Bio-topics

This  tissue provide shape and size of organs and provide motion in body. It is of three types- • Striated       • Unstriated  • Cardiac  Stiriated Muscles - These are voluntary muscles having light and dark      striations. The cells are long, cylindrical and are multinucleated.   They are also called skeletal muscles because they are attached to      bones. They help in voluntary   movements of the body. These muscles feel tiredness. Unstriated Muscles - These are involuntary muscles  without  striations. The cells are long and spindle shaped and are uni-nucleated. They are present in alimentary canal, blood vessels,   bronchi of lungs, iris of eye etc. They help in involuntary     movements.These muscles do not feel tiredness. Cardiac Muscles - These are involuntary muscles  having faint striations.    The cells are long, cylindrical, branched and multinuclea...

Epithelial tissue is the covering or protective tissue in animals. It forms the outer covering like skin, outer covering of organs, inner lining of blood vessels, lungs, oesophagus, etc. It protects the body and controls the movement of materials between the body and the surroundings and between the parts of the body.     i) Squamous epithelial tissue :- This consists of a layer of thin flat cells. It is     present  in the linings of blood vessels, lungs, mouth, oesophagus etc.    ii) Columnar epithelial tissue :-This  consists of tall pillar like cells. It is present in  the walls of the intestine.  Ciliated  columnar epithelial tissue is found in respiratory tract.  iii) Cuboidal epithelial tissue :-  This consists of cone shape cells having a basement  membrane. It forms the lining of kidney, tubules and ducts of salivary glands  and provide mechanical support.  iv) Glandular epithelial tis...

These are  single  layered membranous sac like structures formed from the vesicles of endoplasmic reticulum or golgi bodies. These are - Peroxisomes   or Glyoxisomes .   Peroxisomes    Peroxisomes are formed from pre-existing peroxisomes. These are found in plants showing  “Photorespiration” (C -3 plants). Peroxisomes participate in the process of photorespiration along with choloplast and mitochondria.In peroxisome oxidation of glycolic acid (produced in chloroplast in photorespiration)  occurs.   These are also found in animal cells like “Protozoons” residing in liver or kidney cells. In peroxisomes ,catalases,oxidases enzymes are present. These enzymes assist degradation of toxic materials in cells. Peroxisomes invole in fat-metabolism in animal cells.   Glyoxisomes These are also single layered membrane bound spherical bodies found in cell showing “ Glyoxylate cycle ”  Enzymes of glyoxisomes participate in...

“Centrosome”term was first used by T.Boweri .  This is found mostly in animal cell and some algae.  Each centrosome  includes two pairs of “Centrioles”. Both pairs are placed at the angle of 90⁰ from one another. Centrioles of a pair are termed as “Diplosomes”.  A centriole is composed of nine triplet of microtubules. These triplets are arranged around a hub and embedded in amorphous dense substance.  A circle around centriole is called as centrosphere.RNA is also present in centrosome. Centrosome  participates in cell division.

The membrane surrounding the cytoplasm of the cell is known as “ Plasma membrane or Plasmalemma ” .It is the outermost layer of animal cell while cell wall is present outside of plasmalemma in plant cell. Plsmalemma is a unit membrane and differentially permeable(permeable for some substances). Structure -  The structure of plasma membrane can be understood by “ Fluid-mosaic model ”  given by S.J.Singer & G.Nicolson in1972. According to this model in the middle of membrane bimolecular lipid layer is present. Peripheral proteins are present on outer surface of lipid layer while Intrinsic proteins are embedded in lipid layers. Peripheral proteins can be separated easily while intrinsic proteins cannot be separated easily. Peripheral proteins are glycoproteins and some glycolipids are also present with them. Glycoproteins and glycolipids are specific  with cells. Cells can recognize cell with same glycoproteins and glycolipid. This specification plays important r...

Lysosomes are single membrane bound structures found in animal cells. These were discovered by  D’Duve (Nobel prize-1974).    It is formed by golgi bodies or endoplasmic reticulum. Lysosome contains many digestive enzymes like “proteases,lipases,carbohydratases ,etc”. These become active at the acidic pH.   Many types of lysosomes are found as “Primary lysosomes,secondary lysosomes,residual bodies ,autophagic vacuoles”. Lysosome is considered as “ Suicidal bag of cell”  because its enzyme can digest all the parts of cell when lysosome bursts.   Function – ·      Primary lysosome  helps in digestion of material taken by cell through endocytosis. ·        Lysosomes help in autolysis of injured cells. ·        Lysosomal enzymes facilitates intracellular digestion. ·        Lysosomal enzymes digest food inside protozoans.

Ribosomes are minute structure associated with protein synthesis in the cell.  These are found in all cells, in mitochondria, chloroplast and nucleus of the cell.They are composed of RNA and proteins and not surrounded by any membrane. On the basis of “sedimentation coefficient”. Ribosomes are of two types- 70S ribosome –These are found in mitochondria ,chloroplast and prokaryotic cells like bacterial cell. It is composed of two units ,larger unit is 50S and smaller unit is 30 S. 80S ribosome -These are found in eukaryotic cells.  It’s larger unit is 60S and smaller unit is 40S. Ribosomes Mg + ion is required for union of two subunits of  ribosomes. Function- Ribosomes involves in protein synthesis.