Medical Lad

Structure of the cell INTRODUCTION  Cells are basic units of life. All living organisms are com- posed of many blocks of cells. Each single has all the characteristics of life. Cell is defined as structural and functional unit of the living body. The space outside the cell is called extracellular space. General Characteristics of Cell  Each cell in the body:  1.  Needs nutrition and oxygen. 2.  Produces its own energy necessary for its growth, repair and other activities. 3.  Eliminates carbon dioxide and other metabolic wastes.  4.  Maintains the medium, i.e, the environment for its survival.  5.  Shows immediate response to the entry of invaders such as bacteria or toxic substances into the body.  6.  Reproduces by division. There are some exceptions such as neuron, which do not reproduce.  TISSUE  Tissue is defined as the group of cells having similar function. There...

Different cell junctions  DEFINITION Cell junction is the connection between neighboring cells or the contact between the cell and extracellular matrix. It is also called membrane junction. Connection between two cells is called intercellular junction. Tight junction, gap junction, adherence junc- tion and desmosome are intercellular junctions. Contact between the cell and extracellular matrix are focal adherence and hemidesmosome. CLASSIFICATION   Cell junctions are classified into three types:  1. Occluding junctions. 2. Communicating junctions.  3. Anchoring junctions. OCCLUDING JUNCTIONS  Cell junctions which prevent intercellular exchange of substances are called occluding junctions, i.e. these junctions prevent the movement of ions and molecules from one cell to another cell. Tight junctions belong to this category.   TIGHT JUNCTION  Tight junction is the intercellular occluding junction that prevents ...

Organelles Of Cell CYTOPLASM  Cytoplasm of the cell is the jelly-like material formed by 80% of water. It contains a clear liquid portion called cytosol and various particles of different shape and size. These particles are proteins, carbohydrates, lpids or electrolytes in nature. Cytoplasm also contains many organelles with distinct structure and function.  Cytoplasm is made up of two zones: 1. Ectoplasm: Peripheral part of cytoplasm, situated just beneath the cell membrane. 2. Endoplasm: Inner part of cytoplasm, interposed be- tween the ectoplasm and nucleus.  ORGANELLES IN CYTOPLASM  Cytoplasmic organelles are the cellular structures embed- ded in the cytoplasm. Organelles are considered as small organs of the cell. In Latin the word organelle means small organ. Some organelles are bound by limiting membrane and others do not have limiting membrane. Each organelle is having a definite structure and specific functions. ORGANELLES WI...

Gene is the basic hereditary unit of the cell. It is a portion of DNA molecule that contains the message or code for the synthesis of a specific protein from amino acids. It is like a book that contains the information necessary for protein synthesis.  In the nucleotide of DNA, three of the successive base pairs are together called a triplet or a codon. Each codon codes or forms code word (information) for one amino acid. There are 20 amino acids and there is separate code for each amino acid. For example, the triplet CCA is the code for glycine and GGC is the code for proline. Thus, each gene forms the code word for a particular protein to be synthesized in ribosome (outside the nucleus) from amino acids.  GENETIC DISORDERS  Genetic disorder is a disease or condition that occurs due to absence of a gene or a defective gene or by a chromosomal abnormality. Causes of Genetic Disorders  Genetic disorders occur due to two causes. 1. Genetic ...