Lipids & Proteins and Enzymes

Lipids Lecture 04.27.21 Background: oils, fats, waxes, steroids, cholesterol, and fat - soluble vitamins Lipids are a family of bio-molecules that have the common property of being soluble in organic solvents but not in water (e.g., either, benzene, acetone, chloroform) Unlike the proteins, nucleic acids, and polysaccharides, lipids are NOT polymers Lipids are quite small molecules that have a strong tendency to associate together through noncovalent forces. Lipid a polar, hydrophilic "head region" connected to a very hydrophobic hydrocarbon "tail" portion. There are many types of lipids Fundamental building blocks of many lipids are long-chain carboxylic acids called fatty acids Fatty acids can be saturated, monounsaturated, or polyunsaturated Fatty acids ex: stearic acid-saturated fatty acid ex: Dleic acid cis and trans unsaturated Lauric acid: CH3(CH2)10CO₂H: Coconut Palmitic acid: CH3(CH2) 19 CO₂H: palm Palmitoleic acid: CH₃ (CH₃)₃ CH=CH (CH₂), CO₂H macadamia nuts 2 Physical properties of Fatty Acids Fatty acids fit close together in a pattern Strong attractions between carbon chain - Historical fact In the mid 1940s, Ulf von Evler (Sweden) discovered that lipid extracts of human semen contained active compounds that, on injection into animals stimulated smooth muscles, contraction of relaxation and affected the blood pressure. Because of their presumed origin in the prostate gland, he named these compounds prostaglandins. Prostaglandins Horomone-like substances - Eicosanolds - Broken down quickly Some increase/decrease in blood pressure Several nonsteroidal anti-inflamatory drugs (NSAIDS) SUCH as aspirin block the production of prostaglandins. By doing so, it decreases pain and inflammatory and is a fever reducer. Other examples: Ibuprofen, Naproxen. Saturated fatty acids are usually solids at room temperature Unsaturated fatty acids have lower melting points than saturated fatty acids due to double (fewer interaction) Carbon chains increase, more interaction occurs that require higher melting points Significant amount of energy and higher temperatures. are required to seperate the fatty acids and melt the fars Main functions: . 1. Provide means whereby fat-soluble nutrients leg., Sterols, vitamins) can be absorbed by the body. 2. Structural element of cell, subcellular components 3. Components of horomones and precursors of prostaglandin synthesis Waxes In natural waxes, a long-chain fatty acid is esterified to a long-chain alcohol The head group is weakly hydrophilic, therefore waxes are completly water- insoluble - They are also hydrophobic that they are water repellents: feathers Triglycerids [fats]: Employed in energy storage Consist of three fatty acids bound to a molecule of glycerol Major form of energy storage for animals hibernation A family of lipids composed of three fatty acids bonded through ester bonds to glycerol, a trihydroxy alcohol is Triacylglycerol Triacylglycerol fat that is solid at room temperature Most fats come from animal sources ↳ Stearic acid comes from an animal fat source Another term for triacylglycerol is oil - Some fats come from plant sources Oleic acid comes from olives Monounsaturated Clarge amount of oleic acid) - olive and peanut oil Polyunsaturated Clarge amount of fatty acids with 2 or more double bonds) - corn oils, cotton seeds unsaturated fatty acids because they pack together more tightly. Melting point of animal fats are higher than vegetable oil due to more saturated fatty acid Lipids: Chemical Reactions Hydrogenation converting double bonds to single bonds - Hydrolysis split by water - Saponification soap making Cholesterol in the body is obtained from eating meats, eggs, and milk Synthesized by the liver from fats, carbohydrates, and proteins No cholesterol is present in plant products In our body, if cholesterol exceeds its saturation level in the bile, gallstones may form. ↳ Gallstones are normally 100/ cholesterol with some calcium salt, fatty acids and phospholipids Lipoproteins Most lipids are nonpolar and insoluble in the aqueous environment - They are made more soluble by combining them with phospholipids and proteins to form water-soluble Complexes called lipoproteins ↳ Types of lipoproteins Chylomicrons (formed in the small intestine) very low density lipoprotein (VLDL) In liver transport triacylglyerol, phospholipids, and cholesterol to the tissues. for storage - Low density lipoprotein (LDL) Deposit cholesterol in the arteries, which restrict blood flow, heart attack (bad - - High density lipoprotein (HDL) removes excess chloresterol from the tissues and carry it to the liver where it is converted to bile salts and eliminated good cholesterol) Cell membrane. Lipid bilayers Phospholipids consist of polar and nonpolar parts An alignment of the nonpolar sections toward the center The polar section on the outside produces a barrier that prevents the contents of a cell from mixing with the fluids on the outside of the cell - Participation points starch Carbohydrate - Cholestorol Lipid - Steroid Lipid Glycogen Carbohydrate - Glucose Carbohydrate Unsaturated fat: Lipid Staturated fats have a single bond and unsaturated fats have double bonds. Proteins and Enzymes. Lecture 4 29 21 All proteins in humans are polymers made up of 20 different amino acids. Functions of proteins Proteins provide structure in membranes Proteins build connective tissues Proteins transport Oxygen in blood and muscle .- Proteins defend the body against infection Proteins control metabolic processes as horomones Proteins called enzymes regulate biological reactions such as digestion and cellular metabolism All proteins are polymers Monomers that combine to make proteins are damino acids The important fact is that all of the amino acids incorporated by organisms into proteins are the I form D form amino acids are NEVER found in proteins Types of amino acids Amino acids with aliphatic side chains Amino acids with hydroxyl-or sulfur containing side chains - Aromatic amino acids Basic amino acids Acidic amino acids Only 20 different amino acids in humans Chemically, the dipolar form is called the zwitterion +H3N-CHR-COO An a-amino acid The alpha carbon is the central carbon in an amino acid to which the amine, carboxyl, and side-chain R groups attach. Practical Our nails and hair contain keratin Our skin contains collagen Amino Acids contain 2 functional groups Amino Group (-NH2) HO H2N-C-C-OH Side-chain K group, different for each amino acid - Carboxylic Acid (-COOH) Amino acids can be covalently linked together by formation of an amide bond between amino and carboxyl groups. Amino (N) termius and carboxyl terminus Amino acid residue: Peptide units Dipeptides Tripeptides Oligopeptides Polypeptides Peptides are linear polymers that range from 8 to 400 amino acid residues Nonpolar amino acids have alkyl or aromatic side chains, are hydrophobic Polar amino acids have polar side chains such as -OH, SH, and -CONH₂ that form hydrogen bonds with water, hydrophillic Three main physical categories to describe amino acids: Non polar "hydrophobic" 9 in all Glyane, Alanine, valine, Leucine, Isoleucine, Methionine, Proline, Phenylalanine and Tryptophan Uncharged polar, 6 in all ↳ Serine, Threonine, Asparagine, Glutamine, Tyrosine, Cysteine - Charged polar, S in all ↳ Lysine, Arginine, Glutamic Acid, Aspartic Acid, and Histidine Chemical Structure for Glycine H2N-CH2-COOH PH=1 1H3N-CH2-COOH PH=7: H3N-CH2-COO- PH: 12: H2N-CH2-COO- HC bly . Proteins are long polypeptides Most important for biochemists and biologists is the sequence of amino acids Levels of protein structure The sequence of the amino acids determines its biological. function Primary structure: order of the amino acids held together by peptide bonds ↳ originally defined as structure due to covalent bonding ↳ Linear sequence of amino acids Secondary Structure: Describes the way the amino acids next to or near each other along the polypeptide that is arranged in space ↳ Localized regional structures ↳ 2 classes in secondary Alpha helix: Hydrogen bonds between different turns of the helix, which preserve the shape of the protein Beta pleated sheet: Hydrogen bonds occur between two protein chains that are side by side of a long protein Tertiary Structure: Involves attractions and repulsions - between the side chain groups of the amino acids Hydrophobic Hydrophilic ↳ salt bridge: lonic interactions - Quaternary Structure: Active proteins consist of two or more polypeptide subunits Hydrogen bonds, salt bridges Disulfide links and hydrophobic attractions ↳ Interactions between proteins