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Macromolecules AP Biology Lecture Series Part 2 Big Concepts and Ideas • How are the molecules of biological systems constructed? • Why are particular groups of molecules needed in biological systems? • How do the interactions of biological molecules lead to the emergence of life functions? Macromolecules • Huge (on molecular scale) • Accomplish all life functions • Made predominately of a few common atoms, repeated and in multiple configurations • Can be incredibly complex • Carbohydrates, lipids*, proteins, nucleic acids Macromolecules • Polymer – long molecule consisting of many similar subunits (3 of 4 major molecules are polymers – excludes lipids) – Subunits linked with covalent bonds • Monomers – the repeating subunits of polymers; building blocks • Building/breaking processes rely on H2O Polymer Synthesis & Breakdown • Term note: Synthesis = to make or form • Condensation Reactions – Dehydration reactions (water removed) – Bonds form between two monomers (one donates –OH, other –H) – Forms chain and complexity (anabolic) – Requires energy (endergonic) – Facilitated by enzymes Polymer Synthesis & Breakdown • Term note: Hydro = water; Lysis= to split • Hydrolysis Reactions – Break bonds between monomers using water (H2O goes into reaction) – Reduces complexity (catabolic) – Released energy (exergonic) – Facilitated by enzymes – Allows food to be digested Carbohydrates! Carbohydrates • Sugars or starches (common terms) • Monomer = monosaccharide – C, H, O in repeat w/1:2:1 ratio – # of C’s varies by monomer – Two monomer units = disaccharide • Polymer = polysaccharide • General use: short term energy & structure Carbohydrates Functional groups Critical for metabolic processes Critical in DNA Carbohydrates • Hexose sugars are the most "famous" monosaccharide • Three kinds: Glucose, Galactose, & Fructose • They are typically shown as carbon rings. Carbohydrates • Combine 2 monomers by dehydration synthesis get a "disaccharide” • Glucose + Glucose = Maltose ("Malt sugar") • Glucose + Fructose = Sucrose ("Table sugar") • Glucose + Galactose = Lactose ("Milk sugar") Dehydration Synthesis… Polysaccharides • Massive polymers of sugars are called "polysaccharides” • Two main functions in organisms Energy storage and structure Polysaccharides – Energy storage • Polysaccharides are great for short term storing of energy. • In plants, amylose ("starch") is the major energy storage polysaccharide. • Animals use glycogen for energy storage Polysaccharides - Structure • Cellulose = major component of plant-like cell walls. – Most abundant organic compound on Earth! • The difference between starch and cellulose is in the linkages between glucose units. – Starch = alpha linked. Cellulose = beta linked – Differ in placement of hydroxyl group Cellulose – Strong! Herbivores and Cellulose • Digestive enzymes that break down starch (alpha linkages) can’t break cellulose (beta linkages) due to shape • Humans can’t digest! (insoluble fiber) • What about herbivores (and termites!)?? – Harbor cellulose-digesting prokaryotes in 1st stomach (rumen) – Other mammals - Polysaccharides - Structure • Chitin Use by arthropods (insects, spiders, crustaceans) to build exoskeleton • Also found in fungi cell walls AND dissolving stitches! • Similar to cellulose except has nitrogen-containing group Polysaccharides - Structure • Peptidoglycan = another modified polysaccharide. Used in bacterial cell walls Lipids! Lipids • Class of biomolecules that doesn’t include true polymers – and not big enough to be called “macro” • Mix poorly with water (hydrophobic) • Mostly consist of nonpolar hydrocarbon regions (HC) – Some polar bonds associated with O • Include waxes, some pigments, fats, and oils Lipids • Made up of C, H, and O (notice a pattern??) • Used for long term energy storage and insulation • 3 major groups – Triglycerides – Phospholipids – Steroids Fats (Triglycerides) • Triglyceride (or triacylglycerol) is made of one glycerol & 3 fatty acids. – Fatty acids = long carbon skeleton – C—H bonds = reason fatty acids are hydrophobic • Water molecules bind to each other and exclude the fat • Connected by dehydration synthesis x 3 (ester linkages) Sketch – Simplify Glycerol Fatty acid chains Saturated vs. Unsaturated Fats • Refers to the bonding of carbon in the fatty acids. – Bonding influences shape and properties • Saturated = no double bonds between carbons. – Solid at room temp molecules packed tight – Food fats (butter, lard) Saturated vs. Unsaturated Fats • Unsaturated = at least one double bond. – Not solid at room temp (oils, plants, fish) molecules can’t pack tight because of kinks – Health note – “hydrogenated oil” have been chemically altered to convert to saturated fats!! • Which ones are healthier for you? Fats and Health • Saturated fats contribute to cardiovascular disease – Deposits called plaques form on blood vessel walls, creates bulges and alters flow • Trans fats Chemically altered unsaturated but with trans double bonds – Raise bad cholesterol (LDL) and lower good cholesterol (HDL) Phospholipids • Essential structures of cell membranes • Form fits function (at molecular level) – Polar heads (face outward, come in contact with H2O) – Nonpolar tails (face inward, away from water) – When put in water, they self-assemble into bilayers – Form semi-permeable membranes, regulate transport Steroids • Lipids with carbon skeleton and 4 fused rings • Types of steroids vary by chemical groups attached to rings • Include hormones and cholesterol Steroids • Cholesterol: – Common in animal cell membranes – Produced in liver – Precursor for synthesis of other steroids (including sex hormones) – Fats impact cholesterol levels Proteins! Proteins • Foundation of nearly every dynamic function in an organism • Account for +50% of dry mass • Made of C, H, O, N, and some S • Incredibly diverse and highly specific – Humans Tens of thousands, each with different structure and function Proteins • Most enzymes are proteins Without enzymes, life could not exists! – Enzymes = catalysts; speed up chemical reactions without being used up in the reaction • “Workhorses” that keep cells running Proteins Basic Functions • • • • • • • • Enzymes as catalyst for reactions You’ll create a Structure/support Graphic Organizer for Storage of amino acids these! Transport of substances Hormones that coordinate activities Receptors that allow cells to respond to stimuli Movement via contraction + motor proteins Protection against disease w/defense proteins Protein Monomers & Polymers • Amino Acids building blocks of proteins – 20 standard AA’s that are part of genetic code – 21st Selenocysteine (relatively new!) – Central carbon with 4 attachments • • • • Amino group Carboxyl group Hydrogen R-group (varies): – Also called side chain (important with folding!) Protein Monomers & Polymers • Peptide bonds link amino acids together (dehydration reaction between carboxyl of one AA and amino group of another) • Resulting polymer = polypeptide chain Amino Acids have directionality… N-Terminus C-Terminus Protein Structure • Diversity of AA’s leads to very diverse 3D structures of proteins determines function! • 4 basic levels to structure… Primary Structure • Sequence of AA’s in one polypeptide chain • Determined by genetic code (codon/anticodon matching of RNA to AA’s) – Literally “reading” the RNA instructions • AA’s held together with peptide bonds Secondary Structure • Regular, repeating 3D segments of coils or folds • Form because of hydrogen bonding in the C/N backbone of the polypeptide chain (thus all proteins have similar secondary structure) – All proteins have the same C and N groups – Result of electronegativity! H’s attracted to O’s • 2 shapes Alpha helix and Beta pleated sheet Tertiary Structure • Overall shape of the polypeptide due to interactions between side chains (R groups) • Help stabilize the protein Tertiary Structure • Mechanisms: – Hydrophobic Interaction: AA’s with nonpolar side chains end up at the core of the structure (away from water) • Held together with van der Waals interactions – H bonds between polar side chains – Ionic bonds between +/- side chains – Disulfide Bridges between two cysteine monomers (those with –SH groups) • S of one bonds with S of another Van der Waals Interactions • Weak attractions between molecules due to localized charge fluctuations • Electrons are not always symmetrically distributed – Even nonpolar molecules may have slightly negative and positive regions Quaternary Structure • Two or more polypeptide subunits aggregated into one functional macromolecule – Optional level (not all proteins form this) • Examples: – Collagen (40% of the proteins in a human body!) – Hemoglobin Denaturation • Change in the structure of a protein – Changes, reduces, or destroys function • Conditions that lead to denaturation… Denaturation • Change in the structure of a protein – Changes, reduces, or destroys function • Conditions that lead to denaturation: – Temperature (heat) – pH – Salt concentration – Change of overall environment (e.g. aqueous solution to organic solution) – Chemicals that disrupt tertiary bonds The original foundation… • How might primary structure be altered? • What happens if primary structure is change? Case Example: Sickle-Cell Disease • Altered hemoglobin structure – Mutation leads to valine (hydrophobic) replacing glutamic acid (hydrophilic) in beta chains – Sickle-shaped hemoglobin gets clumpy, doesn’t hold as much O, and can get stuck in blood vessels Understanding Protein Folding • Incredibly complex – don’t know all patterns or reasons! • Several intermediate structures before final • Methods for tracking involve chaperonin proteins – Assist in the proper folding of other proteins Nucleic Acids! Nucleic Acids • Blueprint for proteins + information storage molecules • Composed of C, H, O, N, and P • Two types: DNA & RNA • DNA = genetic material organisms inherit from parents Nucleic Acids • Monomers = nucleotides • Nucleotide Structure: – Phosphate + sugar backbone • Deoxyribose in DNA • Ribose in RNA – Nitrogenous base • • • • Adenine Thymine (Uracil in RNA) Cytosine Guanine RNA vs. DNA