Revision: Biomolecules Biology HSC Science (General) 11th Standard Maharashtra State Board

Metabolism is the sum of the chemical reactions that take place within each cell of a living organism and provide energy for vital processes and for synthesizing new organic material.

Nucleic acids are macromolecules composed of many small units or monomers called nucleotides.

Biomolecules are essential substances produced by our body which are necessary for life.

Carbohydrates that are amorphous solids, tasteless and insoluble in water are catled non-sugars.

Carbohydrates are optically active polyhydroxy aldehydes or polyhydroxy ketones or compounds that can be hydrolysed to polyhydroxy aldehydes or polyhydroxy ketones.

The sugars that reduce the Tollen's reagent and Fehling's solution are called reducing sugars.

Carbohydrates may be defined as optically active polyhydroxy aldehydes or ketones or compounds which produce such units on hydrolysis, such as cellulose, glycogen, starch, etc.

Carbohydrates that are crystalline solids, sweet in taste and soluble in water are called sugars.

Bifunctional organic compounds containing a carboxylic and an amino group either at the same carbon atom or at nearby carbon atoms are called amino acids.

Enzymes are biological catalysts that speed up chemical reactions in living cells without being consumed in the process.

Chemically proteins are polyamides which are high molecular weight polymers of the monomer units, i.e., α-amino acids. OR It can also be defined as proteins are the biopolymers of a large number of α-amino acids and they are naturally occurring polymeric nitrogenous organic compounds containing 16% nitrogen and peptide linkages (-CO-NH-)

The bond that connects α-amino acids to each other is called a peptide bond.

α-Amino acids are carboxylic acids having an amino (–NH₂) group bonded to the α-carbon, that is, the carbon next to the carboxyl (–COOH) group.

Proteins are complex polyamides formed from amino acids. They are essential for the proper growth and maintenance of the body. They have many peptide (-CO–NH )bonds.

Chemically, proteins are polyamides, which are high molecular weight polymers of the monomer units called \[\alpha\]-amino acids.

Nucleic acids are large biological macromolecules that store and transmit genetic information in living organisms.

The unit formed by joining the anomeric carbon of the furanose (sugar) with a nitrogen of a base is called nucleoside.

DNA is a double-stranded nucleic acid that stores and transmits hereditary information and can replicate itself.

A nucleotide is the basic structural unit of nucleic acids, composed of a nitrogenous base, a pentose sugar, and a phosphate group.

A nitrogenous base is an organic molecule (purine or pyrimidine) that carries genetic information in nucleic acids.

RNA is a single-stranded nucleic acid that helps in protein synthesis and information transfer.

A nucleoside consists of a nitrogenous base linked to a pentose sugar without a phosphate group.

A colloidal solution of protein which works as a biological catalyst is known as an enzyme.

A colloidal solution of protein which works as a biological catalyst is known as an enzyme.

A colloidal solution of protein which works as a biological catalyst is known as an enzyme.

• Biomolecules are of two main types: organic and inorganic.
• Organic biomolecules include macromolecules (polysaccharides, polypeptides, polynucleotides) and micromolecules (lipids and secondary metabolites).
• Polysaccharides are built from simple sugars; polypeptides from amino acids; polynucleotides from nucleotides.
• Lipids are formed from fatty acids and glycerol, and may be saturated or unsaturated.
• Inorganic biomolecules include prime elements (C, H, O), macro elements (N, P, K, Ca, Mg, S) and trace elements (e.g., Fe, Zn, Cu, B, Cl, Na, Mo, Ni, Si, Co).

• Carbohydrates are organic biomolecules made of C, H and O, usually fitting the general formula Cx(H₂O)y and existing as aldoses or ketoses.
• They are classified into monosaccharides, disaccharides and polysaccharides; monosaccharides cannot be hydrolysed further, disaccharides are formed by two monosaccharides via glycosidic bonds, and polysaccharides are long polymers.
• Some sugars like digitoxose (C₆H₁₂O₄) and rhamnose (C₆H₁₂O₅) do not obey the typical Cx(H₂O)y formula.
• All monosaccharides are reducing sugars because they possess a free aldehyde or ketone group.
• Cellulose is a linear polymer of β‑D‑glucose, unlike starch and glycogen, which are polymers of α‑glucose and show branching.
• Biologically, carbohydrates supply energy for metabolism; glucose is the main substrate for ATP synthesis, and lactose provides energy to infants.
• Polysaccharides such as starch and glycogen act as storage products and also contribute to structural components of cell membranes and cell walls.

• Lipids are esters of fatty acids with a hydrogen-to-oxygen ratio greater than 2:1.
• They are classified into simple lipids (fats and waxes), compound lipids (phospholipids, glycolipids, lipoproteins) and sterols (derived lipids).
• Simple lipids are esters of fatty acids with various alcohols, while compound lipids typically contain 1 glycerol, 2 fatty acids and either 1 phosphate group (phospholipid) or 1 simple sugar (glycolipid).
• Glycolipids, also called cerebrosides, are abundant in the myelin sheath of nerve cells.
• In plants, sterols occur as phytosterols; the yam plant (Dioscorea) yields the sterol diosgenin, used to manufacture birth‑control pills.

• Proteins are polymers of amino acids (polypeptides) in which amino acids are linked by peptide bonds.
• There are 20 types of amino acids, so proteins are heteropolymers (not homopolymers).
• Amino acids are of two types: essential (must be obtained from diet) and non-essential (can be synthesised in the body).
• Proteins are high molecular weight biomolecules (polyamides) made of α-amino acids with a general structure R-CH(NH₂)-COOH.
• Proteins perform various functions such as enzymatic activity, transport, hormonal regulation, immunity, and sensory reception.
• Proteins are of two main types: fibrous proteins (insoluble, structural, e.g., keratin) and globular proteins (soluble, functional, e.g., enzymes, insulin).
• Collagen is the most abundant protein in animals, while RuBisCO is the most abundant enzyme in the biosphere.

• Nucleic acids are biomacromolecules present in the acid-insoluble fraction and are responsible for the storage and transmission of genetic information (DNA and RNA).
• They are polynucleotides, formed by repeated units called nucleotides.
• Each nucleotide consists of three components: a nitrogenous base, a pentose sugar, and a phosphate group.
• Nitrogenous bases are of two types: purines (adenine, guanine) and pyrimidines (cytosine, thymine, uracil).
• The sugar present is either ribose (in RNA) or 2′-deoxyribose (in DNA).
• DNA is double-stranded and contains bases A, T, G, and C, while RNA is single-stranded and contains A, U, G, and C.
• DNA stores genetic information, while RNA plays a key role in protein synthesis and the expression of genetic information.

• Enzymes are biological catalysts, mostly proteins, that increase the rate of biochemical reactions without being consumed.
• Some enzymes are ribozymes, which are RNA molecules that act like enzymes.
• Enzymes have primary, secondary, and tertiary structures, and their 3D structure determines their specificity and function.
• Each enzyme has a specific active site where the substrate binds to form an enzyme–substrate complex.
• Enzymes are highly specific and lower the activation energy of reactions.
• Enzyme activity is affected by temperature and pH; most enzymes are denatured at high temperatures, while thermophilic enzymes remain stable at 80–90°C.
• Examples of enzymes include amylase (starch → glucose), pepsin (proteins → amino acids), lactase (lactose → glucose + galactose), and maltase (maltose → glucose).

Mechanism of Enzyme Action (Lock and Key model):

1. Enzyme (E) binds to substrate (S) → ES complex (E + S → ES)
2. Product formation: ES → EP
3. Product released: EP → E + P (enzyme regenerated)

• Enzymes work best at 298 K to 313 K (25°C to 40°C) — optimum temperature
• Activity decreases with temperature increase or decrease beyond optimum range; stops at ~273 K

• ES Complex Formation - Substrate (S) binds to the active site of the enzyme (E) to form a highly reactive but short-lived Enzyme-Substrate (ES) complex.
• Induced Fit - Binding of substrate induces the enzyme to alter its shape, fitting more tightly around the substrate.
• Bond Breaking - The active site, now close to the substrate, breaks the chemical bonds of the substrate, forming an Enzyme-Product (EP) complex.
• Product Release - The enzyme releases the product (P) and returns to its original free form, ready to bind another substrate molecule.
• Catalytic Cycle - E + S → ES → EP → E + P. The enzyme is unchanged at the end and repeats the cycle again and again.

• Enzymes are biological catalysts, mostly proteins, that increase the rate of biochemical reactions without being consumed.
• Some enzymes are ribozymes, which are RNA molecules that act like enzymes.
• Enzymes have primary, secondary, and tertiary structures, and their 3D structure determines their specificity and function.
• Each enzyme has a specific active site where the substrate binds to form an enzyme–substrate complex.
• Enzymes are highly specific and lower the activation energy of reactions.
• Enzyme activity is affected by temperature and pH; most enzymes are denatured at high temperatures, while thermophilic enzymes remain stable at 80–90°C.
• Examples of enzymes include amylase (starch → glucose), pepsin (proteins → amino acids), lactase (lactose → glucose + galactose), and maltase (maltose → glucose).

Mechanism of Enzyme Action (Lock and Key model):

1. Enzyme (E) binds to substrate (S) → ES complex (E + S → ES)
2. Product formation: ES → EP
3. Product released: EP → E + P (enzyme regenerated)

• Enzymes work best at 298 K to 313 K (25°C to 40°C) — optimum temperature
• Activity decreases with temperature increase or decrease beyond optimum range; stops at ~273 K

• Enzymes are biological catalysts, mostly proteins, that increase the rate of biochemical reactions without being consumed.
• Some enzymes are ribozymes, which are RNA molecules that act like enzymes.
• Enzymes have primary, secondary, and tertiary structures, and their 3D structure determines their specificity and function.
• Each enzyme has a specific active site where the substrate binds to form an enzyme–substrate complex.
• Enzymes are highly specific and lower the activation energy of reactions.
• Enzyme activity is affected by temperature and pH; most enzymes are denatured at high temperatures, while thermophilic enzymes remain stable at 80–90°C.
• Examples of enzymes include amylase (starch → glucose), pepsin (proteins → amino acids), lactase (lactose → glucose + galactose), and maltase (maltose → glucose).

Mechanism of Enzyme Action (Lock and Key model):

1. Enzyme (E) binds to substrate (S) → ES complex (E + S → ES)
2. Product formation: ES → EP
3. Product released: EP → E + P (enzyme regenerated)

• Enzymes work best at 298 K to 313 K (25°C to 40°C) — optimum temperature
• Activity decreases with temperature increase or decrease beyond optimum range; stops at ~273 K

• Increasing substrate concentration raises enzyme activity only up to a maximum, after which the rate levels off because all active sites become saturated.
• Increasing enzyme concentration generally increases the reaction rate, as more active sites are available for substrate binding.
• Enzyme activity is highest at an optimum temperature; high temperatures denature enzymes (destroy higher‑level structure), while low temperatures reduce their activity.
• Each enzyme has its own optimum pH range; outside this range, activity falls sharply and the enzyme may not function.
• Co‑enzymes, activators and inhibitors also affect enzyme activity: activators (often inorganic ions) enhance activity, inhibitors decrease it, and many enzymes function as a combination of apoenzyme plus co‑enzyme.

• Metabolism is the sum of all biochemical reactions in a cell, including breakdown (catabolism) and synthesis (anabolism) of biomolecules.
• Catabolism releases energy by degrading complex molecules, while anabolism uses energy to build complex molecules from simpler ones.
• Primary metabolites are compounds essential for normal growth and physiology, commonly found in animal tissues (e.g., amino acids, sugars, organic acids).
• Secondary metabolites are mainly found in plant, fungal and bacterial cells and are not directly required for basic survival.
• Important groups of secondary metabolites include terpenes (e.g., carotenoids, rubber), phenolics (e.g., flavonoids, tannins) and nitrogen‑containing compounds (e.g., alkaloids, cyanogenic glycosides).

• Metabolism is the sum of all biochemical reactions in a cell, including breakdown (catabolism) and synthesis (anabolism) of biomolecules.
• Catabolism releases energy by degrading complex molecules, while anabolism uses energy to build complex molecules from simpler ones.
• Primary metabolites are compounds essential for normal growth and physiology, commonly found in animal tissues (e.g., amino acids, sugars, organic acids).
• Secondary metabolites are mainly found in plant, fungal and bacterial cells and are not directly required for basic survival.
• Important groups of secondary metabolites include terpenes (e.g., carotenoids, rubber), phenolics (e.g., flavonoids, tannins) and nitrogen‑containing compounds (e.g., alkaloids, cyanogenic glycosides).