Biology - Biomacromolecules PDF

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Biology Unit 3/4 Biomacromolecules...

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Biology – Biomacromolecules   

Macromolecules [Carbohydrates, Proteins, Nucleic acids] are polymers built from monomers, except lipids are composed of compartments Polymer – Long molecules consisting of many similar (identical) building blocks linked by covalent bonds Monomers – These are the repeating units that make up the polymer

Synthesis and breakdown of polymers 

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Synthesis occurs via a dehydration reaction, where two molecules are covalently bonded to each other and a water is removed Each time another monomer is added another water molecule is removed Breakdown occurs via a hydrolysis reaction, here the bonds are broken by the addition of water molecules Literally meaning hydro; water… lysis; breakage Breakdown of monomers allows them to be reabsorbed back into the blood stream and transported around the body

Carbohydrates; Sugar – fuel for the body     

Monosaccharides are the monomers of carbohydrates they are the “simplest sugar” Disaccharides – Double sugars joined by covalent bonds Polymers of carbohydrates are polysaccharides Depending on the location of the carbonyl group a sugar is either a ketone (middle carbon) or aldehyde (end carbon) Energy is extracted from the breakdown [hydrolysis] of sugar

Monosaccharides - formula (CH2O)n  

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Most common monosaccharide is glucose which is vital for cellular respiration Sugars form into rings as this is their most stable form — Six carbon ringed sugars are called hexoses — Three carbon ringed sugars are trioses — Five carbon ringed sugars are pentoses There are two glucose ring structures alpha and beta Enzymes that hydrolyse starch (- glucose) are unable to hydrolyse cellulose due to differing beta links — Alpha glucose rings have the -OH group positioned down on the first carbon — When alpha molecules are join they form starch — —

Beta glucose rings have the -OH group positioned up on the first carbon When beta glucose molecules are joined they form cellulose

Disaccharide; Consists of two monosaccharides joined together by a glyosidic linkage (covalent bond)

Polysaccharides; Long chains of monosaccharides joined by glyosidic bonds  

Starch, this is stored in plants as starch [polymer of -glucose monomers] granules Amylose is the simplest form of starch and is unbranched

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Amylopectin is highly branched

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Animals store glycogen which is extensively branched Used for energy storage in muscles Larger branching allows for “free ends” so when energy is needed the ends can easily break off

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Cellulose is a strong and tough material used for rigidity in plant cell walls Chitin is a type of derivative from cellulose ( -glucose) and is used to build arthropod exoskeletons

Lipids; diverse group of hydrophobic molecules used for energy storage 

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Lipids aren’t polymers, they are still formed by dehydration reactions and consist of two components glycerol and fatty acid tails (long carbon skeleton), this compound mainly consists of hydrocarbon regions (non-polar) Amphipathic - Hydrophobic tail and hydrophilic head Fats in water separate as water molecules hydrogen bond to one another and have low affinity for fats Formation Three fatty acid molecules are joined to glycerol via an ester linkage which is formed by a dehydration reaction b/w a -OH and -COOH group This results in a ‘triacylglycerol’ – Three fatty acids to one glycerol Saturated and unsaturated fats are dependent upon the type of double bonds within fatty acid chains

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Saturated fatty acid [solid]; No carbon-carbon double bond present The molecule is saturated with hydrogen bonds allowing fatty acids to pack together tightly into a solid

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Unsaturated fatty acid [liquid]; At least one carbon-carbon double The molecule is not saturated with hydrogen bonds, a cis-trans double bond causes a kink in the molecule to occur that prevents the tight packing of lipid molecules and inhibits strong bonds to form Prevention of tight packing means the substance is in a liquid state and requires less energy to break bonds

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Phospholipids    

Similar to fat molecule yet they possesses two fatty acid tails not three and the third -OH group of the glycerol is joined to a phosphate group This forms a hydrophilic head that has an affinity for water When added to water they naturally re-arrange themselves in ways that shield their hydrophobic tails from water Form a boundary b/w the cell and its external environment and forms separate compartments within eukaryotic cells

Proteins; Speed up chemical reactions (enzymes), used for defence, storage, transport and cellular communication, etc.  Bond b/w amino acids is called the peptide bond  Polymer of proteins is a polypeptide, monomers of proteins are amino acids  Structure is critical for function  Amino monomers; Share a basic structure with varying R group    

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side chains Polymerisation of amino acids occurs by a reaction b/w COOH and NH3 functional groups Centre carbon is the alpha carbon Chemical properties of the R-group side chain determine the characteristics of the amino acid; Polar, non-polar, acidic, basic Polypeptide backbone - Repeating sequence of amino acids (not including R groups)

Primary; Sequence of Amino acids

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Primary sequence dictates secondary, tertiary and quaternary structure due to the chemical properties of the backbone and side chains COOH group in amino acids are acidic

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Secondary; Regions stabilised by hydrogen bonds b/w atoms of the

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polypeptide backbone Most basic level of protein folding; -helices and -pleated sheets Partial charges of atoms cause attraction and hydrogen bonding to occur

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Tertiary; 3D shape of a polypeptide resulting from the side chain interactions b/w

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amino acids Hydrophobic side chains are generally located in the core of the polypeptide, away from polar substances Non-polar molecules stay together via van der Whaals interactions Polar and ionic side chains stay together by hydrogen bonds b/w partial positive and negative charges Individually they are weak bonds but together they become strong Covalent bonds called ‘disulphide bridges’ may reinforce the protein shape [present due to sulphur containing amino acids side chains]

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Quaternary; Overall shape of the protein resulting from joining two or more

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polypeptides Haemoglobin is an oxygen-binding protein of red blood cells and is a globular protein with quaternary structure

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Proteins can be denatured causing a change in structure due to pH, temperature, salt concentrations If proteins are transferred from an aqueous polar environment to a nonpolar solvent, the polypeptide chain refolds itself so that hydrophobic regions face outwards and polar hydrophilic regions face inwards

Nucleic Acids; Store, transmit and help express hereditary information  Genes consist of DNA which hold the instructions for determining the structure and function of proteins  Genetic info as DNA → RNA → Protein  Nucleic acids polymers are called polynucleotides and monomers are nucleotides

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Deoxyribonucleic acid; Form in which hereditary information is stored — Directs RNA synthesis and through RNA controls protein synthesis — Does not possess uracil, is double stranded and has a deoxyribose sugar

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Ribonucleic acid; Used to transcribe DNA so proteins can be produced — U, C, A, G – has Uracil instead of thymine, Single stranded and possesses a ribose sugar

 Nucleotides 

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Composed of three parts; Five-carbon sugar (pentose), nitrogen containing base and one of three phosphate groups Portion of a nucleotide without any phosphate groups is called a nucleoside Nitrogenous bases; Called this as the nitrogens tend to take up one hydrogen from solution and act like a base — Pyrimidines; CUT; Cytosol, uracil and Thymine — Purines; Adenine and Guanine Nucleotides are joined by hydrogen bonding by a dehydration reaction...