Chemistry of Life

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Information about Chemistry of Life

Published on November 10, 2008

Author: mswage


Chapter 2 : Chapter 2 The Chemical Context of Life Slide 2: Overview: Chemical Foundations of Biology Slide 3: The bombardier beetle uses chemistry to defend itself Figure 2.1 Slide 4: Concept 2.1: Matter consists of chemicalelements in pure form and in combinationscalled compounds Elements and Compounds : Elements and Compounds Organisms are composed of matter, whichis anything that takes up space and hasmass Slide 6: Matter is made up of elements, substancesthat cannot be broken down to other substances by chemical reactions Slide 7: A compound Is a substance consisting of two or more elements combined in a fixed ratio Has characteristics different from those of its elements Figure 2.2 Essential Elements of Life : Essential Elements of Life Essential elements Include carbon, hydrogen, oxygen, and nitrogen Make up 96% of living matter Slide 9: A few other elements Make up the remaining 4% of living matter Table 2.1 Slide 10: The effects of essential element deficiencies Figure 2.3 Slide 11: Trace elements Are required by an organism in only minute quantities Slide 12: Concept 2.2: An element’s propertiesdepend on the structure of its atoms Slide 13: Each element Consists of a certain kind of atom that is different from those of other elements An atom Is the smallest unit of matter that still retains the properties of an element Subatomic Particles : Subatomic Particles Atoms of each element Are composed of even smaller parts called subatomic particles Slide 15: Relevant subatomic particles include Neutrons, which have no electrical charge Protons, which are positively charged Electrons, which are negatively charged Slide 16: Protons and neutrons Are found in the atomic nucleus Electrons Surround the nucleus in a “cloud” Slide 17: Simplified models of an atom Figure 2.4 Atomic Number and Atomic Mass : Atomic Number and Atomic Mass Atoms of the various elements Differ in their number of subatomic particles Slide 19: The atomic number of an element Is the number of protons Is unique to each element Slide 20: The mass number of an element Is the sum of protons plus neutrons in the nucleus of an atom Is an approximation of the atomic mass of an atom Isotopes : Isotopes Atoms of a given element May occur in different forms Slide 22: Isotopes of a given element Differ in the number of neutrons in the atomic nucleus Have the same number of protons Slide 23: Radioactive isotopes Spontaneously give off particles and energy Slide 24: Can be used in biology Slide 25: Figure 2.5 Slide 26: Can be used in biology The Energy Levels of Electrons : The Energy Levels of Electrons An atom’s electrons Vary in the amount of energy they possess Slide 28: Energy Is defined as the capacity to cause change Potential energy Is the energy that matter possesses because of its location or structure Slide 29: The electrons of an atom Differ in the amounts of potential energy they possess Slide 30: Energy levels Are represented by electron shells Electron Configuration and Chemical Properties : Electron Configuration and Chemical Properties The chemical behavior of an atom Is defined by its electron configuration and distribution Slide 32: The periodic table of the elements Shows the electron distribution for all the elements Slide 33: Valence electrons Are those in the outermost, or valence shell Determine the chemical behavior of an atom Electron Orbitals : Electron Orbitals An orbital Is the three-dimensional space where an electron is found 90% of the time Slide 35: Each electron shell Consists of a specific number of orbitals Slide 36: Concept 2.3: The formation and function of molecules depend on chemical bonding between atoms Covalent Bonds : Covalent Bonds A covalent bond Is the sharing of a pair of valence electrons Slide 38: Figure 2.10 Formation of a covalent bond Slide 39: A molecule Consists of two or more atoms held together by covalent bonds A single bond Is the sharing of one pair of valence electrons A double bond Is the sharing of two pairs of valence electrons Slide 40: (a) (b) Single and double covalent bonds Slide 41: Covalent bonding in compounds Slide 42: Electronegativity Is the attraction of a particular kind of atom for the electrons in a covalent bond The more electronegative an atom The more strongly it pulls shared electrons toward itself Slide 43: In a nonpolar covalent bond The atoms have similar electronegativities Share the electron equally Slide 44: Figure 2.12 In a polar covalent bond The atoms have differing electronegativities Share the electrons unequally Ionic Bonds : Ionic Bonds In some cases, atoms strip electrons away from their bonding partners Slide 46: Electron transfer between two atoms creates ions Ions Are atoms with more or fewer electrons than usual Are charged atoms Slide 47: An anion Is negatively charged ions A cation Is positively charged Slide 48: Figure 2.13 An ionic bond Is an attraction between anions and cations Slide 49: Ionic compounds Are often called salts, which may form crystals Weak Chemical Bonds : Weak Chemical Bonds Several types of weak chemical bonds are important in living systems Hydrogen Bonds : Hydrogen Bonds  –  +  + A hydrogen bond Forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom Van der Waals Interactions : Van der Waals Interactions Van der Waals interactions Occur when transiently positive and negative regions of molecules attract each other Slide 53: Weak chemical bonds Reinforce the shapes of large molecules Help molecules adhere to each other Molecular Shape and Function : Molecular Shape and Function The precise shape of a molecule Is usually very important to its function in the living cell Is determined by the positions of its atoms’ valence orbitals Slide 55: In a covalent bond The s and p orbitals may hybridize, creating specific molecular shapes Slide 57: Molecular shape Determines how biological molecules recognize and respond to one another with specificity Slide 58: Figure 2.17 Slide 59: Concept 2.4: Chemical reactions make and break chemical bonds Slide 60: A Chemical reaction Is the making and breaking of chemical bonds Leads to changes in the composition of matter Slide 61: Chemical reactions Convert reactants to products Slide 62: Photosynthesis Is an example of a chemical reaction Figure 2.18 Slide 63: Chemical equilibrium Is reached when the forward and reverse reaction rates are equal

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