Ch. 5 Structure and Function of Macromolecules

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• Ch. 5 Structure and Function of Macromolecules

D. Knight 2001 AP Biology
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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
• aka dehydration synthesis
• Two molecules combine with loss of water to form
  larger molecule.
• Requires enzymes and energy.
• Hydrolysis
• A molecule splits into two smaller ones with
  addition of water.

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The Molecules of Life

• Living cells synthesize
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

Large polymers form from smaller monomers. New
properties emerge.
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Carbohydrates

• Used as energy and structural molecules
• Contain an aldehyde or a ketone group and one or
  more hydroxyl groups. Soluble
• Organisms use D form but not L.
• Main types
• Monosaccharides
• Disaccharides
• Polysaccharides

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Carbohydrates

• Monosaccharides (CH2O)
• Major cell nutrient, produced during PSN, raw
  material for other molecules.
• 6 Carbon sugars Hexoses
• Glucose, Fructose, Galactose
• 5 Carbon sugars Pentose
• Deoxyribose, Ribose

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Carbohydrates

• Disaccharides
• Sucrose (glucose fructose) table/cane sugar
• Lactose (glucose galactose) milk sugar
  unabsorbed in intestines if individuals lack
  lactase ? diarrhea
• Maltose (glucose glucose) beer, Whoppers!
  formed during hydrolysis of starch by amylase.
• Formed by condensation reactions (glycosidic
  linkage created)

Relative Sweetness of Sugars Sucrose (100),
Glucose (70), Fructose (170), Maltose (30),
Lactose (16), Saccharin (40,000)
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Dissacharide Formation
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Carbohydrates

• Polysaccharides (aka Complex carbos)
• 100s/1000s of monosaccharides long.
• Energy Storage
• Starch (amylose/amylopectin)
• digestible
• Glycogen (highly branched)
• Structural Support
• Cellulose
• Chitin

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Starch Cellulose
Forms ring in aqueous soln
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Lipids

• Largely hydrocarbon insoluble in water
• Dissolve in nonpolar substances (chloroform,
  ether)
• Used for energy storage, structure and chemical
  messenger.
• Lipids with fatty acids
• Glycerides
• Phospholipids
• Waxes
• Lipids with no fatty acids
• Steroids

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Fatty Acids

• Carbon backbone (4 24 carbon atoms)
• Carboxyl group (- COOH)
• Unsaturated
• One or more double bonds in backbone
  
• Saturated
• All single bonds in backbone

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Triglycerides

• Fats/Neutral fats
• Three fatty acids
  and a glycerol
• Condensation
  reaction forms ester linkage.
• Most abundant lipid
• Non-polar, contain no charged/polar functional
  groups
• Functions
• Energy storage in adipocytes
• Insulation

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Phospholipids

• Glycerol backbone
• Two fatty acid tails (hydrophobic)
• Phosphate-containing head (negatively charged
  therefore hydrophilic)
• Amphipathic (both hydrophilic and hydrophobic
  regions)
• Main materials of cell membranes

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Sterols

• Steroids/Sterols
• No fatty acid tails
• Four carbon ring
• In eukaryotic cell membranes
• Cholesterol in animals tissues
• Precursor to sex hormones and bile salts

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Waxes

• Long-chained fatty acids linked to alcohols or
  carbon rings
• Cover plant parts (Cuticle)
• Help conserve water
• Fend off parasites
• Animals
• Protect, Lubricate, Impart pliability to skin and
  hair
• Repel water (bird feathers, exoskeleton of
  insects)

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Amino Acids and the Primary Structure of Proteins

• Proteins
• Enzymes (Metabolism)
• Structures (collagen silk)
• Transport and Movement (Lipoproteins, hemoglobin,
  actin/myosin, tubulin)
• Nutritious (egg white, casein)
• Hormones (chemical messengers, ex. Insulin/growth
  hormone)
• Immune system (antibodies)
• Two Classes Globular and Fibrous
• Proteins are made from a pool of 20 amino acids

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Structure of Amino Acids

• Central carbon atom
• An amino group
• A carboxyl group
• A hydrogen atom
• One or more atoms
  R Group
• Organisms use L form but not D.

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Peptide Bond Formation

• A type of condensation reaction

Peptide Bond
C-terminus
N-terminus
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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 Protein Structure.
• Primary (1)
• Secondary (2)
• Tertiary (3)
• Quarternary (4)

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Primary Structure

• The unique, linear sequence determined by the
  mRNA.
• A change in one a.a. can effect every other level
  of structure (eg. Point mutation in hemoglobin)

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Second Level of Protein Structure

• Hydrogen bonding occurs between amino and
  carbonyl groups of amino acids.
• Structures Formed
• Alpha Helix. Common in fibrous proteins, creates
  elastic properties.
• Beta Sheet. Antiparallel chains form sheet.
• Core of many globular proteins and inelastic
  fibrous proteins.

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Third Level of Protein Structure

• Additional folding of secondary structure and
  bonding between R-groups.
• Hydrogen bonds
• Disulfide bridges (strong)
• Hydrophobic interactions
• Ionic bonding

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Fourth Level of Protein Structure

• Two or more polypeptide chains joined by
• Weak bonds (Hydrogen bonds)
• Covalent bonds between sulfur atoms and R groups
• Collagen (3 helical polypeptides)
• Insulin (2 polypeptides)
• Hemoglobin (4 globular polypeptides)

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Structure of Hair

• Keratin
• Fibrous structural protein

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Four Levels of Protein Structure
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Structural Changes by Denaturation

• Denaturation altering a proteins native
  conformation and activity.
• Disruption of three-dimensional shape of protein
• Temperature thermal agitation
• pH Salts additional H/OH- or ions disrupts
  H-bonding, ionic and disulfide bridges
• Non-Polar Solvents protein turns inside-out
• Some proteins have organic compounds attached
• Glycoproteins, Lipoproteins (common on membranes)

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Nucleotides and The Nucleic Acids

• Nucleotides
• Sugar
• Ribose or Deoxyribose
• Phosphate group
• Bases
• Single or double carbon rings with nitrogen
• Subunits of coenzymes
• NAD and FAD
• ATP
• Energy source for chemical reactions

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Structure of ATP

• ATP
• Three phosphate groups

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Nucleic Acids - DNA and RNA

• Building blocks
• Four kinds of
  nucleotides
• Differ only in component bases

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Single Strand of Nucleic Acid

• A series of
• covalently
• bonded
• nucleotides

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DNA

• Double stranded
• Hydrogen bonds between strands
• Twisted helically
• Four kinds of nucleotide monomers (A, T, C, G)
• Encodes protein-building instructions

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RNAs

• Single stranded
• Four kinds of nucleotide monomers (A, U, C, G)
• Do not encode protein-building instructions
• Key players in the protein-building processes
• mRNA, tRNA, rRNA