RBSE Solutions For Class 12 Biology Chapter 9: Enzymes | Textbook Important Questions & Answers

RBSE Class 12 Biology Chapter 9- Enzymes, provides complete information related to enzymes, the structure of enzymes, properties of enzymes, classification of enzymes, the nomenclature of enzymes, factors affecting the enzymatic action, different modes of enzymatic action, mechanism of enzymes and other theories.

RBSE Solutions for Class 12 help students to perform their best in the exams. By practising these important questions, students can analyze their preparation, get a thorough knowledge about all the important terminologies and at the same time helps them assess their understanding of the material.

The Rajasthan Board Class 12 Biology Chapter 9 important questions are the best study material for both class assignments and other board examinations. By practising these important questions, students can gain deep knowledge about the topics explained in this chapter and also help them to be well prepared for their upcoming examinations.

RBSE Class 12 Biology Chapter 9 Important Questions

RBSE Biology Chapter 9: MCQ Type Questions

Q.1. Which of the following statements is true?

(a) All proteins are enzymes.

(b) All enzymes are proteins.

(c) Most enzymes are proteins.

(d) All of the above.

Sol: (c) Most enzymes are proteins.

Q.2. Which of the following enzymes was obtained from the crystalline form?

(a) Urease.

(b) Catalase.

(c) Amylase.

(d) Aldolase.

Sol: (a) Urease.

Q.3. In what respect are enzymes different from catalysts?

(a) High diffusion rate.

(b) Active at high temperature.

(c) Protein nature.

(d) Used in the reaction.

Sol: (c) Protein nature.

Q.4. The non-protein part of the holoenzyme is called _____.

(a) Apoenzyme.

(b) Conjugated enzymes.

(c) Coenzyme.

(d) All of the above.

Sol: (c) Coenzyme.

Q.5. Which of the following statements is true about non-competitive inhibitors?

(a) Non-competitive inhibitors combine to the active sites of enzymes.

(b) Non-competitive inhibitors decrease the active sites of enzymes.

(c) Non-competitive inhibitors change the structural organization of the enzymes.

(d) Non-competitive inhibitors do not cause any changes in the properties of an enzyme.

Sol:(c) Non-competitive inhibitors change the structural organization of the enzymes.

Q.6. An apoenzyme together with its cofactor forms ____________.

(a) Apoenzyme.

(b) Holoenzyme

(c) Coenzyme.

(d) Conjugated enzymes.

Sol:(b) Holoenzyme.

Q.7. The protein part of the holoenzyme is called ____________.

(a) Apoenzyme.

(b) Conjugated enzymes.

(c) Coenzyme.

(d) All of the above.

Sol: (a) Apoenzyme.

Q.8. Which of the following statements is true about enzymes?

(a) Enzyme activity is affected by pH only.

(b) Enzyme activity is affected by temperature.

(c) Enzyme activity is affected by substrate concentration.

(d) All of the above.

Sol: (d) All of the above.

Q.9. Which was the first enzyme to be discovered in yeast cells?

(a) Zymase.

(b) Lipase.

(c) Isomerase.

(d) Pepsin

Sol:(a) Zymase.

Q.10. Which of the following is the non-proteinaceous enzyme?

(a) Apoenzyme.

(b) Coenzyme.

(c) Ribozyme enzymes.

(d) Conjugated enzymes.

Sol: (c) Ribozyme enzymes.

RBSE Biology Chapter 9:Short Answer Type Questions.

Q.1. What is Coenzyme? Give examples.

Sol. When the non-protein part is loosely associated with the apoenzyme or it can be easily separated and capable of attaching again. These enzymes are called the Coenzyme. NAD, NADP, FAD and Co-A are a few examples of Coenzyme.

Q.2. Where are enzymes found in the living system?

Sol. All enzymes are found in cells, which are unevenly distributed, The enzymes required for respiration are found within the mitochondria of a cell, whereas the enzymes required for photosynthesis are found in the chloroplasts of the plant cells.

Q.3. What are enzymes? How many enzymes are found in Human Cells?

Sol. Enzymes are proteins made by all living organisms and are found everywhere in nature. They are biologically active proteins that catalyze biochemical reactions in cells. There are around 1300 different enzymes found in human cells.

Q.4. List out the factors affecting enzymatic actions.

Sol. The factors affecting enzymatic actions are:

  1. pH value.
  2. Temperature.
  3. Enzyme concentration.
  4. The concentration of substrate.
  5. Enzyme inhibitors and prisons.
  6. The concentration of the end product.

Q.5. What are the functions of Enzymes?

Sol. The enzymes perform a number of functions in our body. These include:

  1. Enzymes help in signal transduction.
  2. Enzymes help in generating energy in the body.
  3. Enzymes are responsible for the movement of ions across the plasma membrane.
  4. Enzymes function to reorganize the internal structure of the cell to regulate cellular activities.
  5. Enzymes break down large molecules of food molecules into smaller substances that can be easily absorbed by the body.
  6. Enzymes perform a number of biochemical reactions, including oxidation, reduction, hydrolysis, etc. to eliminate the non-nutritive substances from the body.

Q.6. What are the catalysts?

Sol. Catalysts are the substances which play an important role in the chemical reaction. This is the phenomenon by which the rate of a chemical reaction can be altered without changing the reactions. i.e. during a chemical reaction, a catalyst remains the same, both in terms of chemical properties and quantity.

Q.7. What are the different types of Enzymes?

Sol. There are six different types and are classified on the basis of functional classes. The six different types are:

  1. Hydrolases – They break chemical bonds when water is added. There are more than 200 types of hydrolases.
  2. Isomerases – There are 4 different sub-categories under this. They bring about structural changes within the molecule.
  3. Ligases – The Ligases enzymes are known to charge the catalysis of a ligation process. An example is DNA ligase which catalyzes ligation or repair of breaks in DNA.
  4. Lyases – They are also called synthase enzymes. They are involved in catalyzing the breakage of bonds without catalysis.
  5. Oxidoreductases – They are involved in catalyzing oxidation and reduction reactions.
  6. Transferases – Involved in the transfer of the functional group from the donor molecule to an acceptor molecule.

Q.8. What is Cofactor?

Sol. Cofactors are non-proteinaceous substances that associate with enzymes. A cofactor is essential for the functioning of an enzyme. An enzyme without a cofactor is called an apoenzyme. An apoenzyme and its cofactor together constitute the holoenzyme.

Q.9. What is competitive inhibition? How can this type of inhibition be stopped?

Sol. An inhibitor or chemical substances, which have a structure similar to the substrate molecule, complete with the substrate in attaching with the active sites of the enzymes are called the competitive inhibition. The presence of such substances lowers the activity of the enzymes. This type of inhibition can be stopped by increasing the concentration of the substrate molecules.

Q.10. How is the rate of enzyme activity accelerated?

Sol. The rate of enzyme activity accelerated by increasing the total amount of enzyme. The rate of reaction increases until the concentration of the substrate becomes a limiting factor. At this stage, the rate of reaction can be increased by increasing the concentration of the substrate.

Q.11.What are the optimum temperature and pH required for the action of an enzyme?

Sol. The optimum temperature required for the action of an enzyme is between 25°C to 55°C and the optimum pH for the enzymatic action is 7.2 – 7.4.

At high-temperature enzymes are deactivated and their action is retarded, similarly, at a very low temperature, they are activated.

Q.12. What are enzyme inhibitors?

Sol. Enzyme inhibitors are substances which alter the catalytic action of the enzyme and consequently slow down or stop the catalysis. Enzyme inhibitors mainly include chemical substances, disease-causing pathogens and pesticide molecules.

Q.13. What is Enzyme Catalysis?

Sol. When there is an increase in the rate of a chemical process by a biological molecule typically an enzyme, the process is known as enzyme catalysis. Such processes involve chemical reactions and the catalysis generally occurs at a localized site known as the active site.

Q.14.What is Enzyme Optima?

Sol. Enzymes are proteins which act as biological catalysts. Most of these enzymes show maximum activity at specific conditions and this is called the enzyme optima. Enzymes activity depends on the temperature, pH and substrate concentration.

Q.15. What is Enzyme made up of?

Sol. Enzymes are nitrogenous organic compounds generally made of proteins and 100 to1000 amino acids. In the formation of amino acids, chains of 100 to 1000 amino acids are folded together to form a unique shape.

Q.16. What are the different types of digestive enzymes?

Sol. The different types of digestive enzymes are given below.

  1. Amylase – It is involved in breaking down large starch molecules, this enzyme is produced in the mouth.
  2. Pepsin – It is involved in breaking down proteins, this is produced in the stomach.
  3. Trypsin – It is involved in breaking down proteins, this is produced in the pancreas.
  4. Pancreatic lipase – It is involved in breaking down fats, once again this enzyme is produced in the pancreas.
  5. Ribonuclease and deoxyribonuclease –It is involved in breaking down DNA and RNA, this enzyme is also produced in pancreas.

Q.17. What is the enzyme-substrate complex?

Sol. Enzymes are macromolecules, which possess high molecular weight. There are numerous active sites on the surface of the enzymes, where the substrate molecules attach to form an unstable complex. This type of complex is called an enzyme-substrate complex. This enzyme-substrate complex breaks to release the product and enzyme.

Q.18. What is a Prosthetic group? Give examples.

Sol. Prosthetic groups are non-protein components of an enzyme, which are firmly attached to proteins and assist the protein in various ways. The attachment of non-protein components to an enzyme cannot be separated easily. Some examples of prosthetic groups are heme, biotin, flavin, iron sulfides, copper and ubiquinone.

Q.19. What are the different types of cofactors?

Sol. There are three kinds of cofactors present in enzymes:

  1. Prosthetic groups: These cofactors are tightly bound to an enzyme at all times. A fad is a prosthetic group present in many enzymes.
  2. Coenzyme: A coenzyme is bound to an enzyme only during catalysis. At all other times, it is detached from the enzyme. NAD+ is a common coenzyme.
  3. Metal ions: For the catalysis of certain enzymes, a metal ion is required at the active site to form coordinate bonds. Zn2+ is a metal ion cofactor used by a number of enzymes.

Q.20. What are digestive enzymes? What is the function of digestive enzymes?

Sol. Digestive enzymes are a group of enzymes, which functions by breaking down the large food particles into a smaller and absorbable form. The hydrochloric acid present in our stomach dissolves bits of food and creates an acidic medium. Enzyme pepsinogen, which is a protein-digesting enzyme is converted to pepsin in this acidic medium. Amylase, Pepsin, Trypsin, Pancreatic lipase, Deoxyribonuclease and Ribonuclease are a list of digestive enzymes.

RBSE Biology Class 12: Long Answer Type Questions

Q.1. What are enzymes? Briefly explain the method of nomenclature of enzymes.

Sol. Enzymes are proteins made by all living organisms and are found everywhere in nature. The word enzyme was coined in 1878 by German Scientist Wilhelm Kuhne. Thus, enzymes play an important role in all living organisms by regulating all the biological processes. There are several methods of nomenclature of enzymes.

Listed below are a few of them.

  • Enzymes are named by adding a suffix case at the end of the name of a substrate catalyzed by enzymes. For example- Sucrase, Maltase, Urease, etc.
  • Enzymes are named on the basis of the type of catalytic reaction governed by the enzymes. For example- Oxidase, Dehydrogenase, etc.
  • In the modern method of nomenclature, enzymes are named by adding the suffix case after both the name of the substrate on which they act and on the type of the catalytic reaction governed by them. For example- Succinate dehydrogenase, etc.
  • In some cases, the traditional names of enzymes have been retained. For example- Pepsin, Trypsin, Chymotrypsin, etc.
  • The International Union of Biochemistry has proposed systematic nomenclature in which some code number is given for each enzyme. In this method of nomenclature, substrate name, type of reaction, catalyzed and other information related to the enzymes are also included.

Q.2. What are the applications of enzymes?

Sol. Enzymes are used in the production of various commercial products. They are used in foods and beverages processing, in producing animal nutrition, in textiles, household cleaning and also in producing fuel for cars and in other energy generation.

Listed below are few of the applications of enzymes in human welfare:

Drugs.

Enzyme action can be inhibited or promoted by the use of drugs which tend to work around the active sites of enzymes.

Beverages

There are many beverages, which are produced by the fermentation and few vary based on many factors. There are different types of enzymes, which are used in the production of beverages. Based on the type of beverages and the type of fermented product the type of the enzyme applied varies. For example, cassava roots, grapes, honey, hops, potatoes and wheat are the list of the fermented products, depending upon these materials enzymes are selected to produce different beverages like beer, wine and other drinks that are produced from plant fermentation.

Food Products

Bread can be considered as the finest example of fermentation in our everyday life.

A small proportion of yeast and sugar is mixed with the batter for making bread. Then one can observe that the bread gets puffed up as a result of fermentation of the sugar by the enzyme action in yeast, which leads to the formation of carbon dioxide gas. This process gives the texture to the bread, which would be missing in the absence of the fermentation process.

Q.3. Brief out the mechanism of Enzyme Reaction.

Sol. The basic mechanism of enzyme action is to catalyze the chemical reactions, which begins with the binding of the substrate with the active site of the enzyme. This active site is a specific area that combines with the substrate.

During the enzyme reaction, any two molecules have to collide for the reaction to occur along with the right orientation and a sufficient amount of energy. The energy between these molecules overcomes the barrier in the reaction, which is called activation energy.

Enzymes are said to possess an active site. The active site is a part of the molecule that has a definite shape and the functional group for the binding of reactant molecules. The molecule binding with the enzyme is called the substrate group. The substrate and the enzyme form an intermediate reaction with low activation energy without any catalysts.

Q.4. Define Lock and Key Theory?

Sol. The mechanism of the formation of the enzyme-substrate complex and the property of specificity of the enzymes is explained by this theory.

Lock and Key Theory.

This theory was postulated by Emil Fisher in 1898. According to the lock and key theory, like a lock can be operated by its key only, similarly, a specific substrate having a specific structure only can bind to with the specific active site present on the surface of a specific enzyme. Here, the enzyme remains unchanged even after the product is released.

Here is the image of Lock and Key Theory.

Lock and Key Theory

Q.5.What are the properties of an Enzyme?

Sol. All enzymes are found with the living cell but are not evenly distributed. The enzymes required for respiration are found within the mitochondria, whereas the enzymes required for photosynthesis are found in the chloroplast. Enzymes can be isolated in a pure form without destroying their catalytic capacity. For a detailed study about the enzymes, the following properties are important. The special properties of enzymes are discussed below:

  • Enzymes are protein in nature.

All enzymes are chemical proteins. Sometimes, organic or inorganic ions or molecules or groups of molecules may be present in them other than the proteins.

  • Enzymes are colloidal in nature.

All enzymes are colloidal in nature. Due to the large surface area, they provide an extensive surface for the biochemical process because of which the reactions complete at a faster rate.

  • The specificity of Enzymes.

All enzymes are specific for their reaction usually when one enzyme catalyses only one reaction or remains functional for a few special chemical bonds. While there are few enzymes which catalyse two or more reactions.

  • The larger size of an Enzyme.

The size of an enzyme being larger provides a large surface to many substrates, which helps in increasing the rate reaction even when the enzymes are present in a smaller amount.

The capacity of an enzyme to react with acidic and basic substrates.

A major part of the enzymes is made up of proteins. These proteins are amphoteric and react with both basic and acidic substrates.

  • Enzyme optima

Most of the enzymes show maximum activity at a specific condition. This is called the enzyme optima. The rate of enzyme activity depends on temperature, pH, substrate concentration, etc.

  • Enzyme Inhibition.

The rate of enzyme activity can be reduced or inhibited by other chemicals. These chemicals are collectively called the enzyme inhibition, which can directly or indirectly reduce the rate of enzyme activity.

Q.6. Brief out the factors affecting the rate of enzyme activity.

Sol. The factors affecting enzymatic actions are:

Temperature

The optimum temperature for an enzyme action is between 20°C to 35°C.10°C rise in the temperature increases the rate of enzyme action by 2 to 3 times. This is because enzymes are proteinaceous in nature and are extremely sensitive to temperature changes.

pH value

All enzymes are sensitive to the pH of the medium. Each enzyme can act on a specific optimum pH value. Most of the enzymes work efficiently at pH ranging between 5.0 to 7.5. Increase or decrease in the pH values affects the action of an enzyme.

Concentration of substrate

At low concentration of substrate, the rate of enzyme activity is less, as the substrates are not attached on all the active sites present on an enzyme surface. On an increase in the concentration of substrate, the enzyme activity also increases.

Enzyme concentration

An adequate concentration of the substrate, the enzyme activity is proportional to the enzyme concentration. On the increase in the enzyme concentration, the activity gradually increases but due to the limitation of substrate concentration at some point it stops and becomes constant. Therefore, the increase of enzyme concentration, along with the substrate reaction, the rate of the enzyme activity also increases.

Concentration of the end product

Due to the increase in the concentration of the end product, the enzyme catalytic activity decreases. This decrease gradually makes the catalytic activity zero at equilibrium condition and after equilibrium condition, the catalytic activity completely stops and at the normal condition, the catalytic activity starts to reverse.

Enzyme inhibitors and prisons.

The molecules, which reduce the catalytic activity of enzymes are called enzyme inhibitors. These enzyme inhibitors are usually associated with active sites of enzymes, which alters the catalytic action and decreases its activity, either by slowing down or by inactivating the enzymes. There are two different types of inhibitor processes – Competitive inhibition and Non-Competitive inhibition.

Q.7. What is Induced-Fit Theory?

Sol. The induced-fit theory was first proposed by Daniel Koshland in 1966.

The induced-fit is a theory that explains the binding of a substrate into an active site of an enzyme that does not have a correct conformation with that of the active site.

According to this theory, the shape and structure of the active sites found on the surface of enzymes are not rigid but are flexible. These active sites are initially not complementary to the substrate molecule but as a specific substrate molecule comes in close proximity of the enzymes it includes a change in the organisation of the active site and binds with it. Thus, enzyme-substrate complexes are formed between a specific substrate with a specific enzyme only.

Here is the image of Induced-Fit Theory.

induced fit theory

Q.8.Brief out the structure of an Enzyme.

Sol. Enzymes are a linear chain of amino acids that generate the three-dimensional structure. The arrangements of amino acid strings in a particular order provides the structure of an enzyme, which in turn, identifies the catalytic activity of the enzyme. The structure of the enzyme is destroyed when it is heated, leading to loss of enzyme activity, which is typically connected to the temperature.

Enzymes are larger than their substrates, and their size varies, which range from sixty-two amino acid residues to an average of two thousand five hundred residues present within fatty acid synthase. Only a small section of the structure is involved in catalysis and is situated next to binding sites. The catalytic site and binding site together constitute the enzyme’s active site. A small number of ribozymes exists, which serves as an RNA-based biological catalyst. It reacts in complex with proteins.

Q.9. Brief out the classification of Enzyme.

Sol. According to the International Union of Biochemistry – IUB, the enzymes are classified into six main categories.

Oxidoreductases – All the enzymes, which catalyze oxidation-reduction reactions are included in this category. They are involved in catalyzing oxidation and reduction reactions. On the basis of their activity, these enzymes are classified into three subgroups

  1. Oxidases
  2. Dehydrogenases
  3. Reductase.

Transferases – These enzymes catalyze the transfer of the functional group molecule to another molecule.

Hydrolases – These enzymes catalyze the hydrolysis reaction either by the addition or removal of water. There are more than 200 types of hydrolases. This group of enzymes include digestive enzymes, which break down the macromolecules into smaller molecules. Most of the hydrolytic reactions are reversible and this type of enzyme may also condense small molecules to form macromolecules.

Lyases – These enzymes catalyze the removal of a group from their substrate molecule by breaking a special type of covalent bonds without hydrolysis. They are also called synthase enzymes. They are involved in catalyzing the breakage of bonds without catalysis.

Isomerases – These enzymes catalyze intramolecular reorganisation in the substrate molecules and convert the substrate into its isomer. They bring about structural changes within the molecule. There are four different sub-categories.

Ligases – These enzymes catalyze reactions in which two compounds are linked together to form a covalent bond between the two. Ligases enzymes are known to charge the catalysis of a ligation process. An example is DNA ligase, which catalyzes ligation or repair of breaks in DNA.

Q.10. What is the Difference Between Induced Fit and Lock and Key Theories?

Sol. Induced fit and lock and key are two different theories proposed to explain the mechanism of the formation of the enzyme-substrate complex and the property of specificity of the enzymes

The induced-fit theory describes the binding of an enzyme and substrate that are not complementary.

The lock and key theory describe the binding of enzymes and substrates that are complementary.

Let us find out more difference between Induced Fit and Lock and Key in a tabular form.

Difference Between Induced Fit and Lock and Key Theories.

Induced Fit Theory

Lock and Key Theory

Explains the mechanism of the enzyme-substrate binding when they are not complementary in shape with each other.

Explains the mechanism of binding of perfectly matching substrate and enzyme with each other.

The shapes are not complementary with each other before binding.

The shapes are complementary with each other before binding.

The binding is flexible compared to Lock and Key theory.

The binding is very strong compared to Induced-Fit theory.

The active site is not static.

The active site is static.

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