Case Study Questions Class 11 Biology Biomolecules

Case Study Questions Class 11 Biology Chapter 9 Biomolecules

CBSE Class 11 Case Study Questions Biology Biomolecules. Important Case Study Questions for Class 11 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Biomolecules.

At Case Study Questions there will given a Paragraph. In where some Important Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks, 4 marks.

CBSE Case Study Questions Class 11 Biology Biomolecules

CASE 1

Enzymes are composed of one or several polypeptide chains. However, there are a number of cases in which non-protein constituents called co-factors are bound to the enzyme to make the enzyme catalytically active. In these instances, the protein portion of the enzymes is called the apoenzyme. Three kinds of cofactors may be identified: prosthetic groups, co-enzymes and metal ions. Prosthetic groups are organic compounds and are distinguished from other cofactors in that they are tightly bound to the apoenzyme. For example, in peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to water and oxygen, haem is the prosthetic group and it is a part of the active site of the enzyme. Co-enzymes are also organic compounds but their association with the apoenzyme is only transient, usually occurring during the course of catalysis. Furthermore, co-enzymes serve as co-factors in a number of different enzyme catalyzed reactions. The essential chemical components of many coenzymes are vitamins, e.g., coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin. A number of enzymes require metal ions for their activity which form coordination bonds with side chains at the active site and at the same time form one or more cordination bonds with the substrate, e.g., zinc is a cofactor for the proteolytic enzyme carboxypeptidase. Catalytic activity is lost when the co-factor is removed from the enzyme which testifies that they play a crucial role in the catalytic activity of the enzyme.

1.) In complex of protein and co-factors, protein is referred as ___________________.

a) Proenzyme

b) Coenzyme

c) Apoenzyme

d.) Proteinase enzyme.

2.) ________________ Co-factor are found very tightly bound to the apoenzyme.

a.) Co-enzyme

b.) Proenzyme

c,) Proteinase

d.) Prosthetic

3.) Enlist the type of co-factor with examples.

4.) Define co-factors.

5.) What result come off if co-factor is removed from the enzyme?

Answer key

1.) c

2.) d

3.) Three kinds of cofactors

  • Prosthetic groups – e.g. Haem
  • Co-enzymes – e.g. Niacin
  • Metal ions – e.g. zinc

4.) Co-factor are the non-protein constituents are bound to the enzyme to make the enzyme catalytically active. Enzymes are composed of one or several polypeptide chains. However, there are a number of cases in which non-protein constituents are bound to the enzyme to make the enzyme catalytically active.

5.) Catalytic activity is lost when the co-factor is removed from the enzyme which testifies that they play a crucial role in the catalytic activity of the enzyme.

CASE 2

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, and change in substrate concentration or binding of specific chemicals that regulate its activity. Temperature and pH 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.

Concentration of Substrate With the increase in substrate concentration, the velocity of the enzymatic reaction rises at first. The reaction ultimately reaches a maximum velocity (Vmax) which is not exceeded by any further rise in concentration of the substrate. This is because the enzyme molecules are fewer than the substrate molecules and after saturation of these molecules, there are no free enzyme molecules to bind with the additional substrate molecules.

The activity of an enzyme is also sensitive to the presence of specific chemicals that bind to the enzyme. When the binding of the chemical shuts off enzyme activity, the process is called inhibition and the chemical is called an inhibitor.

When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as competitive inhibitor. Due to its close structural similarity with the substrate, the inhibitor competes with the substrate for the substrate binding site of the enzyme. Consequently, the substrate cannot bind and as a result, the enzyme action declines, e.g., inhibition of succinic dehydrogenase by malonate which closely resembles the substrate succinate in structure. Such competitive inhibitors are often used in the control of bacterial pathogens.

1.) _______________ is a chemical compound or molecule which is responsible for decrease or stop the enzyme activity by binding to an enzyme.

a.) Catalyser

b) Inhibitor

c) Regulator

d) Controller

2.) _______________ preserve the enzyme and keep them in temporarily inactive state.

a.) Optimum pH

b) Low pH

c) Optimum temperature

d) Low temperature

3.) Give reason – why most of the enzymes destroyed in high temperature condition?

4.) Explain the relation between substrate concentration and enzymatic activity?

5.) Explain competitive inhibition and inhibitor.

Answer key

1.) b

2.) d

3.) Enzymes are composed of one or several polypeptide chains. Almost all enzymes are protein. High temperature condition destroys enzymatic activity because proteins are denatured by heat.

4.) Concentration of Substrate With the increase in substrate concentration, the velocity of the enzymatic reaction rises at first. The reaction ultimately reaches a maximum velocity (Vmax) which is not exceeded by any further rise in concentration of the substrate. This is because the enzyme molecules are fewer than the substrate molecules and after saturation of these molecules, there are no free enzyme molecules to bind with the additional substrate molecules.

5.) When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as competitive inhibitor. Due to its close structural similarity with the substrate, the inhibitor competes with the substrate for the substrate binding site of the enzyme. Consequently, the substrate cannot bind and as a result, the enzyme action declines. This phenomenon is called as competitive inhibition.

CASE 3

Almost all enzymes are proteins. There are some nucleic acids that behave like enzymes. These are called ribozymes. An enzyme like any protein has a primary structure, i.e., amino acid sequence of the protein. An enzyme like any protein has the secondary and the tertiary structure. When you look at a tertiary structure you will notice that the backbone of the protein chain folds upon itself, the chain criss-crosses itself and hence, many crevices or pockets are made. One such pocket is the ‘active site’. An active site of an enzyme is a crevice or pocket into which the substrate fits. Thus enzymes, through their active site, catalyse reactions at a high rate. Enzyme catalysts differ from inorganic catalysts in many ways, but one major difference needs mention. Inorganic catalysts work efficiently at high temperatures and high pressures, while enzymes get damaged at high temperatures (say above 40°C). However, enzymes isolated from organisms who normally live under extremely high temperatures (e.g., hot vents and sulphur springs), are stable and retain their catalytic power even at high temperatures (upto 80°-90°C). Thermal stability is thus an important quality of such enzymes isolated from thermophilic organisms.

1.) _____________ is the pocket like region of an enzyme into which substrate molecules bind.

a) Protein site

b) Co-factors

c) Coenzyme

d) Active site

2.) Identify incorrect statement

Statement 1 – Nucleic acids which behave like enzymes are commonly termed as nucliozymes.

Statement 2 – An enzyme like any protein has a primary, secondary and the tertiary structure.

Statement 3 – Enzyme catalysts differ from inorganic catalysts in many ways.

Statement 4 – All enzymes are proteins.

a.) Only 1

b) Both 1 & 3

c) Only 3

d.) None of the above

3.) How active site of enzymes are formed?

4.) Explain how Enzyme catalysts differ from inorganic catalysts?

5.) What is ribozymes?

Answer key

1.) d

2.) a

3.) Enzyme have primary, secondary and tertiary structure like proteins. In tertiary structure, backbone of the protein chain folds upon itself, the chain criss-crosses itself and leads to the formation of many crevices or pockets are made. These pockets are referred as active site of enzyme. An active site of an enzyme is a crevice or pocket into which the substrate fits.

4.) Enzyme catalysts differ from inorganic catalysts in many ways. Inorganic catalysts work efficiently at high temperatures and high pressures, while enzymes get damaged at high temperatures (above 40°C). There are some exceptions such as enzyme isolated from thermophilic organisms.

5.) There are some nucleic acid behave like an enzymes, these nucleic acid is termed as ribozymes.

CASE 4

Metabolic pathways can lead to a more complex structure from a simpler structure (for example, acetic acid becomes cholesterol) or lead to a simpler structure from a complex structure (for example, glucose becomes lactic acid in our skeletal muscle). The former cases are called biosynthetic pathways or anabolic pathways. The latter constitute degradation and hence are called catabolic pathways. Anabolic pathways, as expected, consume energy. Assembly of a protein from amino acids requires energy input. On the other hand, catabolic pathways lead to the release of energy. For example, when glucose is degraded to lactic acid in our skeletal muscle, energy is liberated. This metabolic pathway from glucose to lactic acid which occurs in 10 metabolic steps is called glycolysis. Living organisms have learnt to trap this energy liberated during degradation and store it in the form of chemical bonds. As and when needed, this bond energy is utilised for biosynthetic, osmotic and mechanical work that we perform. The most important form of energy currency in living systems is the bond energy in a chemical called adenosine triphosphate (ATP).

There are thousands of chemical compounds in a living organism, otherwise called as metabolites or biomolecules, are present at concentrations characteristic of each of them. For example, the blood concentration of glucose in a normal healthy individual is 4.2 mmol/L– 6.1 mmol/L, while that of hormones would be nanograms/mL. The most important fact of biological systems is that all living organisms exist in a steady-state characterised by concentrations of each of these biomolecules. These biomolecules are in a metabolic flux. Any chemical or physical process moves spontaneously to equilibrium. The steady state is a non-equilibrium state. Systems at equilibrium cannot perform work. As living organisms work continuously, they cannot afford to reach equilibrium. Hence the living state is a non-equilibrium steady state to be able to perform work; living process is a constant effort to prevent falling into equilibrium. This is achieved by energy input. Metabolism provides a mechanism for the production of energy. Hence the living state and metabolism are synonymous. Without metabolism there cannot be a living state.

1.) ________________ is the destructive process, which involves complex structure breakdown into simple form.

a) Amphibolic pathway

b) Anabolic pathway

c) Catabolic pathway

d) None of the above

2.) ______________ is the normal glucose concentration in normal healthy individual.

a) 9 mmol/L– 6.8 mmol/L

b) 5 mmol/L– 6.5 mmol/L

c) 0 mmol/L– 7.1 mmol/L

d) 2 mmol/L– 6.1 mmol/L

3.) Give any one example of catabolic reaction that take place in human body.

4.) Give the name of chemical bond in which energy liberated during degradation of metabolites, is stored.

5.) Define anabolic pathways and catabolic pathways.

Answer key

1) c

2.) d

3.) Glucose becomes lactic acid in our skeletal muscle is the catabolic pathway reaction, which constitute degradation of biomolecule and release energy.

4.) In Living organism energy liberated during degradation of metabolites stored in the form of chemical bonds i.e. ATP. Adenosine triphosphate (ATP) is the most important form of energy currency in living systems.

5) Anabolic pathway – Metabolic pathways which leads to a more complex structure from a simpler structure are termed as anabolic pathways or biosynthetic pathways.

Catabolic pathway – Metabolic pathways which leads to a simpler structure from a complex structure are termed as catabolic pathways.

CASE 5

Proteins are heteropolymers containing strings of amino acids. Structure of molecules means different things in different contexts. In inorganic chemistry, the structure invariably refers to the molecular formulae (e.g., NaCl, MgCl2, etc.). Organic chemists always write a two dimensional view of the molecules while representing the structure of the molecules (e.g., benzene, naphthalene, etc.). Physicists conjure up the three dimensional views of molecular structures while biologists describe the protein structure at four levels. The sequence of amino acids i.e., the positional information in a protein – which is the first amino acid, which is second, and so on – is called the primary structure of a protein. A protein is imagined as a line, the left end represented by the first amino acid and the right end represented by the last amino acid. The first amino acid is also called as N-terminal amino acid. The last amino acid is called the C-terminal amino acid. A protein thread does not exist throughout as an extended rigid rod. The thread is folded in the form of a helix, only some portions of the protein thread are arranged in the form of a helix. In proteins, only right handed helices are observed. Other regions of the protein thread are folded into other forms in what is called the secondary structure. In addition, the long protein chain is also folded upon itself like a hollow woollen ball, giving rise to the tertiary structure. This gives us a 3-dimensional view of a protein. Tertiary structure is absolutely necessary for the many biological activities of proteins.

Some proteins are an assembly of more than one polypeptide or subunits. The manner in which these individual folded polypeptides or subunits are arranged with respect to each other (e.g. linear string of spheres, spheres arranged one upon each other in the form of a cube or plate etc.) is the architecture of a protein otherwise called the quaternary structure of a protein (Fig. 9.4 d). Adult human haemoglobin consists of 4 subunits. Two of these are identical to each other. Hence, two subunits of α type and two subunits of β type together constitute the human haemoglobin (Hb).

In a polypeptide or a protein, amino acids are linked by a peptide bond which is formed when the carboxyl (-COOH) group of one amino acid reacts with the amino (-NH2 ) group of the next amino acid with the elimination of a water moiety (the process is called dehydration). In a polysaccharide the individual monosaccharides are linked by a Glycosidic bond. This bond is also formed by dehydration. This bond is formed between two carbon atoms of two adjacent monosaccharides. In a nucleic acid a phosphate moiety links the 3’-carbon of one sugar of one nucleotide to the 5’-carbon of the sugar of the succeeding nucleotide. The bond between the phosphate and hydroxyl group of sugar is an ester bond. As there is one such ester bond on either side, it is called phosphodiester bond. Nucleic acids exhibit a wide variety of secondary structures. For example, one of the secondary structures exhibited by DNA is the famous Watson – Crick Model. This model says that DNA exists as a double helix. The two strands of polynucleotides are antiparallel i.e., run in the opposite direction. The backbone is formed by the sugar-phosphate-sugar chain. The nitrogen bases are projected more or less perpendicular to this backbone but face inside. A and G of one strand compulsorily base pairs with T and C, respectively, on the other strand.There are two hydrogen bonds between A and T and three hydrogen bonds between G and C. Each strand appears like a helical staircase.

1.) To form polypeptide molecules, number of amino acids joined together by _______________ bond.

a.) Covalent bond

b) Glycosidic bond

c) Peptide bond

d) Phosphodiester bond

2.) Number of monosaccharides are joined together by _____________ to form polysaccharide.

a.) Phosphodiester bond

b) Glycosidic bond

c) Hydrogen bond

d) Ester bond

3.) Define N-terminal amino acid and c-terminal amino acid.

4.) Explain how amino acid chain formed in the formation of polypeptide molecule.

5.) Name the bond present between nitrogen bases ( A and G / T and C ) of nucleic acid.

Answer key

1.) c

2) b

3) The first amino acid present in amino acid chain is also called as N-terminal amino acid. The last amino acid is called the C-terminal amino acid.

4) When the carboxyl (-COOH) group of one amino acid reacts with the amino (-NH2) group of the next amino acid, they form peptide bond between them. This way formation of amino acid chain continuous which leads to the polypeptide.

5) The nitrogen bases A and G of one strand compulsorily base pairs with T and C, respectively, there are two hydrogen bonds between A and T and three hydrogen bonds between G and C.

Updated: April 3, 2022 — 3:03 am

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