11th Class

Dauclax, (1883) introduced the nomenclature of enzyme. Usually enzyme names end in suffix-ase to the name of substrate e.g., Lactase acts on lactose, maltase act on maltose, amylase on amylose, sucrase on sucrose, protease on proteins, lipase on lipids and cellulase on cellulose. Sometimes arbitrary names are also popular e.g., Pepsin, Trypsin and Ptylin etc. Few names have been assigned as the basis of the source from which they are extracted e.g., Papain from papaya, bromelain from pineapple (family Bromeliaceae). Enzymes can also be named by adding suffix-ase to the nature of chemical reaction also e.g., Oxidase, dehydrogenase, catalase, DNA polymerase. Modern names are given after chemical action. They are more systamatic, informative but slightly longer. e.g., ATP : D-glucose phosphotransferase. Common simpler names used at the place of systematic names called trivial names. According to older classification : The older classification of enzymes is based on the basis of more...

Molecular weight : Enzymatic proteins are substances of high molecular weight. Bacterial ferredoxin one of the smaller enzymes has molecular weight of 6,000, where as pyruvic dehydrogenase one of the largest-has a molecular weight of 4600000. Amphoteric nature : Each molecule of enzyme possess numerous groups which yield H+ in slightly alkaline solutions and groups which yield OH- ions in slightly acidic solutions. Unlike many other substances, therefore, the enzymatic protein is amphoteric, i.e., capable of ionizing either as an acid or as a base depending upon the acidity of the external solution. Colloidal nature : All enzymes are colloidal in nature  and thus provide large surface area for reaction to take place. They posses extremely low rates of diffusion and form colloidal system in water. Specificity of enzyme : Most of the enzymes are highly specific in their action. A single enzyme will generally catalyze only a single substrate more...

All enzymes are produced in the living cells. About 3,000 enzymes have recorded. These are of two types with regard to the site where they act as : Intracellular enzymes :  Most of the enzymes remain and function inside the cells, They are called the intracellular enzymes or endoenzymes. Some of these enzymes are found in cytoplasmic matrix. Certain enzymes are bound to ribosomes, mitochondria and chloroplast etc. Extracellular enzymes : Certain enzymes leave the cells and function outside them. They are called the extracellular enzymes or exoenzymes. They mainly include the digestive enzymes. e.g., salivary amylase, gastric pepsin, lysozyme present in tears and nasal secretion. Rennet tablets with enzyme renin from calf's stomach are widely used to coagulate protein caseinogen for cheese (casein) formation.

Zymogens or (Enzyme Precursors) : Certain enzymes are produced by the living cells in an inactive (non-functional) form. They are called the zymogens or proenzymes. It is then converted, usually by proteolysis (hydrolysis of the protein), to the active form when it has reached the site of its activity. Pepsinogen and trypsinogen are zymogens produced by gastric glands and pancreas respectively. They are necessary to life because they degrade dietary proteins into amino acids that are used by the cell. Pepsinogen is changed to active pepsin by hydrogen ions in the stomach. Trypsinogen is activated to trypsin by an enzyme enterokinase in the small intestine. Once small amount of pepsin or trypsin is formed, it itself catalyzes the activation of remaining proenzyme. This process is called autocatalytic reaction, or autocatalysis. Isoenzymes (Isozymes) : There are certain enzymes which have slightly different molecular structure but performing the same catalytic function. Such more...

Systematic position                 Phylum          -    Chordata                 Sub phylum -    Vertebrata or Craniata                 Class               -    Amphibia                 Order             -    Salientia or Anura                 Genus            -    Rana                 Species          -    tigrina   Habitat Rana tigrina is the most widely distributed species in Northern India. Generally frogs are found in ponds, tank, pools, ditches, etc. However, they may leave their aquatic habitat to come on land to hunt for their prey, which are mostly insects. Habits (1) Locomotion : (a) Jumping and leaping, (b) Swimming.  Absence of neck is helpful in swimming in water and jumping on land. (2) Feeding : The adult frog is carnivorous. Tadpole (larva of frog) is herbivorous. (3) Croaking : The male frog croaks more...

Systematic position                 Phylum          -  Chordata                 Subphylum   -  Vertebrata or Craniata                 Class                -  Mammalia                 Order              -  Rodentia                 Family             -  Muridal                 Genus            -  Rattus                 Species          -  rattus (Black Rat) Habits and Habitat They are the common house rats which are cosmopolitan in distribution and found all over the world. They are herbivorous, fossorial and nocturnal animals and undergo hibernation. They show sexual dimorphism. They are prolific breeders. Fertilization is internal. The time interval between fertilization and birth (gestation) is about 22 to 23 days. They are completely grown at six to eight months of age. The rat breeds more than four times in a year producing 6-8 young ones in each litter. more...

It connects and supports all the other tissues, the intercellular element predominating. The cellular element is usually scanty. In function this tissue may be mechanical, nutritive and defensive. It is a tissue made up of matrix (abundant intercellular substance or ground substance) and living cells that connects and support different tissues. All connective tissues in the body are formed by mesoderm. Structure There are large intercellular spaces between the cells. Intercellular spaces are filled with large amount of extracellular materials formed of insoluble protein fibres lying in an amorphous, transparent ground substance called matrix. Ageing of an animal body is associated with deterioration in its connective tissues. Functions (1) Their chief function is to bind other tissues together in the organs. (2) Certain connective tissues such as adipose tissues store fat. (3) Skeletal connective tissues like bones and cartilages provide the body with a supporting skeletal frame work. (4) Fluid more...

An epithelium is a tissue composed of one or more layers of cells that cover the body surface and lines its various cavities. It serves for protection, secretion and excretion. The word ‘epithelium’ (G. epi = upon, thele = nipple) was introduced by Ruysch. They are located on the outer surfaces of organs, including the skin. They form the linings of tracts, cavities and vessels. Epithelial tissue evolved first in animal kingdom. It originate from all the three primary germ layers. Structure Cells are arranged in one or more layers, cells are compactly arranged and there is no inter cellular matrix between them. Neighbouring cells are held together by intercellular junctional complexes like desmosomes, tight junctions, interdigitations etc. The cells of lowermost layers always rest on a non living basement membrane or basal lamina. Basement membrane is made up of no cell product of epithelial tissue. It is formed of more...

Glandular epithelium are specialized for secretory activity. A cell, tissue or organ which secretes a useful chemical material is known as gland. Glands are made up of cuboidal epithelial cells which are more secretory. All glands arise as folding of epithelia. The golgi body in gland cells are larger and more secretory. Most of the glands of body are merocrine types. It originate from all three germinal layers. (ecto, meso and endoderm). Liver is the largest gland of the body and lined by glandular epithelium. Types of glands (1) Unicellular gland : It  consist of unicellular gland cells which are called as goblet cells or chalice cells. They secrete mucous and found in mucosa of intestine and stomach. Mucous lubricates the food for easy peristalsis. Their life span is about \[2\,\,\,\,3\] days. (2) Multicellular gland : It consist of many cells and are generally located in underlying connective tissue e.g. more...

Contractility and motility (movement) are fundamental properties of protoplasm. That is why, all cells possess potential motility. Contraction for motility in the cells results essentially from the interaction of two contractile proteins, actin and myosin. These tissues are obviously responsible for movements of organs and locomotion of the body in response to stimuli. These develop from embryonic mesoderm except for those of the iris and ciliary body of eyes, which are ectodermal in origin. About 40% to 50% of our body mass is of muscles. The muscle cells are always elongated, slender and spindle-shaped, fibre-like cells, These are, therefore called muscle fibres. These possess large numbers of myofibrils formed of actin and myosin. Muscle cells lose capacity to divide, multiply and regenerate to a great extent. Study of muscle is called myology. Types of muscle are following – Striated or striped muscles Most muscles of body are striated. These generally more...