Ch. 5 Structure and Function of Macromolecules

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Ch. 5 Structure and Function of Macromolecules

• AP Biology

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Macromolecules

• Most are polymers
• Polymer
• Large molecule consisting of many identical or
  similar building blocks linked by bonds
• Monomer
• Subunits that serve as building blocks for
  polymers

Polyethene is a thermoplastic commodity heavily
used in consumer products (over 60 million tons
are produced worldwide every year).
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A limitless variety of polymers can be built from
a small set of monomers

• Inherent differences between siblings result from
  variations in polymers
• Construction of macromolecules
• 40-50 common monomers and others that occur
  rarely
• Small molecules that are common to all organisms
  are ordered into unique macromolecules

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How Cells Use Organic Compounds

• Biological organisms use the same kinds of
  building blocks.
• All macromolecules (large, complex molecules)
  have specific functions in cells.
• Other than water, macromolecules make up the
  largest percent mass of a cell.

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Condensation and Hydrolysis

• Condensation reactions
• Dehydration reactions
• When two molecules become covalently bonded to
  each other through the loss of a small molecule,
  usually water
• Hydrolysis
• Separation of two molecules by the addition of a
  water molecule

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The Molecules of Life

• Large polymers form from smaller monomers.
• New properties emerge.
• Living cells require/synthesize
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids

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Carbohydrates

• Used as fuel and building material
• Carbs are sugars and their polymers
• Main types
• Monosaccharides
• Disaccharides
• Polysaccharides

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Monosaccharides (CH2O)

• Generally have molecular formulas in some
  multiple of CH2O
• Glucose (C6H12O6) is most common
• In aqueous solution may form rings
• Major nutrients for cells

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Disaccharides

• Two monosaccharides joined by glycosidic linkages
• Glycosidic linkage
• A covalent bond formed between monosaccharides
• Sucrose is most prevalent

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Dissacharide Formation
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Polysaccharides

• 100s to 1000s of monosaccharides long
• Starch
• Storage poly. of plants
• Glycogen
• Storage poly. of animals
• Cellulose
• Structural poly. which is a major component of
  tough plant cell walls
• Chitin
• Structural poly. used by arthropods to build
  exoskeletons

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Starch Cellulose
Forms ring in aqueous solution
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Lipids

• Mostly hydrophobic molecules with diverse
  functions
• Little or no affinity for water
• Used for energy storage and structure
• Main types
• Fats
• Phospholipids
• Steroids

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Fats

• Large molecules, but not polymers
• Fatty acid
• A long carbon skeleton with carboxyl group head
  and a hydrocarbon tail

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Triacylglycerol (Triglyceride)

• Three fatty acids
  linked to one glycerol
  molecule

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Saturated Unsaturated Fats

• Saturated fatty acids
• Fatty acid containing no double bonds between the
  carbon atoms composing the tail
• Solids at room temp.
• Unsaturated fatty acids
• Has one or more double bonded carbons in the tail

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Phospholipids

• Two fatty acid tails linked to one glycerol
  molecule
• Ambivalent behavior toward water
• When in contact with water they form a micelle
  (cluster)

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Steroids

• Lipids characterized by a carbon skeleton,
  consisting of 4 interconnected rings
• Cholesterol
• Important steroid that is a common component of
  the membranes of animal cells
• Many hormones are steroids produced from
  cholesterol

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Proteins

• The molecular tools for most cellular functions
• Used for
• Structural support
• Storage
• Transport of other substances
• Signaling from one part of the organism to the
  other
• Movement
• Defense against foreign substances
• Conformation
• Unique 3-D shape of a protein

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Protein Polypeptides

• Polymers of amino acids connected in a specific
  sequence
• Amino acids
• Organic molecules possessing both carboxyl and
  amino groups
• Acidity is determined by side chains

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Peptide Bonds

• Formed when an enzyme joins amino acids by means
  of condensation
• Polypeptide
• Chains of amino acids linked by peptide bonds

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Protein Conformation

• Conformation (shape) determines function and is
  the result of the linear sequence of amino acids
  in a polypeptide.
• Folding, coiling and the interactions of multiple
  polypeptide chains create a functional protein
• 4 levels of conformation
• Primary
• Secondary
• Tertiary
• Quartinary

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Primary Structure

• Unique, linear sequence of amino acids in a
  protein
• A change in one a.a. can effect every other level
  of structure
• ex. point mutation in hemoglobin

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Secondary Structure

• Hydrogen bonding occurs between amino and
  carbonyl groups of amino acids.
• Structures Formed
• a Helix Common in fibrous proteins, creates
  elastic properties.
• ß Sheet Anti-parallel chains form sheet.

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Tertiary Structure

• Irregular contortions from bonding between side
  chains of various amino acids

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Quartinary Structure

• Overall protein structure that results from
  aggregation of tertiary subunits

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Denaturation

• Unraveling and loss of native conformation of a
  protein
• Can be due to heat, pH, salts, etc.
• Some can renature exactly, others cannot
• Ex cooking an egg

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Nucleic Acids

• Store and transmit hereditary information
• Gene
• A unit of inheritance
• DNA RNA
• Deoxyribonucleic acid Ribonucleic acid
• DNA is like computer software, proteins are like
  hardware
• Genetic info flows from DNA ? RNA ? protein

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DNA Structure

• A polymer with an information-rich sequence of
  nucleotides
• Pyrimidine
• 6 membered ring made of carbon and nitrogen atoms
• Cytosine and thymine
• Purine
• 6 membered ring fused to a five membered ring
• Adenine and guanine
• Phosphodiester
• Covelent bonds holding nucleotides together

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DNA Structure, cont.

• Double helix
• Two chains of nucleotides that spiral around an
  imaginary axis
• Hydrogen bonds
• Hold two chains of nucleotides together
• Adenine pairs with thymine
• Cytosine pairs with guanine
• Two strands of DNA double helix are complimentary

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RNA

• Single stranded
• Four kinds of nucleotide monomers (A, U, C, G)
• Key players in the protein-building processes
• mRNA, tRNA, rRNA

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DNA Protein Importance

• Inheritance is based on precise replication of
  DNA
• We can use DNA and proteins as tape measures of
  evolution
• Linear sequences of nucleotides in DNA molecules
  are passed from parents to offspring
• More distantly related species have chains that
  are less similar

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Review questions

• Section 4.1 page 59, number 1
• Read Inquiry 4.2. Think about the what if
  question.
• Section 5.1 page 69, number 1
• Section 5.2 page 74, number 3
• Self quiz page 91 numbers 1-8.

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