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Chapter2 Biology  Molecules

Chapter2 Biology Molecules






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    Chapter2 Biology  Molecules Chapter2 Biology Molecules Presentation Transcript

    • Biological molecules Ru by Zhao 2009. 9.1
    • Biological molecules
      • Molecular Biology- study of the structure and functioning of biological molecules.
    • Introduction
      • The building blocks of life
      • Polymers 聚合物 macromolecules 高分子
      • Carbohydrates 糖类
      • Lipids 脂类
      • Proteins 蛋白质
      • Water 水
      • Inorganic ions 无机离子
    • Metabolism
      • The sum total of all the biochemical reactions in the body is known as metabolism .
    • The building blocks of life
      • The four most common elements in living organisms are H ydrogen C arbon & O xygen and N itrogen.
    • Polymers and macromolecules
      • The term macro molecule means ’giant molecule’.
      • Polymers is macromolecules made up of many repeating subunits that are similar or identical to each other and are joined end to end like beads on a string.
      • Polymerisation- the same reaction repeated many times for subunits to form polymers.
    • The building blocks of life monosaccharides polysaccharides Organic bases amino acids Fatty acids and glycerol proteins lipids nucleotides Nucleic acids
    • Carbohydrates
      • All carbohydrate contain the elements C arbon H ydrogen & O xygen. The general formula for a carbohydrate is C x (H 2 O) y.
      • There are 3 types:
        • Monosaccharides
        • Disaccharides
        • Polysaccharides
    • Monosaccharides
      • Consist of a single sugar molecule (CH 2 O) n
      • If n=3, triose (glyceraldehyde)
      • If n=5, pentose (fructose, ribose)
      • If n=6, hexose (glucose, galactose)
    • Molecular and structural formulae
      • Glucose
      • Molecular formula C 6 H 12 O 6.
      • Structural formula
    • fructose
    • ribose
    • Isomerism
      • They can exist as isomers:  &  glucose
    • Roles of monosaccharides
      • Monosaccharides are used for
        • Energy
        • Building blocks
    • Disaccharides
      • Formed from two monosaccharides
      • Joined by a glycosidic bond
      • A condensation reaction:
        • glucose + glucose  maltose
        • glucose + galactose  lactose
        • glucose + fructose  sucrose
      • Condensation reaction 缩合反应 : two hydroxyl groups line up together and one combines with a hydrogen atom from the other to form a water molecule.
      • The reverse of this kind of condensation is the addition of water which is known as hydrolysis reaction 水解反应 .
    • Polysaccharides
      • Polymers formed from many monosaccharides
      • Three important examples:
        • Starch
        • Glycogen
        • Cellulose
    • Starch
      • Amylose
      •  -glucose
      • 1,4 glycosidic bonds
      • Spiral structure
      • Amylopectin
      •  -glucose
      • 1,4 and some 1,6 glycosidic bonds
      • Branched structure
    • Starch Insoluble store of glucose in plants formed from two glucose polymers:
    • Glycogen
      • Insoluble compact store of glucose in animals
      •  -glucose units
      • 1,4 and 1,6 glycosidic bonds
      • Branched structure
    • Cellulose
      • Structural polysaccharide in plants
      •  -glucose
      • 1,4 glycosidic bonds
      • H-bonds link adjacent chains
    • summary support Energy source Energy source Energy source function unbranched 1,4  -glucose Cellulose Branched 1,4 & 1,6  -glucose Gylcogen Branched 1,4 & 1,6  -glucose Amylopectin unbranched 1,4  -glucose Amylose glycosidic bonds subunits Type
    • Hydrophilic
      • Molecules which have groups with dipoles are said to be polar . They are attracted to water molecules, because the water molecules also have dipoles.
      • Such molecules are hydrophilic (water-loving), and they tend to be soluble in water.
    • Hydrophobic
      • Molecules which do not have dipoles are said to be non-polar . They are not attracted to water, and they are hydrophobic (water-hating).
    • Lipids
      • Made up of C, H and O
      • Can exist as fats, oils
      • They are insoluble in water
      • They are a good source of energy (38kJ/g)
      • They are poor conductors of heat
      • Most fats & oils are triglycerides
    • ester
      • Alcohol s are molecules containing the –OH functional group.
      • Carboxylic acids make up a homologous series of compounds containing the functional group –COOH .
      • Esters are made of reaction of alcohols and carboxylic acids .
    • Triglycerides
      • Formed by esterification…
      • … a condensation reaction between 3 fatty acids and glycerol:
      Glycerol H C H C C H H H H O O O
    • Fatty acids
      • Carboxyl group (-COOH)
      • attached to a long non-polar hydrocarbon chain (hydrophobic):
      H A saturated fatty acid (no double bonds) H C H H C H H C H C O O H C H H C H H C H H C H H
    • H H C O O H C C C C H A polyunsaturated fatty acid C O O H C H H C H A monounsaturated fatty acid H H H C H H C H H C H H C H H C H H C H H C H H C H
    • Esterification Glycerol Fatty acid H C H C C H H H H O O O C O O H C H H C H H C H H C H H
    • Esterification Glycerol Fatty acid H C H C C H H H H O O O C O O H C H H C H H C H H C H H
    • Esterification H C H C C H H H H O O O C O O H Glycerol Fatty acid H C H H C H H C H H C H
    • Esterification H C H C C H H H H O O O C O O H Ester bond water H C H H C H H C H H C H
    • Esterification
      • This happens three times to form a triglyceride:
      glycerol fatty acids
    • Phospholipids
      • One fatty acid can be replaced
      • by a polar phosphate group:
      glycerol Hydrophobic fatty acids hydrophilic phosphate
    • Functions of lipids
      • Protection of vital organs
      • To prevent evaporation in plants & animals
      • To insulate the body
      • They form the myelin sheath ( 髓鞘 ) around some neurones
      • As a water source (respiration of lipids)
      • As a component of cell membranes
    • Proteins
      • Made from C H O N & sometimes S
      • Long chains of amino acids
      • Properties determined by the aa sequence
      Amino acids
      • ~20 aa
      • Glycine R=H
      • Alanine R=CH 3
      amine carboxyl H C H N C H H O O R
    • Peptide bonding H C H N C H H O O R H C H N C H H O O R
    • Peptide bonding H C H N C H H O O R H C H N C H H O O R
    • Peptide bonding H C H N C H H O O R H C H N C H H O O R
    • Peptide bonding C H N C H H O R H C H N C H O O R water Peptide bond A condensation reaction H O H
    • Peptide bonding H C H N C H O O R A dipeptide C H N C H H O R
    • Primary structure
      • The sequence of aa is known as the primary structure
      • The aa chain is a polypeptide
      • Peptide bond forms between the –COOH and the -NH 2 of adjacent aa
      • This results in the chains folding:
    • Secondary structure  -helix  -pleated sheet
    • Secondary structure
      • A polypeptide chain often coils into an α -helix due to the attraction between the oxygen of the –CO group of one amino acid and the hydrogen of the –NH group of the amino acid four place ahead of it.
    • Secondary structure
      •  -pleated sheet is a looser straight shape .
    • Tertiary structure
      • A protein coils up to form a precise three-dimensional shape is its tertiary structure.
    • Tertiary structure
      • Bonding between R-groups gives rise to a 3D shape
      • H-bonds =O - HN-
      • Ionic bonds –NH 3 - COO-
      • Disulphide bridge ( most stable )
      • --CH 2 S - SCH 2 -
      affected by temp & pH affected by pH affected by reducing agents
    • Quaternary structure
      • The association of different polypeptide chains is called the quaternary structure of the protein.
    • Quaternary structure
      • Some proteins have more than one polypeptide chain
      • Each chain is held together in a precise structure
      • eg Haemoglobin
    • Types of proteins
      • Fibrous proteins
        • e.g. collagen
        • Insoluble
        • structural
      • Globular proteins
        • e.g.enzymes
        • Soluble
        • 3D shape
    • Haemoglobin A complete haemoglobin can carry Four O 2
    • collagen
    • Functions of proteins
      • Enzymes –
      • Transport –
      • Movement –
      • Cell recognition –
      • Channels –
      • Structure –
      • Hormones –
      • Protection –
      • Amylase
      • Haemoglobin
      • Actin & myosin
      • Antigens
      • Membrane proteins
      • Collagen & keratin
      • Insulin
      • Antibodies
    • Water
      • Water is a polar molecule
      • It forms weak hydrogen bonds
      • It remains a liquid over a wide temperature range
      • Water molecules stick to one another = cohesion (surface tension)
      • Water molecules stick to other substances = adhesion (capillarity)
      O H H + + -
    • Water
      • It has a high specific heat capacity – so water can maintain a reasonably constant temperature (homeostasis)
      • It has a high latent heat of vaporisation – so animals use water to cool themselves
      • It is less dense as a solid (ice)…
      • … and ice is a poor conductor
      • Water is a good solvent
    • Inorganic ions
      • Ions are formed individual atoms that have gained or lost one or more electrons and are therefore charged negatively or positively.
      • Many ions are highly soluble in water.
      • The end