Enzyme properties - class-XII
Description: enzyme properties | |
Number of Questions: 62 | |
Created by: Gauri Chanda | |
Tags: biology biomolecules: chemical constituents of living cells enzymes |
Vitamin as a building block is present in ___________.
-
Apoenzyme
-
Alloenzyme
-
Metallic ion
-
Lipoprotein
-
Coenzyme
The vitamins act as part of coenzymes, small molecules that combine with an enzyme to make it active.
Biological catalysts are called as
-
Auxins
-
Gibberellins
-
Enzymes
-
All of the above
Enzymes are biocatalyst. These are proteinaceous substances that are capable of catalysing chemical reactions of biological systems without themselves undergoing any change. The term enzymes were first used by Kuhne in 1877.
What is common among amylase, renin and trypsin?
-
These are all proteins
-
These are proteolytic enzymes
-
These are produced in stomach
-
These act at a pH lower than 7
Amylase is a protein-based enzyme that is secreted by the salivary glands of mouth and is involved in the breakdown of starch. It functions in a neutral pH (pH 7). Renin is also a protein enzyme secreted in the stomach and involved in the coagulation of milk. It functions in a acidic pH. Trypsin is also a protein enzyme that is produced in the small intestine and is a proteolytic enzyme. It also functions in acidic pH. So, the correct answer is 'These are all proteins'.
At boiling temperature, an enzyme is
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Denatured
-
Unaffected
-
Inactivated
-
Killed
The activity of an enzyme can be affected by a change in the conditions which can alter the tertiary structure of the protein. These include temperature, pH, change in substrate concentration or binding of specific chemicals that regulate its activity. Enzymes generally function in a narrow range of temperature and pH. Each enzyme shows its highest activity at a particular temperature and pH called the optimum temperature and optimum pH. Activity declines both below and above the optimum value. Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat. At boiling temperature all proteins including enzymes are denatured.
Which of the following statements is not correct?
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All enzymes are proteins.
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All enzymes are biocatalysts.
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All proteins are enzymes.
-
All enzymes are thermolabile.
All proteins are not enzymes. Proteins are most versatile biochemicals fulfilling a diverse set of structural and functional roles. For example, haemoglobin, keratin, albumin, etc., are all proteins but are not enzymes. Similarly, all enzymes are not proteins. In fact, most of the enzymes, are proteinaceous in nature. But ribozymes are not proteins in nature, they are catalytic RNAs.
Enzymes are basically _________.
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Fat
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Protein
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Nucleic acid
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All of the above
Enzymes are the specialized proteins which are capable of catalyzing reactions in the living cells.
Three of the following statements about enzymes are correct and one is wrong. Which one of the following is wrong?
-
Enzymes require optimum pH for maximal activity.
-
Enzymes are denatured at high temperature but in certain exceptional organisms they are effective even at temperatures 80-90$^o$C.
-
Enzymes are highly specific.
-
Most enzymes are proteins but some are lipids.
Enzymes are the biological catalyst which catalyzes biological reactions within a narrow range of temperature and pH. Certain thermophiles have enzymes which remain functional even at very high temperatures. Most of the enzymes are proteins in nature but a few enzymes are RNA in nature. They are called as catalytic RNAs or ribozymes.
Part of enzyme which combines with non-protein part of form functional enzyme is
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Apoenzyme
-
Coenzyme
-
Prosthetic group
-
None of the above
The conjugate protein consists of two parts protein and non-protein part. Non-protein part is the cofactor and protein part is apoenzymes. Complete conjugate protein is known as Holoenzymes. Apoenzyme is an inactive enzyme. Thus, the correct option is D.
Which one value is required for better enzymatic action?
-
High K$ _i$
-
Low K$ _i$
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Low K$ _m$
-
High K$ _m$
A constant indicating the substrate concentration at which an enzyme catalysed reaction attains half its maximum velocity or 1/2 V$ _{max}$ is known as Michaelis-Menten constant or K$ _m$. Lower K$ _m$ indicates more affinity between the enzyme and substrate and consequently higher reaction rates.
Combination of apoenzyme and coenzyme produces
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Prosthetic group
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Holoenzymes
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Enzyme-substrate complex
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Enzyme-product complex
Nobel Prize for discovering enzymes was given to
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Kuhne
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Duclaux
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Buchner
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Dubrunfaut
Enzymes are basically made of
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Nucleic acids
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Proteins
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Fats
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Vitamins
Who confirmed protein nature of enzymes?
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Monod et al
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Arber et al
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Berzelius
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Northrop
An enzyme acts by
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Reducing the energy of activation.
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Increasing the energy of activation.
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Decreasing the pH.
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Increasing the pH.
The reactants do not undergo chemical change automatically. They do so in transition state. Transition state has more free energy than reactants or products. The inability of reactants to undergo change due to requirement of extra energy for converting them to transition state is called as 'Energy Barrier'. Energy required to overcome energy barrier is called as 'Activation Energy'.
The suffix $-ase$ to enzyme names was proposed by
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Duclaux
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Buchner
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Northrop
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Pasteur
The suffix -ase is used for the nomenclature of the enzyme. It is used at the end of the substrate. For example, the enzyme that breaks down peroxides are known as peroxidases. Hexokinase are the enzyme which helps in synthesis of hexose sugar. In 1898 Duclaux proposed the suffix -ase.
Many enzymes are secreted in inactive form to protect
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Cell proteins
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Mitochondria
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Cell membrane
-
Cell DNA
The enzymes are protein in nature and they are generally produced in inactive form so to protect the intracellular damage of protein. For example, digestive enzymes are secreted in form of zymogens which remains inactive in the cells in which it is produced. The active sites are blocked by the peptide which keeps the enzyme in the inactive stage so the other proteins do not get harmed by the reaction. Cleavage of this peptide cleaves activates the enzyme.
Which is not a trait of enzymes?
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Proteinaceous nature
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Specific in nature
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Speed up rate of biochemical reaction
-
Used up in reaction
Enzymes are proteins which help to catalyze the biochemical reaction. The enzyme has a protein part which is not active is known as apoenzyme. It gets activated by the addition of an organic or inorganic cofactor. It is specific in nature as specific substrate bind at the active site of a particular enzyme. It increases the rate of chemical reactions without being used up. The enzymes lower the activation energy and lead to the formation of activated complex, which is also known as transition state and finally changes to the product.
Enzymes exist in the cells as
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Solid
-
Crystals
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Solution
-
Colloid
Enzymes are proteins which help to catalyze the biochemical reaction. The enzyme has a protein part which is not active is known as apoenzyme. It gets activated on the addition of an organic or inorganic cofactor. It exists as hydrophilic colloid in the cytoplasm which makes it inert and prevents its dissociation. The hydrophilic part of the colloid is present on the surface which interacts with the water.
Which is wrong about enzymes?
-
Enzymes are mostly proteins but some are lipids also
-
Enzymes are highly specific
-
Enzymes require optimum pH and temperature for maximum activity
-
Enzymes are denatured at high temperature
Which is true about enzymes?
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All enzymes are not proteins
-
All enzymes are vitamins
-
All enzymes are proteins
-
All proteins are enzymes
Enzymes are protein in nature. But some enzymes like ribozymes and ribonuclease are RNA based enzymes. It is also known as ribonucleic acid enzymes. These are RNA molecules which helps in the catalysis of a particular reaction. It was discovered in year 1982. The RNA can act as both genetic material and can act as a biocatalyst but different from protein-based enzymes. It acts as a part of ribosome which attaches to the amino acid during protein synthesis. Thomas R. Cech and Sidney Altman discovered catalytic properties of RNA. So, the correct answer is option A.
Enzymes functional in a cell are
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Inducible, constitutive and repressible
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Inducible and repressible
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Inducible only
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Repressible only
Enzymes are inducible in nature because as the substrate molecules attaches to the active site of the enzyme, it induces a conformational change on the active site to fit in properly.
Most of hydrolytic reactions are
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Exothermic
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Endothermic
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Irreversible
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Reversible
Hydrolytic reactions are the reactions which involves breaking of the bond by the addition of water. It can be reversed by the condensation reaction where the joining of two molecule leads to release of water by formation of bonds. Saccharification is the reaction where the complex sugar molecule is broken into its component sugar molecules by hydrolysis. It can be reversed by condensation reaction.
Enzyme generally have?
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Same pH and temperature optima
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Same pH but different temperature optima
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Different pH but same temperature optima
-
All wrong
The optimum temp of enzymes is 20-35°C. They become inactivated at very low temperature and denatured (destroyed) at very high temp i.e. greater than 45°C. Low molecular weight enzymes are comparatively more heat stable. In archaebacterium Pyrococcus furiosus, the optimum temperature of hydrogenase is greater than 95°C. This heat-stable enzyme enables Pyrococcus to grow at 100°C. The optimum pH of most endoenzyme is pH 7.0 (neutral pH). However, digestive enzymes can function at different pH. For example, salivary amylase act best at pH 6.8, pepsin act best at pH2 etc. Any fluctuation in pH from the optimum causes ionization of R-groups of amino acids which decrease the enzyme activity.
Serine proteases are called so because they
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They require serine for their activity
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cleave after serine residues in the substate
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Are inhibited by the presence of free serine
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Have a serine residue at their active sire
Serine proteases are enzymes that cleave peptide bonds in proteins, in which serine serves as a nucleophilic amino acid at enzyme's active site. Serine proteases are responsible for coordinating various physiological functions including digestion, immune response, blood coagulation, and reproduction. Hence, serine proteases are called so because they require serine for their activity.
Specific enzymes are needed for the break-down of a particular substance.
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True
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False
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Either
-
Neither
Mark the INCORRECT statement about the enzyme carboxypeptidase.
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Zinc is the co-factor for this proteolytic enzyme
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It is exopeptidase
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It cleaves the peptide bond at N-terminal end of the polypeptide chain
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It is an enzyme of pancreatic juice
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$\alpha$-amylase
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Glucokinase
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Lactate dehydrogenase
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All of the above
Which one of following vitamin is a precursor of FAD
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Niacin
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Riboflavin
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Thiamine
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Ubiquinor
FAD also is known as Flavin Adenine Dinucleotide. It is a redox-active co-enzyme associated with various proteins. Riboflavin is the precursor of FAD.
The active site of an enzyme is formed by
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Exposed sulphur bonds
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Side chains of the amino acids
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Amino groups of the amino acids
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Carboxyl group of the amino acids
The enzyme active site is composed of the amino acid residues. Side chains of the amino acids are seen in the active site region of the enzyme. The difference in the identity, charge, and spatial orientation of the functional groups located there results in the difference in enzyme specificity.
Read the following statement
(i) The enzymes acts on 'N' terminal of a polypeptide chain is present in A
(ii) The enzymes in 'C' terminal of a polypeptide chain is present in BChoose the option which correctly fills up the blanks
A and B
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Gastric juice Pancreatic juice
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Pancreatic juice Gastric juice
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Pancreatic juice Succus entericus
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Intestine juice Pancreatic Juice
The enzymes are functional at
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0-5$^{\circ}$C
-
15-25$^{\circ}$C
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25-40$^{\circ}$C
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70-85$^{\circ}$C
Enzymes works precisely at certain narrowly optimum conditions, such as appropriate temperature, pH, and ion concentration. Deviation from the optimal conditions adversely affects enzyme activity. Most enzymes have an optimal temperature, at which the rate of reaction is fastest. For human enzymes, the temperature optima are near the human body temperature (35-40$^o$C). Enzymatic reactions occur slowly or not at all at low temperatures. As the temperature increases, molecular motion increases, resulting in more molecular collisions. The rates of most enzyme-controlled reactions, therefore, increase as the temperature increases, within limits. High temperatures rapidly denature most enzymes. The molecular conformation (3-D shape) of the protein becomes altered as the hydrogen bonds responsible for its secondary, tertiary, and quaternary structures are broken. Because this inactivation is usually not reversible, activity is not regained when the enzyme is cooled.
Identify the incorrect statement about enzymes.
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They consist of proteins, with or without a non-protein part.
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They change the rate of the catalyzed reaction.
-
They change the value of $\triangle$G of the reaction.
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They are not sensitive to heat.
Enzymes are biological catalyst which catalyze biological reactions. Most of the enzymes are proteins in nature. Some of the enzymes have non protein part which helps them to carry out reaction. Enzymes change the rate of chemical reaction by bringing about a decrease in free energy requirement. Thus, changing the free energy of the reaction. Because enzymes are proteins, they are highly sensitive to heat. Thus, enzymes catalyze reactions only at physiological conditions of temperature and pH.
In a chemical reaction, the
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Rate depends on the value of $\triangle$G.
-
Rate depends on the activation energy.
-
Entropy change depends in the activation energy.
-
Activation energy depends on the value of $\triangle$G.
Which of the following is the transition state structure of the substrate formed during an enzymatic reaction?
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Permanent but unstable
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Transient and unstable
-
Permanent and stable
-
Transient but stable
Reactions do not undergo chemical changes automatically. They do so in transition states. Transition state has more free energy than reactants or products. Higher free energy helps in collision of transition state reactants. The enzymes binds to substrate molecules and form an unstable transient state called as transition state. The transition state rapidly undergoes degeneration into products and unchanged enzyme molecule.
In presence of an enzyme, the activation energy
-
Increases
-
Decreases
-
First increases and then decreases
-
Activation energy in not affected at all
As the water evaporates from the skin of a swimmer who has just left a pool, the swimmer begins to shiver and goose bumps form on his skin. As the blood vessels under his skin move more internally, the goose bumps that form and the shivering are reactions to counteract the lowering of body temperature. After the swimmer has dried off the shivering stops and his body temperature returns to normal. This is an example of
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Product inhibition
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Disequilibrium
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A negative feedback mechanism
-
A positive feedback mechanism
When there is a drop in body temperature due to a drop in environmental temperature. The sensory receptors on the skin sends signal to the hypothalamus, which increases the body temperature by causing vasoconstriction and prevents blood from flowing closer to the skin, this also causes piloerection or goosebumps, this is to conserve energy and raise the body temperature. Once the swimmer has dried himself the thermosensors of the skin send a feed back of temperature returning to normal to the hypothalamus and the shivering is stopped. This is called negative feedback mechanism.
Who discovered the coenzymes?
-
James Sumner
-
Fritz Lipmann
-
Mayerhoff
-
Eduard Buchner
- Coenzymes are small organic molecules that can be loosely or tightly bound to an enzyme.
- Tightly bound coenzymes can be called as prosthetic groups. Coenzymes were discovered by Fritz Lipmann.
- His work on the coenzyme was awarded Nobel Prize in Physiology or Medicine, in 1953, for his discovery of coenzyme A and its importance for intermediary metabolism.
Hence, option B is the answer.
What is true for an enzyme during a biochemical reaction?
-
It becomes part of the product
-
It is unchanged
-
It is broken down into amino acids
-
It reacts with fatty acids
-
It becomes a polypeptide
Any chemical reaction includes the formation of transition state between reactant and product. The energy required for formation of the transition state is termed as activation energy. Enzymes enhance the rate of reaction by lowering down the activation energy of transition state but themselves remain unchanged. Thus, the correct answer is option B.
Which of the following is iron porphyrin coenzyme or cofactor?
-
Cytochrome
-
FAD
-
CoA
-
NAD
Hemes are the iron containing porphyrins. They are extensively found in nature. These are also present in proteins like haemoglobin and myoglobin. Cytochromes are also a haemoproteins. Cytochrome also act as an integral part of membrane protein.
Biocatalysts were found accidently in Yeast extract by
-
Sumner
-
Kuhne
-
Buchner
-
Pasteur
Biocatalysts were found accidentally in yeast extract by Buchner in 1897. He prepared a yeast extract and added sugar solution to it. After sometime he noticed the alcohol formation in the extract which was a sign of fermentation which took in presence of enzyme. Later on, Sumner crystallized an enzyme known as urease and reported that all enzymes are protein.
Enzyme action comes to a stop when hydration decreases in maturing seeds to
-
$50 - 60$%
-
$30 - 45$%
-
$25 - 30$%
-
$10 - 20$%
The action of lysozyme is
-
Physiological
-
Anatomical
-
Morphological
-
None of the above
Lysozyme are also reffered as muramidase. They are glycoside hydrolases. They catalyzes hydorlysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetly-D-glucosamine residues in peptidoglycan thus they can dissolve bacterial cell wall. It is present in a number of secretions, such as tears, saliva, human milk and mucus. So, its function is physiological.
Thus, the correct answer is option (A).
Metabolic processes in living organisms are catalyzed by
-
Enzymes
-
Nucleotides
-
Nucleosides
-
Lipids
Enzymes are the biomacromolecules that catalyze metabolic processes in living organisms.
Enzymes which transfer electrons are
-
Hydrolyses
-
Hydrogenases
-
Proteases
-
Transaminases
Which one of the following enzymes is NOT made up of polypeptides?
-
Ligase
-
Ribosome
-
Lysozome
-
Chemotropism
Select the correct option:
-
lowering
-
increasing
-
unaltering
-
either (a) or (b)
Enzymes are macromolecular biological catalysts. which accelerates chemical reactions. Catalysts lower the activation energy (energy required to start a reaction.) for reactions. The lower the activation energy for a reaction, the faster the rate.
So, the correct answer is 'lowering'.
-
Ligase
-
Lyase
-
Hydrolase
-
Dehydrogenase
Lyases enzymes catalyse the breakage of specific covalent bonds and removal of group with out hydrolysis producing double bonds or removal of double bonds by adding group,e.g., histidine decarboxylase that splits $C-C$ bond of histidine,forming $CO _2$ and histamine.
Relationship between genes and enzymes was discovered by
-
Waldeyer
-
W. Johannsen
-
Bridges
-
Beadle and tatum
Sir Archibald Garrod proposed that one enzyme is encoded by one gene. This hypothesis called One gene One enzyme hypothesis, was experimentally proved by Beadle and Tatum by using bread mould Neurospora. Beadle and Tatum showed bread mould mutants that were unable to make specific amino acids. In each one, a mutation had disrupted an enzyme needed to build a certain amino acid. This was caused due to specific gene mutation.
The hydrolytic enzymes acting at low pH are
-
$\alpha$-amylases
-
Hydrolases
-
Proteases
-
Pyrimidases
A protease (also called peptidase or proteinase) is any enzyme that performs proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein. Proteases may be classified by the optimal pH in which they are active: acid proteases or neutral proteases or basic proteases.
-
Apoenzyme - Protein
Co - factor - Non-Protein -
Apoenzyme - Non - Protein
Co - factor - Protein -
Apoenzyme - Protein
Co - factor - Protein -
None of the above
Conjugated enzymes ( holoenzymes) are formed of two parts a protein part called apoenzyme and a non-protein part named co-factor. The complete conjugated enzyme consisting of an apoenzyme and a co-factor is called holoenzyme. Holoenzyme is the functional unit of enzyme.
With reference to enzymes, which one of the following statements is true?
-
Apoenzyme = Holoenzyme+ Coenzyme
-
Holoenzyme= Apoenzyme + Coenzyme
-
Coenzyme= Apoenzyme + Holoenzyme
-
Holoenzyme= Coenzyme+ Apoenzyme
Arrange the steps of catalytic action of an enzyme in order and select the correct option.
I. The enzyme release the products of the reaction and the enzyme is free to bind to another substrate.
II. The active site of enzyme is in close proximity of the substrate and breaks the chemical bonds of the subtrate.
III. The binding of sustrate induces the enzyme to alter its shape fitting more tightly around the sustrate.
IV.The substrate binds to the active site of the enzyme.
-
IV, III, II, I
-
III, II, I, IV
-
IV, II, I, III
-
II, I, IV, III
The inorganic catalyst attached to enzymes is called
-
Apoenzyme
-
Lysozyme
-
Activator
-
Inhibitor
An activator is an inorganic catalyst attached to enzymes. The bind to the enzyme and increase its activity.
In biochemical reactions, the enzymes act by
-
By decreasing the energy of the reactants
-
By increasing the activation energy of the reaction
-
By decreasing the activation energy of the reaction
-
By increasing the energy of the products of the reaction
-
By decreasing the energy of the products of the reaction
The minimum energy requirement that must be met for a chemical reaction to occur is called the activation energy. The activation energy is the energy difference between the reactants and the activated complex, also known as transition state. In a chemical reaction, the transition state is defined as the highest-energy state of the system. If the molecules in the reactants collide with enough kinetic energy and this energy is higher than the transition state energy, then the reaction occurs and products form. In other words, the higher the activation energy, the harder it is for a reaction to occur and vice versa. However, if a catalyst is added to the reaction, the activation energy is lowered because a lower-energy transition state is formed. Enzymes can be thought of as biological catalysts that lower activation energy. Enzymes are proteins or RNA molecules that provide alternate reaction pathways with lower activation energies than the original pathways. Enzymes affect the rate of the reaction in both the forward and reverse directions; the reaction proceeds faster because less energy is required for molecules to react when they collide. Thus, the rate constant (k) increases.
So, the correct answer is option C.
If an enzyme has been given the EC code 3.2.1.7, it is likely to be involved in
-
Digestin
-
Redox reaction
-
Isomerization
-
Molecular breakdown
- EC number is a numerical classification scheme is based on the chemical reactions which are catalyzed by them.
- A system of enzyme nomenclature is associated with a name for the corresponding enzyme.
- The number classification can be referred to that enzyme which is involved in digestion.
Division characteristic of Korpe-Kappe theory are
-
Anticlinal
-
T-type
-
Periclinal
-
Irregular
Tyloses
-
Are ballon-like swelling of xylem parenchyma cells in the lumen of vessels
-
Are found in heartwood
-
Make heartwood functional
-
Both (A) and (B)
Select the incorrect match.
-
Dynein is an enzymatic protein
-
Ribosomes are also called as organelle within organelle
-
Minimum $0.01$M concentration of $Mg^{++}$ is required for structural formation of ribosome
-
Peptidyl transferase enzyme ($23$ s-rRNA) helps in the formation of peptide bond during protein synthesis
Study the following lists .
List-I | List-I | ||
---|---|---|---|
(A) | Spongy aril | (I) | Jussiaea |
(B) | Mulhple epidermis | (II) | Pistia |
(C) | Respirato room | (III) | Nerium |
(D) | Root pockets | (IV) | Sagiuaria |
(V) | Nymphaea |
The correct match is ___________.
-
A B C D
I III II V -
II I IV III
-
IV I III I
-
V III I II
In the modern system of nomenclature which one of the following enzyme occupies 6th position _________________.
-
enzyme occupies 6th position
(a) Ligase -
Isomerase
-
Lyase
-
Hydrolase
The nomenclatural type of a specimen selected by the author as substitute of a lost material on which the name of the taxon is base is called.
-
Syntype
-
Neotype
-
Lectotype
-
Paratype
A specimen or illustration used by the author or designated by him as the nomenclature type is called.
-
Isoparatype
-
Isotype
-
Syntype
-
Holotype