Macromolecules Structure
Carbohydrates
monomer: monosaccharides (linked together into polysaccharides by dehydration synthesis) |
functions: energy storage (ex: starch in plants and glycogen in animals) and structural support (ex: cellulose for plan cell walls and chitin for exoskeleton of arthropods and cell walls of fungi) |
have a ratio of CH2O (1 carbon: 2 Hydrogen: 1 Oxygen) |
Proteins
Monomer: amino acids (which are linked by peptide bonds, which are formed by dehydration synthesis between amino and carboxyl groups of adjacent amino acids) |
functions: antibodies, movement, membrane receptors |
Primary Structure- unique sequence of amino acids |
Secondary Structure- folding of the amino acid chain through hydrogen bonds into alpha helices and beta sheets |
Tertiary Structure- overall three-dimensional shape of the protein and often minimizes free energy (hydrophobic interactions, disulfide bridges, H-bonds, ionic bonds) |
Quaternary Structure- arrangement of polypeptides (only occurs in some) ex: hemoglobin |
Denaturation: unfolding of protein structure due to unideal temperature or pH levels |
Lipids
Monomer: N/A because lipids aren't polymers since they are assembled from a variety of components (ex: fats, oils, waxes, & steroids) ALL HYDROPHOBIC |
Function: energy storage, protection, insulation, phospholipid bilayer |
Fats (aka triglycerides): made of a glycerol molecule and 3 fatty acid molecules (fatty acids: nonpolar hydrocarbon chains) |
Saturated Fatty Acids: no double bonds between carbons, pack solidly at room temp, max number of hydrogens, commonly produced by animals) |
Unsaturated Fatty Acids: have some carbon double bonds which result in kinks, liquid at room temp, commonly produced by plants) |
Phospholipids have a hydrophilic (polar) head that includes a phosphate group and 2 hydrophobic fatty acid tails |
Steroids have a carbon skeleton of 4 rings that are fused together (ex: cholesterol in animal cell membranes, and estrogen and testosterone) |
Saturated vs. Unsaturated Fatty Acids
Nucleic Acids
Monomer: nucleotides |
Function: genetic info that codes for amino acid sequences |
DNA and RNA |
Nucleotides are made of 3 parts: nitrogenous base, pentose (5-carbon) sugar (deoxyribose in DNA and ribose in RNA), and the phosphate group (PO4) |
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Chemical Reactions
Covalent Bonds |
Nonpolar covalent bonds: electrons are shared equally |
polar covalent bonds: one atom has a greater electronegativity --> unequal sharing of electrons |
Ionic Bonds |
chemical bonds formed by the attraction of oppositely charged ions |
ex: table salt |
Hydrogen Bonds |
weak chemical interactions that form between a partial positively charged hydrogen atom of one molecule and the strong electronegative oxygen or nitrogen of another molecule |
ex: hydrogen bonds between water |
Van der Waals interactions |
very weak, short-lasting connections that are a result of asymmetrical distribution of electrons within a molecule |
contribute to the 3d shape of molecules |
Acids and Bases
pH scale: Measures relative acidity and alkalinity of aqueous solutions (between 0 and 14) |
Acids: excess of H+ ions and H+>OH- |
Bases: excess of OH- ions and OH->H+ |
Pure water is neutral (pH=7) |
Buffers: substances that minimize changes in pH by accepting H+ from a solution when hydrogen molecules are in excess and donate H+ when hydrogen molecules are depleted |
Buffers are essential in living tissues to minimize pH changes |
Carbonic Acid (H2CO3): important buffer in living systems because it moderates pH changes in blood plasma and the ocean |
Carbon
Major elements of life are carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus CHNOPS |
All organic compounds contain carbon and most contain hydrogen |
Carbon is unparalleled in its ability to form large, complex, and diverse molecules because it has 4 valence electrons, which means it can form up to 4 covalent bonds (which can be single, double, or triple), and it can form large molecules (which can be chains, ring-shaped, or branched) |
Isomers: molecules that have the same molecular formula but differ in atom arrangement, which can result in molecules that are very different in their biological activities (ex: glucose and fructose) |
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Properties of Water
Water molecules are polar |
oxygen region of molecule has a partial negative charge and each hydrogen region has a partial positive positive charge |
Hydrogen bonds form between water molecules |
the slightly negative oxygen atom from one water molecule is attracted to the slightly positive hydrogen end of another molecule |
Each water molecule can form up to 4 hydrogen bonds |
Hydrogen Bonds are key to each of the following properties of water and what makes water unique |
Cohesion: Linking of like molecules |
Adhesion: clinging of one substance to another |
Capillary Action: movement of water molecules up very thin xylem tubes and their evaporation from stomata in plants; the water molecules cling to each other by cohesion and to the walls of the xylem tube by adhesion |
Cohesion is responsible for surface tension, which means that water droplets will resist rupture when stress and pressure are added to the system |
Water has a high specific heat. Specific Heat is the amount of heat required to raise or lower the temperature of a substance by 1 degree Celsius. High specific heat makes the temperature of Earth's oceans relatively stable and able to support vast quantities of life |
Water is less dense as a solid than as a liquid, so ice floats, which keeps larger bodies of water from freezing solid, allowing life to exist in bodies of water |
Water is an important solvent (hydrophilic substances are water soluble and hydrophobic substances are nonpolar and don't dissolve in water). |
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