Post on 01-Jan-2016
Structure/Function of Cell Structure/Function of Cell ComponentsComponents
Living things are made of:Living things are made of: CarbohydratesCarbohydrates LipidsLipids ProteinsProteins Nucleic acidsNucleic acids
CHNOPSCHNOPS CarbonCarbon HydrogenHydrogen NitrogenNitrogen OxygenOxygen PhosphorousPhosphorous SulphurSulphur
Basic ChemistryBasic Chemistry Atoms make bondsAtoms make bonds
– IonicIonic loss/gain of electronsloss/gain of electrons– Covalent Covalent electrons are sharedelectrons are shared
» Polar covalent – unequal sharing of the electronsPolar covalent – unequal sharing of the electrons– Makes the atoms have a partial charge (polarity)Makes the atoms have a partial charge (polarity)
– Hydrogen bondsHydrogen bonds Between a polar covalently bonded hydrogen atom (e.g. to N or O) and another polar Between a polar covalently bonded hydrogen atom (e.g. to N or O) and another polar
covalently bonded atom e.g. oxygen in a carbonyl group.covalently bonded atom e.g. oxygen in a carbonyl group. Polar covalent bonds, only a partial charge so relatively weakPolar covalent bonds, only a partial charge so relatively weak
– Van der waals forcesVan der waals forces Induced polarity (e.g. in C-H bond)Induced polarity (e.g. in C-H bond)
– Hydrophobic InteractionsHydrophobic Interactions Non-polar groups tend to cluster together (away from water)Non-polar groups tend to cluster together (away from water) Polar groups tend to move towards waterPolar groups tend to move towards water
CarbohydratesCarbohydrates
C, H, OC, H, O (CH(CH22O)O)nn
Monosaccharides Monosaccharides - one monomer- one monomer Form rings in solutionForm rings in solution
DisaccharidesDisaccharides - two monomers- two monomers PolysaccharidesPolysaccharides - many monomers- many monomers
Monomers containMonomers contain
»5 Carbon atoms 5 Carbon atoms - pentose- pentose»6 carbon atoms 6 carbon atoms - hexose- hexose
CarbohydratesCarbohydrates
Saccharides can exist in solution as linear Saccharides can exist in solution as linear molecules or rings.molecules or rings.
They interconvert between the two forms, They interconvert between the two forms, but at equilibrium, 99% will be ringbut at equilibrium, 99% will be ring
Structural Variation in Structural Variation in CarbohydratesCarbohydrates
Special carbonsSpecial carbons Carbon atoms 1-5 are chiral (optically active) i.e. OH and H Carbon atoms 1-5 are chiral (optically active) i.e. OH and H
groups on the C atoms can be ordered differently.groups on the C atoms can be ordered differently. For C atoms 2-4 the arrangement of OH and H groups For C atoms 2-4 the arrangement of OH and H groups
determines the monosaccharide . determines the monosaccharide .
Orientation of OH on Carbon 5 (in Hexoses) Orientation of OH on Carbon 5 (in Hexoses) confers D (dextro rotatory) or L (laevorotatory) confers D (dextro rotatory) or L (laevorotatory) formsforms– D points rightD points right– L points leftL points left
Orientation of OH on Carbon 1 (in Hexoses) Orientation of OH on Carbon 1 (in Hexoses) determines determines (down) or (down) or (up) (up)
Forming RingsForming Rings1
3
2
4
5
6
Rings form between C1 and C5. An O atom acts as a bridge (hence the 6 member ring).
DisaccharidesDisaccharides
Two monosaccharides join together with a Two monosaccharides join together with a glycoside bondglycoside bond
Dehydration (condensation) reaction (elimination Dehydration (condensation) reaction (elimination of water)of water)– e.g. maltose (2 x glucose)e.g. maltose (2 x glucose) -D-glucose joined to -D-glucose joined to -D-glucose -D-glucose– join at the C1 (join at the C1 () and C4 atoms) and C4 atoms 1-4 glycoside bond1-4 glycoside bond
1,4, glycosidic bond - cellobiose1,4, glycosidic bond - cellobiose
1,6, glycosidic bond1,6, glycosidic bond 1,2 glycosidic bond -sucrose1,2 glycosidic bond -sucrose
PolysaccharidesPolysaccharides
3 major ones of interest3 major ones of interest– StarchStarch– GlycogenGlycogen– CelluloseCellulose
STARCHSTARCH
Comprised two componentsComprised two components Soluble part (20%) - AMYLOSESoluble part (20%) - AMYLOSE
– Continouous unbranched chain of glucose units Continouous unbranched chain of glucose units (up to 300) joined by (up to 300) joined by 1-4 glycoside bonds.1-4 glycoside bonds.
Insoluble part (80%) – AMYLOPECTINInsoluble part (80%) – AMYLOPECTIN– Shorter Shorter 1-4 chains (24-30), with 1-4 chains (24-30), with 1-6 1-6
branchingbranching
Starch, being insoluble exerts no osmotic pressure, so is useful as a storage polysaccharide
GLYCOGENGLYCOGEN
Animal storage polysaccharideAnimal storage polysaccharide Similar to amylopectin,Similar to amylopectin,
– Lower molecular weightLower molecular weight– More highly branchedMore highly branched 1-4 chains (up to 10), with 1-4 chains (up to 10), with 1-6 branching1-6 branching
CELLULOSECELLULOSE
Linear polymer of glucose units (up to 2800)Linear polymer of glucose units (up to 2800) 1,4, glycosidic bonds1,4, glycosidic bonds
Cellulose fibre - parallel strands held together by Cellulose fibre - parallel strands held together by hydrogen bondshydrogen bonds