Atoms and Bonding - Biology Notes PDF

Atoms and Bonding An atom is basic building block of elements. Atoms and Bonding Carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphate (P), and sulfur (S) make up 98% of all organisms Other important elements are calcium (Ca), potassium (K), sodium (Na), and iron (Fe) Atoms and...

Atoms and Bonding An atom is basic building block of elements. Atoms and Bonding Carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphate (P), and sulfur (S) make up 98% of all organisms Other important elements are calcium (Ca), potassium (K), sodium (Na), and iron (Fe) Atoms and Bonding Covalent bonds: atoms share electrons Most biological molecules are held together by covalent bonds. Carbon mostly interacts through covalent bonds. See how elements bond sheet for details Water Water is an incredibly important compound! Organisms are 70-95% water. Water - Water is a polar molecule. - - This means it has a - O concentration of separated positive and negative + + charges. H + H In contrast, nonpolar + + + molecules have no charge Water This allows water to form hydrogen bonds. These are weak bonds between partially positive and partially negative atoms. Water - - - This allows water to form - O hydrogen bonds. These + + are weak bonds between H + H + + partially positive and - + - - - - - partially negative atoms. - - O O + + + + H + H + H + + H + + + +  Water Water is sticky! ○ Cohesion is water sticking to itself ○ Adhesion is water sticking to other things Water Water strider Water is sticky! ○ Surface tension is the result of hydrogen bonds along the surface of water. This can help aquatic animals survive. Capillary action ○ Capillary action draws water up a tube due to its attraction to charged surfaces. Capillary Action of Xylem in plants Water Water is less dense as a solid (so it floats!) ○ This keeps lakes partially unfrozen in the winter ○ Keeps aquatic life safe! Water Water is a universal solvent. ○ Its polarity lets it dissolve charged molecules easily. This is how we get important nutrients! Water Water has high specific heat. - It takes a lot of energy to raise 1 gram of water by 1˚C. This means water heats up and cools down slowly. Solutions Solutions are made up of solutes and solvents Solute: the dissolved molecule Solvent: does the dissolving Examples: saline solution, oxygen dissolved in water, chocolate milk, lemonade, sugar water Solutions Soluble means that the solute can be dissolved ○ Ex: sugar and salt can dissolve in water Insoluble means that it cannot be dissolved ○ Ex. Sand and fats cannot dissolve in water Solutions Concentration: the amount of solute dissolved in the solvent. Usually given in grams per liter This is a place where unit conversions are very important! pH and Buffers pH is the measure of the concentration of hydrogen ions in a solution. This makes 2 categories of solutions: acids and bases pH and Buffers ACIDS BASES 0-6.99 pH 7.01-14 pH Lots of hydrogen ions Few hydrogen ions Taste sour Taste bitter Example: lemon juice, Example: detergent, stomach acid, vinegar ammonia, hand soap Water is neutral and has a pH of 7. It will break apart when mixed with other substances to form acids and bases pH and Buffers Buffers are solutions that resist change in pH. These are very important biologically! They keep homeostasis! ○ Ex: minor changes in blood pH can be devastating! Buffer system helps maintain blood pH. Enzymes Enzymes function as catalysts to lower the activation energy. A catalyst is a substance that changes the rate of a chemical reaction Substrates (or reactants) are the molecules that the enzyme acts on to make the products. Enzymes Enzymes have a very specific lock and key fit their substrate. Enzymes are reused in chemical reactions Enzymes Enzymes work best in specific environments- like at a specific pH or temperature. Ex: enzymes that function in the stomach have a lower ideal pH-- the stomach is super acidic. Enzymes In the wrong environment, the enzyme unfolds. Chemical Reactions Reactions: old substances are changed into new substances Represented by chemical formulas where reactants go to products 6 CO2 + 6 H2O → C6H12O6 + 6 O2  Chemical Reactions 6 CO2 + 6 H2O → C6H12O6 + 6 O2 Reactant → Product All chemical reactions require a change in energy. Chemical Reactions Exothermic: release heat (energy) Chemical Reactions Endothermic: absorb heat (energy) Chemical Reactions Catalysts: lower the activation energy needed Chemical Reactions Catalysts: lower the activation energy needed Activation energy products reactants Molecules of Life Organic molecules are substances that contain the element carbon (C). The basic unit is called a monomer. Larger molecules formed from many monomers are called polymers. Protein Elements: C, H, O, N Looks like: R backbone Monomer Polymer Protein Examples: ○ Monomer: amino acid ○ Polymer: protein Structural: keratin, collagen… Functional: enzymes, hemoglobin... Carbohydrate Elements: C, H, O Looks like: O Monomer Polymer Carbohydrate Function: quick energy, structure Carbohydrate Examples: ○ Monomer AKA monosaccharides: glucose, fructose ○ Polymer (2) AKA disaccharides: sucrose, lactose ○ Polymer (many) AKA polysaccharides: starch, glycogen, cellulose Lipid Elements: C, H, O Looks like: Monomer Polymer Lipid Function: signaling, structure, energy storage Lipid Examples: ○ Monomer: fatty acid and glycerol ○ Polymer: lipid fats (butter, in meat) oil (olive oil, peanut oil) Lipid Fats: ○ Composed of a glycerol and 3 fatty acids ○ Saturated fats are solid at room temperature Example: butter ○ Unsaturated fats are liquid at room temperature Example: olive oil Nucleic Acid Elements: C, H, O, N, P Looks like: N P Monomer Polymer Nucleic Acid Function: genetic information Nucleic Acid Examples: ○ Monomer: nucleic acid ○ Polymer: DNA and RNA