Text Book Back Questions and Answers - Chapter 8 Biomolecules 11th Biology Botany Guide Samacheer Kalvi Solutions - SaraNextGen [2024-2025]

Updated By SaraNextGen

On April 24, 2024, 11:35 AM

Biomolecules
Text Book Back Questions and Answers
I. Multiple Choice Questions
Choose the correct answer
Question 1 .
The most basic amino acid is
(a) Arginine
(b) Histidine
(c) Glycine
(d) Glutamine
Answer:
(a) Arginine
Question 2.
An example of feedback inhibition is
(a) Cyanide action on cytochrome
(b) Sulpha drug on folic acid synthesiser bacteria
(c) Allosteric inhibition of hexokinase by glucose $-6-$ phosphate
(d) The inhibition of succinic dehydrogenase by malonate
Answer:
(c) Allosteric inhibition of hexokinase by glucose $-6-$ phosphate
Question 3.
Enzymes that catalyse interconversion of optical, geometrical or positional isomers are
(a) Ligases
(b) Lyases
(c) Hydrolases
(d) Isomerases
Answer:
(d) Isomerases
Question 4.
Proteins perform many physiological functions. For example some functions as enzymes. One of the following represents an additional function that some proteins discharge
(a) Antibiotics
(b) Pigment conferring colour to skin
(c) Pigments making colours of flowers
(d) Hormones
Answer:
(d) Hormones
Question 5.
Given below is the diagrammatic representation of one of the categories of small molecular weight

Answer:
(a) Nucleoside
(b) Uracil.
Question 6.
Distinguish between nitrogenous base and a base found in inorganic chemistry.
Answer:
Nitrogenous Base:
1. Nitrogenous bases are organic molecules containing the element nitrogen \& acts as a base in chemical reaction.
2. e.g. Adenine, Thymine
Base:
1. Bases are the substance that release hydroxide $\left(\mathrm{OH}^{-}\right)$ions in aqueous solution.
2. e.g. $\mathrm{NaOH}$ and $\mathrm{Ca}(\mathrm{OH})_2$
Question 7.
What are the factors affecting the rate of enzyme reaction?
Answer:
(a) Temperature: Heating increases molecular motion. Thus the molecules of the substrate and enzyme move more quickly resulting in a greater probability of occurrence of the reaction. The temperature that promotes maximum activity is referred to as optimum temperature.

Temperature
(b) $\mathrm{pH}$ : The optimum $\mathrm{pH}$ is that at which the maximum rate of reaction occurs. Thus the $\mathrm{pH}$ change leads to an alteration of enzyme shape, including the active site. If extremes of $\mathrm{pH}$ are encountered by an enzyme, then it will be denatured.

(c) Substrate Concentration: For a given enzyme concentration, the rate of an enzyme reaction increases with increasing substrate concentration.
(d) Enzyme Concentration: The rate of reaction is directly proportional to the enzyme concentration.

The Michaelis - Menton Constant $(\mathrm{Km})$ and Its Significance:
When the initial rate of reaction of an enzyme is measured over a range of substrate concentrations (with a fixed amount of enzyme) and the results plotted on a graph. With increasing substrate concentration, the velocity increases - rapidly at lower substrate concentration. However the rate increases progressively, above a certain concentration of the substrate the curve flattened out. No further increase in rate occurs. This shows that the enzyme is working at maximum velocity at this point. On the graph, this point of maximum velocity is shown as $\mathrm{V}_{\mathrm{Max}}$.
Question 8.
Briefly outline the classification of enzymes.
Answer:

Enzymes are classified into six groups based on their mode of action.

Question 9.
Write the characteristic feature of DNA.
Answer:
The characteristic feature of DNA.
1. If one strand runs in the $5^{\prime}-3^{\prime}$ direction, the other runs in $3^{\prime}-5^{\prime}$ direction and thus are antiparallel (they run in opposite direction). The $5^{\prime}$ end has the phosphate group and 3 'end has the $\mathrm{OH}$ group.
2. The angle at which the two sugars protrude from the base pairs is about $120^{\circ}$, for the narrow angle and $240^{\circ}$ for the wide angle. The narrow angle between the sugars generates a minor groove and the large angle on the other edge generates major groove.
3. Each base is $0.34 \mathrm{~nm}$ apart and a complete turn of the helix comprises $3.4 \mathrm{~nm}$ or 10 base pairs per turn in the predominant B form of DNA.
4. DNA helical structure has a diameter of $20 \AA$ and a pitch of about $3 \AA . X$ - ray crystal study of DNA takes a stack of about $10 \mathrm{bp}$ to go completely around the helix $\left(360^{\circ}\right)$.
5. Thermodynamic stability of the helix and specificity of base pairing includes
- (a) The hydrogen bonds between the complementary bases of the double helix
- (b) stacking interaction between bases tend to stack about each other perpendicular to the direction of helical axis. Electron cloud interactions $(\Pi-\Pi)$ between the bases in the helical stacks contribute to the stability of the double helix.
6. The phosphodiester linkages gives an inherent polarity to the DNA helix. They form strong covalent bonds, gives the strength and stability to the polynucleotide chain.
7. Plectonemic coiling - the two strands of the DNA are wrapped around each other in a helix, making it impossible to simply move them apart without breaking the entire structure. Whereas in paranemic coiling the two strands simply lie alongside one another, making them easier to pull apart.
8. Based on the helix and the distance between each turns, the DNA is of three forms - A DNA, B DNA and Z DNA.

Question 10.
Explain the structure and function of different types of RNA.
Answer:
1. mRNA (messenger RNA): Single stranded, carries a copy of instructions for assembling amino acids into proteins. It is very unstable and comprises $5 \%$ of total RNA polymer. Prokaryotic mRNA (Polycistronic) carry coding sequences for many polypeptides. Eukaryotic mRNA (Monocistronic) contains information for only one polypeptide.
2. tRNA (transfer RNA): Translates the code from mRNA and transfers amino acids to the ribosome to build proteins. It is highly folded into an elaborate 3D structure and comprises about $15 \%$ of total RNA. It is also called as soluble RNA.
3. rRNA (ribosomal RNA): Single stranded, metabolically stable, makeup the two subunits of ribosomes. It constitutes $80 \%$ of the total RNA. It is a polymer with varied length from $120-3000$ nucleotides and gives ribosomes their shape. Genes for rRNA are highly conserved and employed for phylogenetic studies.

Entrance Examination Questions Solved
Choose the correct answer:
Question 1.
Who invented electron microscope? 
(a) Janssen
(b) Edison
(c) Knoll and Ruska
(d) Landsteiner
Answer:
(c) Knoll and Ruska
Question 2.
Specific proteins responsible for the flow of materials and information into the cellare called 
(a) Membrane receptors
(b) carrier proteins
(c) integral proteins
(d) none of these
Answer:
(b) carrier proteins
Question 3.
Omnis - cellula - e - cellula was given by
(a) Virchow
(b) Hooke
(c) Leeuwenhoek
(d) Robert Brown
Answer:
(a) Virchow
Question 4.
Which of the following is responsible for the mechanical support, protein synthesis and enzyme transport?
(a) cell membrane
(b) mitochondria
(c) dictyosomes
(d) endoplasmic reticulum

Answer:
(d) endoplasmic reticulum
Question 5.
Genes present in the cytoplasm of eukaryotic cells are found in
(a) mitochondria and inherited via egg cytoplasm
(b) lysosomes and peroxisomes
(c) Golgi bodies and smooth endoplasmic reticulum
(d) Plastids inherited via male gametes
Answer:
(a) mitochondria and inherited via egg cytoplasm
Question 6.
In which one the following would you expect to find glyoxysomes?
(a) Endosperm of wheat
(b) Endosperm of castor
(c) Palisade cells in leaf
(d) Root hairs
Answer:
(b) Endosperm of castor
Question 7.
A quantosome is present in 
(a) Mitochondria
(b) Chloroplast
(c) Golgi bodies
(d) ER
Answer:
(b) Chloroplast
Question 8.
In mitochondria the enzyme cytochrome oxidase is present in
(a) Outer mitochondrial membrane
(b) inner mitochondrial membrane
(c) Stroma

(d) Grana
Answer:
(b) inner mitochondrial membrane
Question 9.
Which organelle is present in higher number in secretory cell?
(a) Mitochondria
(b) Chloroplast
(c) Nucleus
(d) Dictyosomes
Answer:
(d) Dictyosomes
Question 10 .
Major site for the synthesis of lipids
(a) Rough ER
(b) smooth ER
(c) Centriole
(d) Lysosome
Answer:
(b) smooth ER
Question 11.
Golgi complex plays a major role in .............
(a) post translational modification of proteins and glycosidation of lipids
(b) translation of proteins
(c) Transcription of proteins
(d) Synthesis of lipid
Answer:
(a) post translational modification of proteins and glycosidation of lipids
Question 12 .
Main arena of various types of activities of a cell is
(a) Nucleus
(b) Mitochondria
(c) Cytoplasm
(d) Chloroplast
Answer:
(c) Cytoplasm

Question 13 .
The thylakoids in chloroplast are arranged in
(a) regular rings
(b) linear array
(c) diagonal direction
(d) stacked discs
Answer:
(d) stacked discs
Question 14 .
Sequences of which of the following is used to know the phylogeny rRNA?
(a) mRNA
(b) rRNA
(c) tRNA
(d) Hn RNA
Answer:
(b) rRNA
Question 15.
Structures between two adjacent cells which is an effective transport pathway?
(a) Plasmodesmata
(b) Middle lamella
(c) Secondary wall layer
(d) Primary wall layer
Answer:
(a) Plasmodesmata
Question 16.
In active transport carrier proteins are used, which use energy in the form of ATP to
(a) transport molecules against concentration gradient of cell wall
(b) transport molecules along concentration gradient of cell membrane
(c) transport molecules against concentration gradient of cell membrane
(d) transport molecules along concentration gradient of cell wall
Answer:
(c) transport molecules against concentration gradient of cell membrane
Question 17.
The main organelle involved in modification and routing of newly synthesised protein to their destinations is
(a) Mitochondria
(b) Glyoxysomes
(c) Spherosomes
(d) Endoplasmic reticulum
Answer:
(d) Endoplasmic reticulum

Question 18.

Algae have cell wall made up of 
(a) Cellulose, galactans and mannans
(b) Cellulose, chitin and glucan
(c) Cellulose, Mannan and peptidoglycan

Answer:
(a) Cellulose, galactans and mannans