MACROMOLECULES

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MACROMOLECULES

• AP BIOLOGY
• CHAPTER 5

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What is a macromolecule?

• Organic molecules that weigh more than 100,000
  daltons
• Constructed of smaller units called monomers
• Polymers can be subdivided into basic units
  called monomers
• By understanding the monomer, we can better
  understand the polymer.

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4 Macromolecules

• Also called bio-molecules
• They are
• CARBOHYDRATES
• LIPIDS
• PROTEINS
• NUCLEIC ACIDS

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Making and Breaking of Macromolecules

• Dehydration synthesis
• AnabolicWhats this???
• Two molecules bonded chemically through use of
  enzymes a loss of water
• EXAMPLE glucose glucose maltose water

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• Hydrolysis
• CatabolicWhats this??
• Bonds between monomers are broken by enzymes and
  the addition of water
• EXAMPLE sucrose water glucose fructose

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CARBOHYDRATES

• Include sugars and their polymers
• Monosaccharides--monomer
• Disaccharides-polymer
• Polysaccharides-macromolecule

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Monosaccharides

• Basic formula is C(H2O)
• Examples
• Glyceraldehyde
• Dihydroxyacetone
• Ribose
• Deoxyribose
• Ribulose
• Glucose
• Glactose
• Fructose

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A Closer Look at Monosaccharides

• Monosacchrides are named by the number of carbons
• Triose3 carbons
• Pentose5 carbons
• Hexose6 carbons
• They are also classified by the location of the
  carbonyl group

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• They are either aldoses (aldehydes)
• Carbonyl (CO) at end of chain
• or ketoses (ketones)
• Carbonyl (CO) not at end of chain
• Must have at least 3 carbons in the chain
• Monosaccharides vary in spatial arrangement
  around the asymmetrical carbon. (See example on
  p. 65)

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Disaccharides

• Double sugars
• Formula C12H22O11
• What is missing in the formula?
• Why is it missingwhat happened?
• EXAMPLES
• Glucose fructose sucrose
• Glucose glucose maltose
• Glucose galactose lactose

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Polysaccharides

• Basic formula (C6H10O5)n
• Capable of acting as structural or storage
  molecules
• Storage polysaccharides
• Starch-plant storage
• Composed entirely of glucose
• Bonds are alpha 1-4 glycoside linkages
• Amylose is simplest form
• Amylopectin is more complex
• Glycogen-animal starch stored where?

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• Structural polysacchrides
• Cellulose
• Made of glucose, but differs in type of 1-4
  linkage
• Beta 1-4 linkage
• This linkage is difficult to break
• Humans do not have the enzyme to break it down
• Fiber is important part of diet
• Some animals have a cecum or rumen that contains
  bacteria that helps in the breakdown
• Termite connection
• Chitin
• Exoskeletons and fungi cell walls

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LIPIDS

• One common characteristic they do not mix with
  water
• Hydrophobic
• Important groups
• Fats
• Phospholipids
• Steroids

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Fats

• Large molecules composed of 2 types of monomers
• Glycerol-(an alcohol containing 3 carbons)
• 3 fatty acid molecules
• Ester bond connects the glycerol and fatty acids
• A bond between a hydroxyl and carboxyl group

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EXAMPLE Triglyceride
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• Fats are either saturated or unsaturated
• Saturated
• Do not contain any double bonds between the
  carbons
• Unsaturated
• Contain double bonds between the carbons
• Double bonds cut down on the number of hydrogen
  atoms
• This causes the molecule to bend at each of the
  double bond sites

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Characteristics of Fats

• Saturated
• Solid at room temp
• Found mostly in animals
• No double bonds

• Unsaturated
• Liquid at room temp
• Found mostly in plants
• Double bonds between carbons

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Function of Fats

• Acts as insulation in higher vertebrates
• Fat layer under skin
• Polar bears
• Serves as energy storage source
• 1 g 9 K of energy
• Eskimos eat blubberhigh energy
• Salmon eaten before hibernation of bears
• Acts as shock absorber for internal organs
• Kidneys, heart have fat around them

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Phospholipids

• Structurally related to fats but contain 2 fatty
  acids and one molecule of phosphate

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• Found in plasma membranes of cells
• Exhibit both polar and non-polar qualities
• Phosphate group is hydrophilic
• Fatty acid area is hydrophobic
• Phospholipid bilayer semi-permeability

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Steroids

• Lipids characterized by a carbon skeleton of 4
  fused rings
• EXAMPLES
• Cholesterol
• Estradiol

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• Cholesterolfound in all animal tissue
• Precursor of many other steroids
• Adds strength to plasma membrane in animals
• Diet connection
• lt 200 mg/ dL
• Artherosclerosis

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PROTEINS

• Proteins make up 50 of the dry weight of most
  cells.
• They are involved in most of what a cell does.
• Proteins are complex in their structure
• 3-D shape is called its conformation.
• The monomer of a protein is an amino acid.

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Myoglobin
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Types of Proteins

• Structural
• Elastin, collagen, and keratin
• Storage Food Source
• Ovalbumin, casein
• Transport
• Hemoglobin, cell membrane proteins
• Hormonal coordinating body activities
• Insulin

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• Contractile movement
• Actin myosin
• Antibodies for defense
• IgE, IgA, IgG
• Enzymes for chemical reactions
• Amylase and proteases (note endings)

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Protein Monomers

• Proteins are composed of amino acids strung
  together like beads.
• There are 20 types of amino acids.
• The sequence of these amino acids in the protein
  is specific and thus important.
• Discuss this idea!
• The polymer of amino acids is called a
  polypeptide.

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• A protein has one or more polypeptides folded
  into a specific conformation.
• This conformation gives the protein chemical
  properties. (Emergent properties)

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Amino Acids

• The differences between the 20 types of amino
  acids are in the side groups that are designated
  as R in a diagram.
• Note the amino (NH2), carboxyl (COOH) and
  hydrogen groups (H) which are found on all amino
  acids.
• The differences in amino acids are in the 20
  different types of R groups.

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 Basic Amino Acid Structure
 

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Amino Acids are Classified into Various Groups

• The side chain (R group) gives each amino acid
  its specific properties.
• Nonpolar (hydrophobic)
• Polar (hydrophilic)
• Charged

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• Hydrophobic (nonpolar) groups
• Attracted to lipids or to other hydrophobic
  groups
• Hydrophilic (polar) groups
• The side group has a partial at one end and a
  partial at the other side
• Attracted to water.

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• Some hydrophilic side groups are charged these
  are sensitive to pH
• Why?
• Carboxyls (COOH) can lose H ion, become
  negatively charged.
• Amines (NH2) can accept a hydrogen ion and become
  positively charged.

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• Amino acids have isomers
• The common enantiomer is called the L form.
• The other form D form is inactive.

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Formation of a Peptide Bond

• Proteins are Amino Acids Linked Together by
  Peptide Bonds
• In proteins the carboxyl group (COOH) of one
  amino acid attaches to the amine group (NH2) of
  the next to form a peptide bond.

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• The reaction requires ATP
• Water is removed
• Note that the R groups stick out to the side of
  the protein chain
• Each protein has a terminal amino group on one
  end and a terminal carboxyl on the other end

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Major Concept!

• A proteins function depends on its specific
  conformation.

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There are 4 Levels of Protein Structure

• Primary
• Refers to the unique sequence of amino acids in
  the protein
• How does a cell know the sequence?

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• Secondary
• Refers to the coiling and bending of the
  polypeptide into sheets
• Alpha Helix
• Beta Pleated Sheet
• Can exist separately or joined

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Beta-pleated sheet
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• Tertiary
• Refers to the folding back of the molecule on
  itself.
• Held together by disulfide bridges and hydrogen
  bonds
• Contributes to stability of the protein

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• Consists of contortions of the side chains
• Hydrophobic interactions end up in center to
  avoid contact with water
• van der Waals forces help hold together
• Hydrogen bonds will help stablize
• How is this possible when they are weak bonds?

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• Quaternary
• Complex structure formed by the interaction of 2
  or more peptide chains

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Quaternary Structure

• Some proteins are composed of several or more
  polypeptide chains that function as one unit.
• See collagen example in book
• See hemoglobin
• Many of these proteins are either fibrous or
  globular.

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Bacterial Enzyme (Protein)
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More on Conformation

• Given amino acid sequence determines protein.
• Interactions of side chains
• Also depends on the environment protein is in
• pH
• Salt content
• temperature

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• The environment can cause the protein to
  unravel.
• This is called denaturation.
• Molecule is biologically inactive.
• Many proteins do this going from an aqueous to
  inorganic environment.
• Chemicals are disrupting the bonds.

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• Some proteins can change back and forth between
  the 2 states.
• One final bit
• Chaperone proteins (chaperonins)
• They assist in protein folding.
• X-ray crystallography is used to understand
  structure

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NUCLEIC ACIDS

• Nucleic acids store carry information
• DNA and RNA
• Genetic material in chromatin/ chromosomes
• Prokaryotes, Eukaryotes, Viruses all contain
  nucleic acids
• Do we need a brief review??

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• Nucleotides are the monomers of nucleic acids
• The proteins do the work, but the DNA codes for
  the proteins.
• Central Dogma of Biology
• DNA ? RNA ? protein

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Nucleic acid strand is a polymer of nucleotides.

• Nucleotides are composed of 3 molecular groups
• Pentose sugar
• Deoxyribose
• Ribose (more oxygen)
• Phosphate group
• Nitrogenous base

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Nitrogen Bases

• 5 Bases Classified as Purines or Pyramidines
• Adenine--purine
• Guanine--purine
• Thymine--pyramidine
• Cytosine--pyramidine
• Uracil (replaces thymine in RNA)
• Pyramidines have single molecular ring
• Purines have double molecular ring

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• Nucleotides are joined to each other by
  phosphodiester bonds (the sides)
• Remember DNA is a double helix and RNA is a
  single helix
• Base-pairing Rule (A-T, C-G, A-U)
• Purines bond with pyrimidines
• Double helix formed
• Hydrogen bonds join the base pairs

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• The sugar is a pentose sugar.
• The pentose is connected to the nitrogenous base.
• Note difference between ribose and deoxyribose.

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