Structure and Function of Large Biological Molecules Macromolecules

+ Structure and Function of Large Biological Molecules

+ Macromolecules n 4 main types: carbohydrates, lipids, proteins, nucleic acids n Large molecules typically made of smaller subunits n Carbs, Nucleic acids, proteins = Polymers – built from monomers

+ Synthesizing and Decomposing Macromolecules: Both processes use enzymes! n Dehydration Synthesis: “adding” monomers together to form a polymer. n Removal of an H 2 O molecule covalently bonds the monomers. n Hydrolysis: Breaking down of polymers into smaller subunits using water. n The H bonding to one monomer and the OH bonding to the other.

+ Carbohydrates Sugars and sugar chains – the fuel and building materials of life

Monosaccharides: Simple Sugars Sugar units have empirical formula: CH 2 O C chains range from 3 -7 + Enantiomers – different sugars! 5 -6 C typically are aromatic!

+ Glucose is Life n C 1 and C 5 bond to form ring n Glucose is a primary cellular fuel source for respiration n Glucose is also used as a building block for many other macromolecules n Can be stored for later use as di- and polysaccharides n 2 forms of the rings α and β http: //pslc. ws/macrog/kidsmac/toon_glu. htm

+ α-glucose and β-glucose

+ Disaccharides Through Dehydration Synthesis n 2 monosaccharides bonded n Linkages are named by the carbons that bond n Glycosidic linkage formed by dehydration synthesis n Maltose is a 1 -4 glycosidic linkage n Sucrose is a 1 -2 glycosidic linkage n Disaccharides: maltose, sucrose, lactose

+ Types of Glycosidic Linkages 1– 4 glycosidic linkage Maltose 1– 2 glycosidic linkage Sucrose

+ Polysaccharides – huge chains of monosaccharides n Each monomer is added through dehydration synthesis n Huge chains are good for storage and even structure n Function of the poly- determined by type of linkage and sugar monomers

+ Storage Polysaccharides n Plants create starch for storage n Glucose monomers = stored energy n Stored in plastids n Formed by 1 -4 glycosidic linkages

+ n Animals synthesize glycogen n Glucose monomers – high branched n Stored in liver and muscle Storage Polysaccharides

Structural Polysaccharides § Cellulose – major component of cell walls § Most abundant organic molecule on earth § Glucose monomers – different linkages! § Different forms of glucose but same 1 -4 linkage! +

+ Cellulose: Tough Cell Walls… Why? n Cellulose is straight chains and never branched n Form parallel chains n Different enzymes to digest! n Fiber n Chitin = exoskeletons

+ Lipids Hydrophobic, diverse molecules

+ Lipid Basics: Hydrophobic energy chains Lipids are diverse in function but similar in their hydrophobicity Typically have large regions that are hydrocarbon chains

+ Building Blocks of Fats n Fatty acid chains n Glycerol

+ Triacylglycerol (TAGs) AKA Triglycerides Ester linkage! Dehydration Synthesis! x 3

+ Saturated and Unsaturated Fats Naturally occurring fatty acids have cis double bonds

+ Cis vs Trans Fats

Figure 5. 12 Hydrophobic tails Hydrophilic head + Choline Phosphate Glycerol Fatty acids Hydrophilic head Hydrophobic tails (a) Structural formula (b) Space-filling model (c) Phospholipid symbol

Figure 5. 13 + Hydrophilic head Hydrophobic tail WATER

+ Steroids n Steroids have 4 carbon ring structures n Can be hormones or cholesterol

+ Proteins Multiple units, multiple uses

+ Functions of Protein n Proteins account for ~50% of the dry mass of most cells n Proteins act as catalysts, play roles in defense, storage, transport, and cellular communication n Greatest diversity in structure and function

Figure 5. 15 -a + Enzymatic proteins Defensive proteins Function: Selective acceleration of chemical reactions Example: Digestive enzymes catalyze the hydrolysis of bonds in food molecules. Function: Protection against disease Example: Antibodies inactivate and help destroy viruses and bacteria. Antibodies Enzyme Virus Bacterium Storage proteins Transport proteins Function: Storage of amino acids Function: Transport of substances Examples: Hemoglobin, the iron-containing protein of vertebrate blood, transports oxygen from the lungs to other parts of the body. Other proteins transport molecules across cell membranes. Examples: Casein, the protein of milk, is the major source of amino acids for baby mammals. Plants have storage proteins in their seeds. Ovalbumin is the protein of egg white, used as an amino acid source for the developing embryo. Transport protein Ovalbumin Amino acids for embryo Cell membrane

Figure 5. 15 -b + Hormonal proteins Receptor proteins Function: Coordination of an organism’s activities Example: Insulin, a hormone secreted by the pancreas, causes other tissues to take up glucose, thus regulating blood sugar concentration Function: Response of cell to chemical stimuli Example: Receptors built into the membrane of a nerve cell detect signaling molecules released by other nerve cells. High blood sugar Insulin secreted Normal blood sugar Receptor protein Signaling molecules Contractile and motor proteins Structural proteins Function: Movement Examples: Motor proteins are responsible for the undulations of cilia and flagella. Actin and myosin proteins are responsible for the contraction of muscles. Function: Support Examples: Keratin is the protein of hair, horns, feathers, and other skin appendages. Insects and spiders use silk fibers to make their cocoons and webs, respectively. Collagen and elastin proteins provide a fibrous framework in animal connective tissues. Actin Myosin Collagen Muscle tissue 100 m Connective tissue 60 m

+ Protein Building Blocks - Peptides n All proteins are made of 20 different amino acids n Amino end n Carboxyl end n R = functional group α CARBON

+ Proteins are Polypeptides n Polymers of peptides are made through the formation of peptide bond n Carboxyl end of one AA bonds to the amino end of adjacent AA n Dehydration reaction to form peptide bond n. N terminus (+) and C terminus (-)

Figure 5. 16 + Nonpolar side chains; hydrophobic Side chain (R group) Glycine (Gly or G) Alanine (Ala or A) Methionine (Met or M) Isoleucine (Ile or I) Leucine (Leu or L) Valine (Val or V) Phenylalanine (Phe or F) Tryptophan (Trp or W) Proline (Pro or P) Polar side chains; hydrophilic Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C) Electrically charged side chains; hydrophilic Tyrosine (Tyr or Y) Asparagine (Asn or N) Glutamine (Gln or Q) Basic (positively charged) Acidic (negatively charged) Aspartic acid (Asp or D) Glutamic acid (Glu or E) Lysine (Lys or K) Arginine (Arg or R) Histidine (His or H)

Figure 5. 16 a + Nonpolar side chains; hydrophobic Side chain Glycine (Gly or G) Methionine (Met or M) Alanine (Ala or A) Valine (Val or V) Phenylalanine (Phe or F) Leucine (Leu or L) Tryptophan (Trp or W) Isoleucine (Ile or I) Proline (Pro or P)

Figure 5. 16 b + Polar side chains; hydrophilic Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C) Tyrosine (Tyr or Y) Asparagine (Asn or N) Glutamine (Gln or Q)

Figure 5. 16 c + Electrically charged side chains; hydrophilic Basic (positively charged) Acidic (negatively charged) Aspartic acid (Asp or D) Glutamic acid (Glu or E) Lysine (Lys or K) Arginine (Arg or R) Histidine (His or H)

Figure 5. 17 + Peptide bond Dehydration synthesis New peptide bond forming Side chains Backbone Amino end (N-terminus) Side chains vary in their charge, polarity, length Peptide Carboxyl end bond (C-terminus)

+ Protein – Structure Dictates Function n 3 D structure of each protein is unique n Structure dictates function n Structure is determined due to 4 levels of folding n Most fundamental level of folding is sequence of AA

Figure 5. 19 + Antibody protein Protein from flu virus

Primary Structure AA Sequence n Sequence of AA n Read in order from N to C n Dictates secondary, tertiary, quaternary levels

+ Secondary Structure n Regions of a peptide chain that are coiled or folded into patterns n Regulated by H bonding of atoms in the peptide backbone n α-Helix n β-sheets

+ Tertiary Structure Overall shape of a protein Stabilized by R groups and how they interact Hydrophobic Interactions Disulfide Bridges

Quaternary Structure The interaction of multiple polypeptide chains Forms a functional protein Separate peptide chains

+ Chaperonins: Protein Folders

+ Protein Structure in a Cell n Folding n Other is spontaneous proteins aid in this process n Denaturation – unraveling/misfolding of a protein

+ Nucleic Acids Blueprints of life

+ Nucleotides n Monomers of nucleotides n 2 types: DNA and RNA n Deoxyribonucleic n Ribonucleic acid

+ DNA to RNA to Protein n Genetic material n Inherited n Codes n DNA for all genes RNA Protein

+ Nucleotides Types n n 2 Types of sugars n Ribose n Deoxyribose 2 Categories of N bases n Purines (Pure As Gold) n n A and G Pyrimidines n C, T, U

+ Polynucleotides – Nucleic Acids n Nucleotides are linked by a phosphodiester bond n Adjacent sugars are linked from 5’ end to first sugar to 3’ of next sugar n. N Bases point inwards and provide “sequence” of DNA

+ Structure of DNA n Double helix n Sugar-phosphates are antiparallel n Bases pair 1 purine to 1 pyrimidine