Structure and Function of Macromolecules Chapter 5 Macromolecules Macromolecules Multiple Units Synthesis of Dimers and Polymers

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1 Structure and Function of Macromolecules Chapter 5 Macromolecules Giant molecules weighing over 100,000 daltons Emergent properties not found in component parts Macromolecules Multiple Units meris = one part a relatively small molecule May repeat to make a more complex molecules two parts Complex molecule made of two units of a monomer many parts A long complex molecule made of similar or identical monomers Dimers & polymers connected by bonds Synthesis of Dimers and Polymers Synthesis by reactions = reactions Because molecule of lost in process One monomer contributes H +, other contributes OH - Process repeats while building polymer Requires input Aided by 5-1

2 Breakdown of Dimers and Polymers Broken down by water + break Bonds between monomers break with addition of H + goes on one monomer OH - goes on the other e.g. During digestion Breakdown large molecules Redistribute parts Re-assemble parts into new polymers elsewhere Four Classes of Macromolecules Carbohydrates and their polymers (single, or simple sugars) e.g. glucose Monomers (two monosaccharides joined by condensation) e.g. sucrose (table sugar) Dimers (many sugars joined by condensation reactions) e.g. cellulose Polymers 5-2

3 Monosaccharides Generalized formula: e.g. C 6 H 12 O 6 (glucose) Name usually ends in Multiple hydroxyl groups One carbonyl group Size of carbon skeleton varies (3-7 carbons long) Most common: Some Monosaccharides Linear Form Monosaccharides Form at Equilibrium Uses for Monosaccharides Major source of for cells most common Used as component parts in Disaccharides (dimers) Polysaccharides (polymers) Carbon skeletons used for of small organic molecules Amino acids Fatty acids Disaccharides Two monosaccharides joined by linkage (dehydration reaction) e.g. maltose (2 glucoses) ingredient in beer production e.g. sucrose (glucose + fructose) transport sugar in plants 5-3

4 Polysaccharides Polymers of sugars (monosaccharides) Several hundred to several thousand monomers linkages Functions related to architecture and position of glycosidic linkages Two groups of polysaccharides polysaccharides Starch Glycogen polysaccharides Cellulose Chitin Storage Polysaccharides Starch repeating glucose monomers Storage in Helical form Amylose (simplest form) unbranched with 1 4 linkages Amylopectin (more complex) branches at 1 6 linkages Storage Polysaccharides Glycogen repeating glucose monomers Storage in (liver and muscle) storage not long-term Can t store enough to sustain for more than a day Similar to amylopectin, but more branched Structural Polysaccharides Cellulose found in cell walls in plants Polymer of glucose (like starch) Every other glucose is upside down Due to differential placement of OH group β-glucose has OH ring α-glucose has OH ring 5-4

5 Starch vs Cellulose with α-glucose 1-4 linkages with β-glucose 1-4 linkages Structure of Cellulose Straight chain (starch is helical) No branching bonding between parallel chains Digestion of Starch and Cellulose Enzymes that digest starch (α-glucose) cannot digest cellulose (β-glucose) Most cannot digest cellulose Use cellulose as fiber to aid movement of food through the gut What can digest cellulose? Some Some Present in the of cows and other ruminants (1 st compartment of stomach) Present in the gut of termites Structural Polysaccharides Chitin Glucose monomer with N-containing branch at #2 carbon Found in cell walls of Found in exoskeletons of Insects Spiders Crustaceans (lobsters, shrimp, etc) 5-5

6 Lipids macromolecules Not polymers ( repeating monomers) Smaller than polymeric macromolecules Mostly polar bonds Grouped together because of affinity for water Major groups Minor groups Waxes Some pigments Lipids Fats Formed by synthesis Glycerol + 3 fatty acids carbon chain, each C has -OH acids Long chain w/ carboxyl functional group on end May be, or may be 3 fatty acids Lipids Fats Purpose: storage Much more compact than polysaccharides Energy rich (, like petroleum) Animals use in (fat) tissue (compact) Also protects organs Plants use in seeds (compact) 5-6

7 Variation of chains of double bonds of double bonds Fatty Acids and Fats fatty acid double bonds All bonds w/ hydrogen Pack together at room temperature Animal origin Fatty Acids and Fats fatty acid One or more bonds in fatty acid tails Can pack tightly at room temperature Plant (or fish) origin Lipids Phospholipids Similar to fats fatty acid tails (not 3) group on third hydroxyl of glycerol Negative charge Polar/charged molecules may associate tail head Phospholipid Cell membrane components 5-7

8 Phospholipid Bilayers in Cell Membrane bilayer Cell membrane components Hydrophobic tails to the of bilayer Hydrophilic heads to the of bilayer Lipids Steroids Lipids with special carbon skeleton Four fused Different functional groups important (Fig. 5.14) Precursor to other steroids e.g. Testosterone e.g. Progesterone e.g. Estrogens Proteins From Greek proteios = first place Important class of molecules More than half the dry-weight of cells Complex Multiple multiple structures Structural Regulate metabolism Accelerate specific reactions in cell 5-8

9 Building Blocks of Proteins All proteins are complex polymers All use same monomers Amino Acids (monomers) = Amino group and carboxylic acid group Polymer of amino acids One or more polypeptides, folded and coiled Amino Acids Organic molecules with both group and group Amino group bonded to α (alpha) carbon variable group, or side chain determines which amino acid R-groups different R-groups give amino acids From hydrogen to complex chains with ring structures and functional groups R-group determines The of amino acid or of amino acid Nonpolar Amino Acids Determined by R-Group Polar Amino Acids Determined by R-Group Electrically Charged Amino Acids Determined by R-Group 5-9

10 Linking Peptides: the Bond Peptides linked by peptide bonds Formed by (condensation) reaction (triggered) by enzymes Reaction is between group and group Polypeptide has amino end and carboxyl end terminus and terminus Polypeptide to Protein Polypeptide long of peptides Protein into unique conformation How it folds determines function Four levels of protein structure Primary Structure Each protein has a unique of amino acids e.g. Lysozyme has 129 amino acids (enzyme that lyses cells) Arranged in a predetermined order Arrangement determined by genetics 20 possible a.a.s at each position ways of arranging a.a.s Change primary structure, can change rest of and change function 5-10

11 Amino Acid Substitution Single amino acid changes protein e.g. Normal hemoglobin to abnormal sickle-cell anemia Hemoglobin has 146 a.a.s Change glutamine to valine in ONE spot Hemoglobin collapses into sickled cells This variant is encoded on DNA and is inherited Normal and Sickled Red Blood Cells Secondary Structure or due to hydrogen bonding Coils e.g. lysozyme Folds sheets e.g. spider silk structure makes spider silk very strong Tertiary Structure Further of polypeptide Hydrophobic interaction Clustering of regions from water bonding Weak bonding Weak Disulfide bridges between cysteine monomers and very strong 5-11

12 Quaternary Structure or polypeptide units aggregated together e.g. collagen Fibrous protein w/coiled helices coiled again in supercoil like rope Makes good connective tissue e.g. hemoglobin Globular protein w/2 α and 2 β chains per hemoglobin molecule Denaturation A change in, or folding Occurs when conditions change concentration Change from to solvent Other chemicals Denaturing makes protein biologically Some can renature (reverse) when conditions change back Others are irreversible e.g. egg whites Protein Structure Overview Primary to Quaternary Nucleic Acids polymers Two types of nucleic acids (Deoxyribonucleic acid) OR (Ribonucleic acid) DNA is the repository of information of instructions for making proteins RNA is the reader, or messenger Directs protein synthesis Proteins mediate all other processes 5-12

13 DNA Storehouse of Instructions for all cellular and intercellular processes Does directly participate in those processes Doesn t even oversee processes Just a repository of the instructions Must be something to read the instructions and to direct synthesis so processes can proceed Reading DNA to Make Proteins DNA holds information RNA picks up the information from the DNA In nucleus in eukaryotes mrna relays information to ribosomes (in cytoplasm) Ribosomes made of RNA and protein RNA bring correct amino acids to ribosome In cytoplasm Polypeptide assembled at ribosome How many kinds of RNA are used in this process? Nucleotides: Component Parts of Nucleic Acids Nucleic acid polymers made from monomers Each nucleotide composed of parts group (5-carbon sugar) or base Pyrimidines smaller Purines larger 5-13

14 6-membered ring of carbon & nitrogen Three pyrimidines differentiated by functional groups (DNA or RNA) _ (DNA only) _ (RNA only) 6-membered ring of carbon & nitrogen Plus 5-membered ring fused to first ring Two purines differentiated by functional groups (DNA or RNA) (DNA or RNA) ucleotides Many nucleotides linked by phosphate groups and sugar of next nucleotide Results in repeating - backbone Appendages are nitrogenous bases Purines or pyrimidines of bases along backbone determines gene (e.g. AGGTAACT) = information to make one protein RNA is strand not very long Double Helix of DNA DNA is stranded very long Spiral form, wound around imaginary axis Sugar-phosphate are on Nitrogenous are in Bases are paired & held by bonds 5-14

15 Complementary Each base has a partner that it pairs with Adenine with Thymine Guanine with Cytosine Always a purine with a pyrimadine Strands are So if one strand reads AGGTAACTT Then the matching strand reads TCCATTGAA Predictable therefore easy to copy DNA DNA must be replicated before cell division Strands separate Each one is a for a new strand to be made Two identical copies are made of DNA makes (heritability) possible Mistakes in DNA Replication Mistakes relatively common Usually corrected by enzymes that check Sometimes mistakes slip through Next generation of cells will replicate change in DNA may resulting 5-15

16 Changing Proteins Help Us Track Evolutionary Relationships Many changes over results in variation in proteins handed down to offspring This results in protein differences in different or groups of organisms Differences in proteins from two populations may until the populations are very different from one another More proteins indicate changes a time ago Example of Evolutionary Relationships Using One Gene 5-16