CBSE Class 11 Biology Biomolecules Notes

 Biomolecules

POINTS TO REMEMBER :

Biomolecules : All the carbon compounds that we get from living tissues.
Macromolecules : Molecules which have molecular weights less than one thousand dalton.
Amino acids : Organic compounds containing an amino group and one carboxyl group (acid group) and both these groups are attached to the same carbon atom called α carbon.

Twenty types of amino acids occur in proteins.
Based on number of amino and carboxyl groups, amino acids can be:

o Acidic: e.g. Glutamic acid
o Basic: e.g. Arginine and lysine
o Neutral: e.g. valine, alanine.

- Aromatic amino acids are tyrosine, phenylalanine, and tryptophan.
- Amino acids are ionizable into zwitterionic form.

Lipids :

- Water insoluble, containing C, H, O.
- They could be simple fatty acids.
- A fatty acid has a carboxyl group attached to an R group.
- The R group may be a methyl group (-CH₃) or ethyl (-C₂H₅) or higher number of-CH₂group (1 carbon to 19 carbon). E.g. palmitic acid with 19 carbons, arachidonic acid has 20 carbons.
- Fatty acids could be saturated (without double bond) or unsaturated (with one more (c=c) double bond.
- Another example of lipid is glycerol which is trihydroxy propane.
- Many lipids may have both glycerol and fatty acids.
- Fatty acids esterified with glycerol to form mono, di or triglycerides.
- These are also called fats and oils based on the melting points.
- Oils have low melting points (e.g. gingely oil).
- Phospholipids are compound lipids with phosphorus and a phosphorylated organic compound. They are found in the cell membrane. e.g., Lecithin.

Nitrogen bases :

Carbon compounds with heterocyclic rings.
Purine: Adenine, Guanine.
Pyrimidine: Cytosine, Uracil, Thymine.
Nucleoside: Nitrogenous base + Sugar e.g., Adenosine, guanosine, thymidine Uridine and cytidine
Nucleotide: Nitrogenous base + Sugar + Phosphate group. e.g., Adenylic acid, thymidylic acid, guanylic acid, uridylic acid and cytidylic acid.
Nucleic acid: Polymer of nucleotides - DNA and RNA.

PRIMARY AND SECONDARY METABOLITES :

Primary metabolites :

o Have identified function.
o Play known roles in physiological function.
o Carbohydrates, amino acids, fats and oils, nitrogen bases are the example of primary metabolites.

Secondary metabolites :

o Have no definite function.
o Have no direct role in normal physiology.
o Alkaloid, favonoides, rubber, essential oils, antibiotics, coloured pigments. Scents, gums, spices are some example.

Biomacromolecules: Biomolecules with molecular weights in the range of ten thousand daltons and above; found in acid insoluble fraction.
Lipids are not strictly macromolecules as their molecular weights do not exceed 800 Da but form a part of the acid insoluble pool.

Proteins :

- Are polymers of amino acids linked by peptide bond.
- Is a heteropolymer not homopolymer.
- Essential amino acids: those can’t be synthesized in our body, have to be supplied through our diet.
- Non-essential amino acids: our body can synthesize it from other sources.
- Collagen is the most abundant protein in animal.
- Ribulose bisphosphate Carboxylase-Oxygenase (RUBISCO) is most abundant protein in the whole biosphere.

POLYSACCHARIDES :

- Acid soluble pillet also has polysaccharides as another class of macromolecules.
- Polysaccharides are the long chain of sugars.
- Cellulose is homopolymer containing only glucose units.
- Starch is a variant of homopolymer of glucose which store energy.
- Glycogen is another homopolymer found in animal.
- Inulin is a polymer of fructose.
- In a polysaccharide chain the right end is called reducing end and left end is non-reducing end.
- Starch form helical secondary structure.
- Starch can hold Iodine (I₂) molecule in its helical portion hence gives blue colour.
- Cellulose dose not contain complex helices and hence cannot hold Iodine (I₂) and not give blue colour.
- Complex sugars have amino-sugar as building blocks. (Glucosamine, N-acetyl galactosamine.)
- Exoskeleton of arthropods made of complex sugar called chitin.
- Complex polysaccharides are heteropolymer.

STRUCTURE OF PROTEINS :

Primary structure:Is found in the form of linear sequence of amino acids. First amino acid is called N-terminal amino acid and last amino acid is called C-terminal amino acid.
Secondary structure:Polypeptide chain undergoes folding or coiling which is stabilized by hydrogen bonding. Right handed helices are observed. e.g., fibrous protein in hair nails.
Tertiary structure:Long protein chain is folded upon itself like a hollow woolen ball. Gives a 3-dimensional view of protein, e.g., myosin.
Quaternary structure:Two or more polypeptides with their folding and coiling are arranged with respect to each other. e.g., Human haemoglobin molecule has 4 peptide chains - 2α and 2β subunits.

NATURE OF BOND LINKING MONOMERS IN A POLYMER :

• Peptide bondb : Formed between the carboxyl (-COOH) group of one amino acid and the amino (-NH2) group of the next amino acid with the elimination of water moiety.
• Glycosidic bondb :
o Individual monosaccharides linked with each other to form polysaccharides.
o This bond is also formed by dehydration.
o Formed between two carbon atoms of two adjacent monosaccharides.

• Phosphodiester bondbb :
o In a nucleic acid a phosphate moiety links the 3’-carbon of one sugar one nucleotide to the 5’-carbon of the sugar of the succeeding nucleotide.
o The bond between the phosphate and hydroxyl group of sugar is an ester bond.
o There is one such ester bond on either side, it is called Phosphodiester bond.
• Anabolic pathways: Lead to formation of more complex molecules from a simpler molecules with the consumption of energy. e.g., Protein from amino acids.
• Catabolic pathway: Lead to formation of simpler molecule from a complex molecule. e.g., Glucose → Lactic Acid.

ENZYMES :

- Are biocatalysts.
- Almost all enzymes are proteins.
- Ribozyme - Nucleic acids that behave like enzymes.
- Has primary, secondary and tertiary structure.
- Active site of an enzyme is a crevice or pocket into which substrate fits.
- Enzymes get damaged at high temperatures.
- Enzymes isolated from thermophilic organisms (live under high temperatures) are thermostable.
- Enzymes accelerate the reactions many folds.
- Enzymes lower the activation energy of reactions.
- The chemicals on which the enzyme acts called substrates.
- Enzyme converts substrates into products.

Nature of enzyme action :

- The substrate binds to the active site of the enzyme, fitting into the active site.
- The binding of the substrate induces the enzymes to alter its shape, fitting more tightly around the substrate.
- Active site now breaks the chemical bond of the substrate and enzyme-product complex is formed.
- The enzyme releases the product.

Factors affecting enzyme activity :

• Temperature :
o Show highest activity at optimum temperature.
o Activity declines above and below the optimum value.

• pH :
o Enzymes function in a narrow range of pH.
o Highest activity at optimum pH.

• Concentration of substrate :
o The velocity of enzymatic reaction rises with increase in substrate concentration till it reaches maximum velocity (V max). Further increase of substrate does not increase the rate of reaction as no free enzyme molecules are available to find with additional substrate.
• Enzyme inhibition: When the binding of a chemical shuts off enzyme activity, the process is called inhibition and chemical is called inhibitor.
• Competitive inhibition: Inhibitor closely resembles the substrate in its molecular structure and inhibits the enzyme activity. E.g., inhibition of succinic dehydrogenase by malonate.

Classification of enzymes :
- Oxidoreductase/dehydrogenases: Catalyse oxidoreduction between 2 substrates.
- Transferases: Catalyse transfer of a group between a pair of substrates.
- Hydrolases: Catalyse hydrolysis of ester, ether, peptide, glycosidic, C-C, P-N bonds.
- Lyases: Catalyse removal of groups from substrates by mechanisms other than hydrolysis leaving a double bond in the product.
- Isomerases: Catalyse inter-conversion of optical, geometric or positional isomers.
- Ligases: Catalyse linking together of 2 compounds.

Cofactors :
• Non-protein constituents found to the enzyme to make it catalytically active.
• Protein portion of enzyme is called apoenzyme.

• Prosthetic groups: Are organic compounds tightly bound to apoenzyme. E.g., haem in peroxydase and catalase.
• Co-enzymes: Organic compounds which loosely bind with enzyme. E.g., NAD, NADP.
• Metal ions: Required for enzyme activity. Form coordination bond with side chains at active site and with substrate. E.g., zinc is a co-factor for enzyme enters stomach?

Important Questions for NCERT Class 11 Biology Biomolecules

Question. ATP is
(a) nucleotide
(b) nucleoside
(c) nucleic acid
(d) vitamin. 
Answer: A

Question. Match the following.
(A) Inhibitor of                (i) Ricin catalytic activity
(B) Possess peptide        (ii) Malonate bonds
(C) Cell wall material      (iii) Chitin in fungi
(D) Secondary                 (iv) Collagen metabolite
Choose the correct option from the following:
     (A) (B) (C) (D)
(a) (ii) (iv) (iii) (i)
(b) (iii) (i) (iv) (ii)
(c) (iii) (iv) (i) (ii)
(d) (ii) (iii) (i) (iv) 
Answer: A

Question. Consider the following statements.
(A) Coenzyme or metal ion that is tightly bound to enzyme protein is called prosthetic group.
(B) A complete catalytic active enzyme with its bound prosthetic group is called apoenzyme.
Select the correct option.
(a) (A) is false but (B) is true.
(b) Both (A) and (B) are true.
(c) (A) is true but (B) is false.
(d) Both (A) and (B) are false. 
Answer: D

Question. Prosthetic groups differ from co-enzymes in that
(a) they require metal ions for their activity
(b) they (prosthetic groups) are tightly bound to apoenzymes
(c) their association with apoenzymes is transient
(d) they can serve as co-factors in a number of enzyme-catalyzed reactions.
Answer: B

Question. Which of the following statements is correct with reference to enzymes?
(a) Holoenzyme = Apoenzyme + Coenzyme
(b) Coenzyme = Apoenzyme + Holoenzyme
(c) Holoenzyme = Coenzyme + Co-factor
(d) Apoenzyme = Holoenzyme + Coenzyme
Answer: A

Question. A non-proteinaceous enzyme is
(a) lysozyme
(b) ribozyme
(c) ligase
(d) deoxyribonuclease.
Answer: B

Question. Which one of the following statements is incorrect?
(a) The competitive inhibitor does not affect the rate of breakdown of the enzyme-substrate complex.
(b) The presence of the competitive inhibitor decreases the Km of the enzyme for the substrate.
(c) A competitive inhibitor reacts reversibly with the enzyme to form an enzyme-inhibitor complex.
(d) In competitive inhibition, the inhibitor molecule is not chemically changed by the enzyme.
Answer: B

Question. Select the option which is not correct with respect to enzyme action.
(a) Substrate binds with enzyme at its active site.
(b) Addition of lot of succinate does not reverse the inhibition of succinic dehydrogenase by malonate.
(c) A non-competitive inhibitor binds the enzyme at a site distinct from that which binds the substrate.
(d) Malonate is a competitive inhibitor of succinic dehydrogenase. 
Answer: B

Question. Transition state structure of the substrate formed during an enzymatic reaction is
(a) transient and unstable
(b) permanent and stable
(c) transient but stable
(d) permanent but unstable. 
Answer: A

Question. The essential chemical components of many coenzymes are
(a) carbohydrates
(b) vitamins
(c) proteins
(d) nucleic acids.
Answer: B

Question. Which of the following statements about enzymes is wrong?
(a) Enzymes are denatured at high temperatures.
(b) Enzymes are mostly proteins but some are lipids also.
(c) Enzymes are highly specific.
(d) Enzymes require optimum pH and temperature for maximum activity.
Answer: B

Question. Three of the following statements about enzymes are correct and one is wrong. Which one is wrong?
(a) Enzymes require optimum pH for maximal activity.
(b) Enzymes are denatured at high temperature but in certain exceptional organisms they are effective even at temperatures 80° - 90°C.
(c) Enzymes are highly specific.
(d) Most enzymes are proteins but some are lipids.
Answer: D

Question. A competitive inhibitor of succinic dehydrogenase is
(a) α-ketoglutarate
(b) malate
(c) malonate
(d) oxaloacetate. 
Answer: C

Question. Modern detergents contain enzyme preparations of
(a) thermoacidophiles
(b) thermophiles
(c) acidophiles
(d) alkaliphiles.
Answer: D

Question. An organic substance bound to an enzyme and essential for its activity is called
(a) isoenzyme
(b) coenzyme
(c) holoenzyme
(d) apoenzyme. 
Answer: B

Question. The catalytic efficiency of two different enzymes can be compared by the
(a) formation of the product
(b) pH of optimum value
(c) Km value
(d) molecular size of the enzyme. 
Answer: C

Question. Which one of the following statements regarding enzyme inhibition is correct?
(a) Competitive inhibition is seen when a substrate competes with an enzyme for binding to an inhibitor protein.
(b) Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme.
(c) Non-competitive inhibition of an enzyme can be overcome by adding large amount of substrate.
(d) Non-competitive inhibitors often bind to the enzyme irreversibly. 
Answer: B

Question. Enzymes, vitamins and hormones can be classified into a single category of biological chemicals, because all of these
(a) help in regulating metabolism
(b) are exclusively synthesized in the body of a living organism as at present
(c) are conjugated proteins
(d) enhance oxidative metabolism. 
Answer: A

Question. In which one of the following enzymes, is copper necessarily associated as an activator?
(a) Carbonic anhydrase
(b) Tryptophanase
(c) Lactic dehydrogenase
(d) Tyrosinase 
Answer: D

Question. Role of an enzyme in reactions is to/as
(a) decrease activation energy
(b) increase activation energy
(c) inorganic catalyst
(d) none of the above. 
Answer: A

Question. Which factor is responsible for inhibition of enzymatic process during feedback?
(a) Substrate
(b) Enzymes
(c) End product
(d) Temperature
Answer: C

Question. Enzymes are not found in
(a) fungi
(b) algae
(c) virus
(d) cyanobacteria.
Answer: C

Question. Co-factor (prosthetic group) is a part of holoenzyme. It is
(a) loosely attached organic part
(b) loosely attached inorganic part
(c) accessory non-protein substance attached firmly
(d) none of these. 
Answer: C

Question. Which is a typical example of ‘feedback inhibition’?
(a) Cyanide and cytochrome reaction
(b) Sulpha drugs and folic acid synthesizer bacteria
(c) Allosteric inhibition of hexokinase by glucose 6-phosphate
(d) Reaction between succinic dehydrogenase and succinic acid 
Answer: C

Question. Enzymes having slightly different molecular structure but performing identical activity are
(a) holoenzymes
(b) isoenzymes
(c) apoenzymes
(d) coenzymes.
Answer: B

Question. After doing the chemical analysis of organic compounds found in living organisms, two fractions were observed namely
(a) acid soluble pool and acid insoluble pool
(b) carbon pool and hydrogen pool
(c) inorganic pool and organic pool
(d) aqueous pool and non-aqueous pool
Answer: A

Question. All the carbon compounds obtained from living tissues are called
(a) biomolecules
(b) inorganic compounds
(c) organic compounds
(d) Only DNA
Answer: A

Question. Identify the term ‘ash’ in terms of living tissue sample analysis from the statements given below.
(a) Organic compounds oxidised to gaseous form (CO2 and water vapour) after burning of the tissue
(b) The material left after burning the tissue, which contains inorganic elements such as calcium, magnesium, etc.
(c) Compounds removed in the form of gases
(d) Compounds which may be soluble in intracellular fluid
Answer: B

Question. Amino acids are organic compounds and are called a-amino acids. Why?
(a) Amino acids are organic compounds containing an amino group and acidic group as substituents on two different carbons
(b) Amino acids are organic compounds containing an amino group and an acidic group as substituents on the same carbon
(c) Amino acids are inorganic compounds containing an amino group and acidic group as substituents on two different carbons
(d) Amino acids are inorganic compounds containing an amino group and acidic group as substituents on the same carbon
Answer: B

Question. Most abundant organic compound on earth is
(a) protein
(b) cellulose
(c) lipids
(d) steroids
Answer: B

Question. Which of the following can synthesise all of the amino acids?
(a) Animals
(b) Plants
(c) Both (a) and (b)
(d) None of these
Answer: B

Question. Which of the following is not an amino acid?
(a) Uracil
(b) Glycine
(c) Tryptophan
(d) Lysine
Answer: A

Question. Which one of the following statements is wrong?
I. Sucrose is a disaccharide.
II. Cellulose is a polysaccharide.
III. Uracil is a pyrimidine.
IV. Glycine is a sulphur containing amino acid.
(a) Both I and II
(b) I, II and IV
(c) II and III
(d) Only IV
Answer: C

Question. Which of the following organic compounds is the main constituent of lecithin?
(a) Arachidonic acid
(b) Phospholipid
(c) Cholesterol
(d) Phosphoprotein
Answer: B

Question. Most abundant lipid in a cell membrane is glycolipid.
(a) True
(b) False
(c) Cannot say
(d) Partially true or false
Answer:B

Question. A nucleoside having a phosphate group forms a
(a) nucleotide
(b) triglyceride
(c) lipid
(d) nitrogen base
Answer: A

Question. Match the following columns.
Column I                      Column II
(Small molecules)       (Large molecules)
A. Amino acids               1. Proteins
B. Fatty acids,glycerol     2. Lipids
C. Nucleotides                3. Polysaccharides
D. Simple sugars            4. Nucleic acids
Codes
     A B C D
(a) 1 2 4 3
(b) 1 2 3 4
(c) 3 2 1 4
(d) 4 3 2 1
Answer: A

Question. Primary metabolites
(a) include glucose and fructose
(b) present in all living tissues
(c) plays known roles in all physiological process
(d) All of the above
Answer: D

Question. Sugar and amino acids are secondary metabolites.
(a) True
(b) False
(c) Cannot say
(d) Partially true or false
Answer: B

Question. Secondary metabolites can be observed in
(a) plant cells
(b) fungal cells
(c) microbial cells
(d) All of these
Answer: D

Question. Choose the correct option.
(a) Pigments – Carotenoids, anthocyanins
(b) Alkaloids – Monoterpenes
(c) Toxins – Morphine
(d) Polymeric substances – Ricin
Answer: A

Question. Which of the following secondary metabolites belong to the group of drugs?
I. Morphine    II. Curcumin
III. Codeine   IV. Vinblastin
V. Abrin
(a) I and II
(b) I and V
(c) II and III
(d) II and IV
Answer: D

Question. What is the common feature in all the compounds found in the acid soluble pool?
(a) They have molecular weights ranging from
18 to around 800 daltons (Da) approximately
(b) They have molecular weights ranging from
18 to around 80 daltons (Da) approximately
(c) They have molecular weights ranging from
80 to around 800 daltons (Da) approximately
(d) None of the above
Answer: A

Question. The least abundant chemical component in living organisms is proteins.
(a) True
(b) False
(c) Cannot say
(d) Partially true or false
Answer: B

Question. Match the following columns.
Column I                  Column II
A. Water                  1. 10-15%
B. Proteins               2. 70-90%
C. Carbohydrates      3. 5-7%
D. Lipids                  4. 3%
E. Nucleic acids        5. 2%
F. Ions                     6. 1%
Codes
     A B C D E F
(a) 1 3 5 6 2 4
(b) 3 2 6 5 4 1
(c) 2 1 4 5 3 6
(d) 6 2 3 4 5 1
Answer: C

Question. Proteins are formed by the condensation of
(a) fatty acids
(b) carbohydrates
(c) amino acids
(d) Both (b) and (c)
Answer: C

Question. Name the most abundant protein in animal world.
(a) RuBisCO
(b) Carboxylase-oxygenase
(c) Collagen
(d) Cellulose
Answer: C
 

Question. Identify the correct pair.
Proteins Functions
(a) Collagen Hormone
(b) Antibody Fights infectious agents
(c) Insulin Intercellular ground substance
(d) Trypsin Enables glucose transport in cell
An​​​swer: B
 

Question. Identify the correct statement pertaining to polysaccharides.
I. The polysaccharides are found as a part of acid insoluble pellet.
II. They are long chains of sugars.
III. They are threads containing different monosaccharides as building blocks.
(a) All statements are correct
(b) All statements are correct except II
(c) Only statement III is correct
(d) Only statement II is correct
Answer: A

Question. Which of the following statements is/are incorrect?
I. Left end of a polysaccharide is called non-reducing end, while right end is called reducing end.
II. Starch and glycogen are branched molecules.
III. Starch and glycogen are the reserve food materials of plant and animals, respectively.
IV. Starch can hold iodine molecules in its helical secondary structure, but cellulose being non-helical, cannot hold iodine.
(a) I and II
(b) All statements are incorrect
(c) Only IV
(d) None of the above
Answer: D

Question. Match the following columns and choose the correct combination from the options given below.
Column I                              Column II
(Chemical compounds)         (Examples)
A. Nitrogen base                  1. RNA
B. Nucleoside                       2. Thymidylic acid
C. Nucleotide                       3. Cytidine
D. Nucleic acid                     4. Uracil
Codes
     A B C D
(a) 1 2 3 4
(b) 1 3 2 4
(c) 4 3 2 1
(d) 4 1 2 3
Answer: C

Question. Name the heterocyclic compounds,which are known as nitrogenous bases.
Choose the most appropriate option.
(a) Adenine, guanine, uracil, cytosine and thymine
(b) Adenine, guanine, uracil and thymine
(c) Adenine, guanine, cytosine, uracil
(d) None of the above
Answer: A

Question. Which one of the following reactions result in the conversion of amino acids to proteins?
(a) Condensation
(b) Phosphorylation
(c) Deamination
(d) Transamination
Answer: A

Question. The following statements describe three orders of structure of the insulin molecule.
I. The molecule consists of two polypeptide chains joined and folded around one another.
II. The sequence and number of amino acids in each polypetide chain is known.
III. The amino acids in each chain are coiled into a helix and held in position by hydrogen bonds.
Which order is described by each statement?
Statement I Statement II Statement III
(a) Primary Secondary Tertiary
(b) Primary Tertiary Secondary
(c) Secondary Tertiary Primary
(d) Quaternary Primary Secondary
Answer: D

Question. A peptide bond is formed between
(a) an aldehyde group and an amino group
(b) an aldehyde group and a carboxyl group
(c) an aldehyde group and an ester group
(d) a carboxyl group and an amino group
Answer: D

Question. A nitrogenous base is linked to the pentose sugar through
(a) hydrogen bond
(b) glycosidic bond
(c) phosphate diester bond
(d) peptide bond
Answer: B

Question. According to Watson and Crick model of DNA
(a) DNA exists as a double helix
(b) The two strands of polynucleotide are antiparallel to each other
(c) The backbone is formed by sugar and nucleic base
(d) Both (a) and (b)
Answer: D

Question. Length of one turn of the helix in b-form DNA is approximately
(a) 3.4 nm
(b) 2 nm
(c) 0.34 nm
(d) 20 nm
Answer: C

Question. Catabolic and anabolic pathways are often coupled in cell because
(a) Both the paths have the same energy
(b) the free energy released from one pathway is used to drive other
(c) the intermediates of a catabolic pathway are used in the anabolic pathway
(d) their enzymes are controlled by their same activators and inhibitors
Answer: C

Question. Choose the correct statements.
I. Bond energy (ATP) is utilised for biosynthesis, osmotic and mechanical work that we perform.
II. When glucose is degraded into lactic acid in our muscles, energy is liberated.
III. Assembly of a protein from amino acid
requires energy.
IV. Majority of metabolic reactions can occur in isolation.
V. There are many examples of uncatalysed metabolic reactions.
(a) IV and V
(b) I and III
(c) I, II and III
(d) None of these
Answer: C

Question. Living state cannot reach equilibrium due to insufficiency of biomolecules.
(a) True
(b) False
(c) Cannot say
(d) Partially true or false
Answer: B

Question. Those nucleic acids, which behave like enzymes are known as
(a) ribozymes
(b) pepzymes
(c) ribose
(d) Both (a) and (b)
Answer: A

Question. Which of the following statements is true?
(a) All enzymes are protein
(b) All proteins are enzyme
(c) All enzymes are not protein
(d) All enzymes and hormones are protein
Answer: C

Question. An enzyme can be synthesised by chemically bonding the molecules of
(a) carbohydrates
(b) amino acids
(c) lipases
(d) CO₂
Answer: B

Question. Enzyme catalysts differ from inorganic catalysts in which way?
(a) Enzyme catalysts are smaller in size and lesser in weight in comparison to that of inorganic catalysts
(b) Inorganic catalysts can work efficiently at high temperature, but enzyme catalysts cannot (except few enzymes)
(c) Inorganic catalysts can work efficiently at high pressure, but enzyme catalysts cannot
(d) Both (b) and (c)
Answer: D

Question. Properties defining enzyme activity include the
(a) correct folding at primary level of organisation
(b) presence or absence of optimum temperature and pH
(c) presence of substrate concentration that increases initially and then attainsVmax
(d) All of the above
Answer: D

Question. Lock and key concept explains the interaction of a particular enzyme molecule with a specific substrate molecule.
(a) True
(b) False
(c) Cannot say
(d) Partially true or false
Answer: A

Question. Michaelis-Menten constant (Km ) is equal to
(a) the rate of enzymatic activity
(b) the rate of reaction
(c) substrate concentration at which the rate of the reaction attains half of its maximum velocity
(d) substrate concentration at which the rate of reaction is maximum
Answer: C

Question. When the binding of the chemical shuts off enzyme activity, the process is called ... A ....and the chemical is called ... B...... .
Fill in the blanks with the correct options.
(a) A–inhibition, B–inhibitor
(b) A–competition, B–inhibitor
(c) A–initiation, B–promoter
(d) None of the above
Answer: A

Question. In competitive inhibition, which of the following is true?
(a) E + IsEI
(b) E + IeEI + SeEIS
(c) S + IsSI
(d) E S+ IeESI
Answer: A

Assertion-Reasoning MCQs

Direction - Each of these questions contains two statements
Assertion (A) and Reason (R). Each of these questions also has four alternative choices, any one of which is the correct answer. You have to select one of the codes
(a), (b), (c) and (d) given below.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true, but R is not the correct explanation of A
(c) A is true, but R is false
(d) A is false, but R is true

Question. Assertion (A) In the solutions of different pH, structure of amino acids changes.
Reason (R) It is because of the ionisable nature of -NH₂ and -COOH groups.
Answer: A

Question. Assertion (A) Eight amino acids are referred to as essential amino acids for humans.
Reason (R) These are synthesised in the human body.
Answer: C

Question. Assertion (A) Arachidic acid is an unsaturated fatty acid.
Reason (R) There are one or more variable double bonds between carbon atoms in unsaturated fatty acids.
Answer: D

Question. Assertion (A) Secondary metabolites are produced in small quantities and their extraction from the plant is difficult and expensive.
Reason (R) Secondary metabolites can be commercially produced by using tissue culture technique.
Answer: B

Question. Assertion (A) Starch is a polymer of glucose.
Reason (R) It is made of several glucose units.
Answer: A

Question. Assertion (A) Enzymes lower down the activation energy of the reactant molecule to make its transition into product easier.
Reason (R) Enzymes are highly substrate specific catalysts.
Answer: B

Question. Assertion (A) Enzymes are not divided into different classes.
Reason (R) All enzymes catalyse the different reactions.
Answer: D

Question. Assertion (A) Competitive inhibitor is also called substrate analogue.
Reason (R) It resembles the enzymes in structure.
Answer: C

Question. Assertion (A) An example of non-competitive inhibitor is cyanide.
Reason (R) Cyanide kills animals by inhibiting cytochrome oxidase.
Answer: B

Please click the link below to download pdf file for CBSE Class 11 Biology Biomolecules Notes