Chapter 1 Highlights

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Chapter 1 Highlights

• Hierarchy of scientific thinking
• Hypothesis?possible explanation-prediction
• Theory? supported by considerable evidence
  (loftier)
• Law? fact, undisputed every time (gravity,
  thermodynamics)
• Control vs. Experimental
• both the same except for the VARIABLE
• Do This
• design an experiment to test a pollutant on
  embryonic chicks in an egg.

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• Characteristics of life
• Made of units called cells
• Reproduce (2 basic kinds)
• Based on a universal genetic code
• Grow and develop
• Need for materials and energy
• Response to environment
• Maintain stable internal environment
• Evolve

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Chapter 2

• The Chemical Context of Life

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Overview Chemical Foundations of Biology

• The bombardier beetle uses chemistry to defend
  itself

Figure 2.1
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• A Bombardier beetle produces and stores two
  reactant chemical compounds, hydroquinone and
  hydrogen-peroxide in separate reservoirs in the
  rear tip of its abdomen. When threatened, the
  beetle contracts muscles that force the two
  reactants through valved tubes into a mixing
  chamber containing water and a mixture of
  catalytic enzymes. When combined, the reactants
  undergo a violent exothermic chemical reaction
  raising the temperature to near the boiling point
  of water. The corresponding pressure buildup
  forces the entrance valves from the reactant
  storage chambers to close thus protecting the
  beetles internal organs. The boiling,
  foul-smelling liquid partially becomes a gas
  (flash evaporation) and is expelled through an
  outlet valve into the atmosphere with a loud
  popping sound. The flow of reactants into the
  reaction chamber and subsequent ejection to the
  atmosphere occurs cyclically at a rate of about
  500 times per second and with the total pulsation
  period lasting for only a fraction of a second.

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Elements and Compounds

• Organisms are composed of matter, whichis
  anything that takes up space and hasmass
• Matter is made up of elements, substancesthat
  cannot be broken down to other substances by
  chemical reactions

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• 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
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Essential Elements of Life

• Essential elements
• Include carbon, hydrogen, oxygen, and nitrogen
  (CHON)
• Make up 96 of living matter
• A few other elements
• Make up the remaining 4 of living matter
  (SPONCH)
• Trace elements
• Are required by an organism in only minute
  quantities

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• The effects of essential element deficiencies

Figure 2.3
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Subatomic Particles

• Atoms of each element
• Are composed of even smaller parts called
  subatomic particles
• Relevant subatomic particles include
• Neutrons, which have no electrical charge
• Protons, which are positively charged
• Electrons, which are negatively charged
• Protons and neutrons
• Are found in the atomic nucleus
• Electrons
• Surround the nucleus in a cloud

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• Simplified models of an atom

Figure 2.4
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Atomic Number and Atomic Mass

• Atoms of the various elements
• Differ in their number of subatomic particles
• The atomic number of an element
• Is the number of protons
• Is unique to each element
• 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

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Isotopes

• Atoms of a given element
• May occur in different forms called isotopes
• Isotopes of a given element
• Differ in the number of neutrons in the atomic
  nucleus
• Have the same number of protons
• -Carbon examples
• 12C ? normal ( protons, neutrons)
• 13C ? ( protons, neutrons)
• 14C ? ( protons, neutrons)

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• Some radioactive (or unstable)
• Spontaneously give off particles and energy
• medical procedures
• good ? 123I used for thyroid analysis
• damaging? 226Radium or 60Cobalt (cancer)
• Can be used in biology

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The Energy Levels of Electrons

• The electrons of an atom
• Differ in the amounts of potential energy they
  possess

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• Energy levels
• Are represented by electron shells

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• The periodic table of the elements
• Shows the electron distribution for all the
  elements

• Valence electrons
• Are those in the outermost, or valence shell
• Determine the chemical behavior of an atom

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Covalent Bonds

• A covalent bond
• Is the sharing of a pair of valence electrons

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• Formation of a covalent bond

Figure 2.10
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• Single and double 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

(a)
(b)
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• Covalent bonding in compounds

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• 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
• In a nonpolar covalent bond
• The atoms have similar electronegativities
• Share the electron equally

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• In a polar covalent bond
• The atoms have differing electronegativities
• Share the electrons unequally

Figure 2.12
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Ionic Bonds

• In some cases, atoms strip electrons away from
  their bonding partners
• Electron transfer between two atoms creates ions
• Ions
• Are atoms with more or fewer electrons than usual
• Are charged atoms
• An anion
• Is negatively charged ions
• A cation
• Is positively charged

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• An ionic bond
• Is an attraction between anions and cations

Figure 2.13
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• Ionic compounds
• Are often called salts, which may form crystals

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Weak Chemical Bonds

• Several types of weak chemical bonds are
  important in living systems
• Weak chemical bonds
• Reinforce the shapes of large molecules
• Help molecules adhere to each other

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Hydrogen Bonds

• A hydrogen bond
• Forms when a hydrogen atom covalently bonded to
  one electronegative atom is also attracted to
  another electronegative atom

?
?
?
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Van der Waals Interactions

• Van der Waals interactions
• Occur when transiently positive and negative
  regions of molecules attract each other

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Bonds in Review

• Covalent
• Strong
• Much to discuss
• Ionic
• Strong too
• Dissociate into ions
• Not much in AP Bio
• NaCl is our go-to example
• Hydrogen
• Weak
• But strength in numbers
• Much to discuss