Structure/Function of Cell Components Living things are made of: Living things are made of: Carbohydrates Carbohydrates Lipids Lipids Proteins Proteins Nucleic acids Nucleic acids CHNOPS CHNOPS Carbon Carbon Hydrogen Hydrogen Nitrogen Nitrogen Oxygen Oxygen Phosphorous Phosphorous Sulphur Sulphur

Basic Chemistry Atoms make bonds Atoms make bonds –Ionicloss/gain of electrons –Covalent electrons are shared »Polar covalent – unequal sharing of the electrons –Makes the atoms have a partial charge (polarity) –Hydrogen bonds 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. 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. Polar covalent bonds, only a partial charge so relatively weak Polar covalent bonds, only a partial charge so relatively weak –Van der waals forces Induced polarity (e.g. in C-H bond) Induced polarity (e.g. in C-H bond) –Hydrophobic 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 water Polar groups tend to move towards water

CARBOHYDRATES

Carbohydrates C, H, O C, H, O (CH 2 O) n (CH 2 O) n Monosaccharides - one monomer Monosaccharides - one monomer Form rings in solution Form rings in solution Disaccharides- two monomers Disaccharides- two monomers Polysaccharides- many monomers Polysaccharides- many monomers Monomers contain Monomers contain »5 Carbon atoms - pentose »6 carbon atoms - hexose

Carbohydrates Saccharides can exist in solution as linear molecules or rings. Saccharides can exist in solution as linear molecules or rings. They interconvert between the two forms, but at equilibrium, 99% will be ring They interconvert between the two forms, but at equilibrium, 99% will be ring

Structural Variation in Carbohydrates Special carbons Special carbons Carbon atoms 1-5 are chiral (optically active) i.e. OH and H groups on the C atoms can be ordered differently. Carbon atoms 1-5 are chiral (optically active) i.e. OH and H groups on the C atoms can be ordered differently. For C atoms 2-4 the arrangement of OH and H groups determines the monosaccharide. For C atoms 2-4 the arrangement of OH and H groups determines the monosaccharide. Orientation of OH on Carbon 5 (in Hexoses) confers D (dextro rotatory) or L (laevorotatory) forms Orientation of OH on Carbon 5 (in Hexoses) confers D (dextro rotatory) or L (laevorotatory) forms –D points right –L points left Orientation of OH on Carbon 1 (in Hexoses) determines  (down) or  (up) Orientation of OH on Carbon 1 (in Hexoses) determines  (down) or  (up)

Numbering

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

Forming Rings Rings form between C1 and C5. An O atom acts as a bridge (hence the 6 member ring).

Disaccharides Two monosaccharides join together with a glycoside bond Two monosaccharides join together with a glycoside bond Dehydration (condensation) reaction (elimination of water) Dehydration (condensation) reaction (elimination of water) –e.g. maltose (2 x glucose) –  -D-glucose joined to  -D-glucose –join at the C1 (  ) and C4 atoms –  1-4 glycoside bond

 1,4, glycosidic bond - cellobiose  1,4, glycosidic bond - cellobiose  1,6, glycosidic bond  1,2 glycosidic bond -sucrose

Polysaccharides 3 major ones of interest 3 major ones of interest –Starch –Glycogen –Cellulose

STARCH Comprised two components Comprised two components Soluble part (20%) - AMYLOSE Soluble part (20%) - AMYLOSE –Continouous unbranched chain of glucose units (up to 300) joined by  1-4 glycoside bonds. Insoluble part (80%) – AMYLOPECTIN Insoluble part (80%) – AMYLOPECTIN –Shorter  1-4 chains (24-30), with  1-6 branching Starch, being insoluble exerts no osmotic pressure, so is useful as a storage polysaccharide

GLYCOGEN Animal storage polysaccharide Animal storage polysaccharide Similar to amylopectin, Similar to amylopectin, –Lower molecular weight –More highly branched –  1-4 chains (up to 10), with  1-6 branching

CELLULOSE Linear polymer of glucose units (up to 2800) Linear polymer of glucose units (up to 2800) –  1,4, glycosidic bonds Cellulose fibre - parallel strands held together by hydrogen bonds Cellulose fibre - parallel strands held together by hydrogen bonds