Download
1 / 64
640 likes | 805 Vues
This chapter explores macromolecules, which are larger molecules constructed from smaller ones, particularly focusing on carbohydrates, lipids, proteins, and nucleic acids. It describes the four major classes, detailing how monomers link to form polymers through condensation reactions. Additionally, it covers the roles of different macromolecules, including energy storage in carbohydrates and the structural function of lipids. Proteins' diverse structures and functions highlight their importance in biological systems. This comprehensive overview provides insights into the chemistry of life.
E N D
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.
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)
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)
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.
