CHAPTER 3: THE CHEMISTRY OF LIFE The Structure and Function of Large Biomolecules

Intro Recap  Essential Elements - CHONPS  Carbon  Hydrogen  Oxygen  Nitrogen  Phosphorus  Sulfur  Make up the 4 major molecules in your body  Carbs  Proteins  Lipids  Nucleic acids

Macromolecules  Huge molecules made of many smaller molecules and atoms  Carbohydrates  Proteins  Nucleic Acids  Lipids don’t count!

Polymers and Monomers  mono = one  Subunits of polymer  poly = many  One polymer is made up of many monomers bonded together MonomerPolymer Sugar

Dehydration Synthesis = Condensation  The way that polymers are assembled  Dehydration – water is removed  Synthesis – to make  Remove water to make a bond

Fig. 5-2a Dehydration removes a water molecule, forming a new bond Short polymerUnlinked monomer Longer polymer Dehydration reaction in the synthesis of a polymer HO H2OH2O H H H (a)

Hydrolysis  The way that polymers are broken down (metabolized)  Hydro – water  Lysis – to cut/break  Add water to break a bond  Where does a lot of hydrolysis happen?

Fig. 5-2b Hydrolysis adds a water molecule, breaking a bond Hydrolysis of a polymer HO H2OH2O H H H (b)

Carbohydrates  Sugars and their polymers  Monosaccharides – one sugar (building block)  Disaccharides – two sugars  Polysaccharides – many sugars  Multiple of the unit CH 2 O  Glucose C 6 H 12 O 6

Sugars  Can be chains or rings (3-7 carbons long)  Have a carbonyl group (>C=O)  Many hydroxyl groups (–OH) Aldoses Glyceraldehyde Ribose GlucoseGalactose Hexoses (C 6 H 12 O 6 ) Pentoses (C 5 H 10 O 5 ) Trioses (C 3 H 6 O 3 )

Fig. 5-4a (a) Linear and ring forms

Fig. 5-4b (b) Abbreviated ring structure

Starch – a polymer of glucose  Plants store sugars for later use (inside plastids)

Functions of carbs in animals  Glucose: chemical fuel for respiration (mono)  Lactose: makes up some solutes in milk (di)  Glycogen: glucose storage in liver and muscles (poly)

Functions of carbs in plants  Fructose: found in fruits; make them sweet (mono)  Sucrose: transported through phloem (di)  Cellulose: components of cell walls (poly)

Fig. 5-8 b Glucose monomer Cellulose molecules Microfibril Cellulose microfibrils in a plant cell wall 0.5 µm 10 µm Cell walls

Starch and Cellulose Digestion  Enzymes that digest starch by hydrolyzing  linkages can’t hydrolyze  linkages in cellulose  Cellulose in human food passes through the digestive tract as insoluble fiber

Chitin – a structural polysaccharide  Found in the exoskeleton of arthropods  Structural support for the cell walls of many fungi

Lipids  Hydrophobic – they mix poorly with water  Mostly hydrocarbon regions – nonpolar

Fats - CHO  1 glycerol (alcohol with 3 carbons) + 3 fatty acids (long chain of CH connected to carboxyl) Fatty acid (palmitic acid) (a) Dehydration reaction in the synthesis of a fat Glycerol

Fig. 5-11b (b) Fat molecule (triacylglycerol) Ester linkage Esterification

Saturated vs. Unsaturated  have the maximum number of hydrogen atoms possible and no double bonds  have one or more double bonds Saturated fatty acids Unsaturated fatty acids

Animal vs. Plant  Most animal fats  No double bonds makes the tail flexible  They can pack together tightly  Solid at room temp  Most plant fats (oils)  Double bonds makes them bent  Can’t pack together  Liquid at room temp  Hydrogenated = added Hs to make them saturated Saturated FatsUnsaturated Fat

What do fats do?  Too much saturated fat is bad for you  Atherosclerosis – plaques of fat in blood vessels  Hydrogenation forms trans fats – even worse!  Store lots of energy  2x as much as carbs!  Cushions vital organs  Insulates the body Bad thingsGood things

Phospholipids – make up cell membranes (b) Space-filling model (c) Structural formula Phospholipid symbol Fatty acids Hydrophilic head Hydrophobic tails Choline Phosphate Glycerol Hydrophobic tails Hydrophilic head  One fatty acid is replaced by a phosphate

Phospholipid Bilayer – Cell Membrane Polar Phosphate Heads Non-Polar Fatty Acid Tails

Steroids  4 fused carbons rings  Hormones – cell to cell signaling (long distance)  Cholesterol – stabilizes cell membranes  Made in liver  Too much is bad

Other functions of lipids  Protection of vital organs  To insulate the body  They form the myelin sheath around some neurons

Proteins – CHON(S)  Needed for almost everything that happens in your cells/body FunctionExample EnzymesAmylase TransportHemoglobin MovementActin, myosin Cell RecognitionAntigens ChannelsMembrane Proteins StructureCollagen, keratin HormonesInsulin ProtectionAntibodies

Polypeptides  Polymers of animo acids  Not a protein – doesn’t have full structure

R groups – ~20 in humans  The R group’s structure determines the property of the amino acid  Example: Alanine = CH 3 CH 3 is nonpolar and so is Alanine Alanine (Ala or A)

Fig. 5-17a Nonpolar Glycine (Gly or G) Alanine (Ala or A) Valine (Val or V) Leucine (Leu or L) Isoleucine (Ile or I ) Methionine (Met or M) Phenylalanine (Phe or F) Tryptophan (Trp or W) Proline (Pro or P)

Fig. 5-17b Polar Asparagine (Asn or N) Glutamine (Gln or Q) Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C) Tyrosine (Tyr or Y)

Fig. 5-17c Acidic Arginine (Arg or R) Histidine (His or H) Aspartic acid (Asp or D) Glutamic acid (Glu or E) Lysine (Lys or K) Basic Electrically charged

Peptide Bond (“polypeptide”)  Made by dehydration synthesis (condensation)

Nucleic Acids - CHONP  Polymer – nucleic acid  Monomer - nucleotide  Hold the information to make polypeptides (on genes)

Nucleic Acids  Each nucleotide has 3 parts:  Nitrogenous base  Sugar  Phosphate group

Sugars  Always 5 carbons:  Ribose – RNA  Deoxyribose – DNA

Nitrogenous Bases  Nitrogen containing rings (c) Nucleoside components: nitrogenous bases Purines Guanine (G) Adenine (A) Cytosine (C) Thymine (T, in DNA)Uracil (U, in RNA) Nitrogenous bases Pyrimidines

Double Helix  DNA strands are complementary  A—T  C—G

Double Helix  Spiral shape of DNA coil  Held together by H- bonds between bases  And van der Waals attractions