The Structure and Function of Macromolecules:

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Chapter 5

• The Structure and Function of Macromolecules
• Large molecules composed of smaller molecules
• Are complex in their structures

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Macromolecules

• Most macromolecules are polymers, built from
  monomers
• Four classes of polymer macromolecule
• ___________________
• Proteins
• Nucleic acids
• _________-(fats)

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The Synthesis of Polymers

• Monomers form larger molecules (polymers) by
  condensation reactions called dehydration
  synthesis

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The Breakdown of Polymers

• Polymers can disassemble by
• Hydrolysis (addition of water molecules)

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Carbohydrates

• Serve as fuel and building material
• Include both sugars and their polymers (starch,
  cellulose, etc.)

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Sugars

• Monosaccharides
• General formula (CH2O)n
• Are the simplest sugars composed of one carbonyl
  group and multiple hydroxyls
• Can be used for fuel, converted into other
  organic molecules or combined into polymers
• Has a Carbon skeleton 3-7 Carbons long
• Classified as _______(carbonyl on end) or
  __________(carbonyl inside the skeleton)

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• Examples of monosaccharides

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• Monosaccharides
• May be linear
• Can form rings (usually do in aqueous solutions)

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• Disaccharides
• Consist of 2 monosaccharides joined by a
  glycosidic linkage
• covalent bond formed between 2 monosaccharides by
  a dehydration reaction
• -what are some common disaccharides?

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Polysaccharides

• Polysaccharides
• Are polymers of sugars
• Serve as storage material or as building material
  for structures that might protect the cell or
  organism

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Storage Polysaccharides

• Starch
• Is a polymer consisting entirely of glucose
  monomers
• Is the major storage form of glucose in plants

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• Storage Polysaccharides
• (Glycogen)
• Consists of glucose monomers
• Is the major storage form of glucose in animals

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Structural Polysaccharides

• Cellulose
• Is a polymer of glucose
• Most abundant organic compound on Earth

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• Cellulose has different glycosidic linkages than
  starch

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• Cellulose is a major component of the tough walls
  that enclose plant cells

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• Cellulose is difficult to digest
• Cows have microbes in their stomachs to
  facilitate this process

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• Structural polysaccharide
• Chitin is found in the exoskeleton of arthropods
• Can be used as surgical thread

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Lipids are a diverse group of hydrophobic
molecules

• Are the one class of large biological molecules
  that do not form polymers
• Fats, phospholipids, steroids classified as
  lipids
• Share the common trait of being hydrophobic

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Triacylglycerol (Fats)

• Are constructed from a glycerol and usually three
  ______________
• _____________ is another name for fat
• Vary in the length and number and
  locations of double bonds they
  contain

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• Saturated fatty acids
• Have the maximum number of hydrogen atoms
  possible
• Have no double bonds..so no kinks in the
  hydrocarbon chain

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• Unsaturated fatty acids
• Have one or more double bonds

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• Phospholipids
• Have only two fatty acids attached to the
  glycerol
• Have a phosphate group instead of a
  third fatty acid

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• Phospholipid structure
• Consists of a hydrophilic phosphate head and
  hydrophobic HC tails

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• The structure of phospholipids
• Make them ideal for a bilayer arrangement found
  in cell membranes

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Steroids

• Steroids
• Are lipids characterized by a carbon skeleton
  consisting of four fused rings
• Characterized by four connected carbon rings with
  various functional groups attached

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• One steroid, ______________
• Is found in cell membranes
• Is a precursor for some hormones
• High amounts of saturated or trans fats can
  affect cholesterol levels which can contribute to
  atherosclerosis.

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Proteins

• Proteins have many structures, resulting in a
  wide range of functions
• Proteins do most of the work in cells and act as
  _________(catalysts of chemical reactions that
  are not consumed)
• Proteins are made of monomers called
  _________________

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• An overview of protein functions refer to Table
  5.1
• Enzymes acceleration of reactions
• Structural support in cells/body
• Storage storage of amino acids
• Transport proteins moves other substances
• Hormones coordination of activities
• Defensive protect against disease
• Contractile/motor movement

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Polypeptides

• Polypeptides
• Are polymers (chains) of amino acids
• A protein
• Consists of one or more polypeptides

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• Amino acids
• Are organic molecules bonded to a hydrogen, a
  carboxyl, an amino group, and a variable side
  chain (R group)
• A.a. differ in their properties due to differing
  side chains, called R groups

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Twenty Amino Acids

• 20 different amino acids make up proteins

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Amino Acid Polymers

• Amino acids
• Are linked by peptide bonds

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Four Levels of Protein Structure

• A proteins specific conformation (shape)
  determines how it functions
• 1. Primary structure is the unique sequence of
  amino acids in a polypeptide

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• 2. Secondary structure
• the folding or coiling of the polypeptide into a
  repeating configuration
• Includes the ? helix and the ? pleated sheet

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• 3. Tertiary Structure
• the overall three-dimensional shape of a
  polypeptide
• Results from interactions between the side chains
  of the various amino acids

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• 4. Quaternary structure
• the overall protein structure that results from
  the aggregation of two or more polypeptide
  subunits

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Sickle-Cell Disease A Simple Change in Primary
Structure

• Sickle-cell disease
• An inherited blood disorder
• Results from a single amino acid substitution in
  the protein hemoglobin
• NOTE STUDY Figure 5.21

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What Determines Protein Conformation?

• A given amino acid sequence can arrange itself
  into a 3-D shape determined by bonds and
  interactions
• Protein conformation (shape) depends on the
  physical and chemical conditions of the proteins
  environment (e.g. temperature, pH, salt
  concentration)

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• Denaturation
• Is when a protein unravels and loses its native
  conformation
• Changes in temperature pH unfold proteins

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The Protein-Folding Problem

• Most proteins probably go through several
  intermediate states on their way to a stable
  conformation
• X-ray crystallography (and NMR) are used to
  determine a proteins 3-D structure

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• Chaperonins (molecular chaperones)
• Are protein molecules that assist in the proper
  folding of other proteins

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Nucleic Acids

• Nucleic acids store and transmit hereditary
  information
• Genes are the units of inheritance
• Program the amino acid sequence of polypeptides
• Are made of nucleic acids
• There are two types of nucleic acids
• Deoxyribonucleic acid (DNA)
• _________________________

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DNA

• -Stores information for the synthesis of specific
  proteins
• -DNA provides
• instructions for self-
• replication and dir-
• ects RNA synthesis
• -DNA directs protein
• synthesis through
• RNA
• All cells except gametes have a complete set of
  DNA

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The Structure of Nucleic Acids

• Nucleic acids
• Exist as polymers called polynucleotides

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• Each polynucleotide
• Consists of monomers called nucleotides
• Monomers consist of a _______(5-C sugar)
  covalently bonded to a phosphate group and a
  nitrogenous base.

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Nucleotide Monomers

• Are made up of nucleosides and phosphate groups
• There are two families
• ___________are 6-
• membered rings of carbon
• and nitrogen
• __________are larger
• with a 6-membered ring
• fused to a 5-ring

Figure 5.26
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Nucleotide Polymers

• made up of nucleotides linked by theOH group on
  the 3 carbon of one nucleotide and the phosphate
  on the 5 carbon on the next
• The sequence of bases along a nucleotide polymer
• Is unique for each gene

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The DNA Double Helix

• Cellular DNA molecules
• Have two poly
• nucleotides that
• spiral around an
• imaginary axis
• Form a double
• helix

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• The DNA double helix
• Consists of two antiparallel nucleotide strands

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DNA and proteins as tape measures of evolution

• If we compare a polypeptide chain of human
  hemoglobin (146 amino acids) with corresponding
  hemoglobin in 5 other vertebrates
• Humans and gorillas differ in only one
• Humans and gibbons differ in 2 a.a.
• Humans and rhesus monkeys differ in 8 a.a.
• Humans and mice differ in 27 a.a.
• Humans and frogs differ in 67 a.a.