Lecture 1 - Chapter 2_1.pptx

The unique properties of water are important for life on earth: high surface tension, lower density of solid than liquid, high heat of vaporization. These properties are a direct result of… a. the size of water molecules. b. the color of water molecules. c. the polarity of water molecul...

The unique properties of water are important for life on earth: high surface tension, lower density of solid than liquid, high heat of vaporization. These properties are a direct result of… a. the size of water molecules. b. the color of water molecules. c. the polarity of water molecules. d. the electronegativity of water molecules. Join.nearpod.com pin =  Chapter 2 Part 1 Chemical Bonding and Biological Macromolecules Learning Objectives Compare and contrast atoms, elements, and molecules. Distinguish polar and nonpolar covalent bonds and their physical-chemical properties. Explain how the properties of water account for the solubility of macromolecules and salts and describe the role of H-bonds in supporting those properties. Consider, in terms of water’s properties, why some molecules are not soluble in water. Chemical Bonding Key Concepts Biological systems exist in aqueous environments. Covalent bonds Are strongest kind of bond in aqueous environment Breaking and forming requires a chemical reaction Join atoms in biological monomers Join monomers to form biological macromolecules Non-covalent interactions Are weaker than covalent bonds in aqueous environments. Are important for stabilizing the 3D structure macromolecules and macromolecular complexes. Allow for transient interactions and rapid structural changes Are disrupted by changes in environmental conditions, for example, temperature and pH Chemical Elements Valence Electrons & Chemical Bonding  Single bond 1 shared e- pair Covalent bonds Free rotation Double bond 2 shared e- pairs Rigid Triple bond 3 shared e- pairs Rigid Electronegativity Low Electronegativity High Electronegativity Polar and Non-Polar Covalent Bonds C Electrons in covalent bonds can be shared unequally Molecular Geometry Unshared e- pairs are important for molecular geometry. Molecular Geometry: Structure- Function C How many covalent bonds can a single atom of oxygen form? a. 0 b. 1 c. 2 d. 3 e. 4 NOTE CHECK Join.nearpod.com pin =  Van der Waals Ion-Dipole Forces strongest weakest Ionic bonds / Hydrogen Hydrophobic electrostatic bonds Forces NON-COVALENT INTERACTIONS Ionic bonds / electrostatic attractions Electron(s) completely transferred from one atom to another. Ion-Dipole Interactions Polar molecules can form ion-dipole interactions Hydrogen Bonds Polar molecules can form hydrogen bonds with other polar molecules  Van der Waals Forces Attraction and repulsion from transient partial charges due to random movement of electrons.  Hydrophobic Interactions Collapse of non-polar molecules/regions of molecules together thus excluding water.  Which of the following molecules could form a hydrogen bond with water? A) B) N C) O NOTE CHECK Join.nearpod.com pin =  Think About It Which of the following accurately shows what happens when the disaccharide lactose dissolves in water? A. B. Galactose Glucose Lactose