AP Biology Exam Review

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AP Biology Exam Review

• Molecules and Cells 25

2
Chemistry of Life 7

• Water
• Organic molecules in organisms
• Free energy changes
• Enzymes

3
Polar water molecule

• Polar covalent bonds ? polarity
• Polarity ? hydrogen bonding and various water
  properties

4
Water properties

• Ex How do the unique chemical and physical
  properties of water make life on earth possible?
• Cohesion transpiration, blood
• Adhesion transpiration
• Ideal solvent xylem and phloem sap, oceans,
  blood, hemolymph
• Density maintaining marine life
• High specific heat maintaining stability
  (homeostasis)

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pH

• H2O H2O ?? H3O- OH-
• Water dissociation H2O ? H OH-
• 1/554 million water molecules dissociates in pure
  water.
• pH 7 when H and OH- equal to 10-7

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Acids and Bases

• Acids pH lt 7
• Ex stomach acid, increasing H gradient
• Bases pH gt 7
• Neutral pH7
• Ex blood, urine, body fluids
• Buffers required to maintain neutrality.
  (homeostasis)

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Buffers

• H2CO3 OH- ?? HCO3- H2O
• HCO3- H ?? H2CO3
• Ex Human red blood cells
• Carbonic acid (H2CO3) and Bicarbonate (HCO3-)
  buffers to maintain blood cell pH.
• How can blood cell pH be raised or lowered?

8
pH

• Make sure you know the general pH of some
  biologically important aqueous solutions blood,
  gastric guices, urine, seawater, etc.

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Dehydrationsynthesis

• Aka condensation reaction
• To break up polymers hydrolysis
• Hydrolytic enzymes (fungus, insect saliva)
  capable of hydrolyzing polymers.

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Organic molecules

• Macromolecules carbohydrates, proteins, lipids,
  nucleic acids, vitamins
• Carbohydrates energy storage (starch in plants,
  glycogen in animals) structural support
  (cellulose, chitin) energy (reactant in cellular
  respiration)
• Ex glucose, fructose, lactose (-ose)
• Human insulin and glucagon lowers and raises
  blood glucose levels. (homeostasis)

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Storage vs. Structure

• Starch, Glycogen Cellulose

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Organic molecules

• Proteins structural support (microtubules,
  microfilaments, intermediate filaments that make
  up muscle fibers), enzymes, regulatory proteins
• Four folding levels primary (peptide bonds
  between amino acids) secondary (hydrogen bonds)
  tertiary (R-group interactions) quaternary
  (multiple peptide interactions)

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Primary
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Secondary

• Alpha helices hair fibers (keratin)
• Beta-pleated sheets silk

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Tertiary

• Important in the formation of active sites of
  enzymes

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Quaternary
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Protein denaturation

• Chaperonin, heat shock proteins

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Membrane proteins
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Organic molecules

• Lipids membrane structure, long term energy
  storage, brain insulation
• Smooth endoplasmic reticulum product stored in
  adipose tissue (made of fat cells)
• Steroid rings sex hormones, cholesterol (animals
  only)
• Phospholipid membrane

20
Organic molecules

• Nucleic acids ATP, GTP, nucleotides
• DNA remains within nucleus of eukaryotes.
• Circular DNA in prokaryotes with plasmids

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Free energy changes

• Governed by two laws of thermodynamics

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First law of thermodynamics

• Conservation of energy
• Ex coupled reactions, nutrient cycling

Coupled reactions happen in the electron
transport chain.
ATP
ADP P
GTP
GDP P
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Second law of thermodynamics

• Entropy
• Ex 10 energy loss in environment, proton
  gradient, diffusion, higher to lower
  concentration (countercurrent exchange),
  depolarization

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Exergonic vs. Endergonic reactions

• What are some of these processes that occur in
  biological systems?

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Effects of enzymes
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Lock and key vs. induced fit model
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General enzyme characteristics

• Effective in small amounts
• Unchanged in a reaction (only substrate changes)
• Doesnt affect equilibrium in chemical reaction
  (speeds up process in either direction)
• Specific to act on substrate molecules
• Cofactors (inorganic metals) or coenzymes
  (vitamins NAD and FAD) assist
• Inhibitors able to affect activity

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Competitiveinhibition

• Example oxygen binding to rubisco instead of
  carbon dioxide ? photorespiration

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Allosteric site

• Commonly called regulatory site
• Example lac and trp operons

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Regulatory pathways

• Negative feedback enables feedback mechanisms
• Ex body temperature regulation

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Trp operon in bacteria only
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Lac operon in bacteria only
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Enzymes

• Enzymes denature with changes in temperature and
  pH.
• Example showing Importance of homeostasis

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Protein receptors
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cAMP as secondary messenger

• Proteins and receptors involved in signal
  amplification

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Cell to cell communication
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Signal transduction pathway
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Signal molecule