building blocks of life an introduction. carbon—the backbone of biological molecules carbon is...
Post on 20-Dec-2015
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Carbon—The Backbone of Biological Molecules
• Carbon is unparalleled in its ability to form large, complex, and diverse molecules
• Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds
Carbon atoms can form diverse molecules by bonding to four other atoms
Electron configuration determines the kinds and number of bonds an atom will form with other atoms
With four valence electrons, carbon can form four covalent bonds with a variety of atoms◦makes large, complex molecules possible
The valences of carbon and its most frequent partners (hydrogen, oxygen, and nitrogen) are the “building code” that governs the architecture of living molecules
Macromolecules
Within cells, small organic molecules are joined together to form larger molecules
Macromolecules are large molecules composed of thousands of covalently connected atoms
polymers built from monomers
• Monomers build polymers linked together by covalent bonds
• Three of the four classes of life’s organic molecules are polymers:◦Carbohydrates◦Proteins◦Nucleic acids◦Lipids
The Synthesis and Breakdown of Polymers
Monomers form larger molecules by condensation reactions called dehydration reactions
Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction
Short polymer Unlinked monomer
Dehydration removes a watermolecule, forming a new bond
Dehydration reaction in the synthesis of a polymer
Longer polymer
Hydrolysis adds a watermolecule, breaking a bond
Hydrolysis of a polymer
Carbohydrates
Sugars and sugar polymersMonosaccharides
◦Simple sugars◦glucose
Carbonyl group
Hydroxyl group
Carbohydrates
Disaccharides◦2 or more monosaccharides joined by glycosidic
linkage, covalent bond by dehydration reaction◦Glucose + fructose sucrose
Carbohydrates
Storage◦Plant starch◦Stored energy can be broken down by
hydrolysis into glucose◦Animal polysaccharide
Glycogen◦Stored in liver and muscles◦Used for short term energy
Carbohydrates
Structure ◦Cellulose: cell walls
Requires an enzyme for animals to break it down◦Chitin: exoskeleton of arthropods and fungi
Lipids
Fats, oils, waxes◦Mix poorly with water◦Fats
Large molecules of glycerol and fatty acid chains connected by dehydration
Proteins
Polymer of amino acids called polypeptidesFunctions
◦Enzymes◦Storage of amino acids◦Hormones◦Motor◦Defense◦Transport◦Receptors for chemical stimuli◦structure
Proteins
Amino acids◦20 amino acids from 1000’s of proteins◦Side chains “R” determines the properties
Hydrophillic:polar Hydrophobic: non polar Hydrophillic: electric charge
Proteins
2°◦Alpha helix: hair◦β pleated sheets: spider web◦Held together by hydrogen bonds between
amino groups
Proteins
3°◦Interactions between side chains “R”
Hydrogen bonds Ionic bonds Disulfide bonds Van der Waals