biological molecules 1 2014 oct 1

8/10/2019 Biological Molecules 1 2014 Oct 1

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NazabayevUniversityUPCSE

Biology

Biological Molecules 1


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Biomolecules 1 Pork Chop Willie 211/6/2014 5:10 AM

Molecules important in biology

WaterInorganic ions

CarbohydratesLipidsNucleic Acids

Proteins


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Students should

Understand the importance of water as a solventin transport, including its dipole nature.



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Students should

Know the difference between monosaccharides,disaccharides and polysaccharides, e.g. glycogen

and starch ( amylose and amylopectin).

Relate the structures of monosaccharides,disaccharides and polysaccharides to their rolesin providing and storing energy



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Students should

Know how monosaccharides join to formdisaccharides ( sucrose, lactose and maltose )

and polysaccharides ( glycogen and amylose )through condensation reactions formingglycosidic bonds , and how these can be splitthrough hydrolysis reactions



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Students should

Know how a triglyceride is synthesised by theformation of ester bonds during condensation

reactions between glycero l and three fatty acids .Know the differences between saturated andunsaturated lipids.



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Chirality "handedness."

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Chirality in lifeThalidomide is a sedative drug that wasprescribed to pregnant women, from 1957 intothe early 60's.

It was present in at least 46 countries underdifferent brand names.When taken during the first trimester ofpregnancy, Thalidomide prevented the propergrowth of the foetus, resulting in horrific birthdefects.



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Why?The Thalidomide molecule is chiral. There are left and right-handed Thalidomides,

just as there are left and right hands.

The drug that was marketed was a 50/50mixture.One of the molecules, say the left one, was asedative, whereas the right one was found laterto cause foetal abnormalities .



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Properties of water that makeit an ideal transport medium

Water is unusual because it is a liquid at roomtemperature whereas other small molecules are

gases. CO 2, 02Water is a polar molecule ; it has an unevenlydistributed electrical charge.The two hydrogens are pushed into a V shapedmolecule

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Dipoles and Hydrogen Bonds

Atoms in molecules are held together becausethey share electrons with each other.

A shared pair of electrons forms a covalentbond - for example in a water molecule, twohydrogen atoms each share a pair of electronswith an oxygen atom.



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Solvent properties of water

Many chemical dissolve easily in water,allowing vital chemical reactions to take place

Chemicals can move about freely in aqueousenvironmentChemicals can react with water itself e.g.hydrolysis and condensation reactions



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Dissolved substances can be transported aroundthe body in blood and lymph in animals and inplants through xylem and phloem .

Ionic molecules e.g.(NaCl) dissolve easily inwater forming ions Na+ which are attracted to Cl -



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Polar molecules dissolve easily in water.Their polar groups e.g. OH group in sugars or

the amine group NH2 in an amino acid ,become surrounded by water and go intosolution.Polar substances are said to be hydrophilic (water loving)



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Non polar , hydrophobic substances such aslipids, do not dissolve in water.

To enable transport in blood, lipids combinewith proteins to form lipoproteins



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Thermal properties of water

Specific heat capacity of water (the amount ofenergy in joules required to raise 1 cm 3 (1g) of

water by 1o

C, is very highBecause in water a large amount of energy isrequired to break the hydrogen bondsWater warms up and cools down slowly

Avoids rapid changes in internal environment



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Monosaccharides



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Condensation reaction to forma Dissacharide

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Glycosidic linksplit byHydrolysis



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Polysaccharides

Polymers made up from simple sugars joined byglycosidic links into long chains.

Three main typesStarch and Cellulose in plants and glycogen inanimals



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StarchMixture of two molecules: Amylose andamylopectin

Amylose straight chain glucose molecules

with 1,4 glycosidic . Position of bondcauses the chain to coil into spiral shape

Amylopectin polymer of glucose withbranches, 1,6 glycosidic link holds eachside branch onto the main chain



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Starch



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Cellulose

Dietary fibreNon starch polysaccharide

Straight chains (1,4 links only)Gives strength to cell walls of plantsMade up of -glucose molecules



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I C ll l i hb i h i f


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In Cellulose neighbouring chains ofglucose molecules are linked by

hydrogen bonds to form microfibrils



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Lipids

(Fats, oils, waxes)Enhance flavour and palatability of foodSupply twice the energy of carbohydrates

37KJ per gram of foodInsoluble in waterSoluble in ethanol

All Lipids are hydrophobic : thats the oneproperty they have in common.Lipids found in every type of cell



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Glycerol and fatty acids



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Formation of a triglyceride



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Unsaturated fats

Monounsaturated fats have one doublebond between two carbon atoms in ach

fatty acid chainPolyunsaturated fats have a largernumber of double bonds.



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Unsaturated fats

Double bond cause kink in thehydrocarbon chain and prevents close

packing.Weak intermolecular bonds betweenunsaturated fats results in oils at roomtemperature.

Vegetable oils and fish good sources ofpolyunsaturated fats.



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Unsaturated fats

Cis double bonds bend carbon chainscis fatty acids are more bulky than trans fatty

acidsCis fatty acids have a lower melting point.Trans fatty acids behave more like saturatedfats than cis fatty acids

Animals cannot metabolise trans fatty acidsfully



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Cholesterol



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Cholesterol

Vital component of cell membranesSteroid sex hormones(such as

progesterone and testosterone ) andsome growth hormones.Bile salts formed from cholesterolMade in the liver from saturated fatsToo high cholesterol can be bad



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Sphingolipids

Fatty acids linkedto Amine groupImportant in cellmembranes

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LipoproteinsLow density lipoppoteins (LDL)

Main cholesterol carrier in the bloodTriglcerides from saturated fats combinewith cholesterolDoes not remove cholesterol from blood

High density lipoproteins (HDL)

Combine with unsaturated fatsTransport cholesterol to liver



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biological molecules 1 2014 oct 1

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