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SAQ 1 a) Microfilaments, composed of the protein …………………… play a key role in cell movement and contraction. Answer: actin b) The cytoskeleton is essential for the proper segregation of chromosomes during …………………… . Answer: mitosis c) The cytoskeleton is crucial for the maintenance of …………………… the balance of solutes inside and outside the cell. Answer: homeostasis. Answer: homeostasis d) The dynamic nature of actin filaments involves constant …………………… and depolymerization. Answer: polymerisation e) Actin-binding proteins like …………………… regulate the branching of actin filaments. Answer: Arp2/3 complex f) In treadmilling, the addition of…………………… to the barbed end occurs while monomers are simultaneously removed from the pointed end. Answer:  G-actin SAQ 2  a) What is the cortical cytoskeleton? The cortical cytoskeleton is a specialized and dynamic part of the cell's cytoskeleton located just beneath the plasma membrane. It is primarily composed of  actin filaments  (micr...

SAQ 1 1. (a) Write answers to the following questions in brief. i.  What is the longest phase of the cell cycle? The longest phase of the cell cycle is  Interphase,  which occupies about 90% of the total duration of the cycle. It is a highly active stage where the cell prepares for division. Interphase has three sub-phases: G1 phase, where the cell grows and synthesizes proteins; S phase, where DNA replication takes place; and G2 phase, where the cell checks for DNA errors and prepares for mitosis. Though no visible division occurs in interphase, it is crucial for the success of mitosis or meiosis. Cells that do not divide frequently may remain in G1 or enter a resting state called G₀ phase. ii.  During which phase of interphase does DNA replication occur?  DNA replication occurs during the S phase (Synthesis phase) of Interphase. In this phase, the entire genetic material of the cell is duplicated so that each daughter cell formed after cell division will recei...

SAQ 1 Mark the correct option: a) The cellular response to a particular signaling molecule depends on the number of     i) receptor     ii) ligand     iii) receptor-ligand complexes Answer:  iii) receptor-ligand complexes b) The binding of receptor to ligand binding is mediated through weak     i) non-covalent forces     ii) covalent forces Answer:  i) non-covalent forces c) Different receptors of the same class that bind different ligands often induce the     i) same cellular responses in a cell     ii) different cellular responses in a cell Answer:  i) same cellular responses in a cell d) Many signaling molecules bind to multiple types of receptors, each of which can activate different intracellular signaling pathways and thus induce     i) same cellular responses     ii) different cellular responses Answer:  ii) different cellular responses SAQ 2 Fill in the blanks: a) The bi...

SAQ 1 Fill in the blanks with appropriate word: a) A condition in which a gene or gene pair suppresses or hinders the expression of another non-allelic gene is called ...................... . Answer:  epistasis b) The phenotype effect gets enhanced because of the effect of ....................... genes. Answer:  cumulative or additive  c) Red eye colour in Drosophila melanogaster is due to the deposition of pigment ...................... . Answer:  drosopterins d) Progeny shows a ratio of ........................ in case of duplicate dominant epistasis.  Answer:  15 : 1 e) Epistasis in which a dominant allele at one locus can mask the expression of both (dominant and recessive) alleles at the second locus occurs due to .......................... gene interaction. Answer:  inhibitory SAQ 2 State whether these statements are 'True' or 'False.' a) Pleiotropy occurs when a gene shows a complementary gene interaction with another gene. Answer:  False b...

SAQ 1 Fill in the blanks: (i) The technique of isolating cells from an organism and allowing them to develop in a suitable artificial environment is known as ...................... . Answer:  cell culture (ii) Hybridoma technique for the production of monoclonal antibodies was developed by ...................... . Answer:  Kohler and Milstein (iii) A cell line obtained from primary cell culture is called ................... . Answer:  secondary cell culture (iv) One example of coagulant is ..................... . Answer:  plasma from heparinized blood (v) Full form of DME medium is ................... . Answer:  Dulbecco's Modified Eagle's SAQ 2 State True or False: i) Finite cell lines are those with a fixed maximum number of cell generations and growth. Answer:  True ii) In the Lag phase, the cell metabolic activity is the highest. Answer:  False   iii) Enzymes like proteases are better to detach the cells off the growing surface than mechanical...

SAQ 1  i. What is a Cell? What Are the Essential Characteristics of Cells? A cell is the basic structural, functional, and biological unit of all living organisms. It is the smallest unit of life and is often referred to as the  "building block of life."  Cells carry out essential functions such as metabolism, energy production, and reproduction. Organisms can be unicellular (made of a single cell) or multicellular (composed of many cells). Discovery of the Cell Robert Hooke discovered the cell structure in 1665 by observing a thin slice of cork, specifically from the cork cambium of the cork oak tree (Quercus suber). The cork cambium is a layer of tissue found in the bark of plants that produces cork. Under his microscope, Hooke saw small, hexagon box-like compartments, which he named "cells" because they resembled the small rooms. These compartments were the cell walls of dead plant cells, a key observation that laid the foundation for the study of cell biology. D...

SAQ 1 a) What would happen if there were substances that could bind to Ga subunits just like GTP does, but could not be hydrolysed by the intrinsic GTPase? If substances were present that could bind to the Gα subunits just like GTP does, but could not be hydrolyzed by the intrinsic GTPase activity, it would lead to a  persistent activation of the G-protein signaling pathway.  This is because the normal process of signal termination in G-protein signaling involves GTP hydrolysis by the intrinsic GTPase activity of the Gα subunit. When GTP is hydrolyzed to GDP, the Gα subunit becomes  inactive,  effectively terminating the signaling cascade. However, if a substance mimics GTP binding but does not undergo hydrolysis, the Gα subunit would remain in its active GTP-bound form indefinitely. This leads to prolonged activation of downstream signaling pathways, such as the activation of second messengers like cAMP, DAG and IP3, and the continuous activation of effector protein...

SAQ i) Match the items in column I with column II: Answer:  a) → iv;    b) → iii;    c) → vii;    d) → viii;    e) → vi;    f) → i;    g) → ii;    h) → x;    i) → v;    j) → xi;    k) → ix ii) Fill in the blanks: a) Autophagy includes the formation of three different vesicles including ....................., which circularizes to form ......................, which then fuses with a lysosome to form the ..................... . Answer:  phagophore, autophagosome, autolysosome b) Apoptosis can be mediated by two modes or pathways, ....................... or ....................... . Answer:  intrinsic, extrinsic c) Pharmacological inhibitors such as ....................... block the lysosomal proton transport and thus autophagy. Answer:  Bafilomycin A1 d) ...................... is released from the mitochondria upon MOMP and binds to the adapter protein Apaf1 to form the ...

The endosymbiotic theory is the scientific explanation that proposes how certain organelles, specifically  mitochondria and chloroplasts,  originated within eukaryotic cells. It suggests that these organelles were once independent, free-living bacteria that were engulfed by a primitive eukaryotic cell. Instead of being digested, these bacteria formed a mutually beneficial relationship with the host cell, eventually becoming integrated into the cell as permanent organelles. This theory is supported by evidence such as the presence of their own DNA, similarities to bacterial ribosomes, and the double membrane structure of these organelles. Historical Context and Development The concept of endosymbiotic theory was first introduced by Russian botanist  Konstantin Mereschkowski  in 1905, who proposed that chloroplasts originated from symbiotic relationships between eukaryotic cells and free-living cyanobacteria. This idea was further explored by  Ivan Wallin  in...

SAQ 1 Fill in the blanks   a) .......................... discovered plasma membrane. Answer:   Karl Nageli and C. Cramer b) The phospholipid contains ......................... charged phosphate group in the hydrophilic part of head. Answer:  Negatively c) ........................... proposed Sandwich (lipid-protein) model of cell membrane. Answer:  Danielli and Davson d) The protein layer present in cell membrane model proposed by Robertson is .......................... thick. Answer:  20 A° e) The proteins are aligned properly with the help of ........................... within the lipid bilayer in membrane. Answer:  Transmembrane segments SAQ 2 i) Answer in one word: a) Complex integral proteins transmit signals via plasma membrane. Answer:  Receptors b) The cellular processes such as movement, growth, division etc. are regulated by this property of membrane. Answer:  Fluidity c) No energy is required for transter of substances from high concent...