Macromolecules The building blocks of life…
Macromolecules • Cells are composed of several types of biological macromolecules. • These function as energy-storage molecules, structural components, and in information storage, and are primarily composed of carbon, hydrogen and oxygen.
Carbohydrates • carbon, hydrogen & oxygen in a 1:2:1 ratio • exist as monosaccharides, disaccharides and polysaccharides • among the most abundant molecules on Earth
Monosaccharides • “single sugars” • general formula is (CH2O)n • glucose (top) and ribose (bottom) are monosaccharides
Disaccharides • “double sugars” • formed by dehydration synthesis from two monosaccharides • sucrose, maltose, and lactose are all disaccharides
Synthesis of Maltose - glucose -glucose maltose
Polysaccharides • straight or branched chains of monosaccharides connected by glycosidic linkages • storage (e.g. starch, glycogen) or structural (e.g. cellulose, chitin)
Polysaccharide Structure
Proteins • proteins are chains of amino acids connected by peptide linkages • order of amino acids for a particular protein is determined by the gene which codes for it
Amino Acid Structure • all amino acids have the same basic structure • “R” group is different for each amino acid amino group carboxyl group
Peptide Linkages cysteine glycine peptide linkage
Levels of Protein Structure • Primary • the specific sequence of amino acids • coded by DNA
Secondary • the folding or coiling of the amino acid chain • caused by interactions between “R” groups • -Helix • -Pleated Sheet
Tertiary • the unique three-dimensional shape of the protein • enzymes are globular proteins • collagen is a fibrous protein
Quaternary • interactions between separate polypeptide chains, or “subunits” • hemoglobin is composed of four subunits
Lipids • lipids are a group of hydrophobic molecules • “neutral fats” are uncharged lipids composed of glycerol and fatty acids • fats are solid at room temperature • oils are liquid at room temperature • steroids and phospholipids are amphiphilic
steroids all have the same basic structure of four fused hydrocarbon rings cholesterol is used to synthesize many other steroids in the body Steroid Structure cholesterol
Phospholipid Structure • glycerol backbone has two fatty acids and one charged inorganic phosphate group attached • primary component of cell membranes
Triglycerides • triglycerides are neutral fats • glycerol is the “backbone” molecule • fatty acids attach to glycerol by ester linkages • saturated fatty acids have no double bonds between carbons • unsaturated fatty acids have at least one double bond between carbons
Triglyceride Synthesis 3 fatty acids glycerol ester linkage triglyceride
Nucleic Acids • Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA) • composed of nitrogen-containing “bases” attached to a backbone of alternating pentose sugars and inorganic phosphate • function in information storage (DNA) and transfer (RNA)
“Bases” of DNA & RNA
DNA • deoxyribose sugar • adenine, guanine, cytosine, thymine bases • arranged in a double helix
RNA • ribose sugar • adenine, guanine, cytosine, uracil bases • single-stranded
References • MIT Biology Hypertextbook(1996) http://esg-www.mit.edu:8001/esgbio/lm/sugars/sugars.html (3/9/2001) • Farabee, M.J., (2001) An Online Biology Book. Chemistry 2: Water and Organic Molecules http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookCHEM2.html (3/9/2002) • A.C.D. Labs (2002) ChemSketch (Freeware), available for download at http://www.acdlabs.com/. Used for molecular structure diagrams.
