Preparation of solid derivatives of Carbonyl compounds (aldehydes & ketones) :- 2, 4- Dintrophenylhydrazones, Semicarbazones

The systematic procedure that involves several steps and preparations is carried out to identify unknown compounds to some extent. The preparation of derivatives usually establishes the identification of the unknown with certainty. Here the term derivative is simply referred to a compound prepared from an unknown, in order to identify the unknown compound. An ideal derivative should be a crystalline, easily purified solid with a sharp melting point, which can be prepared readily from the unknown in one direct and unambiguous step.

Many carbonyl compounds can be synthesized from the esterification reaction. There are excellent and conveniently prepared derivatives which use to identify carbonyl compounds. Oximes, Phenyl hydrazones, 2, 4-dinitrophenylhydrazones and semicarbazones are some of the best derivatives of aldehydes and ketones. In the preparation of each of these types of derivatives, the elimination of a water molecule between a molecule of the carbonyl compound and a molecule of the reagent is involved.

Dinitrophenylhydrazine is relatively sensitive to shock and friction. It is a red to orange solid usually supplied wet to reduce its explosive hazard. This is often used as a qualitative test for carbonyl groups, associated with aldehydes and ketones. The hydrazone derivatives can be used as evidence toward the identity of the original compound. These are usually yellow-red colour crystals. Crystals of different hydrazones have characteristic melting and boiling points allowing the identification of the unknown substance.

Semicarbazone is one of the most commonly used derivatives to identify aldehydes and ketones. It is a derivative of an aldehyde or ketone formed by a condensation reaction between a ketone or aldehyde and the reagent; semicarbazide. As semicarbazides are not very stable in the free form, they are usually stored in the laboratory in the form of their hydrochloride salts. Many semicarbazones are off white, crystalline solids, useful for the identification of the parent carbonyl group by melting point analysis.

Controlling metabolism at cellular level: Compartmentation

Metabolism is composed of reaction sequences termed as metabolic pathways. The changes at each step in a metabolic pathway are regulated in order to maintain the stability and survival of the organism. Mainly there are four ways of controlling metabolism. Such one important way of controlling metabolism at cellular level is compartmentation.

When considering a eukaryotic cell; it’s composed of many different compartments known as sub cellular organelles in contrast to a prokaryotic cell. Each organelle contributes a specific metabolic function with different enzymatic activities under different conditions. These metabolic pathways needed to be interconnected to maintain the metabolism. Therefore compartmentation allows the distribution of metabolites and enzymes between the membranes bounded organelles. It’s the method that enables the cell to obtain different metabolic activities at the same time for more energy efficiency. For an example, glycolysis occurs in the cytoplasm and provides the mitochondria substrates such as pyruvates from carbohydrate oxidation. TCA cycle occurs within the mitochondrion matrix while oxidative phosphorylation occurs in mitochondria inner membrane. However, altogether all these three processes are included in one metabolism called ‘cell respiration’. Enzymes of each process are found where the processes take place.

Fat metabolism is another one good example for compartmentation. Fatty acids synthesis takes place in cytoplasm. Cytoplasm contains the required enzymes for the anabolism of fatty acid synthesis. But these fatty acids are degregaded in mitochondria supplying Acetyl Co A for TCA cycle. Mitochondria also contain the enzymes require for the catabolism of fat.

RNA polymerase allows RNA synthesis by using a template of DNA strand. It catalyzes the synthesis of RNA. RNA synthesis takes place in nucleus. DNA transcription also occurs in nucleus. Therefore both the RNA polymerase and DNA templates are available, so that the RNA synthesis is favorable. When considering protein synthesis, all the organelles used for it are close to one another. The nucleolus makes ribosome which synthesizes proteins. Endoplasmic reticulum is near the nucleus to receive Ribosomes and synthesized proteins. The Golgi apparatus is also near the endoplasmic reticulum for storing, packaging and distribution. Therefore all the activities within a cell are cooperated with one another.

Hence, compartmentation helps metabolic controlling by maintaining substrates, regulators and enzymes in separate locations with only favoured access between them.

Plant senescence in brief

Senescence

Senescence is an important program in which the function of a cell/tissue/whole plant naturally leads to its death.

Senescence involves in plant aging.

When tissues senesce they produce enzymes which can recycle the “expensive” materials and reroute the sub-units to somewhere else that growth takes place.

Overall senescence

·         Occurs in the whole plant.

·         Death takes place right after flower and setting.

·         When the flower dies the whole plant dies too.

·         Ex: Asteraceae ( Sun flower)

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Top senescence

·         After the growth season the part above the ground dies remaining the underground part that can grow for several years.

·         Therefore a rhizome is present.

·         Ex: Weed, Grass

       

Deciduous senescence

·         In dry seasons like winter and summer, the leaves falls and trunk remains.

·         Leaves fall due to avoid the heavy transpiration occurs in the dry season.

·         Ex: Deciduous plants

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Progressive senescence

·         Older parts die due to the senescence and the new organs and tissues continue their development.

·         Ex: Green trees

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As above mentioned, senescence can occur in cells as well as tissues.

Cell senescence

·         Can be described according to the senescence in cell membrane and organelle level.

Senescence in cell membrane

Lipid phase change

·         Plasma membrane has the fluid mosaic structure.

·         This structure changes as the liquid crystalline state changes into the solid-gel state.

·         Therefore the membrane gets inflexible and hard.

Degradation and preoxidation of lipids

·         Lipid content gets decreased.

·         It occurs as the lipid synthesis decreases and lipase content increases.

·         Phospholipase, lipoxygenase, MDA and active O₂ content increase.

Increase in Phospholipase activity

·         Mainly the activity of Phospholipase D takes place in plants.

Biomembrane degradation and leakage

·         The equilibrium of ions breaks down.

·         Metabolisms get disordered.

Senescence in organelle level

·         Ribosomes and RER break down.

·         Chloroplasts collapse and mitochondrion cristae are swollen.

·           As the vacuoles break down, all the toxics inside them is released to the cell plasma.

·         Therefore the autophagy takes place and the senescence of organelles activates.

Characteristics of sp, sp2, sp3- hybrid orbitals

Characteristics of sp-hybrid orbital

·         Results from mixing of one s and one p-orbital.

·         Equivalent and symmetrical.

·         All orbitals have the same shape and energy.

·         Shape is oval shape which is in between spherical and pear shape.

·         Sp- hybrid orbitals are collinear. That means they are aligned in a straight line in opposite direction.

Characteristics of sp²-hybrid orbital

·         Results from mixing of one s-orbital and two p-orbitals.

·         They have the same shape and energy.

·         Lie in one plane.

·         Shape tends more towards the pear shape as the contribution of p-orbital is greater than the contribution of s orbital.

·         Spatial arrangement is trigonal. Angle between each pair is 120^o

Characteristics of sp³- hybrid orbital

·         Results from combination of one s-orbital and three p-orbitals.

·         Orbitals are equivalent and symmetrical.

·         Same shape and energy.

·         Arranged in tetrahedral angle where the angle between each pair is 109.5^o

·         Pear shaped but the lobes are much spread and somewhat shorter in length than the original p-orbitals.

Introduction to Nervous system

§ All animals are capable of corresponding to their surroundings. They gather stimuli from the environment by sensory receptors and the motor effectors react to it.

§  Most invertebrates and vertebrates process and integrate the information from the receptors and issue the instructions to the motor effectors. This process is done by the nervous system. It connects the receptors and effectors by the large network of nerve cells.

§  These nerve cells are called as “Neurons”.

§  The nervous system is principally consisting of Neurons and Glial cells.

Neurons

§  Consists of large cell body with cytoplasmic extensions.

§  Cell body is large containing the nucleus.

§  Other organelles such as mitochondria, ER, Golgi apparatus, microfilaments are present in the cell body.

§  Also Nissel bodies which are groups of ribosome are present in the cell body.

§  Two types of cytoplasmic extensions; Dendrites and Axon.

Dendrites	Axon
·         One or more can be extend from the cell body	·         Single Axon extends from the cell body
·         Can branch forming dentritic spines.	·         Branches only at the terminal end.
·         Schwann cells are not present. Myelin sheath is not present.	·         Schwann cells are present. Myelin sheath is present.
·         Radius tapers.	·         Constant radius
·         Short	·         Much longer
·         Transmit signals into the cell body.	·          Transmit signals away from the cell body.

§  Neurons communicate with other cells via synapses.Synaptic Bulbs at the Axon terminal ends are important to form these synapses.

Structure of Synapses

                               

Structural classes of neurons

  §  Bipolar neuron: One dendrite and one axon attached to the cell body.

  §  Pseudounipolar neuron: One extension from the cell body. That is an axon.

  §  Multipolar neuron: Many dendrites and one axon.

           

          

                   

Functional types of neurons

  §  Sensory neurons: Transmit massages from the receptors.

  §  Motor neurons: Transmit massages to the motor effectors.

  §  Intermediate neurons: Connect sensory and motor neurons.

Glial cells

  §  Non-neuronal, supporting cells.

  §  Support neurons both structurally and functionally.

  §  Large numbers of different types are present.

  §  Ex: Schwann cells

Mainly Nervous system can be divided in to two sections as Central Nervous System and Peripheral Nervous System. 

§  

Basis of biochemical tests; Biuret test, Benedict test, Iodine/potassium iodide test, Emulsion test

Biuret test
A test for peptide bonds to identify proteins.

In the presence of dil.copper sulphate in alkaline solution, nitrogen atoms in the peptide chain form a purple complex with copper(ll) ions. Biuret is a compound derived from urea which also contains the –CONH- group and  gives a positive result.

Benedict test

A test for sugar

Reducing sugars- Benedict’s solution contains copper sulphate. Reducing sugars reduce soluble blue copper sulphate. Here the containing copper(ll) ions will change to insoluble red- brown copper oxide containing copper(l). This is seen as the precipitate.

Non-reducing sugars- The disaccharide will hydrolysed to its monosaccharide elements by boiling with dil. HCl. Such as Sucrose will be hydrolysed to glucose and fructose which are both reducing sugars. That will give the reducing sugar results with the Benedict’s test.

Iodine/potassium iodide test

A test for starch.

What is given at last is a poly-iodide complex formed with starch.

Emulsion test

A test for Lipids

Lipids are iinsoluble with water. Adding water to a solution of the lipid in alcohol results in an emulsion of lipid droplets or micelles in the water. These reflect light and give a white, opalescent appearance.

Test for phenols:- Phenol, 2-napthol, Catechol, Resorcinol

Azo-dye formation

Procedure	Observation
2drops of aniline were dissolved in 1ml of con.HCl and 3ml of water were shaken in a test tube. It was kept in ice. Also 20% sodium nitrite solution and phenol dissolved in NaOH were kept in ice. Few drops of sodium nitrite were added to the cold aniline. Maintaining the temperature around 0-4°C this prepared diazonium solution was added to the cold phenol.	Phenol: intense orange colour dye 2-napthol: red colour dye Catechol: dark brownish dye Resorcinol: red colour dye

UNSOLVED PROBLEMS IN PHYSICS

1. Are all the (measurable) dimensionless parameters that characterize the physical universe calculable in principle or are some merely determined by historical or quantum mechanical accident and uncalculable?

1.  Einstein put it more crisply: did God have a choice in creating the universe? Imagine the Old One sitting at his control console, preparing to set off the Big Bang. "How fast should I set the speed of light?" "How much charge should I give this little speck called an electron?" "What value should I give to Planck's constant, the parameter that determines the size of the tiny packets -- the quanta -- in which energy shall be parceled?" Was he randomly dashing off numbers to meet a deadline? Or do the values have to be what they are because of a deep, hidden logic? These kinds of questions come to a point with a conundrum involving a mysterious number called alpha. If you square the charge of the electron and then divide it by the speed of light times Planck's constant, all the dimensions (mass, time and distance) cancel out, yielding a so-called "pure number" -- alpha, which is just slightly over 1/137. But why is it not precisely 1/137 or some other value entirely? Physicists and even mystics have tried in vain to explain why.

1. How can quantum gravity help explain the origin of the universe?

1.  Two of the great theories of modern physics are the standard model, which uses quantum mechanics to describe the subatomic particles and the forces they obey, and general relativity, the theory of gravity. Physicists have long hoped that merging the two into a "theory of everything" -- quantum gravity -- would yield a deeper understanding of the universe, including how it spontaneously popped into existence with the Big Bang. The leading candidate for this merger is String theory, or M theory, as the latest, souped-up version is called (with the M standing for "magic," "mystery," or "mother of all theories").

1. What is the lifetime of the proton and how do we understand it? 

1. It used to be considered gospel that protons, unlike, say, neutrons, live forever, never decaying into smaller pieces. Then in the 1970's, theorists realized that their candidates for a grand unified theory, merging all the forces except gravity, implied that protons must be unstable. Wait long enough and, very occasionally, one should break down. The trick is to catch it in the act. Sitting in underground laboratories, shielded from cosmic rays and other disturbances, experimenters have whiled away the years watching large tanks of water, waiting for a proton inside one of the atoms to give up the ghost. So far the fatality rate is zero, meaning that either protons are perfectly stable or their lifetime is enormous -- an estimated billion trillion trillion years or more.

1. Is nature supersymmetric, and if so, how is supersymmetry broken? 

1. Many physicists believe that unifying all the forces, including gravity, into a single theory would require showing that two very different kinds of particles are actually intimately related, a phenomenon called supersymmetry. The first, fermions, are loosely described as the building blocks of matter, like protons, electrons and neutrons. They clump together to make stuff. The others, the bosons, are the particles that carry forces, like photons, conveyors of light. With supersymmetry, every fermion would have a boson twin, and vice versa. Physicists, with their compulsion for coining funny names, call the so-called superpartners "sparticles": For the electron, there would be the selectron; for the photon, the photino. But since the sparticles have not been observed in nature, physicists would also have to explain why, in the jargon, the symmetry is "broken": the mathematical perfection that existed at the moment of creation was knocked out of kilter as the universe cooled and congealed into its present lopsided state.

1. Why does the universe appear to have one time and three space dimensions? 

1. "Just because" is not considered an acceptable answer. And just because people can't imagine moving in extra directions, beyond up-and-down, left-and-right, and back-and-forth, doesn't mean that the universe had to be designed that way. According to superstring theory, in fact, there must be six more spatial dimensions, each one curled up too tiny to detect. If the theory is right, then why did only three of them unfurl, leaving us with this comparatively claustrophobic dominion?

1. Why does the cosmological constant have the value that it has? Is it zero and is it really constant? Until recently cosmologists thought the universe was expanding at a steady clip. But recent observations indicate that the expansion may be getting faster and faster. This slight acceleration is described by a number called the cosmological constant. Whether the constant turns out to be zero, as earlier believed, or some very tiny number, physicists are at a loss to explain why. According to some fundamental calculations, it should be huge -- some 10¹⁰ to 10¹²² times as big as has been observed. The universe, in other words, should be ballooning in leaps and bounds. Since it is not, there must be some mechanism suppressing the effect. If the universe were perfectly supersymmetric, the cosmological constant would become canceled out entirely. But since the symmetry, if it exists at all, appears to be broken, the constant would still remain far too large. Things would get even more confusing if the constant turned out to vary over time.

1. What are the fundamental degrees of freedom of M-theory (the theory whose low-energy limit is eleven-dimensional supergravity and that subsumes the five consistent superstring theories) and does the theory describe nature? For years, one big strike against superstring theory was that there were five versions. Which, if any, described the universe? The rivals have been recently reconciled into an overarching 11-dimensional framework called M theory, but only by introducing complications. Before M theory, all the subatomic particles were said to be made from tiny superstrings. M theory adds to the subatomic mix even weirder objects called "branes" -- like membranes but with as many as nine dimensions. The question now is, Which is more fundamental -- are strings made from branes or vice versa? Or is there something else even more basic that no one has thought of yet? Finally, is any of this real, or is M theory just a fascinating mind game?

1. What is the resolution of the black hole information paradox? According to quantum theory, information -- whether it describes the velocity of a particle or the precise manner in which ink marks or pixels are arranged on a document -- cannot disappear from the universe. But the physicists Kip Thorne, John Preskill and Stephen Hawking have a standing bet: what would happen if you dropped a copy of the Encyclopaedia Britannica down a black hole? It does not matter whether there are other identical copies elsewhere in the cosmos. As defined in physics, information is not the same as meaning, but simply refers to the binary digits, or some other code, used to precisely describe an object or pattern. So it seems that the information in those particular books would be swallowed up and gone forever. And that is supposed to be impossible. Dr. Hawking and Dr. Thorne believe the information would indeed disappear and that quantum mechanics will just have to deal with it. Dr. Preskill speculates that the information doesn't really vanish: it may be displayed somehow on the surface of the black hole, as on a cosmic movie screen.

1. Why is gravity so much weaker than the other forces, like electromagnetism? A magnet can pick up a paper clip even though the gravity of the whole earth is pulling back on the other end. According to one recent proposal, gravity is actually much stronger. It just seems weak because most of it is trapped in one of those extra dimensions. If its full force could be tapped using high-powered particle accelerators, it might be possible to create miniature black holes. Though seemingly of interest to the solid waste disposal industry, the black holes would probably evaporate almost as soon as they were formed.

1. Can we quantitatively understand quark and gluon confinement in quantum chromodynamics and the existence of a mass gap? Quantum chromodynamics, or QCD, is the theory describing the strong nuclear force. Carried by gluons, it binds quarks into particles like protons and neutrons. According to the theory, the tiny subparticles are permanently confined. You can't pull a quark or a gluon from a proton because the strong force gets stronger with distance and snaps them right back inside. But physicists have yet to prove conclusively that quarks and gluons can never escape. When they try to do so, the calculations go haywire. And they cannot explain why all particles that feel the strong force must have at least a tiny amount of mass, why it cannot be zero. Some hope to find an answer in M theory, maybe one that would also throw more light on the nature of gravity.

Found on http://www.oglethorpe.edu/