Chemistry 2 Marks Questions

1. The chemical name of vitamin A is retinol.

The deficiency of vitamin A leads to xerophthalmia and night blindness. Important Sources of Vitamin ‘A’: Milk, butter, egg, fish, and fish oil (Cod liver oil). It can also be synthesised in the body from carotenoids present in carrots, tomatoes, ripe mangoes etc. Carotenoids are the precursors of vitamin A.

2. The chemical name of vitamin C is ascorbic acid. The deficiency of vitamin C leads to scurvy.

Important Sources of Vitamin C: Citrus fruits (oranges, lemon, grape fruit, lime etc.), amla, cabbage, guava etc.

Essential amino acids : Those amino acids which are not synthesised by our body are called essential amino acids. They must be part of our diet. Their deficiency leads to diseases such as Kwashiorkor (water balance in the body is disturbed). Valine, leucine, isoleucine, phenyl alanine, methionine, tryptophan, threonine, lyslne, arginine and histadine are ten essential amino acids.
Non-essential amino acids: The amino acids, which can be synthesised in the body, are known as non - essential amino acid. They are also called dispersable amino acids e.g., glycine, alanine, seriqe, cysteine, glutamine, tyrosine, proline, aspartic acid, asparagine, glutamic acid.

Difference between globular protein and fibrous protein:

	Fibrous protein	Globular protein
1.	It is a fibre-like structure formed by the polypeptide chain. These proteins are held together by strong hydrogen and disulphide bonds.	The polypeptide chain in this protein is folded around itself, giving rise to a spherical Structure.
2.	It is usually insoluble in water, but soluble in strong acids and bases.	It is usually soluble in water, acids, bases and salts.
3.	They have comparatively stronger intermolecular forces of attraction.	They have weak intermolecular hydrogen bonding.
4.	Example: Collagen, fibroin, myosin, hair, skin,silk, wool, etc.	Egg, albumin, casein of milk, insulin.

Monosaccharides: Ribose, 2-deoxyribose, galactose and fructose.
Disaccharides: Maltose and lactose.

Two major functions of carbohydrates in plants are following:

1. Structural material for plant cell walls: The polysaccharide cellulose acts as the chief structural material of the plant cell walls.
2. Reserve food material: The polysaccharide starch is the major reserve food material in the plants. It is stored in seeds and act as the reserve food material for the tiny plant till it is capable of making its own food by photosynthesis.

Complete hydrolysis of RNA yields a pentose sugar (D-ribose), phosphoric acid and nitrogen containing heterocyclic compounds (called bases). Such as guanine (G), cytosine (C), Uracil (U), Adenine (A).
There is no relationship among the quantities of four bases obtained on complete hydrolysis of RNA. It is because base sequence in RNA is not fixed but depends on base sequence in DNA i.e., the base sequence in a specific RNA is controlled by that of DNA which is controlling RNA synthesis (i.e., transcription). The base sequence in DNA indirectly controls the sequence of amino acids in the protein.

Vitamins are classified into two groups depending upon their solubility in water or fat.

1. Fat soluble vitamins: Vitamins which are soluble in fat and oils but insoluble in water. These are Vitamins A, D, E, and K.
2. Water soluble vitamins: Vitamins which are soluble in water. These are B group vitamin and vitamin C.

Vitamin K is responsible for the coagulation of blood.

The structural differences between DNA and RNA are as follows:
The functional differences between DNA and RNA are as follows:

	DNA	RNA
1.	DNA is the chemical basis of heredity.	RNA is not responsible for heredity.
2.	DNA molecules do not synthesise proteins, but transfer coded message for the synthesis of proteins in the cells.	Proteins are synthesised by RNA molecules in the cells.

Nucleic acids are biomolecules found in the nuclei of all living cells, as one of the constituents of chromosomes. There are mainly two types of nucleic acids - deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are also known as polynucleotides as they are longchain polymers of nucleotides.
Two main functions of nucleic acids are:

1. DNA is responsible for the transmission of inherent characters from one generation to the next. This process of transmission is called heredity.
2. Nucleic acids (both DNA and RNA) are responsible for protein synthesis in a cell. Even though the proteins are actually synthesised by the various RNA molecules in a cell, the message for the synthesis of a particular protein is present in DNA.

In DNA, sugar is Deoxyribose while in RNA, it is ribose./DNA is as double stranded while RNA is single stranded. The common bases present in both are adenine, cytosine & guanine.

1. Peptide linkage: A link between two amino acids with loss of water/–CO-NH –.
2. The six-membered cyclic structure of glucose is called pyranose structure in analogy with pyran heterocyclic compound/or structure.

Fat soluble; Vitamin A, D, E and K.

Name	Sources	Deficiency diseases
Vit. A	Milk, butter, kidneys, egg yolk, liver, fish oil, etc.	Xerophthalmia-night-blindness.
Vit. D	Butter, liver, kidneys, egg yolk, fish oil, etc.	Rickets, osteomalacia.
Vit. E group	Green vegetables, oil, egg yolk, wheat, animal tissues.	Sterility (impotency) and muscular atrophy.
Vit. K	Carrots, lettuce, cabbage, tomatoes, liver, egg yolk, cheese; synthesized by colon bacteroa.	Haemorrhages, excessive bleeding in injury, poor coagulation of blood.

The four bases present in DNA are Adenine, Guanine, Thymine and Cytosine Thymine is not present in RNA.

1. Peptide linkage: A link between two amino acid with loss of water.

-CO-NH-

Peptide Linkage

2. Biocatalysts: Are the catalysts which increase the rate of metabolism./biochemicalreactions.

Amino acids which must be supplied in our diet are called Essential Amino Acids eg. Leucine, Isoleucine, Valine.
Amino acids which can be made by our bodies and not required in our diet are called non-essential Amino Acids eg. Glycine, Alanine.

Products of hydrolysis of sucrose are: Glucose and Fructose. Becuase Carbonyl group of sucrose is not free.

1. Invert sugar: Hydrolysis of sucrose brings about a change in a sign of rotation from dextro (+) to laevo (-) and the product is named as invert sugar.
2. Polypeptides are the polymers of amino acids.

Vitamin B and vitamin C are soluble in water.Deficiency diseases due to vitamin B are: Beri Beri, Cheilosis, Convulsions, Pernicious anaemia
Deficiency diseases due to vitamin C is: Scurvy
Sources of vitamin B: milk/yeast/green vegetables/cereals.
Source of vitamin C: citrus fruits.

1. Peptide linkage: A link formed between two amino acids with loss of water.

- CO - NH -

Peptide linkage.

2. Glycosidic linkage: A link in two monosaccharides units through oxygen atom. For ex. in a disaccharide.

A zwitter ion is a dipolar ion formed by neutralisation of acidic and basic centres present within the molecule.

Tertiary structure of protein includes folding and twisting of secondary structure of proteins. It has compact and folded structure. It involves H-bonding, disulphide linkage, ionic or salt bridges and hydrophobic interactions.

Avitaminosis: Lack of more than one vitamin causes multiple deficiency diseases called avitaminosis.

Nucleoside consists of a base joined to sugar molecule, e.g., adenosine contains adenine and ribose, guanosine contains guanine and ribose, cytidine contains cytosine and ribose.

The pH at which there is no net migration of the amino acid under the influence of an applied electric field is called isoelectric point. For example, the isoelectric point of glycine is 6.1.

Polypeptide: If more than ten a-amino acids are joined together by peptide bond (-CONH-) the polyamide thus formed is called polypeptide.

The spontaneous change of specific rotation of an optically active substance with time is called mutarotation.

Amino acids behave like salts rather than simple amines or carboxylic acids. This behaviour is due to the presence of both acidic (carboxyl group) and basic (amino group) groups in the same molecule. In aqueous solution, the carboxyl group can lose a proton and amino group can accept a proton, giving rise to a dipolar ion known as zwitter ion.

Polysaccharides are the carbohydrates which on hydrolysis give a large number of molecules of monosaccharides. For example, starch or cellulose.

Van der Waals interactions, disulphide bridges, dipolar interactions (ionic) and hydrogen bonding.

1. Carbohydrates act as biofuel to provide energy for functioning of living organisms.
2. They act as constituents of cell walls.

1. Peptide linkage.
2. Protein synthesis occurs at the ribosome in the cytoplasm.

Cellulose is a linear polymer made up of D-(+)-glucose molecules linked by bglycosidic bonds.

Amino acids are the building blocks of proteins which are essential for the growth and maintenance of life.

Amylose is water soluble linear polymer of a-glucose. Amylopectin is water insoluble branched chain polymer of a-glucose.

The sequence in which amino acids are linked together with the help of peptide bonds form native state of protein.

Protein found in a biological system with a unique three-dimensional structure and biological activity is called a native protein. When a protein in its native form, is subjected to physical change like change in temperature or chemical change like change in pH, the hydrogen bonds are disturbed. Due to this, Globules unfold and helix gets uncoiled and protein loses its biological activity. This is called denaturation of protein.

When an egg is boiled, the soluble globular protein, albumin present in it is converted into insoluble fibrous protein. During this denaturation (i) biological activity is lost and (ii) secondary and tertiary structures of albumin protein are destroyed while the primary structure (representing the sequence of amino acids) remains intact.

Anomers are stereoisomers which differ in orientation of -OH only around C-l, e.g., a-glucose and b-glucose.

Sucrose is dextrorotatory but on hydrolysis it gives an equimolar mixture of D-(+)- glucose and D-(-)-fructose which is laevorotatory. This change of specific rotation from dextrorotation to laevorotation is known as inversion of sugar.

During osazone formation, the reaction occurs only at C-1 and C-2. As glucose and fructose differ from each other only in the arrangement of atoms at C-1 and C-2, therefore they give the same osazone.

Enzymes are globular proteins which are biological catalysts. They are highly specific in their action.

• Purines: adenine and guanine.
• Pyrimidines: cytosine and thymine in DNA and cytosine and uracil in RNA.