Category: Maharashtra State Board Notes

By going through these Maharashtra State Board 12th Science Biology Notes Chapter 4 Molecular Basis of Inheritance students can recall all the concepts quickly.

Maharashtra State Board 12th Biology Notes Chapter 4 Molecular Basis of Inheritance

The Discovery of DNA-

1. Nuclein:

• Isolated by Friedrich Miescher, in 1869, from the nuclei of pus cells.
• It is an acidic substance with high phosphorus content.

2. There are two types of nucleic acids – DNA  (deoxyribonucleic acid) and RNA (ribonucleic : acid).

The Genetic Material is a DNA-

1. Initially proteins (and not DNA) were ; considered as genetic material because :

• Proteins are large, complex molecules and store information required to govern cell metabolism. Hence, it was assumed that variations found in species were caused by proteins.
• DNA was considered as a small, simple : molecule whose composition varies little ; among species.
• Variations in the DNA molecules are different j than the variation in shape, electrical charge J and function shown by proteins.

2. Various experiments which proved that DNA (and not protein) was the genetic material are as follows :

A. Griffith’s experiments :

• In 1928, Frederick Griffith, carried out an experiment with two strains of bacterium Streptococcus pneumoniae: S-type (Virulent, smooth, pathogenic and encapsulated) and R-type (Non-virulent, rough, non-pathogenic and non-capsulated).
• He observed that on injecting a mixture of heat-killed S bacteria and live R bacteria, the mice died.
• Griffith obtained live S-strain bacteria from the blood of the dead mice.
• Conclusion: Live R-strain bacteria must have picked up something (transforming principle) from the heat-killed S bacterium and got transformed into S-type.

B. Avery, McCarty and MacLeod’s experiment:

• Purified DNA, RNA, proteins, etc. from heat killed cells of S-strain and mixed with R-strain bacteria separately.
• Only DNA was able to transform avirulent R-strain into virulent S-strain.
• When DNA was digested with DNase, there was no transformation.
• Thus, in 1944, they proved that the DNA is a genetic material (transforming principle), but all biologists were not convinced.

C. Hershey-Chase Experiment :

• Hershey and Chase worked with bacteriophages.
• TWo types of bacteriophages were used in the experiment – type one where DNA was labelled with radioactive phosphorus and type two where protein coat was labelled with radioactive sulphur.
• Steps : infection, blending, centrifugation.
• Experiment proved that DNA is the genetic material which enters bacterial cell and not protein.

DNA packaging-

A. Packaging in Prokaryotes :

• E. coli cell size : 2-3μ.
• The nucleoid : Small, circular, highly folded, naked DNA (1100μm long in perimeter, contains about 4.6 million base pairs), nuclear membrane, nucleolus are absent.
• Negatively charged circular DNA (350 μm in diameter).
• Folding / looping : Size reduction to 30 μm in diameter.
• Coiling and supercoiling of each domain : Size reduction to 2μ in diameter.
• Positively charged HU (Histone like DNA binding proteins) proteins : Assist in coiling.
• DNA gyrase and DNA topoisomerase I : Maintain super coiled state.

B. Packaging in Eukaryotes :

• Presence of nuclear membrane, nucleolus and thread-like chromosomes.
• To accommodate long DNA molecule (2.2 m in a typical mammalian cell) in such a small nucleus (10^-6 m), it is condensed, coiled and supercoiled.
• R. Kornberg in 1974 reported that DNA is associated with histone and non-histone proteins in the chromosomes.
• Histones: A set of positively charged, basic proteins, rich in basic amino acid residues lysine and arginine.
• Nucleosome: Consists of nucleosome core (two molecules of each of histone proteins viz. H₂A, H₂B, H₃ and H₄ forming histone octamer) and negatively charged DNA (146 bps) that wraps around the histone octamer by 1 3/4 turns.
• H₁ protein binds the DNA thread where it enters and leaves the nucleosome.
• Adjacent nucleosomes are linked with linker DNA (varies in length from 8 to 114 bp, average length of linker DNA is about 54 bp). [Note : Technically nucleosome includes nucleosome core, DNA wrapped around it (146 bp) and one adjacent linker DNA (54 bp), thus, each nucleosome contains 200 bp of DNA.]
• Packaging involves formation of – Beads on string, Solenoid fibre (looks like coiled telephone wire, 30 nm diameter/300 Å), Chromatin fibre and Chromosome.
• Non-Histone Chromosomal Proteins (NHC) : Additional sets of proteins that contribute to the packaging of chromatin at a higher level.

C. Heterochromatin and Euchromatin :

1. Heterochromatin :

• This term was proposed by Heitz.
• Genetically (transcriptionally) almost inactive, darkly stained, condensed parts of chromonema/chromosomes observed in eukaryotic cells, during interphase and early prophase.
• Located near centromere, telomeres are also interrelated.
• Heterochromatin is 2 to 3 times richer in DNA than in the euchromatin.

2. Euchromatin : Genetically (transcriptionally) . active, lightly stained, fast replicating regions of chromonema which are in non-condensed state.

DNA Replication-

1. Functions of DNA :

• Regulates and controls all the cellular activities.
• DNA replicates and gets distributed equally to the daughter cells when the cell divides.
• Carrier of genetic information.
• Heterocatalytic function : Directs the synthesis of chemical molecules other than itself. E.g. Synthesis of RNA (transcription), synthesis of protein (Translation), etc.
• Autocatalytic function : Directs the synthesis of DNA itself. E.g. Replication.
• A master molecule of a cell that initiates, guides, regulates and controls the process of protein synthesis.

2. Replication is the process by which DNA duplicates itself and forms two copies that are identical to it.
3. In eukaryotes, replication of DNA occurs once, in the S-phase of interphase.
4. The steps involved in DNA replication :

• Activation of Nucleotides
• Point of Origin or Initiation point
• Unwinding of DNA molecule
• Formation of Y-shaped replicating fork
• Synthesis of new strands
• Leading and Lagging strand
• Formation of daughter DNA molecules

5. Enzymes and proteins involved in DNA replication :

• Phosphorylase
• Helicase
• Single strand binding proteins (SSBP)
• Primase
• DNA polymerase
• DNA ligase
• Super-helix relaxing enzyme
• DNA gyrase (Topoisomerase)

6. Semiconservative replication : In each daughter DNA molecule, one strand is parental and the other one is newly synthesized. Thus, 50% mother DNA is conserved.
7. Experimental confirmation of semiconservative DNA replication : Given by Matthew Meselson and Franklin Stahl (1958). They used light and heavy isotopes of nitrogen and equilibrium-density-gradient-centrifugation technique.

Protein synthesis-

1. Central Dogma :

(1) Postulated by F.H.C. Crick in 1958.

Transcription Translation
(2) In eukaryotes, DNA transcription takes place in nucleus and translation occurs in cytoplasm. In prokaryotes, both the processes occur in cytoplasm.
(3) Central dogma in retroviruses : Temin (1970) and Baltimore (1970)

2. Transcription :

(1) Transcription is the process of copying of genetic information from one (template) strand of DNA into a complementary single stranded RNA transcript.
(2) Occurs in the nucleus during Gx and G2 phases of cell cycle.

(3) Catalyzed by RNA polymerase :
(i) Prokaryotes : One type of RNA polymerase.
(ii) Eukaryotes :

• RNA polymerase-I : Transcription of r-RNA.
• RNA polymerase-II : Transcription of m-RNA and heterogeneous nuclear- RNA (or hnRNA).
• RNA polymerase-III : Transcription of t-RNA and small nuclear-RNA (snRNA).

(4) Transcription Unit: Transcription unit (Each transcribed segment of DNA) consists of the promoter, the structural gene and the terminator.

(i) The promoter :

• Located towards 5′ end of structural gene, i.e. upstream.
• Provides binding site for enzyme RNA polymerase.

(ii) Structural genes :

• Template strand : DNA strand having 3′->5′ polarity.
• Sense strand : The other strand of DNA having 5′->3′ polarity.

(iii) The terminator :

• Located at 3′ end of coding strand, i.e. downstream.
• Defines the end of the transcription process.

(5) Three stages of transcription : Initiation, Elongation and Termination.
(6) Transcription unit and the gene :

• Gene : The DNA sequence coding for m-RNA/t-RNA or r-RNA.
• Cistron : A segment of DNA coding for a polypeptide.
• Monocistronic gene : A single structural gene in transcription unit.
• Polycistronic gene : One transcription unit having a set of various structural genes.
• Interrupted genes (Split genes) :
  Structural genes with both exons and introns).
  • Exons : The coding sequences or express sequences.
  • Introns : The non-coding sequences.
  • Only exons appear in processed m-RNA in eukaryotes.
• In bacteria. m-RNA does not require any processing because it has no introns.

(7) Processing of hnRNA :

• Primary transcript or hnRNA is non¬functional and contains both exons and introns.
• Processing of hnRNA results in functional m-RNA.
• hnRNA undergoes capping, tailing and splicing.
  • Capping : Methylated guanosine tri¬phosphate is added to 5′ end of hnRNA.
  • Tailing : Polyadenylation take place at 3′ end.
  • Splicing : Removal of introns.
• DNA ligase joins exons in a definite sequence (order).
• The fully processed hnRNA is called m-RNA.

(8) Genetic Code :

• Yanofski and Sarabhai (1964) : Provided evidence that DNA carries the information for the protein synthesis as the sequence of nucleotides.
• F.H.C. Crick : According to Crick the information for protein synthesis is stored in the form of coded language (cryptogram) called genetic code. He gave evidence for the triplet nature of genetic code, by using “frame-shift mutation”.
• G. Gamow (1954) : Suggested that codon is a sequence of three consecutive nucleotides on m-RNA.
• Cracking of genetic code : M. Nirenberg, Matthaei, Ochoa and Har Gobind Khorana : Deciphered complete genetic code by using artificial m-RNA templates (homopolymers and copolymers) and cell free system of protein synthesis. Synthesized artificial poly-U RNA.

(a) M. Nirenberg and Matthaei : Synthesis of poly-U, m-RNA and polypeptide that consisted of only phenylalanine.
(b) Har Gobind Khorana : Devised a technique for synthesis of artificial m-RNA with repeated sequences of known nucleotides.
(c) Severo Ochoa : The enzyme polynucleotide phosphorylase polymerizes RNA with defined sequences in a template-independent manner (i.e. enzymatic synthesis of RNA).

(9) Replication and transcription are based on complementarity principle.
(10) During translation, complementarity principle is not applicable as, genetic information is transferred from a polymer of nucleotides to a polymer of amino acids.

(11) Characteristics of Genetic code :

• Triplet code : Codon (sequence of three consecutive nucleotides), specifies one particular amino acid.
• Polarity : Genetic code is always read in 5′ -» 3′ direction.
• Non-overlapping code : Each single nucleotide is a part of only one codon.
• Commaless : There is no gap between successive codons.
• Degeneracy of genetic code : Two or more codons can specify the same amino acid. E.g. Cysteine has two codons, while isoleucin has three codons.
  Degeneracy of the code is explained by Wobble hypothesis.
• Universal code : In all living organisms the specific codon specifies same amino acid. E.g. codon AUG always specifies amino acid methionine.
• Non-ambiguous code : Each codon specifies a particular amino acid.
• Initiation codon : AUG, Codes for amino acid methionine.
• Termination codons : UAA, UAG and UGA : They do not code for any amino acid. They stop the process of elongation of polypeptide chain.
• Codon : A triplet of nucleotides present on DNA that codes for specific amino acid. E.g. AUG is codon.
• Anticodon : Triplet of nucleotides present on the anticodon loop of t-RNA, which is complementary to codon on m-RNA.
• Wobble hypothesis : In codon-anticodon pairing the third base may not be complementary.

(12) Mutation recombination :

(i) Mutation : A sudden heritable change in the DNA sequence that results in the change of genotype.
(ii) Mutation and recombination is raw material for evolution as it generates variations.
(iii) Types of mutations :

• Chromosomal mutations : Loss (deletion) or gain (insertion/ duplication) of a segment of DNA results in alteration in the chromosome.
• Point mutations : Involve change in a single base pair of DNA. E.g. mutation that results in Sickle-cell anaemia.
• Deletion or insertion of base pairs of DNA : It causes frame-shift mutations or deletion mutation.

(13) t-RNA – the adapter molecule :

• t-RNA can read the codon and also can bind with the amino acid. So t-RNA is considered as an adapter molecule.
• Cloverleaf structure (2 dimensional) of t-RNA has 3 loops and 4 arms.
• For every amino acid, there is specific t-RNA.
• Initiator t-RNA is specific for methionine.
• There are no t-RNAs for stop codons.
• In the actual structure, the t-RNA molecule looks like inverted L (3 dimensional structure).

3. Translation – protein synthesis :

• Translation is the process in which sequence of codons on m-RNA is decoded and accordingly amino acids are added in specific sequence to form a polypeptide on ribosomes.
• It requires 20 different amino acids, m-RNA, t-RNA, ribosomes, ATP Mg⁺⁺ ions, enzymes, elongation, translocation and release factors.
• Translation involves
  • Activation of amino acids and formation of AA-t-RNA complex.
  • Formation of polypeptide chain : initiation, elongation, termination.

Regulation of gene expression-

In eukaryotes, the regulation of gene expression can be at different levels like

• Transcriptional level (formation of primary transcript).
• Processing level (regulation of splicing).
• Transport of m-RNA from nucleus to the cytoplasm.
• Translational level.

Operon concept-

1. A transcriptional control mechanism of gene regulation.
2. Francois Jacob and Jacques Monod (1961) : Explained that metabolic pathways are regulated as a unit.
3. Lac operon of E. coli :

(1) An inducible operon.
(2) The operon is switched on by a chemical inducer-lactose present in the medium.
(3) Lac operon consists of the following components :

• Regulator gene (repressor gene)
• Promoter gene
• Operator gene
• Structural genes : z (codes for galactosidase), y (codes for β-galactoside permease) and a (codes for transacetylase). These enzymes are involved in lactose metabolism.

4. Inducer is not a component of operon.

Genomics-

1. The term Genome was introduced by H. Winkler in 1920.
2. Genome : The total genetic constitution of an organism or a complete copy of genetic information (DNA) or one complete set of chromosomes (monoploid or haploid) of an organism.
3. Genomics (term coined by T.H. Roderick in 1986) : The study of genomes through analysis, sequencing and mapping of genes along with the study of their functions.
4. Two types of Genomics :

• Structural genomics : Involves mapping, sequencing and analysis of genome.
• Functional genomics : Involves the study of functions of all gene sequences and their expressions in organisms.

5. Application of genomics :

• Structural and functional genomics are used in the improvement of crop plant, human health and livestock.
• The knowledge and understanding acquired by genomics research can be applied in medicine, biotechnology and social sciences.
• It helps in the treatment of genetic disorders through gene therapy.
• To develop transgenic crops having more desirable characters.
• Genetic markers have applications in forensic analysis.
• Genomics can lead to introduce new gene in microbes to produce enzymes, therapeutic proteins and even biofuels.

Human Genome Project-

1. Initiated in 1990 under the International administration of the Human Genome Organization (HUGO).
2. Coordinated by the US Department of Energy and National Institute of Health, some universities across the United States and various international partners.
3. Started in 1990 and completed in 2003.

4. Aims of HGP :

• Mapping the entire human genome at the level • of nucleotide sequences.
• To store the information collected from the, project in databases.
• To develop tools and techniques for analysis of the data.
• Transfer of the related technologies to the * private sectors, such as industries.
• Taking care of the legal, ethical and social issues which may arise from project.
• To provide complete and accurate sequence of the 3 billion DNA base pairs that make up the human genome.
• To find out the estimated number of human ; genes. Now about 33,000 genes have been : estimated to be present in humans.
• To sequence the genomes of several other organisms such as bacteria e.g. E.coli, Caenorhabditis elegans, Saccharomyces cerevisiae, Drosophil, rice, Arabidopsis), Mus musculus etc.

5. HGP was closely associated with rapid development of Bioinformatics.
6. Significance :

• Increased knowledge about the functions of genes and proteins.
• A major impact in the fields like Medicine, Biotechnology and the Life sciences.
• Increased understanding of gene structure and function in other species, such studies will enhance understanding of human evolution.

7. Comparative genome sizes of humans and other model organisms.

DNA Fingerprinting-

1. Every individual has its unique genetic make- up, called its Fingerprint.
2. Reasons for Uniqueness of fingerprint :

• Recombination of paternal and maternal genes, because of which we differ from our parents.
• Infrequent mutations that occur during gamete J formation (cell division).

3. The DNA profiling or DNA fingerprinting j technique (developed by Dr. Alec Jeffreys in 1984) identifies a person with the help of DNA restriction analysis.

4. It is based on identification of nucleotide sequence present in DNA.

• About 99.9% of nucleotide sequence in all persons, is same.
• Variable Number of Tandem Repeats (VNTRs) : Unusual sequences of 20 – 100 base pairs, which are repeated several times.
• As the length of the regions having VNTRs is different in each individual, they are the key factor in DNA profiling.

5. Steps involved in DNA finger printing :

• Isolation of DNA
• Restriction digestion
• Gel electrophoresis
• Southern blotting
• Selection of DNA probe
• Hybridization
• Photography

6. Application of DNA fingerprinting :

•  Used in forensic sciences to solve rape and murder cases.
• Finds out the biological father or mother or both, of the child, in case of disputed parentage.
• Used in pedigree analysis in cats, dogs, horses and humans.

Know the scientist :
Dr. Lalji Singh (1947-2017) :

• Father of DNA fingerprinting in India.
• A unique segment obtained from Y chromosome of female banded krait snake (banded krait minor – B_KM-DNA) was used by him to develop probe for DNA fingerprinting.

His contributions :

• Established laboratories for research in fields like genetics, population biology, structural biology and transgenics.
• Established centre for DNA Fingerprinting and Diagnostics (CDFD) for all species and several diseases.
• Founded laboratory for Conservation of Endangered Species (LaCONES).
• Applied of DNA fingerprinting technology for wildlife conservation, forensics, evolution and phylogenetic research.

By going through these Maharashtra State Board 12th Science Biology Notes Chapter 9 Control and Co-ordination students can recall all the concepts quickly.

Maharashtra State Board 12th Biology Notes Chapter 9 Control and Co-ordination

Introduction-

• Plants show control and coordination by sending chemical signals and bringing about various types of movements.
• Animals control and coordinate the body’s activities by electrical and chemical signals.
• The nervous system and endocrine control system are two coordinating systems in them.

Nervous Coordination

Nervous System in Hydra-

• Hydra → diffused nervous system in the form of nerve net.
• Two nerve nets in the mesoglea, one connected towards the epidermis and second towards the gastro-dermis.
• Sensory cells scattered in the body wall and tentacles, but no sense organs
• No sensory and motor nerves.

Nervous System in Planaria (flatworm)-

• Primitive animal with a central nervous system (CNS) located on the ventral side of body.
• Mass of cerebral or cephalic ganglion appearing like an inverted U-shaped brain.
• Ventral pair of nerves arising from ganglia. Interconnected to each other by transverse nerve or commissure in a ladder like manner.
• The peripheral nerve plexus arising laterally from VNC.

Neural tissue-

1. Two types of cells in neural tissue – the neurons and the neuroglia or glial cells.
2. Nerve is bundle of axons. Outside the CNS, it is called nerve while inside it is called tract.
3. Types of nerves : Sensory (with sensory * fibres), motor (with motor fibres) and mixed * type (with both sensory and motor fibres).
4. Neurons/Nerve cells :

• Neuron is structural and functional unit of * the nervous system.
• Each multipolar neuron has three parts – cyton : or cell body, dendron and axon.

5. Grey matter and white matter :

• Grey matter is darker part of CNS. This is due to presence of cytons.
• White matter is lighter part of CNS. This is due to presence of myelin sheaths around axons.

In PNS however, the accumulation of cyton causes a swelling on the nerve. Such a swelling is called ganglion, [cytons within CNS form nuclei while those in PNS form ganglia]

6. Connective tissue layers in a nerve are :

• Endoneurium : covers each nerve fibre
• Perineurium : covers each nerve bundle having a number of neurons
• Epineurium : covers many nerve bundles to form a peripheral nerve

7. Neuroglial cells :

• More in number than the neurons.
• They are supporting cells of the Central Nervous System (CNS) and Peripheral Nervous System (PNS).
• Neurilemma is the plasma membrane of Schwann cell.

8. Tjrpes of neuroglial cells :

Synapse-

1. Junction between two nerve cells with a minute gap (synaptic cleft) in between them which allows transmission of impulse by a neurotransmitter bridge.
2. When the telodendria are connected to muscle fibre, it is called motor end plate or neuro¬muscular junction.
3. Properties of nerve fibres :

•  Excitability/Irritability
• Conductivity
• Stimulus
• Summation effect
• All or none law
• Refractory period
• Synaptic delay
• Synaptic fatigue
• Velocity

4. Types of synapses : Electrical synapse and Chemical synapse.

(1) Electrical synapses are found in those places of the body requiring fastest response as in the defence reflexes.
(2) A chemical synapse between a motor neuron and a muscle cell is called a neuromuscular junction or motor end plate.
There are three components of a typical chemical synapse.

• The pre-synaptic terminal
• The synaptic cleft
• The post-synaptic neuron

5. Transmission of nerve impulse across a synapse :

• This transmission takes place with the help of neurotransmitters.
• Once the neurotransmitters bind to the receptors of the post-synaptic cell, the action is either excitatory or inhibitory depending on the type of neurotransmitter.
• The enzyme like acetyl cholinesterase destroys the neurotransmitter after the transmission and the synapse is ready to receive a new impulse.

Transmission of nerve impulse along the axon-

• The excitable neurons transmit the impulse through changes in electrical charges across the neuronal membrane.
• The external tissue fluid has both Na+ and K+ ions.
• This process is called sodium pump or Na-K exchange pump.
• Generation of nerve impulse : Occurs through depolarization.
• Saltatory conduction takes place in medullated nerve fibres.

Human Nervous System-

1. Central nervous system (CNS) :

• Brain is enclosed within the brain box/ cranium of the skull, whereas the spinal cord lies in the vertebral canal of the vertebral column.
• Inner to these bony structures, there are 3 protective membranes called meninges.

2. Meninges :

3. CSF (cerebrospinal fluid) :

• About 100-120 cc lymph like extra cellular . fluid with specific gravity of 1.005, present in and around the CNS.
• It is secreted by the pia mater, the choroid plexuses and the ependymal cells lining the ventricles of the brain and central canal of spinal cord.

4. Functions of meninges and CSF :

• Shock absorber, protection, prevention of desiccation.
• Maintaining constant pressure inside as well as outside the CNS.
• Exchange of nutrients and wastes between blood and brain tissue.
• Supply of oxygen to the brain.

5. The Human brain :

• Encephalology : Study of all aspects of the brain.
• About 1300-1400 g in weight -and 1300-1500 cc in volume

6. Functional areas of cerebrum :

Areas	Functions
1. Frontal lobe	Motor area → controls voluntary motor activities or movements of muscles. Premotor area → higher centre for involuntary movements and autonomus nervous system.Association area → coordination between sensation and movements. Broca’s area → motor speech area.
2. Parietal lobes	Somaesthetic sensation of pain, pressure, temperature, taste
3. Temporal lobes	Centres for smell (olfactory), hearing (auditory), speech and emotions.
4. Occipital lobes	Visual area mainly for sense of vision.
5. Wernicke’s area	Present partly in temporal, parietal and occipital lobes. Sensory speech area.
6. Basal nuclei or basal ganglia	Control precise muscular activities at subconscious level.
7. Corpus striatum	At the floor of cerebrum is the largest basal nucleus.

7. Parts of the Hindbrain (Rhombencephalon) :

8. Parts of the Midbrain (Mesencephalon):

9. Parts of the Hindbrain (Rhombencephalon) :

10. Ventricles of brain : The cavities present in the different parts of the brain are called ventricles.

11. Important terms associated with brain.

• Corpus callosum : Transverse band of nerve fibres which connects right and left cerebral hemisphere. It is the largest commissure of the brain.
• Cerebral cortex : The outer surface of cerebrum, composed of grey matter.
• Cerebral medulla : Inner part composed of white matter.
• Gyri (elevations) and Sulci (depressions) : convolutions and grooves on the surface of cerebrum.
• Central sulcus : Between frontal lobe and the parietal lobes.
• Parieto-occipital sulcus : Between parietal and occipital lobes.
• Lateral or Sylvian sulcus : Between temporal lobe and frontal and parietal lobes.
• Insula or insular cortex : Fifth lobe which is folded deep within the lateral sulcus.
• Foramen of Monroe : Narrow opening through which two lateral ventricles communicate with diocoel (third ventricle).
• Pineal gland : Vestigial 3rd eye and an important endocrine gland, producing hormones melatonin and serotonin.
• Habenular commissure : Connects two thalami.
• RAS (Reticular Activating System) : Relay centre as it transmits all sensory impulses except those of olfactory to the cerebrum. Situated in thalami.
• Aqueduct of Sylvius or iter : Connection between third and fourth ventricle through hypothalamus and midbrain.
• Limbic system : A complex neuronal circuit formed by the hypothalamus, amygdala, parts of epithalamus and thalamus, hippocampus and other areas.
• Optic chiasma : Crossing of the two optic nerves.
• Corpora quadrigemina : Four rounded elevations on the dorsal surface of the midbrain. The two superior colliculi are involved in visual reflexes and the two inferior colliculi are for auditory reflexes.
• Crura cerebri : Two thick fibrous tracks, also called cerebral peduncles, situated in the floor midbrain.
• Red nucleus : Grey matter near the centre of the midbrain, controlling posture. and muscle tone, modifying some motor activities and motor coordination.
• Pons varolii : Rounded bulge on the underside of the brain stem.
• Brain stem : Consist of midbrain, pons and medulla.
• Arbor vitae : The mixing of white matter with the grey matter showing a branched tree-like pattern.
• Cerebellar peduncles : Three pairs of myelinated nerve bundles connecting cerebellum to the other parts of CNS.
• A pair of lateral – foramina of Luschka and a median – foramen of Magendie :
  apertures on the posterior choroid plexus.

12. Spinal Cord :

• Spinal cord is the lower extension of the medulla oblongata of the brain.
• It lies within the neural canal of the vertebral column and is surrounded by three meninges.
• Externally, the spinal cord appears as long cylindrical rod.
• It is 42 to 45 cm long and 2.0 to 2.5 cm broad.
• Conus medullaris : Terminal nervous part of the spinal cord.
• Filum terminate : Thread like non-nervous extension.
• 31 pairs of spinal nerves arise from lateral sides of the spinal cord.
• Cauda equina – Filum terminale with some spinal nerves running parallel to it. (appearing like a horse-tail)

13. T. S. of spinal cord :

• The spinal cord has a deep, narrow dorsal fissure and a broad ventral fissure.
• The inner grey matter is H-shaped and the outer white matter surrounds it.
• Grey matter is divisible into six horns, namely dorsal, lateral and ventral horns.
• The white matter is divisible into 6 columns or funiculi, namely dorsal, lateral and ventral funiculi.
• The dorsal and ventral horns extend out of the spinal cord as dorsal root and ventral root.
• The dorsal root has dorsal root ganglion which is a collection of unipolar sensory neurons. No such ganglia on ventral root.
• The adjustor/association or inter-neurons lie inside the grey matter.
• The white matter consists mainly of bundles of myelinated nerve fibre called ascending and descending tracts.

Functions :

• The spinal cord is the main centre for the most reflex actions.
• It provides pathway for conduction of sensory and motor impulses.

14. Peripheral Nervous System (PNS) : The peripheral nervous system connects the central nervous system to the different parts of the body having receptors and effectors.

Two types of peripheral nerves :

1. Cranial nerves : arise from the brain.
2. Spinal nerves : arise from the spinal cord.

15. Cranial Nerves :

16. Spinal Nerves:

• Thirty-one pairs of spinal nerves originate from the spinal cord.
• Spinal Nerves : All spinal nerves are mixed nerves.

17. Formation of a typical spinal nerve :

• Each spinal nerve is formed inside the neural canal of vertebral column.
• The dorsal sensory and the ventral motor nerves together form the mixed spinal nerve.
• As soon as it emerges out of vertebral column, it shows three branches, viz.
  a. Ramus dorsalis
  b. Ramus ventralis
  c. Ramus communicans

18. Reflex Action :

(1) It is a quick, automatic, involuntary and spontaneous response to stimulus,
(2) The path along which the action is carried out is called reflex arc.
(3) Components of a reflex arc :

a. Receptor/sense organ
b. Sensory/afferent neuron
c. Association/adjustor neuron
d. Motor/efferent neuron
e. Effector organ

(4) Types of reflexes :

a. Somatic and visceral
b. Cranial and spinal
c. Simple [monosynaptic] and complex [polysynaptic]
d. Unconditional and conditional
table

(5) According to recent studies, the ANS is under the control of CNS and nerves arising from it (PNS).
According to this view, the PNS is divided into
(i) Somatic nervous system
(ii) Autonomic nervous system

19. Autonomic Nervous System (ANS) :

• Autonomic nervous system transmits impulses from CNS to the involuntary organs and smooth muscles of the body.
• It includes – autonomic ganglia,
  preganglionic fibres and postganglionic fibres.
• Autonomic ganglia include
  • Sympathetic ganglia – present near CNS in the form of sympathetic cord.
  • Parasympathetic ganglia – present near or on the effector organs.
• Preganglionic fibres arise from grey matter of CNS and end at autonomic ganglia.
• Postganglionic fibres arise from autonomic ganglia to the effector organs.
  Autonomic nervous system consists of sympathetic and parasympathetic nervous system.

(1) Sympathetic Nervous System (SNS) :

• Also called thoraco-lumbar outflow.
• Consists of 22 pairs of sympathetic ganglia which lie near vertebral column.
• Post ganglion is neuron which produce adrenaline. Hence they are called adrenergic fibres.
• It works in emergencies. It is also called 3 Fs system [fright, fight and flight]. It has excitatory and stimulating effect on most organs of the body.

(2) Parasympathetic Nervous System:

• It is also called cranio-sacral outflow.
• It consists of ganglia which are very close or within the wall of the effector organs.
• Acetyicholine is produced at the terminal end of postganglionlc nerve at the effector organ. Hence these are also called cholinergic fibres.
• All activities which are stimulated by the sympathetic system are brought back to normal by this system. Hence it is also called housekeeping system.

Comparison between Sympathetic and Parasympathetic Nervous System :

Sensory Receptors-

1. Specialised structures in the body modified to receive the various stimuli from the external or internal environment.

2. Classification of receptors : Receptors are classified on the basis of their location, function and their sensitivity to specific stimuli. Their classification is given in the following chart.

Types of exteroceptors and interoceptors, their locations and functions :

3. Eye :

• The eyes are a pair of sensory organs of vision located in the orbit of skull.
• Each eye is spherical/rounded and called eyeball.
• Wall of the eyeball is made up of 3 layers : (1) sclera, (2) choroid (3) retina.

Generation of image/Mechanism of vision :

4. Ear :

• The human ear is called statoacoustic organ as it has two functions – hearing and body equilibrium.
• Anatomically the ear is made up of three divisions : the external ear, middle ear and inner ear.

(3) The organ of hearing :

• Organ of Corti is a pea sized structure located on basilar membrane. It has a sensory epithelium over the basilar membrane.
• The sensory cells have sensory hair on their free end so also called hair cell. In between the rows of hair cells are present supporting cells.
• Hair cells have long stiff microvilli called stereocillia on their apical surfaces. Above these stereocilia, is a jelly like membrane called tectorial membrane.
• This organ acts as a transducer, converting sound vibrations into nerve impulses.

(4) Other parts of the ear :

• Besides the cochlea, the internal ear also has the vestibular apparatus.
• It is composed of three semi-circular canals and the utriculo saccular region.
• All three semi-circular canals lie in different planes at right angles to each other.
• These canals are filled with endolymph. The base of each of the canal has an ampulla in which there is a sensory ridge called crista. The structure is crista ampullaris.
• The vestibule has two sensory spots – macula of saccule and utricle. The utricle is larger than saccule.

(5) Mechanism of Hearing :

Disorders of nervous system-

1. Psychological disorders :

Commonly called mental disorders. There is a wide range of conditions that affect the mood, thinking or behaviour.
Some of the major categories of psychological disorders are :

• Intellectual disability (earlier known as mental retardation),
• Autism spectrum disorder
• Bipolar disorder
• Depression
• Anxiety disorder
• ADHD (Attention Deficit Hyperactivity Disorder)
• Stress related disorders.

2. Parkinson’s disease :

• Degeneration of dopamine-producing neurons in the CNS causes Parkinson’s disease.
• Symptoms develop gradually over the years.
• Symptoms are tremors, stiffness, difficulty in walking, balance and coordination.

3. Alzheimer’s disease :

• It is the most common form of dementia.
• Its incidence increases with the age.
• Symptoms include the loss of cognitive functioning- thinking, remembering, reasoning and behavioural abilities. It interferes with the person’s daily life and activities.

Chemical Coordination

Endocrine system –

1. The cells in organisms communicate with each other through chemical signals. These cells are broadly of four types as follows :

• Autocrines : Cells release secretion to stimulate themselves.
• Paracrines : Cells release secretion to stimulate neighbouring cells.
• Endocrines : Cells release secretion to stimulate distant cells.
• Pheromones : Cells/Organs release secretions to stimulate other organism.

2. Chemical coordination is carried out by secretions of ductless glands or endocrine glands. Hence this chemical coordination system is also called the endocrine system.

3. Endocrine system :

• The endocrine system controls body activities by means of chemical messengers called hormones.
• Hormones are released directly into the blood.

4. Properties of Hormones :

• They act as chemical messengers and are effective in very low concentration.
• Hormones can function as regulators that inhibit or stimulate or modify specific processes.
• Hypersecretion or Hyposecretion of hormones leads to various disorders.
• These are metabolised after their function and are excreted through urine.

5. Mechanism of hormone action :

• Hormones are released in a very small quantity.
• They produce their effect on the target organs/cells by binding to hormone receptors.
• The hormone receptors may be on the cell membrane or may be intracellular.
• A hormone receptor complex is formed and . this leads to biochemical change in the target tissue.

(a) Mode of hormone action through membrane receptors :

• Hormones like catecholamines, peptide and polypeptide hormones are not lipid soluble. Therefore they cannot enter their target cells through plasma membrane.
• Molecules of amino acid derivatives, peptide hormones bind to specific receptor molecules located on the plasma membrane.
• The hormone receptor complex causes the release of an enzyme adenylate cyclase from the receptor site. This enzyme forms cyclic AMP from ATP of the cell.
• The hormone acts as the first messenger and cAMP is the second messenger.

(b) Mode of hormone action through intracellular receptors :

• Steroid and thyroid hormones are lipid soluble and easily pass through plasma membrane of target cell into the cytoplasm.
• In the cytoplasm, they bind to specific intra¬cellular receptor proteins forming a hormone-receptor complex that enters the nucleus.
• In the nucleus, the hormone receptor complex binds to a specific regulatory site of DNA.

Major endocrine glands-

1. Hypothalamus :

• Ectodermal in origin.
• Forms the floor of diencephalon.
• Major function is to maintain homeostasis.
• Controls the secretory activity of pituitary gland by the release and inhibiting hormones.
• All hormones of hypothalamus are peptide hormones.

2. Hormones of hypothalamus :

• Somatotropin/GHRF
• Somatostatin/GHRIF
• Adrenocorticotropin Releasing Hormone
• Thyrotropin Releasing Factor .
• Gonadotropin Releasing Hormone (GnRH)
• Prolactin Inhibiting Hormone (Prolactostatin)
• Gastrin Releasing Peptide (GRP)
• Gastric Inhibitory Polypeptide (GIP)

3. Pituitary gland or hypophysis :

(1) External morphology :

• Pea sized reddish-grey coloured gland.
• Controls almost all other endocrine glands, hence previously it was called the master endocrine gland.
• However, hypothalamus controls it through the releasing and inhibiting factors.
• Located just below the hypothalamus and is attached to it by a stalk called infundibulum or hypophyseal stalk.
• Remains lodged in a bony depression called sella turcica of the sphenoid bone.
• Consists of two lobes called anterior lobe (Adenohypophysis) and posterior lobe (Neurohypophysis). Intermediate lobe (Pars intermedia) is a small reduced part lying in the cleft between the anterior and posterior lobe.
• Neurohypophysis is connected directly to the hypothalamus by axon fibres forming hypothalamo- hypophyseal tract,
• Adenohypophysis and intermediate lobe are connected to the hypothalamus through hypothalamo- hypophyseal portal system.

(2) Parts, morphology, histology and functions of pituitary in a glance :

(3) Hypothalamo – Hypophyseal portal system :

• Various hormones secreted by hypothalamus reach the pituitary gland through this portal system.
• The portal vein collects blood from various parts of hypothalamus and opens into anterior lobe of pituitary.
• From pituitary, the vein finally carries the blood into the superior vena cava.

(4) Hormones of pituitary and their role :

4. Pineal gland :

• The pineal body/pineal gland is given off from the roof of diencephalon. It is located between the two cerebral hemispheres.
• The pineal gland is sensitive to the biochemical signals of light.
• It secretes a hormone called melatonin also known as sleep hormone.

5. Thyroid gland :

(1) Morphology :

• It is the largest endocrine gland.
• The two lobes of thyroid gland are connected a non-secretory band called isthmus.

(2) Internal structure :

• The thyroid lobes are composed of rounded follicles held together by interfollicular connective tissue called stroma.
• The stroma contains blood capillaries and small group of parafollicular cell or ‘C’ cells.
• Thyroid follicles Eire composed of cuboidal epithelium resting on a basement membrane and is filled with a gelatinous colloid.

(3) Thyroid hormones :

• The two hormones secreted by the follicular cells are Thyroxine/tetra iodothyronine/T₄ (four atoms of iodine) and Triiodothyronine or T₃ (three atoms of iodine).
• Parafollicular cells produce a hormone thyrocalcitonin whose production is not under the control of TSH.

(4) Formation of T₃ and T₄ :

• Thyroxine is synthesized by attaching iodine to amino acid tyrosine by enzymatic action.
• The amino acid tyrosine molecule binds to iodine to produce Monoiodotyronine (T₁) or 2 atoms of iodine to produce Diiodothyroninc (T₂).
• T₁ and T₂ molecules bind end to end to make colloidal mass inside the follicle. They are further metabolised to prepare T₃ and T₄.

(5) Functions of Thyroid hormones :

• Regulation of the basal metabolic rate of body.
• Regulation of metabolism by stimulating protein synthesis and promotes growth of body tissues.
• Calorigenic effect as it helps in thermoregulation by increasing heat production.
• Increases action of neuro transmitters – adrenaline and nor adrenaline.
• Supports the process of RBC production and maintenance of water and electrolyte balance.
• Regulates reproductive cycles in females.
• Parafollicular cells or ‘C’ cells produce thyrocalcitonin hormone, which regulates calcium metabolism.
• Calcitonin is the active form of hormone, which is hypocalcemic hormone. It regulates the concentration of calcium and phosphorus in the blood.

(6) Disorders related to thyroid gland :

6. Parathyroid gland :

• Situated on the posterior surface of the lobes of thyroid gland.
• 2 pairs, named as superior and inferior parathyroid glands.
• Cells are arranged in a compact mass.

(4) Hormones :

• The parathyroid secretes a peptide hormone called parathormone (PTH). It is also called
  Collip’s hormone.
• Regulates calcium and phosphate balance between blood and other tissues. It is a hyper calcemic hormone. Release of parathormone increases blood calcium level.
• It stimulates osteoclast of bones to stimulate bone resorption.
• Thus, parathormone and calcitonin are antagonistic hormones.

(5) Disorders :

Hyposecretion of parathormone	Hypersecretion of parathormone
Parathyroid tetany or hypocalcaemic tetany.	Osteoporosis.
Lowers concentration of calcium in the blood. This increases excitability of nerves and muscles causing muscle twitch and spasm.	Responsible for more resorption of calcium from bones i.e., demineralization of bones resulting in softening, bending and fracture of bone.

7. Thymus gland :

(1) Located in the upper part of thorax on the dorsal side of the heart just behind sternum.
(2) Prominent gland at birth till puberty but gets gradually atrophied in the adult due to action of sex hormones.

(3) Functions:

• Secretes the hormone thymosin.
• Important role in the development of immune system by maturation of T-lymphocytes.

8. Adrenal gland/Suprarenal gland:

(1) Adrenal glands have dual origin from mesoderm and ectoderm.”
(2) Located on the upper border of each kidney.
(3) Small. conical yellowish glands having two distinct regions, outer cortex and inner medulla.

(A) Adrenal cortex (outer)	(B) Adrenal medulla (inner)
Derived from embryonic mesoderm. Secretes many hormones together called corticoids. Main two hormones : (1) Glucocorticoids (2) Mineralocorticoids	Derived from embryonic ectoderm. Secretes main two hormones (1)   Adrenaline (epinephrine) (Emergency hormone, also called 3F hormone – (fight, flight and fright). (2)   Noradrenaline (norepinephrine). (Regulates the blood pressure under normal condition, acts as vasoconstrictor)

(4) Three concentric regions of adrenal cortex :

(5) Disorders related to Adrenal cortex :

9. Pancreas :

• Develops from endoderm.
• It is heterocrine i,e. both exocrine and endocrine gland.
• Endocrine cells of pancreas form groups of cells called Islets of Langerhans.
• There are four kinds of cells in islets of

Langerhans which secrete hormones.

• Alpha (α) cells (20%) secrete glucagon.
• Beta (β) cells (70%) secrete insulin.
• Delta ((δ) cell (5%) secrete somatostatin
• PP cells or F cells (5%) secrete pancreatic polypeptide (PP).

Disorder related to pancreas : Diabetes mellitus

• Hyperglycemia i.e. It leads to increased blood glucose level.
• Cause : Under activity of Beta cells, which results in reduced secretion of insulin.
• Types of diabetes :

(1) TYPE-1 diabetes i.e. insulin dependent diabetes mellitus (IDDM)
(2) TYPE-2 diabetes i.e. Non insulin dependent diabetes mellitus (NIDDMj.

• Diabetes causes glucosuria, excessive urination and dehydration of body tissues, degradation of fats and increase in formation of ketone bodies (ketosis).
• Administration of insulin lowers blood glucose level.

10. Gonads : Gonads are sex organs (the testes and the ovaries).

(1) Ovaries :

(2) Testes : Testes secrete male sex hormones called androgens such as testosterone.

Testosterone :

• It is secreted from interstitial cells or Leydig cells by the influence of luteinising hormone (LH).
• Rise in testosterone level in blood above normal inhibits LH secretion.
• It is also responsible for appearance of secondary sexual characters such as facial and pubic hair, deepening of voice, broadening of shoulders, male aggressiveness, etc.

11. Placenta :

• Temporary endocrine source in pregnant women which forms intimate connection between foetus and uterine wall of the mother for physiological exchange of the materials.
• During pregnancy, placenta secretes hormones such as estrogen, progesterone, HCG (Human Chorionic Gonadotropin) and human placental progesterone.

12. Diffused endocrine glands :

(1) Gastro-intestinal tract : Certain cells of gastrointestinal mucosa are endocrine in function. Their hormones play vital role in digestive processes and flow of digestive juices.

Hormone of GI tract	Function
1. Gastrin	Stimulates gastric glands to produce gastric juice.
2. Secretin	Responsible for secretion of pancreatic juice and bile from pancreas and liver.
3. Cholecystokinin CCK/ Pancreozymin PZ :	Stimulates gall bladder to release bile and stimulates the pancreas to release its enzymes.
4. Entero-gastrone/Gastric inhibitory peptide (GIP)	Slows gastric contractions and inhibits the secretion of gastric juice.

(2) Kidney :

• Hormones of kidney – renin, erythropoietin and calcitriol (calcitriol is the active form of vitamin cholecalciferol -D3).
• Renin along with angiotensin helps in maintaining the blood pressure in the renal artery by vasoconstriction.
• Erythropoietin stimulates erythropoiesis.
• Calcitriol helps in absorbing calcium from the stomach.

(3) Heart :

• Hormone of heart-Atrial natriuretic Factor /ANE
• Increases sodium excretion [natriuresis] along with water by kidneys.
• Reduces blood pressure by lowering blood volume.

13. Hormone therapy/HT :

• Use of hormones in medical treatment.
• Required for the patients during pregnancy, menopause, osteoporosis, growth hormone deficiency, insulin resistance, cancer, etc.

By going through these Maharashtra State Board 12th Science Chemistry Notes Chapter 8 Transition and Inner Transition Elements students can recall all the concepts quickly.

Maharashtra State Board 12th Chemistry Notes Chapter 8 Transition and Inner Transition Elements

d – Series :

• 3d-Series : ₂₁Sc to ₃₀Zn
• 4d-Series: ₃₉Y to ₄₈Cd
• 5d-Series : ₅₇La to ₈₀Hg
• 5d-Series : ₈₉Ac to ₁₁₂Cn

Electronic Configuration :

• 3d-Series: [Ar] 3d^1-10 4s^1-2
• 4d-Series:[Kr] 4d^1-10 5s^1-2
• 5d-Series: [Xe] 4f¹⁴ 5d^1-10 6s^1-2
• 6d- Series: [Rn] 5f¹⁴ 6d^1-10 7s^1-2

Electronic configuration	Expected	Observed
(i) 24Cr (ii) 29Cu	[Ar] 3d44y2 [Ar] 3d9 As2	[Ar] 3d5 As1 [Ar] 3d10 As1

For 3d-Series :

• Atomic radii decrease from Sc to Cu
• Ionic radii decrease from Sc to Ni
• First ionisation enthalpy increases from Sc to Zn.

Transition elements show variable oxidation states common being + 2.

1 Bohr Magneton (B.M) = \(\frac{e h}{4 \pi m_{\mathrm{e}} c}\)

Spin only formula : \(\mu=\sqrt{n(n+2)}\)

KMnO₄

Preparation from MnO₂

Strong oxidising agent

• in acidic medium
• in neutral or weakly alkaline medium

K₂Cr₂O₇ :

Preparation from chromite ore :

Metallurgy :

1. Metal extraction processes –

• Pyrometallurgy
• Hydrometallurgy
• Electrometallurgy

2. Steps involved in the extraction of pure metal-

• Concentration
• Conversion of an ore into oxides
• Reduction of an ore
• Refining of metals

3. Extraction of iron from haematite ore by Blast furnace

f-Block elements :

Lanthanoids : _{5 8}Ce to _{7 1}Lu
Actinoids : _{9 0}Th to _{1 0 3}Lr

Electronic configuration :

Lanthanoids : [Xe] 4f^1-14 5d^0-1 6s²
Actinoids : [Rn] 5f^1-14 6d^0-1 7s²

Position in periodic table :

f-Block elements	Group	Period
Lanthanoids	3	6
Actinoids	3	7

Lanthanoid contraction, Actinoid contraction

By going through these Maharashtra State Board 12th Science Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18 students can recall all the concepts quickly.

Maharashtra State Board 12th Chemistry Notes Chapter 7 Elements of Groups 16, 17 and 18

Atomic, physical and chemical properties of group 16,17 and 18 elements-

Group 16 elements-

O to Po:

• Atomic size, M.P., B.P., Density increase
• Ionisation enthalpy, electronegativity decrease
• Hydrides (H₂X) : Bond angle, bond energy decrease Reducing power increases
• Oxides (EO₂, EO₃) (E = S, Se, Te, Po)
• Halides (EX₆, EX₄, EX2) (E = S, Se, Te)
• Reacts with metals to form compounds

Allotropes :

• O : O₂, O₃ (Ozone)
• S : Rhombic, monoclinic, cyclo-S6
• Se : red, grey
• Te : Crystalline, amorphous
• Po : α, β

Group 17 elements-

F to I (At):

• Atomic size, Density increase
• Ionisation enthalpy, electronegativity decrease
• (Haloacids, HX) : Acidity, reducing character increase Stability decrease
• Oxides of halogens (Most of them are unstable)
• Interhalogen compounds
• Metal halides

Group 18 elements-

He to Xe (Rn):

• Atomic size, density, M.P., B.P., increase
• Ionisation enthalpy, decreases
• Chemically inert towards hydrogen, oxygen
• krypton and Xenon form fluorides

Oxoacids of sulphur-

Oxoacids of halogens-

O₂ – Preparation –

O₂ –
2Ca + O₂ → 2CaO
C + O₂ → CO₂

Simple oxides-

Acidic (CO₂, SO₂, etc.)
Basic (CaO, BaO, etc.)
Amphoteric (Al₂O3, Zno, etc.)

Ozone –

Oxidising property: (i) PbS_(S) + 4O_3(g) → PbSO₄ + 4O_2(g)
(ii) 2KI + H₂O +O₃ →2KOH + I₂ + O₂
(iii) NO_(g) + O_3(g) → NO_2(g) + O_2(g)
Bleaching property O₃ → O + O₂
Reducing property : BaO₂ + O₃ → BaO + 2O₂
H₂O₂ + O₃ → H₂O + 2O₂

SO₂ – preparation

S_(S) + O_2(g) → SO_2(g)
Na₂SO₃ + H₂SO_4(aq) → Na₂SO₄ + H₂O_(I) + SO_2(g)

SO₂ –

2NaoH + SO₂ → Na₂SO₃ + H₂O
Na₂SO₃ + H₂O + SO₂ → 2NaSO₃
2Fe³⁺ + SO₂ + 2H₂O → 2Fe²⁺ + SO₄ ^2- + 4H⁺

H₂SO₄ (Manufacture)—Contact process—(Catalyst V₂O₅)

H₂SO₄ – 

C + 2H₂SO₄ → CO₂ + 2H₂O + 2SO₂
S + 2H₂SO₄ → 3SO₂ + 2H₂O
Cu + 2H₂SO₄ → CuSO₄ + SO₂ + 2H₂O

NaCl + H₂SO₄ → NaHSO₄ + HCl
KNO₃ + H₂SO₄ → KHSO₄ + HNO₃
CaF₂ + H₂SO₄ → CaSO₄ + 2HF

Chlorine Preparation –

MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H₂O
4NaCl + MnO₂ + 4H₂SO₄ → 4NaHSO₄ + MnCl₂ + 2H₂O + Cl₂

NaCl ⇌ Na⁺ + Cl^–

Cl₂ –

2Al + 3Cl₂ → 2AlCl₃
P₄ + 6Cl₂ → 4PCl₃
H₂ + Cl₂ → 2HCl
8NH₃ (Excess) + 3Cl₂ → 6NH₄Cl + N₂
2Ca(OH)₂ + 2Cl₂ → Ca(OCl)₂ + CaCl₂ + 2H₂O

2FeSO₄ + H₂SO₄ + Cl₂ → Fe₂(SO₄)₃ + 2HCl
Cl₂ + H₂O → HCl + HOCl

HCl : Preparation –

HCl –

HCl_(g) + H₂O_(l) → H₃O⁺ + Cl^–(aq)
NH₃ + HCl → NH₄Cl
Au + 4H⁺ + NO^–₃ + 4Cl^– → AuCl^–₄ + NO + 2H₂O

Interhalogen Compounds-

Compounds of Xenon-

Compound	Hybridisation	Structure
(i) XeF2	sp3d	linear
(ii) XeF4	sp3d2	square planar
(iii) XeF6	sp3d3	distorted octahedral
(iv) Xe03	sp3	pyramidal

 

By going through these Maharashtra State Board 12th Science Chemistry Notes Chapter 6 Chemical Kinetics students can recall all the concepts quickly.

Maharashtra State Board 12th Chemistry Notes Chapter 6 Chemical Kinetics

→ For a reaction, aA + bB → cC + dD
Average rate = \(-\frac{1}{a} \frac{\Delta[\mathrm{A}]}{\Delta t}=-\frac{1}{b} \frac{\Delta[\mathrm{B}]}{\Delta t}=-\frac{1}{c} \frac{\Delta[C]}{\Delta t}=-\frac{1}{d} \frac{\Delta[\mathrm{D}]}{\Delta t}\)

→ Rate law : Rate = k [A]^a x [B]^b

→ k = \(\frac{2.303}{t}\) log₁₀ \(\frac{[\mathrm{A}]_{0}}{[\mathrm{~A}]_{\mathrm{t}}}\) (For first order reaction)

→ t_1/2 = \(\frac{0.693}{k}\) (For first order reaction)

→ k = \(\frac{[\mathrm{A}]_{0}-[\mathrm{A}]_{t}}{t}\) (For zero order reaction)

→ t_1/2 = \(\frac{[\mathrm{A}]_{0}}{2 k}\)(For zero order reaction)

→ k = Ae^-Ea/RT (Arrhenius equation)

→ log₁₀k =log₁₀A – \(\frac{E_{a}}{2.303 R \mathrm{~T}}\)

→ log₁₀\(\frac{k_{2}}{k_{1}}=\frac{E_{a}\left(T_{2}-T_{1}\right)}{2.303 R \times T_{1} \times T_{2}}\)

By going through these Maharashtra State Board 12th Science Chemistry Notes Chapter 5 Electrochemistry students can recall all the concepts quickly.

Maharashtra State Board 12th Chemistry Notes Chapter 5 Electrochemistry

→ Electrical conductance (G) = \(\frac{1}{R}\)Ω^-1 2 or S

→ Cell constant = \(\frac{l}{a}\) cm^-1 (m^-1)

→ Conductivity(k) = \(\frac{\text { Cell constant }}{\text { Resistance }}\)

→ Molar Conductivity(∧_m) = \(\frac{\kappa}{C}\) (k in Ω^-1 m^-1 and C in mol^-3) OR
∧_m = \(\frac{\kappa \times 1000}{C}\) (k in Ω^-1 cm^-1 and C in mol dm^-3)

→ Kohlrausch’s law : ∧₀ = \(\lambda_{+}^{0}+\lambda_{-}^{0}\)

→ Degree of dissociation (α) = \(\frac{\Lambda_{\mathrm{m}}}{\Lambda_{0}}\)

→ Dissociation constant (Ka) = \(\frac{\bigwedge_{\mathrm{m}}^{2} C}{\Lambda_{0}\left(\Lambda_{0}-\Lambda_{\mathrm{m}}\right)}\)

→ 1 Faraday = 96500 C (Change on one mole of electrons)

→ E°_cell = E°_red (cathode) – E°_red (anode)

→ E_Mⁿ⁺/M = E°_Mⁿ⁺/M – \(\frac{0.0592}{n}\) log₁₀[Mⁿ⁺]

→ E_cell = E°_cell – \(\frac{0.0592}{n} \log _{10} \frac{[\text { Products }]}{[\text { Reactants }]}\)

→ ΔG° = – nFE°_cell

→ ΔG = -nFE_cell

→ ΔG°= -RTlnK

→ E°_cell = \(\frac{0.0592}{n}\) log₁₀K
For spontaneous cell reaction : E_cell > 0; ΔG < 0

By going through these Maharashtra State Board 12th Science Chemistry Notes Chapter 4 Chemical Thermodynamics students can recall all the concepts quickly.

Maharashtra State Board 12th Chemistry Notes Chapter 4 Chemical Thermodynamics

→ W = -P (V₂ – V₁) = -PΔV (For expansion)

→ W = P (V₂ – V₁) = PΔV (For compression)

→ W_max = -2.303 nRT log₁₀ \(\frac{V_{2}}{V_{1}}\)

→ W_max= -2.303 nRT log₁₀ \(\frac{P_{1}}{P_{2}}\)

→ ΔU = q + W

→ H = U + PV

→ ΔH = ΔU + PΔV

→ ΔH = ΔU + ΔnRT

→ Hess’s law : ΔH = ΔH₁ + ΔH₂ + ΔH₃

→ ΔS = \(\frac{q_{\mathrm{rev}}}{T}=\frac{\Delta H}{T}\)

→ G = H – TS

→ ΔG = ΔH – TΔS

→ ΔG°= – 2.303 RTlog₁₀K

→ (i) ΔG = 0, the system is at equilibrium
(ii) ΔG < 0, the process is spontaneous
(iii) ΔG > 0, the process is non-spontaneous.

By going through these Maharashtra State Board 12th Science Chemistry Notes Chapter 3 Ionic Equilibria students can recall all the concepts quickly.

Maharashtra State Board 12th Chemistry Notes Chapter 3 Ionic Equilibria

→ Formulae on Ostwald’s dilution law:

→ K_w = [H₃O⁺] × [OH^–], at 25°C K_w = 1 × 10^-14

→ pH = -log₁₀[H⁺]; pOH = -log₁₀[OH^–]

→ pH + pOH = 14

→ Acidic buffer solution: pH = PK_a + log₁₀ \(\frac { [salt] }{ [acid] }\)

→ Basic buffer solution: pOH = pK_b + log₁₀ \(\frac { [salt] }{ [acid] }\)

→ PK_a = – log₁₀ K_a; pK_b = – log₁₀ K_b

→ Solubility product:

k_sp = (xs)^x (ys)^y = x^xy^y x (S)^x+y

By going through these Maharashtra State Board 12th Science Chemistry Notes Chapter 2 Solutions students can recall all the concepts quickly.

Maharashtra State Board 12th Chemistry Notes Chapter 2 Solutions

→ Henry’s law : S = K_HP

→ Raoult’s law : P_soln = x₁P₀

→ Mole fractions, x₁ + x₂ = 1

→ P_soln = P°₁x₁ + P°₂x₂

→ P_soln = (P°₂ – P°₁)x₂ + P°₁

→ Mole fractions of components in vapour phase : y₁ = \(\frac{x_{1} P_{1}^{0}}{P}\) and y₂ = \(\frac{x_{2} P_{2}^{0}}{P}\)

→ For ideal solutions : ΔV_mix = 0; Δ_mixH = 0

→ Relative lowering of vapour pressure = \(\frac{P^{0}-P}{P^{0}}\), x₂ = \(\frac{P^{0}-P}{P^{0}}\)

→ \(\frac{P^{0}-P}{P^{0}}=\frac{W_{2} \times M_{1}}{W_{1} \times M_{2}}\)

→ Δ T_b = K_b x m and Δ T_f — K_f x m

→ ΔT_b = K_b x \(\frac{W_{2} \times 1000}{W_{1} \times M_{2}}\)

→ ΔT_f = K_f x \(\frac{W_{2} \times 1000}{W_{1} \times M_{2}}\)

→ π = cRT and π = \(\frac{W R T}{M \times V}\)

→ i = \(\frac{Colligative property of electrolyte solution}{Colligative property of nonelectrolyte solution of the same concentration}\)

→ Van’t Hoff factor (i) = \(\frac{\Delta T_{\mathrm{b}(\mathrm{ob})}}{\Delta T_{\mathrm{b}(\mathrm{th})}}=\frac{\Delta P_{(\mathrm{ob})}}{\Delta P_{(\mathrm{th})}}=\frac{\Delta T_{\mathrm{f}(\mathrm{ob})}}{\Delta T_{\mathrm{f}(\mathrm{th})}}=\frac{\pi_{\mathrm{ob}}}{\pi_{\mathrm{th}}}=\frac{M_{\mathrm{th}}}{M_{\mathrm{ob}}}\)

→ Colligative properties considering van’t Hoff factor :

→ α = \(\frac{i-1}{n-1}\) (for dissociation)

By going through these Maharashtra State Board 12th Science Chemistry Notes Chapter 1 Solid State students can recall all the concepts quickly.

Maharashtra State Board 12th Chemistry Notes Chapter 1 Solid State

Solids-

• Crystalline
• Amorphous

Crystalline solids-

• Ionic crystals
• Covalent network crystals
• Molecular crystals
• Metallic crystals

Crystal systems-

• Cubic
• Orthorhombic
• Tetragonal
• Monoclinic
• Rhombohedral
• Triclinic
• Hexagonal

Classification of crystal systems (Bravais lattices) :

Cubic lattice –

1. Simple cubic or primitive
2. Body centred cubic
3. Face centred cubic

Number of atoms in the unit cell :

Packing efficiency :

Number of tetrahedral voids = 2 Number of atoms
Number of octahedral voids = Number of atoms

Relation between radius (r) of an atom and edge length (a) of cubic unit cell

Density of the crystal: p = \(=\frac{n \times M}{a^{3} \times N_{\mathrm{A}}}\)

Defects in solids-

(1) Point defects-

1. Vacancy defects (Schottky defects)
2. Interstitial defects (Frenkel defects)
3. Impurity defects-
   • Substitutional impurity defects
   • Interstitial impurity defects

(2) Nonstoichiometric defects

• Metal deficiency defect
• Metal excess defect

Conducting solids-

• Conductors
• Semiconductors
• Insulators

Semiconductors –

• Intrinsic
• Extrinsic
• n-type
• p-type

Magnetic properties-

• Diamagnetic
• Paramagnetic
• Ferromagnetic

(1) Diamagnetism is due to the presence of all paired electrons in the substance.
(2) Paramagnetism is due to the presence of one or more unpaired electrons in the substance.