Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 14 Biomolecules Notes

Bio chemistry: The field of studying about the chemistry behind the biological processes is called bio chemistry.

Carbohydrates: Carbohydrates are the most abundant organic compounds in every living organism. They are also known as saccharides. In general carbohydrates are hydrates of carbon, containing hydrogen and oxygen in the same ratio as in water. They are also defined as polyhydroxy aldehydes or ketones.

Dextro rotatory: Dextro rotatory compounds rotate the plane of plane polarised light in clockwise direction. Dextro rotatory compounds are represented as D – (+).

Levo rotatory: Levo rotatory compounds rotate the plane of plane polarised light is anticlockwise direction. Levo rotatory compounds are represented as L – (-).

Monosaccharides: Monosaccharides are carbohydrates that cannot be hydrolysed further and are also called simple sugars. Monosaccharides have general formula Cn(H20)n. While there are many monosaccharides known only about 20 of them occur in nature. Some common examples are glucose, fructose, ribose, erythrose.

Glucose: It is a simple sugar. It is present in honey, sweet fruits such as grapes and mangoes etc therefore glucose is also called as grape sugar. Human blood contains about lOOmg/dL of glucose.

Anomers: The conversion of the achiral aldehyde carbon into a chiral one leading the possibility two isomers. These two isomers differ only in the configuration of Cj – carbon. These isomers are called anomers.

Mutarotation: The slow interconversion of a – D glucose and p – D glucose via open chain form untill equilibrium is established giving constant specific rotation (+53°). This phenomenon is called mutarotation.

Epimerisation: Sugar differing in configuration at an asymmetric centre is known as epimers. The process by which one epimer is converted into other is called epimerisation.

Bio chemistry: The field of studying about the chemistry behind the biological processes is called bio chemistry.

Carbohydrates: Carbohydrates are the most abundant organic compounds in every living organism. They are also known as saccharides. In general carbohydrates are hydrates of carbon, containing hydrogen and oxygen in the same ratio as in water. They are also defined as polyhydroxy aldehydes or ketones.

Dextro rotatory: Dextro rotatory compounds rotate the plane of plane polarised light in clockwise direction. Dextro rotatory compounds are represented as D – (+).

Levo rotatory: Levo rotatory compounds rotate the plane of plane polarised light is anticlockwise direction. Levo rotatory compounds are represented as L – (-).

Monosaccharides: Monosaccharides are carbohydrates that cannot be hydrolysed further and are also called simple sugars. Monosaccharides have general formula Cn(H20)n. While there are many monosaccharides known only about 20 of them occur in nature. Some common examples are glucose, fructose, ribose, erythrose.

Glucose: It is a simple sugar. It is present in honey, sweet fruits such as grapes and mangoes etc therefore glucose is also called as grape sugar. Human blood contains about lOOmg/dL of glucose.

Anomers: The conversion of the achiral aldehyde carbon into a chiral one leading the possibility two isomers. These two isomers differ only in the configuration of Cj – carbon. These isomers are called anomers.

Mutarotation: The slow interconversion of a – D glucose and p – D glucose via open chain form untill equilibrium is established giving constant specific rotation (+53°). This phenomenon is called mutarotation.

Epimerisation: Sugar differing in configuration at an asymmetric centre is known as epimers. The process by which one epimer is converted into other is called epimerisation.

Bio chemistry: The field of studying about the chemistry behind the biological processes is called bio chemistry.

Carbohydrates: Carbohydrates are the most abundant organic compounds in every living organism. They are also known as saccharides. In general carbohydrates are hydrates of carbon, containing hydrogen and oxygen in the same ratio as in water. They are also defined as polyhydroxy aldehydes or ketones.

Dextro rotatory: Dextro rotatory compounds rotate the plane of plane polarised light in clockwise direction. Dextro rotatory compounds are represented as D – (+).

Levo rotatory: Levo rotatory compounds rotate the plane of plane polarised light is anticlockwise direction. Levo rotatory compounds are represented as L – (-).

Monosaccharides: Monosaccharides are carbohydrates that cannot be hydrolysed further and are also called simple sugars. Monosaccharides have general formula Cn(H20)n. While there are many monosaccharides known only about 20 of them occur in nature. Some common examples are glucose, fructose, ribose, erythrose.

Glucose: It is a simple sugar. It is present in honey, sweet fruits such as grapes and mangoes etc therefore glucose is also called as grape sugar. Human blood contains about lOOmg/dL of glucose.

Anomers: The conversion of the achiral aldehyde carbon into a chiral one leading the possibility two isomers. These two isomers differ only in the configuration of Cj – carbon. These isomers are called anomers.

Mutarotation: The slow interconversion of a – D glucose and p – D glucose via open chain form untill equilibrium is established giving constant specific rotation (+53°). This phenomenon is called mutarotation.

Epimerisation: Sugar differing in configuration at an asymmetric centre is known as epimers. The process by which one epimer is converted into other is called epimerisation.

Fructose: Fructose is another commonly known monosaccharide having the same molecular formula as glucose. It is laevorotatory and a ketohexose. It is present abundantly in fruits and hence it is also called as fruit sugar.

Disaccharides: They are sugars that yield two molecules of monosaccharides on hydrolysis. This reaction is usually catalysed by dilute acid or enzyme. In disaccharides two monosaccharides are linked by oxide linkage called glycosidic linkage.

Invert sugar: During hydrolysis of sucrose the optical rotation of the reaction mixture changes from dextro to levo. Hence, sucrose is also called invert sugar.

Polysaccharides: Polysaccharides consist of large number of monosaccharide units bonded together by glycosidic bonds and are the most common form of carbohydrates. Since, they do not have sweet taste polysaccharides are called as non-sugars. They form linear and branched chain molecules.

Starch: Starch is used for energy storage in plants. Potatoes, com, wheat and rice are the rich sources of starch. It is a polymer of glucose in which glucose molecules are lined by a(l,4) glycosidic bonds. Starch can be separated into two fractions namely, water soluble amylose and water insoluble amylopectin. Starch contains about 20 % of amylase and about 80% of amylocpectin.

Cellulose : Cellulose is the major constituent of plant cell walls. Cotton is almost pure cellulose. On hydrolysis cellulose yields D-glucose molecules. Cellulose is a straight chain polysaccharide. The glucose molecules are linked by P(l,4) glycosidic bond.

Glycogen: Glycogen is the storage polysaccharide of animals. It is present in the liver and muscles of animals. Glycogen is also called as animal starch. On hydrolysis it gives glucose molecules.

Importance of carbohydrates:

  1. Carbohydrates, widely distributed in plants and animals, acts mainly as energy sources and structural polymers.
  2. Carbohydrate is stored in the body as glycogen and in plant as starch.
  3. Carbohydrates such as cellulose which is the primary components of plant cell wall, is used to make paper, furniture (wood) and cloths (cotton)
  4. Simple sugar glucose serves as an instant source of energy.
  5. Ribose sugars are one of the components of nucleic acids.
  6. Modified carbohydrates such as hyaluronate (glycosaminoglycans) act as shock absorber and lubricant.

Proteins: Proteins are most abundant biomolecules in all living organisms. The term protein is derived from Greek word “proteious” meaning primary or holding first place.

Amino acids: Amino acids are compounds which contain an amino group and a carboxylic acid group.

Isoelectric point: At a specific pH value the net charge of an amino acid is neutral is called isoelectric point.

Peptide bond: The carboxyl group of the first amino acid react with the amino group of the second amino acid to give an amide linkage between these amino acids. This amide linkage is called peptide bond.

Denaturation: The process of protein losing its higher order structure without losing the primary structure is called denaturation.

Importance of proteins:

  1. All biochemical reactions occur in the living systems are catalysed by the catalytic proteins called enzymes.
  2. Proteins such as keratin, collagen acts as structural back bones.
  3. Proteins are used for transporting molecules (Haemoglobin), organelles (Kinesins) in the cell and control the movement of molecules in and out of the cells (Transporters). ‘
  4. Antibodies help the body to fight various diseases
  5. Proteins are used as messengers to coordinate many functions. Insulin & glucagon controls the glucose level in the blood.
  6. Proteins act as receptors that detect presence of certain signal molecules and activate the proper response.
  7. Proteins are also used to store metals such as iron (Ferritin) etc.

Enzymes: There are many biochemical reactions that occur in our living cells. Digestion of food and harvesting the energy from them, and synthesis of necessary molecules required for various cellular functions are examples for such reactions. All these reactions are catalysed by special proteins called enzymes.

Lipids: They are organic molecules that are soluble in organic solvents such as chloroform and methanol and are insoluble in water. The word lipid is derived from the Greek word ‘lipos’ meaning fat.

Biological importance of lipids:

  1. Lipids are the integral component of cell membrane. They are necessary of structural integrity of the cell.
  2. The main function of triglycerides in animals is as an energy reserve. They yield more energy than carbohydrates and proteins.
  3. They act as protective coating in aquatic organisms.
  4. Lipids of connective tissue give protection to internal organs.
  5. Lipids help in the absorption and transport of fat soluble vitamins.
  6. They are essential for activation of enzymes such as lipases.
  7. Lipids act as emulsifier in fat metabolism.

Vitamins: Vitamins are small organic compounds that cannot be synthesised by our body but are essential for certain function.

Fat soluble vitamins: These vitamins absorbed best when taken with fatty food and are stored in fatty tissues and livers. These vitamins do not dissolve in water. Hence they are called fat soluble vitamins. Vitamin A, D, E & K are fat-soluble vitamins.

Water soluble vitamins: Vitamins B and C are readily soluble in water.

Nucleic acids: The inherent characteristics of each and every species are transmitted from one generation to the next. It has been observed that the particles in nucleus of the cell are responsible for the transmission of these characteristics. They are called chromosomes and are made up of proteins and another type of biomolecules called nucleic acids.

Nucleosides and nucleotides: The molecule without the phosphate group (molecule consists of sugar and base only) is called a nucleosides. A nucleotide is derived from a nucleoside by the addition of a molecule of phosphoric acid or phosphate unit.

Types of RNA molecules: RNA molecules are classified according to their structure and function into three major types,

  1. Ribosomal RNA (r-RNA)
  2. Messenger RNA (m-RNA)
  3. Transfer RNA (t-RNA) ‘

DNA finger printing: One of the most accurate methods for placing an individual at the scene of a crime has been a fingerprint. With the advent of recombinant DNA technology, a more powerful tool is now available is called DNA finger printing.

Hormones: Hormone is an organic substance that is secreted by one tissue into the blood system and induces a physiological response in other tissues. It is an intercellular signalling molecule.

Samacheer Kalvi 12th Chemistry Notes

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