Biomolecules Biomolecules Monomers Polymers Carbohydrates monosaccharides polysaccharides fatty acids triglycerides Proteins amino acids polypeptides Nucleic Acids nucleotides DNA, RNA Carbohydrates Carbohydrates 3 categories contain carbon, hydrogen, & oxygen, usually in a 1:2:1 ratio general formula: (CH 2O) x n; n = # of C atoms highly polar molecules: many OH groups water soluble simple carbohydrates are sugars (mono- and disaccharides) glucose (C 6H 12O 6) is a major energy source for cells Polysaccharides Carbohydrates Monosaccharides (simple sugars) pentoses - 5 carbons (C5H10O5) hexoses - 6 carbons (C 6H 12O 6) Function: Glucose storage Fig. 2.2 1
Biol 219 Lec 3 Fall 2016 Dehydration Synthesis example Dehydration (condensation) reactions build up polymers from monomers. A-OH + H-B A B + H2O a water molecule is removed to form the new covalent bond Hydrolysis reactions break down polymers into monomers. A B + H 2O A-OH + H-B a water molecule is added to split the covalent bond Mostly non-polar molecules, rich in C-H bonds Classes of : 1. Fatty acids 2. Triglycerides 3. Phospholipids 4. Steroids 5. Eicosanoids Mostly insoluble in H2 O Functions: cell membrane (phospholipids, cholesterol) energy reserves (triglycerides ~2x as much as carbs per gram) signaling molecules (steroid hormones and eicosanoids) 10 Fatty acids may be: Fatty acids - building blocks (monomers) of most lipids - long carbon chains with H atoms attached ( hydrocarbon tail ) - one end has a carboxyl group (-COOH) Hydrocarbon tail Saturated - each C atom in the tail has 4 single covalent bonds 2 bonds to 2 adjacent C atoms 2 bonds to 2 H atoms saturated with hydrogen atoms carboxyl group Unsaturated - 1 or more DOUBLE covalent bonds between C atoms forms a kink in the tail monounsaturated 1 DB polyunsaturated 2 or more DBs 2
Biol 219 Lec 3 Fall 2016 Fatty Acids FYI: not on test Fatty acids Partially hydrogenated oils and trans fats chemically modified unsaturated fats; solidified with H hydrogenation adding H to fatty acids: unsaturated saturated trans double bonded fatty acids produced as a byproduct produced in manufacturing of some margarines & vegetable shortening increase risk of heart disease lowers HDL ( good cholesterol); raises LDL ( bad cholesterol) U.S. FDA now requires labeling of trans fats Most lipids are hydrophobic, which means they are insoluble in aqueous solutions but soluble in organic solvents. Most lipids are made from two kinds of molecules: glycerol and fatty acids joined by dehydration synthesis. On J uly 25, 2008, California bec ame the firs t s tate to ban trans fats in res taurants effec tiv e J anuary 1, 2010. 15 Phospholipids Triglycerides phosphate group links together: diglyceride (2 fatty acids + glycerol) and a nonlipid group amphipathic molecules - non-polar tail & polar head + Main function: - Energy storage in adipose tissue, liver and muscle cells Also padding and protection for some organs 18 3
Biol 219 Lec 3 Fall 2016 Phospholipids Steroids 4 hydrocarbon e.g. phosopholipid bilayer cell membrane hydrophilic heads face water Cholesterol - component of cell membranes; H2O inside cell & H2O outside cell hydrophobic - precursor to other steroids tails face each other Steroid hormones e.g. micelles droplets formed in H2O hydrophilic rings Types: - e.g., estrogen and testosterone (sex hormones) heads face water - other steroid hormones are important in metabolism and mineral balance e.g., cortisol, aldosterone ICF ECF Hydrophobic 19 20 Proteins Eicosanoids - modified fatty acids with a 5 C ring, - many function as paracrine substances ( local hormones ) - direct local cellular activity (vs. true hormones which are released into the bloodstream and travel throughout the body) Types: prostaglandin s prostacyclins thromboxanes Proteins Amino Acids building blocks of protein central carbon atom hydrogen atom amino group (-NH2) carboxyl group (-COOH) variable R group can be polar, non-polar, acidic (-) or basic (+) 23 4
Peptides combination of two or more amino acids Peptide bond links adjacent aa s (carboxyl group & amino group) Due to hydrogen bonding α-helix β-pleated sheet β-turns Fig. 2.3 Fig. 2.3 Disulfide bonds and weak bonds stabilize the tertiary structure of proteins. Fig. 2.3 5
Tertiary structure 3-dimensional folding from: 1) R group interactions mostly determine tertiary structure 2) interactions between polypeptide & surrounding H2O or lipid molecules 3) inner R group interactions Quaternary structure interaction among 2 or more protein subunits e.g. globular (hemoglobin) or fibrous (collagen or keratin) 31 Fig. 2.3 Protein Structure Fibrous proteins Pleated sheets or chains of helices Insoluble in water Important structural function (collagen, keratin) Globular proteins Complex tertiary structure Soluble in water Lipid carriers in blood, enzymes Protein Denaturation - unfolding of proteins due to drop in ph and/or increased temperature à causes hydrogen bonds to break (= shape change) Nucleic Acids Can be reversible (mild changes) or irreversible (extreme changes) 35 6
Nucleic Acids Deoxyribonucleic acid(dna) forms the genetic code inside each cell and regulates most of the activities that take place in our cells throughout a lifetime. Ribonucleic acid (RNA) relays instructions from the genes in the cell s nucleus to guide each cell s assembly of amino acids into proteins by the ribosomes in the cytoplasm. Nucleic Acids Nucleotides are the building blocks (monomers) of DNA and RNA Nucleotides have 3 molecular parts: 1. pentose sugar (ribose or deoxyribose) 2. phosphate group 3. nitrogenous base (5 types: A, G, T, C, U) 38 The Nitrogenous Bases Purines double ring Adenine (A) Guanine (G) Pyrimidines single ring Cytosine (C) Thymine (T) DNA only Uracil (U) RNA only Fig. 2.4 40 Deoxyribonucleic acid (DNA) DNA located in cell s nucleus stores genetic information sugar is deoxyribose sugar + phosphate form backbone nitrogenous bases point inward à Forming: double stranded double helix structure 41 7
DNA DNA strands are held together by hydrogen bonds between complementary nitrogenous bases Complementary base pairs shape and polarity of bases only allows formation of H bonds between: adenine (A) --- --- thymine (T) --- guanine (G) --- cytosine (C) Ribonucleic Acid (RNA) sugar is ribose mostly single stranded (also 2º and 3º structures in trna and rrna)... base pairing: A...U, G...C... Classes of RNA messenger (mrna) transfer (trna) ribosomal (rrna) RNA relays instructions from the genes in the cell s nucleus to guide each cell s assembly of amino acids into proteins by the ribosomes in the cytoplasm. 43 44 (1) Sugar: DNA = deoxyribose RNA = ribose DNA vs. RNA Adenosine Triphosphate (ATP) a high-energy nucleotide (2) Nitrogenous bases: DNA = A G C T RNA = A G C U (3) Strands: DNA = double stranded RNA = mostly single stranded ATP is the energy currency molecule of the cell Phosphorylation - addition a high-energy phosphate group to ADP to form ATP 45 8