`1AP Biology Study Guide Chapter 2 v Atomic structure is the basis of life s chemistry Ø Living and non- living things are composed of atoms Ø Element pure substance only one kind of atom Ø Living things are composed mainly of Carbon Hydrogen Nitrogen Sulfur Phosphorous Oxygen Ø Number of protons identifies and element Ø Number of protons atomic number Ø For electrical neutrality numbers of protons is the number of electrons Ø Mass numbers = protons + neutrons Ø Behavior of electrons determines whether a chemical bond will form and what shape the bond will have Ø Atoms bonded together = molecule v Ionic bonds Ø Ions are charged particles that form when atoms lose or gain electrons Anion gain electron Cation lose electron Ø Result from the electrical attractions between ions and opposite charges Ø Resulting molecules = salt Ø Ionic attractions weak = salts dissolve easily in water v Covalent bonds Ø Two atoms share a pair of electrons Ø Stability by full outer shells Ø Each contributes one of the pair of the electrons Ø Very strong bonds, lost of energy to break Ø Degree of sharing electrons is not always equal Ø Electronegativity the attractive force that an atomic nucleus exerts on electrons Depends on number of protons and distance between the nucleus and electrons Ø Similar electronegativity s non- polar covalent bonds equal sharing Ø Different electronegativity elections near the most attractive atom v Hydrogen bonds Ø Any polar molecule can react with any other polar molecule through hydrogen bonds v Functional groups Ø Small groups of atoms with specific chemical properties Ø Confer these properties to large molecules Ø One biological molecule may contain many functional groups
v Macromolecules Ø Most biological molecules are polymers made by covalent bonding of smaller molecules called monomers Ø Lipids don t polymerize, non- covalent forces maintain the interaction between the lipid monomers Ø Nucleic acids four nucleotide monomers Ø Carbohydrates formed by linking similar sugar monomers à polysaccharides Ø Proteins combinations of 20 amino acids (different ones) Ø Polymers are formed and broken apart in reactions involving water Condensation/dehydration synthesis remove water link monomers Hydrolysis add water break polymers into monomers v Carbohydrates Ø Store energy Ø Transport food energy in complex organisms Ø Structural molecule that give many organisms their shapes
Ø Recognition of signaling molecule that can trigger specific biological responses Ø Monosaccharaides are simple sugars Ø Pentose are 5- carbon sugars Ø Ribose and deoxyribose are the backbones of RNA and DNA Ø Hexoses (C6H12O6) include glucose multose mannose and galactose Ø Monosaccharaides are covalently bonded by condensation that form glycosidic linkages Glucose + fructose = sucrose Ø Polysaccharides are large polymers of monosaccharaides the chains can be branching Starches a family of polysaccharides of glucose Glycogen highly branched polymer of glucose main energy storage molecule in mammals Cellulose the most abundant carbon containing (organic) biological compound on earth good structural material v Lipids Ø Hydrocarbons Ø Insoluble in water because of mainly nonpolar covalent bonds Ø When close together weak but additive Vander Waals interactions hold them together Ø Store energy in C- C of C- H bonds Ø Play structural role in cell membrane Ø Fat in animal bodies serves as thermal insulation Ø Triglycerides (simple lipids) Fats solid at room temperature Oil liquid at room temperature Very little polarity and are extremely hydrophobic Consist of Three fatty acids non- polar hydrocarbon chain attached to a polar carboxyl group (- COOH) (carboxylic acid) One glycerol an alcohol with three hydroxyl (- OH) groups Synthesis of a triglyceride involved 3 condensation reactions Fatty acid chains can differ in length and structure Saturated all bonds between carbon atoms are single, they are saturated with hydrogen Unsaturated hydrocarbon chains contain one or more double bonds these acids cause kinks in the chains and prevent molecules from packaging together tightly Fatty acids are amphipathic, they have a hydrophilic end and a hydrophobic tail Phospholipid two fatty acids and a phosphate compound bound to glycerol Phosphate group has a negative charge, making that part of the molecule hydrophilic
In an aqueous environment phospholipids form a bilayer The non- polar hydrophobic tails pack together and the phosphate containing heads face outward interacting with water This created a phospholipid bilayer Because of Van der Waals forces v Chemical Ø Chemical reactions occur when atoms have enough energy to combine or change bonding partners Ø Metabolism the sum total of all chemical reactions occurring in a biological system at a given time Metabolic reactions involve energy changes Ø Energy Potential the energy of state or position or stored energy Kinetic the energy of movement (the type of energy that does work) that makes things change Energy can be converted from one form to another Ø Metabolism Anabolic reactions link simple molecules to form more complex ones Require energy inputs energy is captured in the chemical bonds that form Catabolic reactions break down complex molecules into simpler ones Energy stored in the chemical bonds is released Ø The laws of thermodynamics apply to all matter and energy transformations in the universe First law energy is neither created nor destroyed Second law disorder (entropy) tends to increase When energy is converted from one form to another some of tat energy becomes unavailable for doing work Ø If a chemical reaction increase entropy its products are more disordered or random than its reactants Ø If there are fewer products than reactants the disorder is reduced this requires energy to achieve Ø As a result of energy transformation disorder tends to increase Ø Some energy is always lost to random thermal motion (enthalpy)