BIOL 260 - Chapter 2: The Chemical Level of Organization (PDF)

The Chemical Level of Organization Unless otherwise indicated, An Introduction to the Human Body Lecture Slides by Yancy Aquino for Skyline College are derivative of OpenStax A&P Instructor Resources and are licensed CC BY....

The Chemical Level of Organization Unless otherwise indicated, An Introduction to the Human Body Lecture Slides by Yancy Aquino for Skyline College are derivative of OpenStax A&P Instructor Resources and are licensed CC BY. 1 Figure 2.2 Elements of the Human Body 2 } smallest quantity of an element that retains the unique properties of that element } made up of even smaller subatomic particles, three types of which are important: the proton, neutron, and electron. } number of positively-charged protons and non-charged (“neutral”) neutrons, gives mass to the atom, and the number of each in the nucleus of the atom determine the element } number of negatively-charged electrons that “spin” around the nucleus at close to the speed of light equals the number of protons } atomic number ◦ number of protons in the nucleus of the atom, identifies the element } mass number ◦ sum of the number of protons and neutrons in its nucleus } periodic table of the elements ◦ a chart identifying the 92 elements found in nature, as well as several larger, unstable elements discovered experimentally 4 The Periodic Table of the Elements (credit: R.A. Dragoset, A. Musgrove, C.W. Clark, W.C. Martin) } one of the different forms of an element, distinguished from one another by different numbers of neutrons Figure 2.5: Isotopes of Hydrogen } Protium, designated 1H, has one proton and no neutrons. It is by far the most abundant isotope of hydrogen in nature. Deuterium, designated 2H, has one proton and one neutron. Tritium, designated 3H, has two neutrons. 6  } Electron Shells } Electrons orbit the atomic nucleus at distinct levels of energy called electron shells. (a) With one electron, hydrogen only half-fills its electron shell. Helium also has a single shell, but its two electrons completely fill it. (b) The electrons of carbon completely fill its first electron shell, but only half- fills its second. (c) Neon, an element that does not occur in the body, has 10 electrons, filling both of its electron shells. 7  } Ionic Bonding (a) Sodium readily donates the solitary electron in its valence shell to chlorine, which needs only one electron to have a full valence shell. (b) The opposite electrical charges of the resulting sodium cation and chloride anion result in the formation of a bond of attraction called an ionic bond. (c) The attraction of many sodium and chloride ions results in the formation of large groupings called crystals. 8 } covalent bond ◦ share electrons in a mutually stabilizing relationship 9 } polar molecule ◦ a molecule that contains regions that have opposite electrical charges ◦ Polar molecules occur when atoms share electrons unequally, in polar covalent bonds Figure 2.10 Polar Covalent Bonds in a Water Molecule 10 } hydrogen bond ◦ formed when a weakly positive hydrogen atom already bonded to one electronegative atom (for example, the oxygen in the water molecule) is attracted to another electronegative atom from another molecule ◦ hydrogen bonds always include hydrogen that is already part of a polar molecule Figure 2.11 Hydrogen Bonds between Water Molecules 11 } Characteristics of Chemical Reactions ◦ Reactant – substances that enter into the reaction ◦ Product – produced by a chemical reaction 12  Enzymes } Enzymes decrease the activation energy required for a given chemical reaction to occur. (a) Without an enzyme, the energy input needed for a reaction to begin is high. (b) With the help of an enzyme, less energy is needed for a reaction to begin. } Lubricant and Cushion } A Component of Liquid Mixtures ◦ solution – consists of a solvent that dissolves a substance called a solute; homogeneous ◦ colloid – somewhat like a heavy solution – solute particles consist of tiny clumps of molecules large enough to make the liquid mixture opaque ◦ suspension – liquid mixture in which a heavier substance is suspended temporarily in a liquid, but over time, settles out 14 Figure 2.14 Dehydration Synthesis and Hydrolysis 15 Figure 2.15 Dissociation of Sodium Chloride in Water Notice that the crystals of sodium chloride dissociate not into molecules of NaCl, but into Na cations and Cl + – anions, each completely surrounded by water molecules. 16  } Disaccharides } Monosaccharides ◦ pair of monosaccharides ◦ monomer of carbohydrates 17 } Polysaccharides ◦ contain a few to a thousand or more monosaccharides 18 } lipid ◦ is one of a highly diverse group of compounds made up mostly of hydrocarbons } Triglyceride ◦ one of the most common dietary lipid groups, and the type found most abundantly in body tissues ◦ commonly referred to as a fat – glycerol backbone and Three fatty acids 19 } saturated fatty acids ◦ no double carbon bonds anywhere ◦ solid or semi- solid at room temperature } monounsaturated fatty acids ◦ with one double carbon bond are kinked at that bond ◦ are liquid at room temperature } Polyunsaturated fatty acids ◦ two or more double Figure 2.22 Fatty Acid Shapes carbon bonds ◦ liquid at room temperature 20 } Phospholipid ◦ bond between the glycerol component of a lipid and a phosphorous molecule ◦ generated from a diglyceride, a glycerol with just two fatty acid chains ◦ third binding site on the glycerol is taken up by the phosphate group, which in turn is attached to a polar “head” region of the molecule 21 } Steroid ◦ compound (referred to as a sterol) has as its foundation a set of four hydrocarbon rings bonded to a variety of other atoms and molecules } Prostaglandin ◦ group of signaling molecules, but prostaglandins are derived from unsaturated fatty acids 22 } protein ◦ organic molecule composed of amino acids linked by peptide bonds ◦ amino acid – molecule composed of an amino group and a carboxyl group 23 } Shape of Proteins (a) Primary structure is the sequence of amino acids that make up the polypeptide chain. (b) Secondary structure, an alpha-helix or a beta- pleated sheet, maintained by hydrogen bonds between amino acids (c) Tertiary structure is a result of further folding and bonding of secondary structure. (d) Quaternary structure is a result of interactions between two or more tertiary subunits. The example shown here is hemoglobin. 24 } Function as Enzymes Figure 2.27 Steps in an Enzymatic Reaction a) Substrates approach active sites on enzyme. b) Substrates bind to active sites, producing an enzyme–substrate complex. (c) Changes internal to the enzyme–substrate complex facilitate interaction of the substrates. (d) Products are released and enzyme returns to its original form, ready to facilitate another enzymatic reaction. 25