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

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)

NumberingNumbering

2

6

54

3

1

The molecules are isomers, they differ in the orientation of H and OH on C2-4.

Note Fructose differs in the position of the carbonyl – important in forming rings

down, down, up up

The OH group on the carbon next to the oxygen (C1)

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