Transcript Slide 1
The Structure and Function of Macromolecules Chapter 5 • Macromolecules - larger molecules made from smaller ones. • 4 major classes of macromolecules: carbohydrates, lipids, proteins, and nucleic acids. • 3 of these are polymers because they are made from individual building blocks called monomers. • Monomers - joined together through condensation or dehydration reaction (form macromolecules) • Requires energy; uses covalent bonds (links together monomers) • Water produced. Water produced as by-product • Hydrolysis breaks polymers into monomers. • Water added to polymer; breaks bonds, creates monomers (i.e. digestive process in animals) Carbohydrates • 1Carbohydrates - sugars (monomers) and polymers. • AMonosaccharides - simple sugars. • BDisaccharides - double sugars (monosaccharides linked together) • CPolysaccharides - polymers of monosaccharides. • Sugars named with –ose. • Monosaccharides needed for cellular work. • Help to synthesize other macromolecules. • 2 monosaccharides joined by glycosidic linkage to form disaccharide via dehydration. • Maltose - 2 glucose molecules. • Sucrose - 1 glucose, 1 fructose. • Polysaccharides - energy storage. • Starch - energy storage polysaccharide for plants. • Starch stored in plants plastids. • Herbivores access starch for energy. • Animals store energy as glycogen. • Humans - in liver and muscles. • Cellulose – polysaccharide; plant cell walls. • Many herbivores cannot digest cellulose (develop relationships with microbes) • Chitin - polysaccharide - makes up exoskeleton of arthropods (like crustaceans). • Chitin - found in fungi; functions as structural support. Chitin is used in surgery Lipids • Lipids - no polymers (exception) • Lipids nonpolar (no affinity for water) • Fat made from glycerol and fatty acids. • Glycerol - 3 carbon molecule with hydroxyl group and fatty acid; consists of carboxyl group attached to long carbon skeleton. • The 3 fatty acids in a fat can be same or different. • No carbon-carbon double bonds, molecule is saturated fatty acid (hydrogen at every possible position) • Form bad fats - solid at room temperature (butter, lard) No double-double bonds • 1+ carbon-carbon double bonds molecule is unsaturated fatty acid formed by removal of hydrogen atoms from carbon skeleton. • Form good fats - liquid at room temperature (oils) • Purpose of fat - energy storage. • Gram of fat stores 2X as much energy as gram of polysaccharide. • Fat also cushions vital organs. • Layer of fat can also function as insulation. • Phospholipids - 2 fatty acids attached to glycerol, phosphate group at 3rd position. • Fatty acid tails are hydrophobic, phosphate group and attachments form hydrophilic head. • When phospholipids added to water, self-assemble with hydrophobic tails pointing toward center, hydrophilic heads on outside. • Phospholipids in cell form bilayer; major component of cell membrane. Hydrophilic Hydrophobic • Steroids - lipids with carbon skeleton consisting of 4 fused carbon rings. • Cholesterol - component in animal cell membranes. • Cholesterol – also forms hormones (i.e. testosterone, estrogen) Cholesterol Proteins • Proteins - support, storage, transport, defenses, and enzymes. • Made in ribosomes in cell. • Proteins - amino acids linked together to form polymer. • 20 different amino acids that can be linked together to form thousands of different proteins. • Amino acids link - polypeptides combine to form proteins. • Amino acids made of hydrogen atom, carboxyl group, amino group, variable R group (or side chain). • R group makes amino acids different from one another. • R groups have different properties (i.e. hydrophobic) - form amino acids with different properties. • Amino acids joined by peptide bonds when dehydration reaction removes hydroxyl group from carboxyl end of 1 amino acid and hydrogen from amino group of another. • Shape of protein determines function. • Shapes - 3 dimensional determined by sequence of amino acids. • Primary structure of protein linear sequence of amino acids determined by genetics; problem in sequence can cause problem in ending protein created. • Secondary structure - hydrogen bonds at regular intervals along polypeptide backbone. • Two shapes are usually formed: alpha coils or beta sheets. • Tertiary structure determined by variety of interactions among R groups and between R groups and polypeptide backbone. • Interactions include hydrogen bonds, van der Waals forces, and ionic bonds. • Disulfide bridges help stabilize form. • Quarternary structure - joining of 2+ polypeptide subunits. • Collagen and hemoglobin examples. • Protein’s shape can change due to environment. • pH, temperature, or salinity (salt concentrations) change - protein can denature (starts to fall apart) • Some proteins can return to functional shape after denaturation, others cannot, especially in crowded environment of cell. Nucleic acids • Amino acid sequence of polypeptide programmed by a gene (regions of DNA, polymer of nucleic acids) • 2 types of nucleic acids: ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). • DNA gives information so RNA can create proteins. • Flow of genetic information - DNA > RNA -> protein. • Protein synthesis occurs in ribosomes. • Monomers of nucleic acids nucleotides. • Nucleotides made up of 3 parts: nitrogen base, five-carbon sugar, and phosphate group. • Nitrogen bases, rings of carbon and nitrogen, come in 2 types: purines and pyrimidines. • Pyrimidines - cytosine (C), thymine (T), and uracil (U in RNA only). • Purines - adenine (A) and guanine (G). • Pyrimidines - single six-membered ring; purines - five-membered ring. • In RNA - sugar is ribose; DNA sugar is deoxyribose. • Difference between sugars is lack of oxygen atom on carbon two in deoxyribose. • Nitrogen base sequence is different for different genes. • Genes are normally hundreds to thousands of nucleotides long. • The number of possible combinations of the four DNA bases is limitless. • RNA single-stranded - linear shape. • DNA forms double helix. • Sugar and phosphate forms backbone of double helix while nitrogen bases form connection between backbones. • Adenine (A) always pairs with thymine (T) guanine (G) with cytosine (C). • Due to six and five membered rings –shapes are compatible. • Know sequence of one side of double helix - figure out other. • Two strands are complementary. http://www.emunix.emich.edu/~rwinning/genetics/pics/dna2.gif • DNA used to show evolutionary similarities between species. • Two species that appear to be closely-related based on fossil and molecular evidence also more similar in DNA and protein sequences than more distantly related species.