The nucleus is the processing unit of the cell. It is a double membrane-bound organelle which contains the genetic material for inheritance. The nuclear membrane contains pores that allow the transfer of materials from the nucleus to the cytoplasm. The nucleus is the brain of the cell as it controls various functions such as cell… Continue reading Nucleus in cells
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Osmosis in selectively permeable membrane
Osmosis is the movement of water across a semi-permeable membrane. Osmosis is a selective process since the membrane does not allow all molecules to pass through it. Water is usually the only free flowing molecule across this membrane. Isotonic, hypotonic solutions, hypertonic solutions Isotonic solutions are those which have the same solute and pH concentration… Continue reading Osmosis in selectively permeable membrane
Structural Organization of Cells
Prokaryotic & Eukaryotic cells Two types of cell; Prokaryotic and Eukaryotic cells. Prokaryotic cells are primitive and lack well defined nucleus. Eukaryotic cells are more advanced and have well defined nucleus. Cell structure in Eukaryotic cells Eukaryotic cells have the most well defined structure. These cells have cell membrane, membrane bound cell organelles and a… Continue reading Structural Organization of Cells
Fundamental Unit Of Life
Life, as we know it, took billions of years to evolve. From the very first precursor of life to the multitude of multicellular organisms that we see around us today, the most basic unit of all these is the cell. All About Cells Cells are the basic structural and functional unit of life. Cell was… Continue reading Fundamental Unit Of Life
Isotopes
Isotopes are defined as the atoms of the same element, having the same atomic number ( number of protons ) but different mass numbers ( number of protons+neutrons ).For example: In the case of Hydrogen we have:Atoms of different elements with different atomic numbers, which have the same mass number, are known as isobars.For example,… Continue reading Isotopes
Orbits
Orbits are energy shells surrounding the nucleus in which electrons revolve. Electron distribution in different orbits The distribution was suggested by Bohr and Bury; The maximum number of electrons present in a shell is given by the formula 2n2, where ‘n’ is the orbit number or energy level index, 1,2,3,…. The maximum number of electrons… Continue reading Orbits
Neil Bohr Model
Properties of electrons, protons and neutrons Bohr’s Model of an atom Bohr came up with these postulates to overcome the objections raised against Rutherford’s model: Electrons revolve around the nucleus in stable orbits without emission of radiant energy. Each orbit has a definite energy and is called an energy shell or energy level. An orbit… Continue reading Neil Bohr Model
Rutherford`s model of an atom
Rutherford concluded the model of the atom from the α-particle scattering experiment as: (i) There is a positively charged centre in an atom called the nucleus. Nearly all the mass of an atom resides in the nucleus. (ii) The electrons revolve around the nucleus in well-defined orbits. (iii) The size of the nucleus is very… Continue reading Rutherford`s model of an atom
Rutherford Model
Rutherford’s experiment and observations In this experiment, fast-moving alpha (α)-particles were made to fall on a thin gold foil. His observations were: A major fraction of the α-particles bombarded towards the gold sheet passed through it without any deflection, and hence most of the space in an atom is empty. Some of the α-particles were deflected… Continue reading Rutherford Model
Radioactivity
Radioactivity Radioactivity is the term for the process by which an unstable nucleus of an atom loses energy by giving out particles. It does so by giving out particles such as alpha and beta particles. This process is spontaneous. An atom is unstable if the nucleus has an imbalance, meaning a difference in the protons… Continue reading Radioactivity