Gaurav Gupta sir

2022-03-15 19:26:17 NEURAL CONTROL AND COORDINATION: ✯ ❥˙ ｡.....

POINTS TO REMEMBER :-

Action potential : A sudden change in the electrical charges in the plasma membrane of a nerve fibre.

Aqueous humour : The thin watery fluid that occupy space between lens and cornea in eye.

Blind spot : A spot on ratina which is free from rods and cones and lack the ability for vision.

Cerebrospinal fluid : An alkaline fluid present in between inner two layer of meninges.

Cerebellum : A part of hind brain that controls the balance and posture of the body.

Cochlea : A spirally coiled part of internal ear which is responsible for hearing.

Corpus callosum : A curved thick bundle of nerve fibres that joins two cerebral hemisphere.

Depolarisation : A condition when polarity of the plasma membrane of nerve fibre is reversed.

Endolymph : The fluid filled within membranous labyrinth.

Eustachian tube : A tube which connect ear cavity with the pharynx.



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2022-03-14 14:31:44 Important One Liners on Electric Charges
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If an object is attracted by another charged body, the first object may be oppositely charged or not charged because we know both an uncharged object and an oppositely charged object are attracted by another charged object.

If an object is positively charged it loses some of its electrons. The mass of an electron is 9.11*10^-31 kg. So, if a positively charged body loses ‘n’ number of electrons, it mass decrease by the amount n*9.11E^-31kg.

Though gold is a costly metal it is used in electroscope because of the property malleability. This means very thin and light sheets can be formed from gold simply by hammering or rolling and hence the deflection of the light gold plates increases.

The divergence of the plates of the Gold-leaf oscilloscope depends only on the presence of a charge, not on the quality of charge i.e. positive or negative. So, if the charge changes from positive to negative and vice versa the degree of divergence of the plates remains the same.

The same charges repel each other. So, they try to maintain maximum distance from each other and hence they try to remain at the outer surface of an object. If the charge remains on the inner surface or throughout the body, they will repel each other with greater force.

The human body is a good conductor and hence the charge produced by friction flew through his body to the ground. We can tackle the problem simply by holding the brass rod with the help of some insulated holder.

If the apparatus is initially in contact with some positively charged body and then comes in contact with another charged body and if the divergence increases we can deduce that the second body is also positively charged. If the divergence decreases then the second body must be negatively charged.

According to electrostatic series, glass is situated above silk. So, if the glass is rubbed with silk, the positive charge on glass and negative charge on silk is produced. Similarly, we can predict what is the nature of charge if we rub two di-electric substances together.

1 Coulomb means 3*10^9 Electro Static Unit of charge. Coulomb and ESU are two different units of charge and their conversion formula is necessary. Coulomb is the unit of charge in the SI system and esu is the unit of charge in the CGS system.

The two spheres are oppositely charged by the same amount. So if they come in contact, both of their charges are neutralized. So they become uncharged and don’t attract or repel each other. Open / Comment

2022-03-12 20:07:53 Stereoisomerism: This type of isomerism arises because of different spatial arrangement.

Geometrical isomerism: It arises in heteroleptic complexes due to different possible geometrical arrangements of ligands.

Optical isomerism: Optical isomers are those isomers which are non-superimposable mirror images.

Valence bond theory:

According to this theory, the metal atom or ion under the influence of ligands can use its (n-1)d, ns, np or ns, np, nd orbitals for hybridisation to yield a set of equivalent orbitals of definite geometry such as octahedral, tetrahedral, and square planar.

These hybridised orbitals are allowed to overlap with ligand orbitals that can donate electron pairs for bonding.

Coordination Number and Type of hybridisation Shape of hybrid
4 Tetrahedral
4 Square planar
5 Trigonalbipyramidal
6 (nd orbitals are involved – outer orbital complex or high spin or spin free complex) Octahedral
6 d orbitals are involved –inner orbital or low spin or spin paired complex)

Magnetic properties of coordination compounds:

A coordination compound is paramagnetic in nature if it has unpaired electrons and

diamagnetic if all the electrons in the coordination compound are paired.

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Crystal Field Theory:

It assumes the ligands to be point charges and there is electrostatic force of attraction between ligands and metal atom or ion.

It is theoretical assumption.
Crystal field splitting in octahedral coordination complexes:


Crystal field splitting in tetrahedral coordination complexes:


For the same metal, the same ligands and metal-ligand distances, the difference in energy between eg and t2g level is

Metal carbonyls:

Metal carbonyls are homoleptic complexes in which carbon monoxide (CO) acts as the ligand.

Example:
The metal-carbon bond in metal carbonyls possess both s and p character.

The M–C bond is formed by the donation of lone pair of electrons from the carbonyl carbon into a vacant orbital of the metal.

The M–C bond is formed by the donation of a pair of electrons from a filled d orbital of metal into the vacant antibonding orbital of carbon monoxide.

The metal to ligand bonding creates a synergic effect which strengthens the bond between CO and the metal. Open / Comment

2022-03-04 16:34:39 Father of Biology : Aristole
Father of Modern Biology: Linnaeus
Father of Antibiotics fb: Alexander Fleming
Father of Taxonomy : Carolus Linnaeus
Father of Immunology : Edward Jenner
Father of Microbiology : Anton van Leenuwenhoek
Father of Modern Microbiology : Louis Pasteur
Father of Medical Microbiology : Robert Koch
Father of Pathology : Rudolph Virchow
Father of Bacteriology : Robert Koch
Father of Virology : W.M.Stanley
Father of Embryology : Aristotle
Father of Modern Embryology : Ernst Von Baer
Father of Physiology : Stephan Hales
Father of Modern experimental physiology : Calude Bernard
Father of Genetics : Rev. Gregor Mendel
Father of Modern Genetics : Bateson
Father of Human Genetics/ Biochemical genetics : Arachibald Garrod
Father of Experimental Genetics : T.H. Morgan
Father of Haploid Genetics / Neurospora Genetics : Dodge
Father of Ecology : Theophrastus
Father of Cloning : Ian Willmut
Father of Plant anatomy : Grew
Father of Histology (Microscopic anatomy) : Malpighi
Father of Cytology : Robert Hooke
Father of modern Cytology : Swanson
Father of Paleontology : Leonard da Vinci
Father of modern Paleontology : Cuvier
Father of Concept of Evolution: Empedocles
Father of Botany: Theophrastus
Father of Modern Botany : Bauhin
Father of Zoology : Aristotle
Father of Biochemistry : Liebig
Father of Epidemiology : John Snow
Father of Plant Pathology : de Bary
Father of Modern Pathology : Rudolf Virchow
Father of Genetic Engineering : Paul Berg
Father of Gene therapy : Anderson
Father of Ethology : Konard Lorentz
Father of Endocrinology : Thomas Addison
Father of Eugenics : Galton
Father of Gerantology : Korenchevsk
Father of Palynology : Erdtman
Father of Stress physiology : Hans Selye
Father of Electrocardiography : Einthoven
Father of DNA Fingerprinting : Alec Jeffery
Father of Mycology : Micheli
Father of Bryology : Hedwig
Father of Phycology:Father of ATP cycle: Lipmann
Father of Chemotherapy :Father of Anatomy : Herophilus
Father of Modern Anatomy : Andreas Vesalius
Father of actinobiology / radiation biology : HJVS Muller
Father of Homeopathy : Hahnemann
Father of Ayurveda : Charka
Father of Surgery and Plastic Surgery : Susruta
Father of Blood circulation : William Harvey
Father of Medicine : Hippocrates
Father of Blood Group : Landsteiner
Father of Polio Vaccine : Jonas Salk
Father of Green Revolution: Norman Borlaug Open / Comment

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2022-01-28 17:38:32 Notes on Chemical Bonding
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Chemical bond:-

Chemical bond is the attractive force which holds various constituents together in a molecule.

There are three types of chemical bonds: Ionic Bond, Covalent Bond, Co-ordinate Bond.

Octet Rule:

Atoms form chemical bonds in order to complete their octet i.e. eight electrons in their valence shell.

Lewis Structures:

Pair of bonded electrons is by means of a ‘dash’ (-) usually called a ‘bond’.

Lone pairs or ‘non-bonded’ electrons are represented by ‘dots’.

Electrons present in the last shell of atoms are called valence electrons.

Exceptions to the Octet Rule:

Species with odd number of electrons: NO, NO2,

Incomplete octet for the central atom: LiCl, BeH2 and BCl3

Expanded octet for the central atom: PF5, SF6 and H2SO4

Formal Charge:

Formal charge is the difference between the number of valence electrons in an isolated atom and number of electrons assigned to that atoms in Lewis structure.

Formal charge = [Total number of valence electrons in the free atom ) - (Total number of lone pairs of electrons) -1/2(Total number of shared electrons i.e. bonding electrons)]

Resonance:

For molecules and ions showing resonance it is not possible to draw a single Lewis structure.

All the properties of such species can only be explained by two or more Lewis structures. Example: Resonance of O3

Ionic Bonding:

Formation of Ionic Bond:
Formation of ionic bond takes place between a metal and a non-metal by transfer of electron.

Formation of gaseous cations

A(g) + I.E. → A+ (g) + e

Ionization Energy

Formation of gaseous anions

X(g) + e → X- (g) + E.A

Electron Affinity

Packing of ions of opposite charges to form ionic solids

A+ (g) + X- (g) →AX (s) +Energy

Lattice energy

Conditions required of formation of ionic bonds:

Low I.E of cation.

High E.A of anion.

High lattice energy.

Covalent Bonding:

Covalent bond is formed between two non-metals by sharing of electrons.

Electron pairs which participate in bonding are called bond pairs.

Electron pairs which do not participate in bonding are called lone pairs.

There could be single, double or triple covalent bonds between two elements depending on the number of electrons being shared.

VSEPR (Valence Shell Electron Pair Repulsion) Theory:

The shape of the molecule is determined by repulsions between all of the electron pairs present in the valence shell.

Order of the repulsion: Lone pair.Lone pair > Lone pair. Bond pair > Bond pair. Bond pair.

Repulsion among the bond pairs is directly proportional to the bond order and electronegativity difference between the central atom and the other atoms. Open / Comment

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