Notes Ghar

CHAPTER-10 CELL CYCLE AND CELL DIVISION The sequence of events by which a cell duplicates its genome, synthesizes the other constituents of cells and eventually divides into two daughter cells is called cell cycle. DNA synthesis occurs in one specific stage of cell division but distribution of chromosome in cells occurs in complex series of events during cell division. Phases of Cell cycle Human cell divides once in approximately 24 hours, which may vary in different organisms. In yeasts it takes about 90 minutes to complete the cell division process. Cell cycle is divided into two basic phases- Interphase - it is the phase between two successive M phases. Interphase lasts for 95% of a cell cycle. This phase is called as resting phase but during this period the cells prepare itself for nuclear division by cell growth. M Phase - when the actual cell division or mitosis occurs. It starts with karyokinesis (nuclear division) or duplication of chromosome and end with cytokinesis or divisio

CHAPTER-09 BIOMOLECULES Chemicals or molecules present in the living organism are known as biomolecules. Biomolecules are divided into two types- inorganic and organic. Inorganic biomolecules includes minerals, gases and water and organic biomolecules includes carbohydrates, fats, proteins, nucleic acids, vitamins, etc. Different biomolecules can be classified as aldehyde, ketones and aromatic compounds as chemical forms. The amino acids, nucleotides and fatty acids can be classified as biochemical forms. Except lipids, macromolecules are formed by polymerization of sub-units called monomers. Proteins are polymers of amino acids. Amino acids are linked by  peptide bond  formed by dehydration between COOH group of one amino acids and NH3 group of next with the removal of H2O. In nucleic acids, the phosphate molecules links 3’ C of sugar of one nucleoside to the 5’ C of sugar of next nucleosides releasing two water molecules to form 3’-5’  phosphodiester bond. In polysaccharides, the mon

CHAPTER-08 CELL: STRUCTURE AND FUNCTIONS Study of form, structure, and composition of cell is called  cytology . Cell is the structural and functional unit of life. In unicellular organism (amoeba, paramecium, yeast, bacteria) single cell performs all the essential functions of life. In multicellular organism, different kinds of tissues perform different function and have division of labour. Anton Von Leeuwenhoek first saw and described a live cell. Robert Brown later discovered the nucleus. Metthias Schleiden and Theodore Schwann( 1938) proposed the cell theory which was later modified by Rudolf Virchow(1855)- All living organisms are composed of cells and products of cells. All cells arise from pre-existing cells. Prokaryotic cells Eukaryotic cells Membrane bound nucleus is absent. Cells are smaller in size. Single chromosome is present. Membrane bound organelles are absent. Membrane bound nucleus is present. Cells are larger in size. More than one chromosome is present. Membrane bou