
      • Present in connective tissue
      • Threads of collagen known as Tendon
    • Elastin
      • In connective tissue
      • Threads of Elastin known as Ligament
    • Keratin


    • Rubisco
      • Present in chloroplast.
      • Most abundant protein on the earth
    • Albumin
      • Maintain B.C.O.P
      • In milk as Lactoalbumin
      • In egg yolk as Ovabumin
      • In blood as Serum albumin
    • Globin
      • Present with Haemoglobin
    • Histone protein
      • Present with eukaryotic DNA
      • In it Lysine and Arginine amino acids are present in more amount.
    • Compound
    • Derived


    They are sugar molecules and acts as an energy source, help to control blood glucose and insulin metabolism.

    Carbohydrate (Hydrates of carbon, CnH2nOn)


    (sweet in taste)

    • Glucose
    • Fructose
    • Galactose

    (made by two monosaccharaides)

    •  Maltose= Glucose + Glucose
    • Lactose= Glucose + Galactose
    • Sucrose = Glucose + Fructose

    Polysaccharides (made by thousands of monosaccharaides, also called glycan).

    Amino Acids (General Structure, Classification, Significance)

    Based on structure & chemical nature

    • Aliphatic side chain Glycine, Alanine, Valine, Leucine, isoleucine
    • OH group containing AA Serine, Threonine
    • “S” containing AA cysteine, Methionine
    • Acidic amino acids Aspartic acid, Asparagine, Glutamic acid, Glutamine
    • Basic amino acids Histidine, Arginine, Tyrosine, Lysine
    • Aromatic amino acids Phenylamine. Tyrosine, Tryptophan
    • Imino acids Proline

    Based on Polarity

    • Hydrophilic (polar)
    • Hydrophobic (Non-polar)

    Based on Metabolic fate

    • Glucogenic
    • Ketogenic
    • Both

    Nutritional Classification

    • Essential
      • Phenylalanine, Valine Tryptophan PVT.
      • Threonine Isoleucine Methionine TIM
      • Histidine Arginine Leucine Lysine HALL
    • Nonessential
    • Semi essential


    They are fatty compounds that perform a variety of functions in our body. They are part of the cell membranes and help to control what goes in and out of the cells.

    Nucleic Acid

    Nucleic acids are polynucleotides. A nucleic acid has three chemical distinct components-heterocyclic compound (nitrogenous base), polysaccharides (ribose/ deoxyribose sugar) and phosphate or phosphoric acid.

    Nitrogenous Base

    • Adenine
    • Guanine
    • Cytosine
    • Thymine
    • Uracil

    Nucleic Acids


    Three types

    • mRNA
    • rRNA
    • tRNA
    • Genetic material in eukaryotes
    • Helical chains are bonded by hydrogen bonds between the nitrogenous bases
    • Double bonds between adenine and thymine
    • Triple bonds between guanine and cytosine

    Base in Nucleic Acids






    Proteinaceous substances which are capable of catalyzing chemical reactions of biological origin without themselves undergoing any change. They are commonly referred as biocatalysts. Nucleic acids that behave like enzymes are called ribozymes.

    $$\text{E + S} \rightleftharpoons \text{ES} \rightleftharpoons \text{EP} \rightleftharpoons \text{E + P} $$

    Factor That Affect Enzyme Activity

    • Temperature
    • pH
    • Concentration of enzymes and substrates
    • Inhibitors

    Types of Enzymes

    • Oxidoreductases
    • Transferases
    • Hydrolases
    • Lyases
    • Isomerases
    • Ligases


    Non- protein constituents that are bound to the enzyme and make the enzyme catalytically active.


    Compounds that bind to the enzyme transiently during the course of the reaction.

    Prosthetic Groups

    Organic substances that are bound very tightly to the enzyme.