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Transcript
Chapter 2 General Chemistry Carbon Compounds Enzymes General Chemistry • Atoms – Basic unit of matter – Made up of a dense core called the nucleus (protons and neutrons) surrounded by electrons Elements and Isotopes • Elements are pure substances that consist of only one type of atom • Isotopes are atoms of an element that have the same number of protons, but a different number of neutrons • Why do we care as biologists? They make very good identification markers for certain biological molecules like proteins and DNA Chemical Compounds • Elements can be combined in definite proportions to form compounds – CO2, H2O, C6H12O6, NaCl – The smallest unit of any compound is called a molecule Chemical Bonds • Valence (outside) electrons determine the type of bond that will form • An atom always wants to have 8 valance electrons Yahoo! Video Detail for 02-12CovalentBonds.mov • Covalent Bonds – Electrons are shared between atoms – Very strong bond – A single covalent bond (2 electrons are shared) is shown by a single line between atoms C-C – A double bond (4 electrons are shared) is shown as two lines C=C • Ionic Bonds – One atom gives up an electron or electrons to another atom – Not as strong as a covalent bond – Atoms that gain or lose electrons are called ions. NaCl Na+ and ClMovies from lecture May 26 Water • We are 85% Water. It is so important to us because it is polar – Polar means it has a slightly positive side and a slightly negative side • The polarity of water is so important to us because this is what makes water such a good solvent. – Ionic compounds like NaCl can be easily dissolved in water. Hydrogen Bonds • Very important to biological systems • Holds water molecules together and DNA molecules – The slightly negative end of one molecule is attracted to the slightly positive hydrogen atom on another molecule – A bond strong enough to hold molecules together, but not so much that they can’t be separated easily. Solutions • Solutions consist of a solvent (the substance that does the dissolving) and a solute (the substance that is dissolved) Name the solvent and the solute in the following example: Sea Water Water = Solvent Salt = Solute Acids and Bases When water separates… H2O H+ + OH• If the concentration of H+ is higher than water, the solution is an acid • If the concentration of H+ is lower than water the solution is a base pH Scale • pH 7 = Neutral (pure water) • pH < 7 = Acid • pH > 7 = Base Buffers • Binds with H+ ions when concentration is too high (too acidic) • Releases H+ ions when concentration is too low (too basic) • Prevents sharp changes in pH in biological systems • Ex. Blood bicarbonate buffer system • CO2 + H2O H2CO3 HCO3- + H+ – When too much CO2 builds up in the blood (acidic), more HCO3- is produced This system works with the kidneys which eliminate the HCO3- (a base) when the pH is too high (part of the excretory system) Don’t forget this is all part of Homeostasis!!! Organic Compounds • Organic compounds are carbon compounds that make up living things or that come from living things. • The four elements that make up 99% of all living things are: C, H, O, N, P Biomacromolecules • Bio = life • Macro = big • Biomacromolecules = big molecules that make up life • There are four classes of biomacromolecules Biomacromolecules are Polymers • Poly = many • Meric = units – A polymer is made up of many units • A monomer is the subunit of any polymer – A polymer is made up of many monomers Carbohydrates • Made up of the elements C, H, O in a 1:2:1 ratio – Example: Glucose C6H12O6 • The most important function of carbohydrates is energy storage • Another important function is building material for plants, fungi and bacterial cell walls Carbohydrates = Sugar • Saccharide = sugar • Mono = one – Monosaccharide = one sugar – Examples: Glucose, fructose, galactose – Quick, easy energy • Disaccharide = two sugars • Examples: lactose, maltose, sucrose • Also quick, easy energy Polysaccharides • Polysaccharides = many sugars • Long lasting energy storage • Building materials for plants Starch • Polymer made up of glucose monomers • Energy storage molecule of plants Cellulose • Polymer made up of glucose monomers • Building material of plants • Cannot be digested by humans • Cows have a stomach that contains rumen to digest cellulose Glycogen • Polymer made up of glucose subunits • Energy storage molecule of animals – Found in liver and muscle cells – Gives quick burst of energy for fight or flight mode Glycogen gives us that quick burst of energy for fight or flight Lipids • Primary function is energy storage • Also makes up cell membranes, waxes, steroids • Contains the elements C,H,O Lipids are Hydrophobic Hydro = water Phobic = fear Hydrophobic = afraid of water Hydrophobic = non polar Think of Italian salad dressing or a freshly waxed car Fats are lipids • Fats are for energy storage • Gram for gram, they provide more energy than carbohydrates • Fats often have a polar (water soluble) head and non polar, fatty acid tails – There are three main types of fatty acid tails • Saturated Fats – Have C-C single bonds, straight tails, and are “saturated” with hydrogen atoms. – Solid at room temperature – Examples include: Butter, Animal fat – Can contribute to heart disease because they raise levels of cholesterol in the blood • Unsaturated Fats – Have C=C double bonds that are “unsaturated” with hydrogen atoms – Liquid at room temperature – Tails have “kinked chains” – Oils • Trans fats – A hydrogenated fat used in the manufacture of margarine and snack foods. – We can’t digest large amounts of trans fats so they become incorporated into our cell membranes which prevents them from functioning properly Butter vs. Margarine • Butter is high in both saturated fat and cholesterol which contribute to heart disease • Hard, butter-like margarines contain high amounts of trans fats which are also unhealthy. • Soft margarines contain the least amount of harmful fats and are high in unsaturated plant fats Nucleic Acids • Class of Biomacromolecules that includes DNA and RNA – The monomer is the nucleotide – Contains the elements C,H,O,N,P – The function of a nucleic acid is to store and transmit genetic information • The nucleotide consists of three parts: – phosphate group – five carbon sugar – nitrogenous base • The difference between DNA and RNA – DNA has the sugar Deoxyribose – RNA contains the sugar Ribose – DNA is double stranded – RNA is single stranded Proteins • Class of Biomacromolecules that contains the elements C,H,O,N • Proteins are polymers • Monomer of proteins are amino acids • Proteins are sometimes called polypeptides because amino acids are held together by peptide bonds Peptide bonds • Peptide bonds are formed by dehydration/synthesis reactions – Dehydration means that water is removed during the bond formation What do proteins do? • Proteins have many important functions • Their shape determines the function of the protein • The shape is determined by the “R” groups that are part of each amino acid So, what do proteins do? • Some have important structural roles – Skin, hair, nails, muscle tissue, connective tissue, bones and skin are all made up of protein • Another very important role of proteins is the enzyme – A biological catalyst • A catalyst speeds up chemical reactions Enzymes are very specific • Enzymes have a very specific area (active site) that binds to the reactants of the chemical reaction (substrates) • Nothing else can bind and work the same Enzymes are Sensitive • Heat and pH changes can affect the activity of an enzyme • Remember shape determines function, if we change the shape of the protein, it won’t work anymore Enzymes are Sensitive • pH changes can change shape of protein altering function of enzyme • Heat can cause the enzyme to fall apart (denature) • Cold causes the enzyme to function more slowly • Mutations in the DNA can change the shape and function of an enzyme Enzymes in the human body have an optimum temperature of around 37º C, enzymes from plants and invertebrates may have lower optimum temperatures. Some bacteria living in hot springs have enzymes with much higher optimum temperatures Enzyme Graphs Some things to remember about enzymes… • When more substrate is added, enzymes can produce more product until a plateau is reached • When more enzyme is added, more product can be formed • Enzymes are reusable