100 Rapid Questions By HR On Bio Chemistry Part – 2
Q – 1 How does the formation of the enzyme-substrate complex explain the reduction of the activation energy of chemical reactions?
Ans- The enzyme possibly works as a test tube within which reagents meet to form products. With the facilitation of the meeting provided by enzymes it is easier for collisions between reagents to occur and thus the activation energy of the chemical reaction is reduced. This is one of the explanatory hypotheses.
Q – 2 What are the main theoretical models that try to explain the formation of the enzyme-substrate complex?
Ans- There are two main models that explain the formation of the enzyme-substrate complex the lock and key model and the induced fit model.
In the lock and key model, the enzyme has a region with specific spatial conformation for the binding of the substrate. In the induced fit model, the binding of the substrate induces a change in the spatial configuration of the enzyme for the substrate to fit.
Enzyme Activity: lock and key model induced fit model
Q – 3 What is meant by substrates of enzymatic reactions?
Ans- Substrates are reagent molecules upon which enzymes act.
The enzyme has spatial binding sites for the attachment of its substrate. These sites are called activation centers of the enzyme. Substrates bind to theses centers forming the enzyme-substrate complex.
Enzyme Activity: enzyme-substrate complex
Q – 4 What are enzymes? What is the importance of enzymes for the living beings?
Ans- Enzymes are proteins that are catalysts of chemical reactions. From Chemistry, it is known that catalysts are non-consumable substances that reduce the activation energy necessary for a chemical reaction to occur.
Enzymes are highly specific to the reactions they catalyze. They are of vital importance for life because most part of chemical reaction of the cells and tissues are catalyzed by enzymes. Without enzymatic action, those reactions would not occur or would not happen in the required speed for the biological processes in which they participate.
Q – 5 What amount of catalyst is consumed in the reaction it catalyzes?
Ans- Catalysts are not consumed in the reactions they catalyze.
Q – 6 What are catalysts?
Ans- Catalysts are substances that reduce the activation energy of a chemical reaction, facilitating it or making it energetically viable.
The catalyst increases the speed of the chemical reaction.
Q – 7 What are respectively some remarkable functions of myosin, CD4, albumin, keratin, immunoglobulin, reverse transcriptase, hemoglobin, and insulin?
Ans- Myosin is a protein that associated to actin produces the muscular contraction. CD4 is a membrane protein of some lymphocytes, the cells that are infected by HIV. Albumin is an energy storage protein and an important regulator of the blood osmolarity. Keratin is a protein with structural function present in the epidermis and skin appendages of vertebrates. Immunoglobulins are the antibodies, specific proteins that attack and inactivate strange agents that enter the body.
Reverse transcriptase is the enzyme responsible for the transcription of RNA and formation of DNA in the life cycle of retroviruses. Hemoglobin is the protein that carries oxygen from the lungs to the cells. Insulin is a hormone secreted by the pancreas that participates in the metabolism of glucose.
Q – 8 What is the difference between essential and natural amino acids?
Ans- Essential amino acids are those that the organism is not able to synthesize and that need to be ingested by the individual. Natural amino acids are those that are produced by the organism.
There are living species that produce every amino acid they need, for example, the bacteria Escherichia coli that does not have essential amino acids. Other species, like humans, need to obtain essential amino acids from the diet.
Among the twenty different known amino acids that form proteins, humans can make twelve of them and the remaining eight needs to be taken from the proteins they ingest with food.
The essential amino acids for humans are phenylalanine, histidine, isoleucine, lysine, methionine, threonine, tryptophane and valine.
Q – 9 In sickle cell anemia, a hereditary disease, there is substitution of one amino acid by other in one of the four-polypeptide chains of hemoglobin. In this case, are all of the structural levels of the protein modified?
Ans- In sickle cell disease, there is change in the primary protein structure of one of the polypeptide chains that form hemoglobin: the amino acid glutamic acid is substituted by the amino acid valine in the ß chain. The spatial conformation of the molecule in addition is also affected and modified by this primary “mistake” and the modification creates a different (sickle) shape of the red blood cells.
Modified, sickled, red blood cells sometimes aggregate and obstruct the peripheral circulation causing tissue hypoxia and the pain crisis typical of sickle cell anemia.
Q – 10 Is it expected a change in the primary, in the secondary or in the tertiary structure of a protein to produce more functional consequences?
Ans- Any change of the protein structure is relevant if it alters its biological activity. Changes in the primary protein structure are more important because they are modifications in the composition of the molecule and such composition determines all other structures of the protein.
Q – 11 What are some factors that can lead to protein denaturizing?
Ans- Protein denaturizing can be caused by temperature variation, pH change, and changes in the concentration of surrounding solutes and by other processes. Most proteins are denatured after certain elevation of temperature or when in very acid or very basic solutions. This is one of the main reasons, why it is necessary for the organisms to keep adequate temperature and stable pH.
Q – 12 How can denaturizing be classified regarding its reversibility?
Ans- Protein denaturizing can be a reversible or an irreversible process, i.e., it can be possible or impossible to make the protein regain its original spatial conformation.
Q – 13 What is protein denaturizing? Is there any change in the primary structure when a protein is denaturized?
Ans- Secondary, tertiary, and quaternary structures of proteins are spatial structures. Denaturizing is modification in any of these spatial structures that makes the protein deficient or biologically inactive.
After denaturizing, the primary protein structure is not affected.
Protein Structure Review – Image Diversity: denaturized protein
Q – 14 What is the quaternary structure of a protein? Do all proteins have quaternary structure?
Ans- The quaternary protein structure is the spatial conformation due to interactions among polypeptide chains that form the protein.
Only those proteins made of two or more polypeptide chains have quaternary structure. Insulin (two chains), hemoglobin (four chains), and the immunoglobulins (antibodies, four chains) are some examples of protein having quaternary structure.
Protein Structure Review – Image Diversity: protein quaternary structure
Q – 15 What is the tertiary structure of a protein? What are the main types of tertiary structure?
Ans- The tertiary protein structure is a spatial conformation additional to the secondary structure in which the alpha helix or the beta-sheet folds up itself. The forces that keep the tertiary structure generally are interactions between the -R groups of the amino acids and between other parts of the protein and water molecules of the solution.
The main types of tertiary structure of proteins are the globular proteins and the fibrous proteins.
Q – 16 What is the difference between the alpha helix and the beta-sheet protein conformations?
Ans- Alpha helix and beta-sheet conformations are the two main types of secondary structure of a protein molecule. According to the primary protein structure, its secondary structure can be of one type or other.
In the alpha-helix structure, the polypeptide curls longitudinally by the action of hydrogen bonds forming a spiral, or helix. In the beta-sheet conformation, the protein is more distended and the hydrogen bonds form a zig-zag-shaped protein structure called B-strand. Many assembled beta-strands make a beta-sheet.
Q – 17 What is the secondary structure of a protein?
Ans- The secondary protein structure is generated by the manner its amino acids interact through intermolecular bond. These interactions create a spatial conformation of the polypeptide filament. The two most studied secondary conformations of proteins are the alpha helix and the beta-sheet.
Q – 18 What is the primary structure of a protein? What is the importance of the primary structure?
Ans- The primary protein structure is the linear sequence of amino acids that form the molecule.
The primary structure is the basis of the protein identity. Modification of only one amino acid of the primary structure creates a different protein. This different protein can be inactive or even can have other biological function.
Q – 19 Is there any situation in which DNA is made based on a RNA template? What is the enzyme involved?
Ans- The process in which DNA is synthesized having as template a RNA chain is called reverse transcription. In cells infected by retroviruses (RNA viruses, like the AIDS or SARS viruses) reverse transcription occurs and DNA is made from information contained in the viral RNA.
Viral RNA within the host cell produces DNA with the help of an enzyme called reverse transcriptase. Based on that DNA the host cell then make viral proteins, new virus are assembled and viral replication occurs.
Q – 20 Concerning their biological function what is the difference between DNA and RNA?
Ans- DNA is the source of information for RNA production (transcription) and thus for protein synthesis. DNA is still the basis of heredity due to its replication capability.
The messenger RNA is the template for protein synthesis (translation). In this process, tRNA and rRNA also participate since the first carries amino acids for the polypeptide chain formation and the second is a structural constituent of ribosomes (the organelles where proteins are made).
Q – 21 What are the three main types of RNA? What is meant by heterogeneous RNA?
Ans- Messenger RNA, or mRNA, transfer RNA, or tRNA, and ribosomal RNA, or rRNA, are the three main types of RNA.
The newly formed RNA molecule, a precursor of mRNA, is called heterogeneous RNA (hnRNA). The heterogeneous RNA bears portions called introns and portions called exons. The hnRNA is processed in many chemical steps, introns are removed, and mRNA is created formed only of exons, the biologically active nucleotide sequences.
Q – 22 What are similarities and differences between the transcription process and the replication processes?
Ans- A DNA polynucleotide chain serves as template in replication (DNA duplication) as well in transcription (RNA formation). In both processes, the pairing of the two-polynucleotide chains of the original DNA molecule is broken by the breaking of hydrogen bonds for the chains to be exposed as templates. The reaction is catalyzed by specific enzymes in transcription and in replication.
In replication, the enzyme DNA polymerase catalyzes the formation of a new polynucleotide chain using free nucleotides in solution and putting them in the new chain according to the DNA template exposed and to the rule A-T, C-G. In transcription, the enzyme RNApolymerase makes a new polynucletide chain according to the DNA template exposed obeying, however, the rule A-U, C-G.
In replication, the original template DNA chain is kept bound by hydrogen bonds to the newly formed DNA chain and a new DNA molecule is then created. In transcription the association between the template DNA chain and the newly formed RNA is undid and RNA constituted of only one polynucleotide chain is liberated.
Q – 23 How the production of RNA called? What is the enzyme that catalyzes the process?
Ans- The making of RNA from information contained in DNA is called transcription. The enzyme that catalyzes the process is the RNA polymerase.
Q – 24 Does RNA molecule have two polynucleotide chains likewise DNA?
Ans- Only DNA has two polynucleotide chains. RNA is formed just by one polynucleotide chain.
Nucleic Acid Review – Image Diversity: RNA molecule
Q – 25 Where can RNA are found within cells?
Ans- In the eukaryote cell nucleus, RNA can be found dispersed in the nuclear fluid, along with DNA, and as the main constituent of the nucleolus. In cytosol (in eukaryotes or in bacteria) RNA molecules can be found free, as structural constituent of ribosomes (organelles specialized in protein synthesis) or even associated to them in the process of making proteins. Mitochondria and chloroplasts also have their own DNA and RNA.
Q – 26 One characteristic of the DNA molecule is its replication capability. What are the consequences of failures during DNA replication?
Ans- Ideally, a DNA molecule should replicate in a perfect way. Sometimes however failures in the duplication occur, with alteration (deletion, addition, or substitution) of one or more nucleotides in the molecule.
Those mistakes, or mutations, therefore make changes in the protein synthesis process too. For example, the production of an important protein for cells or tissues may be suppressed new utile or inutile proteins can be created, etc. The mistake in the DNA duplication and the resulting production of altered genetic material are some of the main creative forces for the biological evolution and the diversity of species.
Q – 27 Does DNA replication occur in cell division?
Ans- Yes. DNA replication occurs in mitosis as well in meiosis.
Q – 28 Because of DNA replication, two DNA molecules come to existence. Why is not it correct to assert that two “new” DNA molecules are created? What is the name given to the process concerning that fact?
Ans- During replication each chain of the DNA molecule act pairing new nucleotides and after the process, two newly formed chains made with the union of these nucleotides appear. Then two DNA molecules are created, each with one chain from the original molecule and one newly chain formed by new nucleotides. Thus, it is not entirely correct to assert that the replication produces two new molecules of DNA. It is better to affirm that two new half-molecules are created.
For this phenomenon DNA, replication is called semi conservative replication.
Q – 29 What are the chemical bonds of the DNA molecule that are broken for the replication process to occur?
Ans- During the DNA replication, process hydrogen bonds between nitrogen-containing bases of the polynucleotide chains are broken.
Q – 30 How do the two complementary nucleotide chains of the DNA facilitate the replication process of the molecule?
Ans- The fact that the DNA molecule is made of two polynucleotide chains whose nitrogen-containing bases form hydrogen bonds facilitates the duplication of the molecule. During the DNA replication, the binding of the two chains is broken and each of them serves as template for the formation of a new nucleotide sequence along it, with the help of the enzyme DNA polymerase and obeying the pairing rule A-T, C-G.
At the end of the process two double helix of DNA are produced, each made of an original template chain and of a new synthesized polynucleotide chain.
Q – 31 Why is not it correct to assert that DNA self-replicates?
Ans- DNA is not completely autonomous in its duplication process because the replication does not occur without enzymatic activity. Therefore, it is not entirely correct to assert that DNA self-replicates.
Q – 32 What is the name of the DNA duplication process? What is the main enzyme that participates in it?
Ans- The process of copying, or duplication, of the DNA molecule is called replication. The enzyme that participates in the formation of a new DNA chain is the DNA polymerase. There are also other important enzymes in the replication process, the helicase, the gyrase and the ligase.
Q – 33 Which type of chemical bond maintains the pairing of each chain in the DNA molecule?
Ans- To form the DNA molecule, purine bases bind to pyrimidine bases by intermolecular bonds called hydrogen bonds. Hydrogen bonds occur when there is hydrogen near one of these electronegative elements: fluorine, oxygen, or nitrogen.
In such conditions hydrogen looks like having, lost electron for those elements and a very strong polarization is created. The highly positive hydrogen attracts pairs of electrons of other molecules making a hydrogen bond.
Q – 34 What is the numeric relation between pyrimidine and purine bases in the DNA molecule? Is that relation valid in RNA molecules?
Ans- The DNA molecule is made of two bound polynucleotide chains that form a helical structure (the double helix). The binding of the two chains is between their nitrogen-containing bases and it always obey the following rules: adenine (A), a purine base, binds with thymine (T), a pyrimidine base, and guanine (G), a purine base, binds to cytosine (C), a pyrimidine base.
Therefore in one molecule of DNA there will be same number of adenine (A) and thymine (T) and same number of cytosine (C) and guanine (G). The quantities of purine and of pyrimidine bases so will also be the same in a 50% proportion for each type. The relation A = T and C = G, or A/T = C/G = 1, is called Chargaff’s relation and the pairing rules described above are known as Chargaff’s rules.
In RNA, there are not two nucleotide chains. RNA is a simple chain molecule and there is no necessary proportionality of nitrogen-containing bases to form it.
Q – 35 What is the rule for the pairing of nitrogen-containing bases in the DNA molecule and in the RNA? Is this last question appropriate?
Ans- The rule for the pairing of nitrogen-containing bases of the polynucleotide chains that form the DNA molecule is pyrimidine base binds to purine base, under the condition that thymine (T) binds to adenine (A), and cytosine (C) binds to guanine (G).
In RNA, there is no binding between nitrogen-containing bases. That is because RNA is formed of only one polynucleotide chain; differently, DNA is formed of two chains. It is not correct so to question about base pairing in RNA.
Q – 36 According to the Watson – Crick Model how many polynucleotide chains does a DNA molecule has?
Ans- The DNA molecule is formed by two polynucleotide chains bound in antiparallel mode (5′-3′ to 3′-5′) and forming a helical structure.
Q – 37 Who were James Watson, Francis Crik and Maurice Wilkins?
Ans- Watson (North American), Crick (British) and Wilkins (New Zealander) were the discoverers of the molecular structure of DNA, the double helix made of two polynucleotide chains paired by their nitrogen-containing bases. They won the Nobel Prize of Medicine in 1962 for the discovery.
Q – 38 Bacteria are prokaryotic cells, i.e., they do not have membrane-delimited nucleus. Eukaryotes have cells with delimited nucleus. Where in these types of cells can DNA are found?
Ans- In eukaryotic cells, DNA is found within the cell nucleus. In prokaryotic cells, DNA is found dispersed in the cytosol, the fluid space inside the cell.
Other DNA molecules can also be found within mitochondria and chloroplasts, specialized organelles of eukaryotic cells.
Q – 39 Which are the nucleotides “portions” that bind in the formation of nucleic acids? What is meant by the 5′ and 3′ extremities of nucleic acids?
Ans- The phosphate group of one nucleotide binds to the pentose of the other nucleotide and so on to make the polynucleotide chain.
Each extremity of a DNA or RNA chain can be distinguished from the other extremity according to their terminal chemical entity. The phosphate-ended extremity is called 5′-extremity and the pentose-ended extremity is called 3′-extremity. So DNA or RNA chains can be run along the 5′-3′ way or along the 3′-5′ way. These ways are important in several biological functions of DNA and RNA since some reactions specifically occur following one way or the other way.
Q – 40 Into which two groups can the nitrogen-containing bases that form DNA and RNA be classified? What is the criterion used in that classification?
Ans- The nitrogen-containing bases that form DNA and RNA are classified as pyrimidine and purine bases.
By the analysis of the structural formulas of those nitrogen-containing bases, it is possible to realize that three of them, cytosine, thymine and uracil, have only one nitrogenized carbon ring. The others, adenine and guanine, have two nitrogenized associated carbon rings.
Q – 41 What are pentoses? To what organic group do pentoses belong? Are nucleotides formed of only one type of pentose?
Ans- Pentoses are carbohydrates made of five carbons. Deoxyribose is the pentose that constitutes DNA nucleotides and ribose is the pentose that is part of RNA nucleotides.
Q – 42 Of what units are, nucleic acids constituted. What are the chemical entities that compose that unit?
Ans- Nucleic acids are formed by sequences of nucleotides.
Nucleotides are constituted by one molecule of sugar (ribose in DNA and deoxyribose in RNA) bound to one molecule of phosphate and to one nitrogen-containing base (adenine, uracil, cytosine, or guanine, in RNA, and adenine, thymine, cytosine, and guanine, in DNA).
Q – 43 What are nucleic acids? What is the historic origin of this name?
Ans- DNA and RNA, the nucleic acids, are the molecules responsible for the hereditary information that commands the protein synthesis in the living beings. The name “nucleic” derives from the fact that they were discovered (by the Swiss biochemist Friedrich Miescher, in 1869) within the cell nucleus. In that time, it was not known that those substances contained the hereditary information.
Q – 44 What are zymogens?
Ans- Zymogens, or proenzymes, are enzymes secreted in inactive form. Under certain conditions, a zymogen shifts to the active form of the enzyme. Zymogen secretions in general happen because the enzyme activity can harm the secretory tissue.
For example, the pepsinogen secreted by the stomach becomes active under acid pH turning into the enzyme pepsin. Other well-known zymogens are trypsinogen and chymotrypsinogen. Enzymes are secreted by the exocrine pancreas and respectively trypsin and chymotrypsin.
Q – 45 What are allosteric enzymes?
Ans- Allosteric enzymes are those that have more activation center and to which other substances called allosteric regulators bind.
Allosteric regulators can be allosteric inhibitors or allosteric activators. The interaction between an allosteric enzyme and the allosteric inhibitor disallows the binding of the substrate to the enzyme. The interaction between the allosteric enzyme and the allosteric activator allows the binding of the substrate to the enzyme and sometimes increases the affinity of the enzyme for the substrate. This regulatory phenomenon of the enzyme activity is called allosterism.
Q – 46 What is the action mechanism of the antiretroviral drugs called protease inhibitors and used against HIV infection?
Ans- Protease inhibitors are some of the antiretroviral drugs used to treat HIV infection. Protease is an enzyme necessary for the assembling of the HIV after the synthesis of its proteins within the host cell. The protease inhibitor binds to the activation center of the enzyme blocking the formation of the enzyme-substrate complex and the enzyme activity thus impairing the viral replication.
Q – 47 What is the action mechanism of the antibiotic penicillin?
Ans- Penicillin, discovered by the Scottish doctor Alexander Fleming, in 1928, is a drug that inhibits enzymes necessary for the synthesis of peptidoglycans, a constituent of the bacterial cell wall. With the inhibition, the bacterial population stops to grow because there is no new cell wall formation.
Fleming won the Nobel Prize in Medicine for the discovery of penicillin.
Q – 48 For the enzymatic reaction what is the effect of a substance with the same spatial conformation of an enzymatic substrate? How is this type of substance known?
Ans- Substances that “simulate” substrates can bind to the activation center of enzymes thus blocking the true substrates to bind to these enzymes and paralyzing the enzymatic reaction. Such “fake substrates” are called enzyme inhibitors.
The binding of enzyme inhibitors to enzymes can be reversible or irreversible.
Many medical drugs, for example, some antibiotics, antivirals, antineoplastics, antihypertensives and even sildenafil (trade name Viagra), are enzyme inhibitors that block enzyme activity.
Q – 49 What is the relation between vitamins and enzyme cofactors?
Ans- Many vitamins are enzyme cofactors that cannot be synthesized by the organism and must be obtained from the diet.
Q – 50 What are enzyme cofactors?
Ans- Some enzymes need other associated molecules to work. These molecules are called enzyme cofactors and they can be, for example, organic ions, like mineral salts, or organic molecules.
Inactive enzymes for not being bound to their cofactors are called apoenzymes. Active enzymes bound to their cofactors are called holoenzymes.
Q – 51 Since pepsin is a gastric enzyme does it, has acid or basic optimum pH? What happen to pepsin when it passes to the duodenum?
Ans- Pepsin acts within the stomach so its optimum pH is around 2, an acid pH. When the enzyme passes to the duodenum, it meets a higher pH and its enzyme activity ends.
Q – 52 Do enzymes act better under acid or basic pH?
Ans- Most enzymes act in pH between 6 and 8, a range that corresponds to the general acidic level of cells and blood. There are enzymes however, that act only under very acid or very basic pH. Therefore, enzyme activity depends on a pH interval.
In the stomach, for example, the gastric juice has a very low pH, around 2, and there the enzyme pepsin acts intensively digesting proteins. In the duodenum, pancreatic secretions increase the pH of the enteric juice for the action of other digestive enzymes, for example, trypsin.
Q – 53 Does pH affect the enzyme activity?
Ans- The concentration of hydrogen ions in solution affects the enzyme activity. Each enzyme has maximal efficiency under an optimum pH.
Since pH is one of the factors for the denaturation of proteins, if an enzyme is submitted to a pH level under which, it is denaturated there will be no enzymatic activity.
Q – 54 How is the cooling of organs and tissues for medical transplantations associated with the effect of temperature upon enzymatic reactions?
Ans- The molecular degradation during the decomposition of organs and tissues is catalyzed by enzymes. The cooling to adequate temperatures of some organs and tissues destined to transplantation reduces that enzyme activity and thus lessens the natural decomposition process.
By the same rational the cooling reduces the metabolic work of cells and prevents that, they degrade their own structures to obtain energy. Elevation of temperature later revert denaturation of enzymes and the organs and tissues also preserved by other specific techniques may be grafted into the receptors.
Q – 55 Concerning enzymatic reactions how different, are the graphic curve of the variation of the speed of a reaction as function of substrate concentration and the curve of variation of the speed of a reaction as function of temperature?
Ans- The curve of variation of speed of the enzymatic reaction as function of growing substrate concentration is a growing curves until the point where it stabilizes due to the saturation of the activation centers of the enzymes.
The curve of variation of speed of the enzymatic reaction as function of growing temperature has a crescent portion, reaches a peak (the optimum temperature) then it decreases, and reaches zero in the point of inactivity of the enzymes by denaturation.
Q – 56 How does temperature affect the action of enzymes upon their substrates?
Ans- There are defined temperature ranges under which enzymes operate. There is a specific temperature-level where the enzymes have maximum efficiency. Therefore, temperature variations affect enzymatic activity and the speed of the reactions they catalyze.
In addition, as proteins, enzymes can be denaturated under extreme temperatures.
Q – 57 How does the substrate concentration affect the speed of enzymatic reactions?
Ans- Initially as substrate concentration increases the speed of the reaction increases, this happens because free activation centers of the enzyme bind to free substrates. Once all activation centers of the available enzymes become bound to their substrates new increments of the substrate concentration will have no effect in the speed of the reaction.
Q – 58 What are the main factors that alter the speed of enzymatic reactions?
Ans- The main factors that change the speed of enzymatic reactions are temperature, pH and substrate concentration (quantity).
Q – 59 What happen to a denaturated enzyme regarding its functionality? How that result can be explained with the help of the lock and key model?
Ans- According to the lock and key model, the enzyme functionality depends entirely on the integrity of the activation center, a molecular region with specific spatial characteristics. After the denaturation the spatial conformation of the protein is modified, the activation center is destroyed and the enzyme loses its catalytic activity.
Q – 60 Why can it be said that the enzymatic action is highly specific?
Ans- The enzymatic action is highly specific because only specific substrates of one enzyme bind to the activation center of that enzyme. Each enzyme generally catalyzes only a specific chemical reaction.
Q – 61 What is the activation center of an enzyme? Is it the key or the lock of the lock and key model?
Ans- The activation center is a region of the enzyme produced by its spatial conformation to which the substrate binds. In the lock and key model, the activation center is the lock and the substrate is the key.
Q – 62 On what structural level of the enzyme (primary, secondary, tertiary, or quaternary) does the enzyme-substrate interaction depend?
Ans- The substrate binds to the enzyme in the activation centers. These are specific three-dimensional sites and thus they depend on the protein tertiary and quaternary structures. The primary and secondary structures however condition the other structures and so they are equally important.
Q – 63 What is Hoffman degradation method?
Ans- Benz amide on treatment with bromide and Caustic potash produce aniline
C6H5NH2+2KBr+2H2O+K2CO3àC6H5CoNH2+Br2+4KOH
Q – 64 Polymers of vinyl chloride are.
Ans- Polymers of Vinyl chloride are called PVC and it is used as plastic.
Q – 65 Which type of reactions did Acetylene undergoes?
Ans- Acetylene undergoes both additions as well as substitution reactions
Q – 66 What is saytzeff’s rule?
Ans- The formation Alkenes by the dehydration of alcohols (using concentrated H2SO4) the hydrogen atom will be removed (to remove as water) from the adjacent carbon atom linked to the less number of hydrogen atoms.
Example: In the dehydration of Butane – 2Ol
2Butane is formed
CH3-CH=CH-CH3+H2Oàconcentrated H2SO4àCh3-CH2-CH-CH3
But2-ene
Q – 67 What is kararch effect?
Ans- In the addition of the hydrogen, halide to unsaturated alkenes in the presence of peroxides the halide adds to the carbon atom linked to more number of hydrogen atoms and hydrogen adds to the carbon atom linked to lesser number of hydrogen atoms. This is called Peroxide effect (or) Kharasch effect.
CH3-CH2-CH2BRàCH3-CH=CH2+HBr-
N Prophyl bromide
Q – 68 What is markownikoff’s rule?
Ans- In addition, of hydrogen halides to the unsymmetrical alkens, Hydrogen is added to the carbon atom containing more number of hydrogen atoms and halide is added to the carbon atoms containing lesser number of hydrogen atoms.
Ex; CH2-CHBr-CH3àCH3-CH=CH2+HBr–
Iso Prophyl Bromide
Q – 69 Why ethylene undergoes electrophilic addition reactions?
Ans- Ethylene is unsaturated Hydrocarbon. Due to the presence of loosely bound pi electrons between two carbon atoms ethylene CH2=CH2 is more reactive towards addition reactions.
Q – 70 Which form of isomers of a substance is more stable?
Ans- Trans -Isomer of a substance is more stable than Cis-Isomer.
Q – 71 Define Geometrical Isomerism.
Ans- Isomers, which differ in the orientation of groups around the double bounded carbon atoms, are called geometrical Isomers. It is also called as Cis-Trans Isomerism.
Q – 72 What are enantimorphs and diastereomers ?
Ans- Optical Isomers of a substance that are mirror images of each other are called Enantiomers (or) Enantimorphs. Ex: d and L – Lactic acid
Optical Isomers of a substance that are not mirror images of each other are called Diastereomers. Ex: d-Tartaric and meso -Tartaric acids
Q – 73 What are dextrorotary compounds and Levi rotary compounds?
Ans- Compounds that rotate the plane polarized light to the right are called Dextro rotatory compounds and that rotate the plane polarized light to the left are called Leavo rotatory.
Q – 74 What is racemic mixture? Why it is optically inactive?
Ans- Optical Isomers of a substance that are mirror images of each other are called Enantiomers (or) Enantimorphs. Ex: d and L – Lactic acid
Optical Isomers of a substance that are not mirror images of each other are called Diastereomers. Ex: d-Tartaric and meso -Tartaric acids
Q – 75 How can we calculate the number of possible optical Isomers for a given Compound?
Ans- 2n-Where n is the number of asymmetric carbon atoms.
Q – 76 What is optical Isomerism? Which compounds exhibit optical Isomerism?
Ans- Isomers, which differ in the rotation of the plane polarized light, are called Optical Isomerism.
Q – 77 What is Isomerism?
Ans- Compounds with same molecular formula but different properties are called Isomers and the phenomenon is called Isomerism.
Q – 78 What is function group?
Ans- An atom or group of atoms, which determine the characteristic properties of the Substance it, is called functional group.
Q – 79 Name the first synthetic organic compound. Who proposed it and from which compound?
Ans- The first synthetic organic compound is Urea.
It was prepared by Wohler from ammonium cynate.
NH4CNO……………………NH2-CO-NH2
Q – 80 Define the Phenomenon catenation. Which element has maximum Catenation ability?
Ans- Carbon has maximum catenation ability. The self-linkage of the atoms of elements to produce long chains is called catenation.
Q – 81 To calculate the e.m.f of the cell when does the nelsons equation is use?
Ans- The Nernst equation is useful to calculate the e.m.f of the cell when the concentrations of solution are different from unity.
Q – 82 Nelsons equation for any cell reaction is given by.
Ans- E = Eo + (2.303RT /nF) log [Oxidation form]/[reduced form]
Q – 83 Which electrode acts as reference electrode and gives its potential value?
Ans- Standard hydrogen electrode was taken as reference electrode whose potential is assumed zero.
Q – 84 What is Galvanic cell?
Ans- A Galvanic cell or voltaic cell or electrochemical cell is a system in which a spontaneous chemical oxidation- reduction occurs and generates electrical energy.
Q – 85 Define first law of Faraday
Ans- The amount of substance liberated, dissolved, or deposited at an electrode is directly proportional to the quantity of electricity passed through the electrolyte.
Q – 86 How can you determine the dissociation constants of electrolyte?
Ans- The strength of the Electrolyte
Q – 87 In electronic conductors, what is the reason for flow of current?
Ans- Reason for flow of current is that moment of free electrons from higher negative potential to a lower positive potential region.
Q – 88 Which branch of science deals with the transformation of chemical energy into electrical energy and vice versa?
Ans- Electrochemistry
Q – 89 What is the lattice energy of Nacl?
Ans- –796.69k.j
Q – 90 What does Hess law states?
Ans- Hess law states that the heat of reaction is same whether the reaction takes place in one or several states. Therefore Q=Q1+Q2+Q3+…
Q – 91 Define standard feat of formation
Ans- The amount of heat liberated of absorbed when one mole of compound is formed in its standard state from its elements in their standard state is called standard heat of formation ( Hf *)
Q – 92 Define heat of Combustion
Ans- The amount of heat liberated when one mole of any substance is completely burnt in oxygen is called heat of combustion H is negative for heat of combustion.
Q – 93 How can you determine the reaction, taking place at constant pressure delta (H)?
Ans- The difference of Enthalpy’s of products and reactants H=Hp-Hr
Q – 94 What is Internal energy?
Ans- Every substance poses definite amount of energy called internal energy or intrinsic energy (E).
Q – 95 The expression q=delta (E)-W is? What does it states?
Ans- 1st law of thermodynamics may be represented as q= E-W
According to this law the energy can neither be created nor destroyed, but can be converted into one form to another.
Q – 96 What is Kc?
Ans- Kc is the equilibrium constants when the concentrations are expressed in moles/litre
Kc = product of concentrate ions of products / product of concentrate ions of reactants
Q – 97 Who proposed law of mass action? What does it states?
Ans- Laws of mass action were proposed by Gulberg and Waage. The rate of chemical reaction is directly proportional to the product of the active masses of the reactants (molar concentrations of the reactants)
Q – 98 Define Equilibrium state
Ans- The chemical reaction at one time the rate of forward and backward reaction becomes equal that state is called Equilibrium state.
Q – 99 How do you define the molecularity of a reaction?
Ans- The number of species participating in the slowest step of the reaction is called molecularity of the reaction.
Q – 100 Ina chemical reaction lowers the rate of reaction the greater will be.
Ans- The activation energy
Q – 101 What is activation energy?
Ans- The difference between Threshold energy and average energy of the molecules is called activation energy.
Q – 102 What is Threshold energy?
Ans- The minimum amount of energy required for the reaction to takes place is called threshold energy.
Q – 103 Rate equation of first order reaction is.
Ans- dx/dt = K * (a-x)
where ‘a’ is the initial concentration of reactants
‘x’ is the amount reacted in time t seconds
Q – 104 Give the integrated equation for first order reaction.
Ans- K = (2.303 / t) * log (a / a-x)
Q – 105 Define order of reaction
Ans- The order of reaction is the number of moles whose concentrations determine the rate of a reaction at a given temperature
Q – 106 Reactions catalyzed by light are called as.
Ans- Photo catalyzed or Photosensitised reactions
Q – 107 Catalyst used in Bio-Chemical reactions is called.
Ans- Enzymes
Q – 108 In some reactions, Rate of reaction is directly proportional to.
Ans- Concentration of catalyst
Q – 109 Which equation gives the relation between specific rate (k) and Temperature?
Ans- Arrhenius equation K = Ae-E a / R T
Q – 110 For every 10 degrees rise of temperature, the rate of reaction is generally.
Ans- Doubled
Q – 111 What does the expression -dc/dt indicates?
Ans- Rate of reaction can be expressed as -dc/dt where dc is small decreasing concentration in time dt seconds, (-) sign indicates that the concentration decreases with time.
Q – 112 What does Thermodynamics helps in predicting?
Ans- Predicting the feasibility of reaction and does not indicate the rate of chemical reaction
Q – 113 Chemical kinetics deals with study of.
Ans- Rates and mechanisms of chemical and Biochemical reactions
Q – 114 Name the best indicator
Ans- Phenolphthalein, PH range 8.3 to 10.0
Q – 115 PH of buffer solution is calculated by.
Ans- Henderson’s equation