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Answer Kev F.Y. Life Sciences paper I Q.P. code 754909 Exam held on 2lst November 2016 Q.1 A Fill in the blanks 1. Lysine orArginine 2. Amino or N and Carboxyl or C 3. Starch or Glycogen 4. Hemoglobin orname of any enzyme 5. 4oC B Match the column l. a-v 2.b-iv J. C-r 4. d-iii 5. e-vi c. 1' Euchromatin: Chromatin that does not stain darkly in an interphase nucleus. It represents the major genes and is involved in transcription. 2' Sarcomere: A structural unit of a myofibril in striated muscle, consisting of a dark band and light bands. It is the segment between two neighbouring Z-lines many me 4' Histone: A group of f1ve. small basic proteins,occurring in the nucleus of eukaryotic cells, that organize DNA strands into nucleosomes by forming riolecular complexes u.ouna which the DNA winds. 5' Intermediate Filament: Any of a group ofprotein filaments that are a component of the cytoskeleton in animal cells, are composed of a variety of proteins such as lamins and keratins, and provide structural support for the cytoplasm and nucleus. Intermediate filaments are intermediate in diameter betwoen microfilaments and microtubules. D. 1. True 2. False 3. False 4. False 5. True Q.2 A. l. Physical Properties of w o Each physical property of water: . With significance : *1 2. Classification of proteins o Classification(Structu { Ptimary, Structural and { Simple, Conju o With Examples: 2 o Functions ( At least 4) r' I Mark / Function / Composition) : 2 Marks , Tertiary and Quaternary ional and Derived B. l. Diffusion and Osmosis o Compare (2 points): 2 o Contrast (2 Points): 2 o Example: I Mark arks 2. Buffers o o o Definition: lMark Example(s): I Mark Significance: 3 Marks 3. Monosaccharide o o o Definition: lMark Structure / Example(s): I Mark Functions: 3 Marks 4. Polysaccharide that cannot . Cellulose: I Mark o Structure: 2 Marks o Function / Significance digested by human eason (Why it cannot be digested): 2 Marks Q.3 A) f . With a neat and labelled iagram, explain ultra structure of bacterial cell Ans: Diagram: 5 marks Description: 5 mks ffiilcruffioFA i*fulding of rpf*stna finarubr#ne $d u€l* &NAeoilud inm n flag*ilurn srni6 inefusian hsffl 2. Factors influencing micro$ial growth- Any five of the following and their effects- 2 mks each Solutes and Water Acidity, pH Temperature, Oxygen Requirer{rents Pressure,Radiation Q.3B) 5mks .Qd!dl*lUcnr HmmIhtI{ nFffiFftrbghr, trffidqqrgr!frrgE' 2. Endosymbiont theory- both mi t, a) from prokaryotic ast and b) prokaryotic photosynthetic unicellular orgganism unicellular non photosynthetic bacterial 3. Isolation of microorganisms i) Broth Cultureii)Serial dilution - ndria- 2.5 mks each. any two techniques of the following- 2.5 mks each iii)Streak plating iv)Spread Plate v)Pour plate technique 4. Gl and S phase in Cell cycle with their significance The Cell withyrmark significance with%mark significance (DNA replication)- 2 mks description with%mark significance 2 mks description Gr Phase (Growth)- 2 mks description s Phase Q.4. A) Attempt any one of the following: 10 marks 1. Explain in detail Euchromatin and Heterochromatin. Answer: (2 marks definitions * 8 marks discussion of properties) chromatin is found in two varieties: Euchromatin and Heterochromatin. The concept of heterochromatin was described by Emil Heitz in 192g. The two forms were distinguished cytologically by how intensely they stained the euchromatin is less intense in an interphase nucleus, while heterochromatin stains intensely, indicating tighter packing. Heterochromatin Condensed in Interphase Heterochromatin DNA is Latereplicating Euchromatin NOT condensed in Interphase Euchromatin DNA is Early replicating t Heterochromatin DNA is methvlated I Histones from heterochromatin are DNA is NOT methvlated Histones from euchromatin are NOT I I I t ! methylated methylated Heterochromatin is transcdption.allv Euchromatin is transcriptionally INACTIVE ACTIVE Heterochromatin DOES NOT participate in genetic recor4bination Heterochromatin has a gre arious Euchromatinparticipates in genetic recombination EuchromatinDoEs NOT have a gregarious instinct instinct 2. what are microfilaments? Exprain their role in muscle contraction. Answer: @escription of sarcomere 5 marks * mechanism of contractlon 5 marks) A skeletal muscle comprises a bundle of muscle cells, or myofibers.Each muscle cell is tin and s that extend the end to s, the functional ine and contains several dark bands (Z-line From the German word.,,zwischenscheibe,, dillt:fres. "td the I+bands) On either meaning "the band between side of the Z lines are the lightly stained I bands, composed of actin filamen[s. These thin filaments extend from both sides of the Zline to interdigitate with myosin thick filaments that make up the A band. The lhe lqk-stairred region containing both thick and thin filaments (. only myosin thick filaments (the H zone). A s composed only of actin filaments located at staining A band or A zone is loctted between myosin filaments. Q-bgd: Ani$otropic). A lightly staining H zone made up of only myosin filaments is located in the center 0f the A band. (H-Zone = F.oto the German word,,Heller" meaning "Bright"). In the centre of the HZone is the M-line (MJine from the German word 'Mittel" meaning "Middle') : ntrosln - MI I r-r actln MIM I r--1 | Bands and lines in lhe contrastlle apparalue of skeletal muscle Sliding Filament Theory of musclo contraction: ' An action potential inducpd at the neuromuscular junction is propagated along the sarcolemma of the skeletal muscle. The sarcolemma contains regions known as T-fubules. As the action potential is ' propagated along the T- tubule, it membrane gets depolarized. ' This leads to increase in permeability of the sarcoplasmic reticulum to calcium ions" ' Calcium ions then diffuse from the sarcoplasmic reticulum into the sarcoplasm. I I In skeletal muscles, T.pO..ygrin proteins are attached to the actin filament blocking the sites where myosin cFn bind to actin filament. And troponin remains attached to tropomyosin. When calcium ions bind {o troponin, this causes troponin to change conformation and move tropomyosin. When tropomyosin the myosin binding sites on actin are uncovered, allowing }o_ve$, myosin heads to bind tp actin. Thus yosin forms cross-bridges between actin filaments. The myosin head which i$ bound to actin flexes, pulling the actin filament along with it. This causes the actin fifament to slide by the myosin hhrn.nt. Then the myosin head feleases from the actin filament and unflexes. This step requires energy which is supplied by hydrolysis of ATP. This frees the myosin head to bind to a different actin molecule, farther up the actin filament. The entire process is repe{ted many times. Thus, the myosin "walksi'along the actin filament, moving the actin filament more and more each time. Thus the muscle contractsr Q.4. B) Attempt any two of the following: 5 marks each 1. using a neat and labeled diagpam explain the structure of a Nucleus Nuclear envelope and pores: The 4uclear envelope, otherwise known as nuclear membrane, consists of two cellular membranes, an inner and an outer membrane, ananged parallel to one another and separated by 10 to 50 nanomehes (nm). The nuclear envelope completely encloses the nucleus and separates the cell's genetic material from the surrounding cytoplasm, serving as a barrier to prevent maoromolecules from diffusing freely between the nucleoplasm and the cytoplasm. The outer nuclear membrane is continuous with the membrane of the rough endoplasnlic reticulum (RER), and is similarly studded with ribosomes.Nuclear pores, which ptovide aqueous channels through the envelope, are composed of multiple proteins, collectively referred to as nucleoporins. Nuclear Lamina: The nuclear lamina is composed mostly of lamin proteins. Like all proteins, lamins are synthesized in the cytoplasm and later transported to the nucleus interior, where they are assembled before being incorporated into the existing network of nuclear lamina. Chromosomes: The cell nucleus pontains the majority of the cell,s genetic material in the form of multiple linear DNA molecules organized into structures called chromosomes. Nucleolus: The nucleolus is a discrete densely stained structure found in the nucleus. It is not surrounded by a membrane, and is sometimes called a suborganelle. It forms around tandem repeats of rDNA, DNA coding for ribosomal RNA GRNA).These regions are called nucleolar organizer regions (NOR). The main roles of the nucleolus are to synthesize rRNA and assemble ribosomes" 2. write a note on: structure of Gram negative bacterial cell wall Answer: @iagram 2 marks + Description 3 marks) The walls of Gram negative bactqria have a low peptigoglycan content of approximately 5 to 15 Yo ered of wall bacteria cell ell. of ow constituieJtire bacteria is sim f cross-linking many of the peptide chains are not crossJinked and Superimposed on the thin layer of peptidoglycan layer of Gram negative bacteria is an outer wall layer the major component of which is Lipopolysaccharide (Lps). 1. Lipids: The lipids which are apart of Gram negative cell wall are contained within the Lipid A region of the outer cell wall layer of Gram negative bacteria. The Lipid region consists of phosphorylated glucoseamine which is isterified with long chain A fatty acids like lauric acid, myristic acid and palmitic acid in a ratio of 1:1:l]thus this region of the molecule is hydrophobic and is arranged such that its orientation is towards the inner cell wall layer so as to shield it from water. 2. Polvsaccharide: the polysaccharide component of the outer membrane of the cell wall of Gram negative bacteria consists of two distinct regions: (a) R-core region - The R.core region is attached to one of the glucoseamine residues of the Lpid A region. The R-core region is made up of two cores The inner core in tum consists of two regions, one made up of ketodeoxyoctonate (KDO) and the other of diheptose. The outer core is made up of oligosaccharides i.e. short cirains of sugars. (b) O-side chain - The R-oore possess a hydrophobic O-side chain which is mainly composed of sugars. It is much longer than the R-core region and has many repeaiing trisaccharide, tefrasaccharide and pentasaccharide units. 3. Write a note on: Larnpbrush Chromosomes Answer: o t o o The existence of lampbrush chromosomes supports the concept that chromatin is organized in a series ofloops. Lampbrush chromosomes occur in a limited phase of meiosis during oogenesis in amphibian oocytes. The lampbrush chromosome is a bivalent (2 pairs of sister chromatids held together by chiasmata). The chromosome strands (20 nm diameter fibers consisting of two double strands of DNA) are dotted with about 5000 chromomeres (dark staining irregular structures also o o o seen in interphase chromosomes). Twin loops (length 400-800 nm) emerge from chromomeres. An identical pattem of twinned loops occurs on both pairs of sister chromatids. Loops show a gradual increase of electron density from the chromomere around the loop and back to the chromomere. The average length of loops corresponds to the average length of RNA transcripts in these oocytes, but is much longer than the average length of RNA transcribed in somatic cells. Functions of Lampbrush chromosomes: (a) Synthesis of RNA: Functions of lampbrush chromosomes involve synthesis of RNA and protein by their loops. RNA is synthesized only at the thin insertion and then carried aroundihe loops to the thick insertion. There it may be either destroyed or released into nucieus. (b) Formation of yolk material: 10 4. Write a note on: Structure of flagellum Answer: (Structure 3 marks * Diagram 2 marks)) ' Flagella are attached to strucfures known as basal bodies,which in turn are anchored to the plasma membrane. From the basal bodies the microtubule ,,backbone,, extends, pushing the plasma membrane out with it. ' Within the flagella, nine outer doublet microfubules surround a central pair of singlet microtubules (Figure below). "r This characteristic"g + 2" arrangement of microfubules is viewed in cross section Each doublet microtubule consists of A and B tubules: the A tubule is a complete microtubule with 13 protofilaments, while the B tubule contains protofilaments. l0 ' 'Ihe flagellar structures are held together by three sets of protein cross-links: (a) The central pair of singlet microtubuleJ are connected by bridges. O) A set of linkers, composed of the protein nexi4 joins adjacent outer doublet microtubules. (c) Radial spokes, which radiate from the central singlets to each doublets, form the third linkage system. A tubule of the outer InnErdy*ein N(xin Spulk*hrnd fudlal:9poke nrmttmb(ft t1 Q.s I Primary o o o structure of protein Definition: lMark Structure: 2 Marks Functions / Specific Features/ Examples: 2 Marks 2. Water as Universal Solvent " Definition: lMark o o 3. Reasons: 2 Marks Importance:2 Marks Any two of the following media components Solid MediaSemi solidLiquid/broth media - 2.5 marks each OR Synthetic Non synthetic media Or Basic, Enriched, Selective, Differential media 4' Animal cell, with cell components ( at least five- Cell wall, nucleus, mitochondria, lysosomes, centrosomes, golgi bodies, rough ER etc) diagrammatic with p"op.. labels -5 mks, if no labels only 3 marks plnocytotlc voslde lysosome Golgl wslder rough ER smooth ER (no rlbosomes) centrlolar (2) Each compmed olll nlcrotubrla trlplrtr. mlcrotubilhs coll(plasma cytoplasm mombranG dbosome @e.*.*m*rtnriiOci t2 5. Draw a neat and labeled diagram of Nucleus Euchonudn Nuclsarpors Parinuclearspact llelarochromatln P6dnucleghr 6hrsindtln Intranucleahr drromaffn onvelopo hn$rmembeng Oulerrnombrane 6. Write a note on plant cell wall: Answer: @escription 3 marks * Diagram 2 marks) The plant cell wall is multi-layered and consists of up to three sections. From the outermost layer of the cell wall, these layers are identified as the middle lamella, primary cell wall, and secondary cell wall. While all plant cells have a middle lamella and prirnary cell wall, not all have a secondary cell wall. Middle lamella - outer cell wall layer that contains polysaccharides called pectins. Pectins aid in cell adhesion by helping the cell walls of adjacent cells to binh to one . . . another. Primary cell wall - layer formed between the middle lamella and plasma membrane in growing plant cells. It is primarily composed of cellulose microirbrils contained within a gel-like matrix of hemicellulose fibers and pectin polysaccharides. The primary cell wall provides the strength and flexibility needed io allow for cell growth. Secondary cell wall - layer formed between the primary cell wall andplasma membrane in some plant cells. Once the primary cell wall has stopped dividing and gtowing, it may thicken to form a secondary cell wall. This rigid layer strenghens and supports the cell. In addition to cellulose and hemicellulose, some secondary cell walls contain lignin. Lignin strengthens the cell wall and aids in water conductivitv in plant vascular tissue cells. Plant Cell Wall Function A major role of the cell wall is to form a framework for the cell to prevent over expansion. Cellulose fibers, structural proteins, and other polysaccharides he$ to maintain the shape and form of the cell. Additional functions of the cell wall include: Support - the cell wall provides mechanical strength and support. It also controls the . . . direction of cell growth. Withstand turgor pressure - turgor pressure is the force exerted against the cell wall as the contents of the cell push the plasma membrane against the ceil wall. This pressure helps a plant to remain rigid and erect, but can also cause a cell to rupture. Regulate growth - sends signals for the cell to enter the cell cycle in order to divide and grow. 13 Regulate diffusion - the cell wall is porous allowing some substances, including proteins, to pass into the cell while keeping other substances out. Communication - cells communicate with one another via plasmodesmata (pores or channels between plant cell walls that allow molecules and iommunication signals to pass between individual plant cells). Protection - provides a barrier to protect against plant viruses and other pathogens. It also helps to prevent water loss. storage - stores carbohydrates for use in plant growth, especially in seeds. $r{lddl€ J* tamella L- I4