11th biology ch.2 notes_ilmi stars academy.pdf

ILMI STARS ACADEMY 1st Year Biology Federal Board + KPK Board Chapter 2: Biological Molecules Notes _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. B...

ILMI STARS ACADEMY 1st Year Biology Federal Board + KPK Board Chapter 2: Biological Molecules Notes _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. Biomolecules a) Definition Molecules that are occur in the bodies of living organisms are called biomolecules or biological molecules b) Examples Carbohydrates, proteins, lipids, DNA, RNA etc. Composition of Protoplasm i) Protoplasm  The living content of the cell is called protoplasm  It includes cytoplasm and nucleoplasm  All most all metabolic reactions occur in protoplasm ii) Composition  Protoplasm of living things is made some elements called bioelements and compounds called biological compounds.  Organic compounds exist as molecules known as biological molecules  Inorganic compounds occur in the form of minerals Bioelements a) Definition  Elements that make the bodies of living organisms are called bioelements b) Number  Out of 92 natural elements, 25 are bioelements  16 bioelements are found in human body c) Types  There are three types of bioelements _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  Major Bioelements  Six bioelements make 99% of the protoplasm and are called major bioelements  These O (65%), C (18%) , H (10%), N (3%), Ca (2%) and P (1%)  Minor Bioelements  Bioelements that are found less than 1% are called minor bioelements  They are K (0.35%), S (O.25%), Cl (0.15%), Na (0.15%) and Mg (0.05%)  Trace Bioelements  Bioelements that occur less than 0.01 % are known as trace elements  They are iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), and Iodine (I)  Iron is required by all forms of life, other trace elements are required only by a certain species. Fundamental Biomolecules  They are four  Carbohydrates, proteins, lipids and nucleic acids _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. a) Carbohydrates  Found in cell inclusions  Used as fuels for metabolic activities b) Proteins  Proteins are present in membranes, ribosome, cytoskeleton, and make enzymes of the cell c) Lipids  Structural part of membranes  Present in cell inclusions  Lipids provide reserved energy source, shape, protect and insulate the cells d) Nucleic Acids  DNA is present in chromosomes, controls all cellular activities  RNA is present in nucleoplasm and cytoplasm. It transmits genetic information and takes part in protein synthesis. _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. CONDENSATION 1) Definition The process in which micromolecules combine and make macromolecule by the removal of water is known as condensation 2) Mechanism  Hydroxyl group of one molecule combines with Hydrogen atom of other molecule. As a result water is removed and a bond is formed.  Condensation is also called dehydration synthesis because water is removed (dehydration) and bond is formed (synthesis).  Condensation involves use of enzymes in the cell 3) Diagram 4) Examples  Proteins are formed by condensation of amino acids  Nucleic acids are formed by condensation of nucleotides  Starch, cellulose, glycogen are formed by condensation of glucose 5) Reactants  Reactants in condensation are micromolecules also called monomers (mono = 1, mer = unit) 6) Products  Products of condensation process are macromolecules that are also called polymers. _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  When two monomers combine product is called dimer (di =two, mer = unit) and when many monomers combine by condensation the product is called polymer (poly = many, mer = unit) HYDROLYSIS 1) Definition Breakdown of polymer (macromolecule) into its monomers (micromolecules) by addition of water is called hydrolysis (hydro = water, lysis = breakdown). It is reverse of condensation 2) Mechanism  Hydroxyl group (OH) of water is attached to one molecule and hydrogen atom (H) is attached to other monomer.  Hydrolysis involves use of enzymes in the cell 3) Diagram _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. 4) Examples All food digestion reactions are examples of hydrolysis e.g.  Protein is hydrolyzed (by protease) into amino acids  Lipid hydrolyzed (by lipase) into fatty acids and glycerol  Carbohydrate is hydrolyzed (by carbohydrase) into simple sugars 5) Reactants  Reactants in hydrolysis are polymers (macromolecules) 6) Products  Products of hydrolysis are monomers (micromolecules) (Can you differentiate between condensation and hydrolysis?) PROPERTIES OF WATER 1) High Polarity a) Introduction  Presence of polar bond in a compound is termed as polarity  Covalent bond formed due to unequal sharing of electrons between atoms having greater difference of electronegativity _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  More electronegative attract shared electrons more closer to it, thus, it gets partial negative charge and other atom gets partial positive charge b) Polarity of water  In water, two hydrogen atoms are bonded to one highly electronegative atom of oxygen. Thus, O-H bonds in water are highly polar  Oxygen is partially negative whereas hydrogen atoms are partially positive c) Significance  Polar nature makes water universal solvent for polar substances  Non-polar substances having charged groups are also water soluble  Ionic compounds and electrolytes dissociate into their ions when dissolved in water.  All biochemical reactions occur in aqueous medium of the cell because water provides favorable conditions for reactions e.g. formation of ions in water. 2) Hydrogen Bonding a) Introduction  Hydrogen bonding is a type of intermolecular forces  Force of attraction between highly electronegative atom(partially –ve) of one molecule and partially +ve hydrogen atom of another molecule is called hydrogen bonding  Hydrogen bond is represented by dotted line  Hydrogen bonds break easily by increasing temperature and by larger change in pH. b) Hydrogen bonding in water  Water is a polar substance  Partially negative oxygen atom of one water molecule attracts partially positive hydrogen of other water molecule _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. c) Significance  Hydrogen bonding makes water a good solvent  It gives water properties of cohesion and adhesion 3) Adhesion & Cohesion a) Introduction  Force of attraction between water molecules is called cohesion  Force of attraction between water molecules and polar surfaces is called adhesion b) Adhesion & Cohesion in Water  Cohesive and adhesive properties of water are due to hydrogen bonding c) Significance  Adhesion and cohesion make water a good transport medium.  Water circulates in the bodies of living organisms and acts as transport medium 4) High Specific Heat a) Introduction  Specific heat capacity of water is the number of calories required to raise temperature of 1g water by 1 oC  It is 1 Calorie or 4.18 joules per gram b) High Heat Capacity  Water has high heat capacity due to hydrogen bonding  Much of heat absorbed by water molecules is utilized in breakdown of hydrogen bonding  Very large amount of heat can increase very little temperature of water _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. c) Significance  Due to high specific heat capacity water acts as temperature stabilizer or regulator in hot environments  It protects living things from sudden thermal changes 5) High Heat of Vaporization a) Introduction  Amount of heat required to convert unit mass of a liquid into gaseous form (vapours) is called heat of vaporization b) Heat of Vapourization of Water  Number of calories required to convert 1g of water into vapours.  Water has high heat of vapourization due to hydrogen bonding  It is 574 Calories per gram c) Significance  High heat of vapourization means that a lot of heat can be lost with minimal loss of water.  Loss of only 2ml water out of littre (1000ml) lowers temperature of remaining 998ml water by 1 oC  When an organism sweats, body heat is used to vapourize sweat, thus cooling the animal 6) Hydrophobic Exclusion a) Introduction  Reduction of contact area between water and hydrophobic substances which are placed in water is called hydrophobic exclusion b) Exclusion of lipids  When few drops of oil are placed on water surface they tend to unit (coalesce) to make single drop _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. c) Significance  Hydrophobic exclusion helps in maintaining integrity lipid bilayer of cell membranes 7) Ionization a) Introduction  Dissociation of a molecule into ions is called ionization  It is reversible process b) Ionization of water  Water molecules ionize into equal number of hydrogen ions and hydroxyl ions c) Significance  Ionization of water molecules is maintained at equilibrium at 25 oC  H+ and –OH ions affect and take part in many reactions that occur in cells e.g. it helps to maintain or change pH of medium 8) Lower Density of Ice a) Introduction  Ice is less dense than liquid water, therefore it floats on water surface b) Structure of Ice  Ice has giant lattice structure _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  It shows maximum number of hydrogen bonds per water molecule  Lattice has large intermolecular spaces i.e. it has loose packing of molecules. Therefore ice has less density c) Significance  In freezing weather, ice forms on the surface of ponds and lakes  Layer of ice provides insulating layer above the below water, this provides living environment for organisms until ice melts Carbohydrates a) Introduction  Carbohydrates are generally known as sugars because more familiar carbohydrates are sweet in taste.  In Greek ‘Sakcharon’ is used for sugars so carbohydrates are also known as saccharides  Chemically carbohydrates are polyhydroxy aldehydes or polyhydroxy ketones _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. b) Classification of Carbohydrates  Classification of carbohydrates is bases on carbohydrate units  There are three types of carbohydrates i) Monosaccharaides ii) Oligosaccharides iii) Polysaccharides c) Comparison of types _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. Monosaccharides 1) Introduction  Monosaccharides are true carbohydrates which are either polyhydroxy aldehydes or polyhydroxy ketones  All the carbon atoms except one carbon have one hydroxyl group. The carbon lacking the hydroxyl group is part of aldehyde or ketone group _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  General formula of monosaccharides is CnH2nOn, where ‘n’ is the number of carbon atoms  The range of carbon atoms in monosaccharides is 3 to 7. 2) Classification Classification of monosaccharides is based on either functional group or number of carbon atoms a) Based on Functional Group Based on functional group there are two types of monosaccharides; i) Aldoses or Aldo Sugars  They contain aldehyde group in their structure  e.g. glucose ii) Ketoses or Keto Sugars  They contain ketonic group in their structural formula  e.g. fructose _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. b) Based on No.of Carbon Atoms based on number of carbon atoms, monosaccharides are classified into 5 groups I. II. III. IV. V. Trioses : contain 3 carbon atoms e.g. glyceraldehyde Tetroses: contain 4 carbon atoms e.g. erythrose Pentoses: contain 5 carbon atoms e.g. ribose Hexoses: contain 6 carbon atoms e.g. glucose Heptoses: contain 7 carbon atoms e.g. glucoheptose 3) Chemical Structure of Monosaccharides Two types of structures are observed in monosaccharides;  Open chain structures in crystalline forms  Closed chain or ring structures in solutions Ring structures are mostly formed by pentoses and hexoses _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. a) Open Chain Structures  Ends of carbon chain are free b) Ring Structures  Ends of carbon chain are connected to each other  Two types of rings are formed i) Furanose  It is five membered ring; 1 O + 4 C atoms  Oxygen atom is linked with C1 and C4  e.g. in ribose oxygen atom aldehyde reacts with C4. As a result OH group is transferred from C4 to C1 and oxygen links to C4  All pentoses and ketohexoses are converted into furanose ring _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. ii) Pyranose  Pyranose is six membered ring; 1O + 5C  Oxygen atom is linked with C1 and C5  Only aldohexoses are converted into pyranose _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. iii) and Forms Each pentose and hexose molecule in ring structure exist in either in form depending on position of H and OH group on C1   or Form: if OH group is found downward on C1 it is called sugar Form: if OH group is present upward on C1 it is called sugar Stereoisomerism in Monosaccharides (Glucose) 1) Introduction  Molecules that have same molecular formula but different arrangement of atoms in 3D space are called stereoisomers. This phenomenon is known as stereoisomerism.  Monosaccharides have different types of stereoisomers;  Enantiomers  Epimers  Diastereoisomers _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. 2) Enantiomers i) Definition Those stereoisomers which are non-superimposable mirror images of one another are called enantiomers ii) Example  D-Glucose and L-Glucose are enantiomers of each other  D-Glucose is also called right handed form  L-Glucose is also called left handed form 3) Artificial Sweeteners  Laboratory manufactured sugars are left handed and used as sweeteners whereas as naturally occurring sugars are right handed.  L-sugars are not digested in our body because enzymes in body have active sites designed for L-sugars _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. Oligosaccharides 1) Definition Carbohydrates which yield 2 to 10 monosaccharide units upon hydrolysis are called oligosaccharides (oligo = few) 2) Classification Based on number of monosaccharide units, oligosaccharides are classified as  Disaccharides  Trisaccharides  Tetrasaccharides and so on …………………………………………….. 3) Disaccharides i) Introduction  Oligosaccharides which yield two monosaccharide units upon hydrolysis are called disaccharides  They are less sweet and less soluble in water  Their general formula is C12H22O11  Some common examples are maltose, sucrose, and lactose ii) Sucrose  It is commonly used as cane sugar  It is widely used as sweetener at home for making sweet dishes  In plants it is also called transport disaccharide because food is transported in the form of sucrose. Because;  Sucrose is very soluble in water  Relatively unreactive chemically  Can be transported in high concentrations _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  It is formed by condensation of -glucose and -fructose which can be obtained by hydrolysis of sucrose  -OH group at C-1 of glucose reacts with –OH group of C-2 of fructose, water is released and two units are linked together. The bond formed is called 1,2-glycosidic linkage iii) Maltose      It is commonly used as malt sugar It is an intermediate produced in breakdown of starch and glycogen Maltose is generally found in germinating seeds It is formed by condensation of two -glucose molecules -OH group at C-1 of one glucose reacts with –OH group at C-4 of other molecule. The bond formed is known as -1,4-glycosidic linkage _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. iv) Lactose  It is commonly used as milk sugar  It is formed by -galactose and -glucose.  -OH group at C-1 of galactose reacts with –OH group at C-4 of glucose, water is released and bond is formed called -1,4-glycosidic linkage _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. Polysaccharides a) Definition  Carbohydrates that produce more than 10 monosaccharide units on hydrolysis are called polysaccharides  It is the largest group of carbohydrates b) Types  There are two types of polysaccharides a) Homopolysaccharides: these are composed of only one type of monosaccharides e.g. starch, glycogen, cellulose, chitin etc. b) Heteropolysaccharides: agar, pectin, peptidoglycan etc. c) General Functions  Polysaccharides function as food, energy reservoir,(starch, glycogen)  They are convenient storage molecule because;  Almost insoluble in water due to their large size  Exert no osmotic and chemical influence of the cell  They fold into compact shapes  Are easily converted into simple sugars by hydrolysis  Play structural role (cellulose, chitin) d) Examples _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  Some common examples are; starch, cellulose, chitin 2) STARCH a) Introduction  It is homopolysaccharides made of hundreds of -glucose.  Plant store food as starch in stem, root and seeds  Starch is digested in oral cavity and small intestine as; b) Confirmatory Test  Presence of starch is confirmed by iodine test. Starch gives blue color with iodine c) Types  There are two types of starch i.e. amylose and amylopectin i) Amylose  It is unbranched (linear)  Glucose units are linked by -1,4-glycosidic linkages  It soluble in hot water ii) Amylopectin  It is branched  -1,6-glycosidic linkages  It is completely insoluble in water _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. 3) GLYCOGEN a) Introduction  It is a homopolysaccharides composed of -glucoses.  It is storage carbohydrate of animals. It is mainly stored in liver and muscles. Therefore it is also known as animal’s starch.  The digestion of glycogen is also quite similar to that of starch. b) Confirmatory Test  The presence of glycogen in a given sample can also be confirmed by iodine test as it gives red colour with iodine solution. c) Structure  Structure of glycogen resembles with amylopectin starch but glycogen has much more branching than amylopectin _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. 4) Cellulose a) Introduction  Cellulose is most abundant carbohydrate on earth.  It is also a homopolysaccharides but unlike starch and glycogen it is formed by the condensation of hundreds of -glucoses.  Cotton and paper are the pure forms of cellulose  It is structural carbohydrate of plants as it is major constituent of plant cell wall. _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. b) Confirmatory Test  Cellulose shows no colour with iodine solution. c) Structure  Structure of cellulose resembles with amylose starch in such a way that it has un-branched structure but it has -1, 4-glycosidic linkages between glucose residues.  Therefore, in a cellulose chain, the -glucoses are alternatively arranged in upright and inverted manner 5) Chitin a) Introduction  Chitin is the second most abundant organic molecule on earth.  It is also a homopolysaccharides.  It is a structural carbohydrate found in the cell walls of fungi and in the exoskeleton of arthropods.  Due to the occurrence of chitin in fungal cell wall, it is also known as fungal cellulose. b) Structure  Chitin is the derivative of N-acetyl glucosamine which is a modified form of glucose. _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  It has an un-branched structure like cellulose in which alternative upright and inverted N-acetyl glucosamine residues are linked together by -1, 4glycosidic linkages PROTEINS 1) Introduction  Proteins are the main structural components of the cell.  Chemically proteins can be defined as polymers of amino acids or polypeptide chains.  A protein may consist of a single polypeptide or more than one polypeptide 2) Chemical Composition  All proteins contain C, H, O and N, while some contains P, S.  Few proteins have Fe, I and Mg incorporated into the molecule 3) Amino acids  Amino acids are the building blocks of proteins.  Among many only 20 are commonly found in proteins.  Amino acid consists of a central carbon atom called alpha carbon. _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  Alpha carbon is attached to 4 different groups  a hydrogen atom,  an amino group (-NH2),  a carboxyl group (-OOH) and  a variable group known as-R group.  The R group has a different structure in each of the 20 biologically  Two simplest amino acids i.e., glycine and alanine 4) Dipeptides, Tripeptides & Polypeptides a) Introduction  Dipeptides and polypeptides are formed by the condensation of amino acids on the ribosome in the process called translation  mRNA is formed from DNA and sent to ribosome. Ribosome translates mRNA into protein b) Peptide Bond Formation  An amino acid reacts with another amino acid,  The -OH from carboxylic group of one amino acid and -H from amino group of other amino acid combine and released as a water molecule,  As a result a bond is established between C of carboxylic acid group and N of amino group of two amino acids called peptide bond.  A product of two amino acids is formed which is known as dipeptide. _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. c) Dipeptide  A dipeptide has two ends; one is called amino or -N terminal end while other is called carboxylic acid or -C terminal end.  A new amino acid can be added in this chain from its carboxylic acid or-C terminal end in the same way. d) Tripeptide  Tripeptide is s a product of three amino acids e) Polypeptide & Protein _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  When several amino acids are linked together by many peptide bonds, the polypeptide chain is formed  A protein may consist of a single polypeptide or more than one polypeptide Structural Conformations in Proteins 1) Introduction  Particular form, shape or structure is called conformation  Proteins show following structural conformations  Primary Structure  Secondary Structure  Tertiary Structure  Quaternary Structure 2) Structural Conformations i) Primary Structure  A linear polypeptide with a specific sequence and number of amino acid is called primary structure.  It is shown by all proteins at the time of their synthesis on ribosomal surface.  After synthesis a protein does not remain in its primary structure but can be changed into some other structural ii) Secondary Structure  A helical ( -helix) or flattened sheets ( -pleated sheet) like structures are called secondary structures _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  These are established by H-bonding between opposite charge bearing groups of different amino acids. iii) Tertiary Structure  In some proteins -helix fold again and again by ionic bonds and disulfide bridges to form a globular shaped structure called the tertiary structure. iv) Quaternary Structure Some proteins exist in very complex structure in which more than one globule is attached together by hydrophobic interaction. Such structures are called quaternary structures _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. Summary _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube. Significance of Amino Acid Sequence Introduction _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  Sequence of amino acid in a polypeptide is a characteristic feature of primary structure of protein  It is responsible for proper functioning of protein  It is determined by the sequence of nucleotide in DNA Change in Sequence  Point mutation, change of single or few nucleotides in DNA  Due to point mutation the sequence of amino acid in a particular protein (polypeptide) may be disturbed  It causes severe defects in the body as it happens in sickle cell anemia, a hereditary disease. Example: Sickle Cell Anemia a) Normal RBCs  Normal red blood cells are disc-shaped and look like doughnuts without holes in the centre.  They move easily through blood vessels.  Red blood cells contain an iron-rich protein called haemoglobin.  This protein carries oxygen from the lungs to the rest of the body.  Normal haemoglobin (HbA) contains four polypeptides i.e.  two -chains which consist of 141 amino acids each _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  two -chains which consist of 146 amino acids each b) Sickle Shaped RBCs  Formed in Sickle Cell Anemia  Sickle cells contain abnormal haemoglobin (HbS)  Sickle haemoglobin (HbS) makes cell sickle shaped or crescent shaped.  Sickle cells are stiff and sticky  They tend to block blood flow in the blood vessels of the limbs and organs  Blocked blood flow can cause pain and organ damage c) Cause of Sickle Cell Anemia  Sickle cell anemia is caused by a point mutation in -globin gene  In this only one nucleotide is replaced by another _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.  It causes a change in amino acid sequence of -chain of hemoglobin  Glutamic acid is replaced by valine at position number six in -chain _____________________________________________________________________________________________ Give your feedback at our Whatsapp # 0312-5969383 & Subscribe our channel ILMI STARS ACADEMY on youtube.