proteins and nucleic acids - ms. bagby ap...
TRANSCRIPT
Proteins and Nucleic Acids
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Chapter 5 Macromolecules: Proteins
Proteins
• Most structurally & functionally diverse group of biomolecules.
• Function:
o Involved in almost everything
o Enzymes
o Structure (keratin, collagen)
o Carriers & transport (membrane channels)
o Receptors & binding (defense)
o Contraction (actin & myosin)
o Signaling (hormones)
o Storage (bean seed proteins)
• Structure:
o Monomer = amino acids
� 20 different amino acids
o Polymer = polypeptide
� Protein can be 1 or more polypeptide
chains folded & bonded together.
� Large & complex molecules
� Complex 3-D shape
• Amino Acids
o Structure:
� Central Carbon
� Amino Group
� Carboxyl Group (acid)
� R Group (side chain)
• Variable group
• Confers unique chemical properties of the amino
acid.
• Nonpolar Amino Acids (Hydrophobic) WHY?
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• Polar Amino Acids (Hydrophilic) WHY?
Building Proteins
• Peptide Bonds: dehydration synthesis
o Linking NH2 of 1 amino acid to COOH of
another.
o C–N bond
• Polypeptide Chains
o N-terminal = NH2 end
o C-terminal = COOH end
o Repeated sequence (N-C-C) is the
polypeptide backbone
� Grow in one direction
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Protein Structure & Function
• Function depends on structure.
o 3-D structure
� Twisted, folded, coiled into unique shape.
• All starts with the order of amino acids.
o What determines that order of amino acids?
Primary (1°) Structure
• Order of amino acids in chain
o Amino acid sequence determined by DNA
o Slight change in amino acid sequence can affect
protein’s structure & it’s function
� Even just one amino acid change can make
all the difference!
Secondary (2°) Structure
• Folding along short sections of polypeptide
o interaction between adjacent amino acids
o H bonds between R groups
o α-helix
o β-pleated sheet
Tertiary (3°) Structure
• Determined by interactions between R
groups
o Hydrophobic interactions
� Effect of water in cell
o Anchored by disulfide bridges
(H & ionic bonds)
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Quaternary (4°) Structure
• Joins together more than 1 polypeptide chain.
o Only then is it a functional protein.
Protein Structure Review
Denature a protein
• Disrupt 3° structure
o pH salt temperature
� Unravel or denature protein.
� Disrupts H bonds, ionic bonds & disulfide bridges.
• Some proteins can return to their functional shape after denaturation, many cannot.
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Chapter 5 Macromolecules: Nucleic Acids
Nucleic Acids
• Function:
o Store & transmit hereditary information
• Examples:
o RNA (ribonucleic acid)
o DNA (deoxyribonucleic acid)
• Structure:
o Monomers = nucleotides
Nucleotides
• 3 parts
o Nitrogen Base (C-N ring)
o Pentose Sugar (5C)
� Ribose in RNA
� Deoxyribose in DNA
o PO4 group
• 2 Types of Nucleotides
o Different Nitrogen bases
o Purines
� Double ring N base
� Adenine (A)
� Guanine (G)
o Pyrimidines
� Single ring N base
� Cytosine (C)
� Thymine (T)
� Uracil (U)
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Nucleic Polymer
• Backbone
o Sugar to PO4 bond
o Phosphodiester bond
� New base added to sugar of previous base
� Polymer grows in one direction
o N bases hang off the sugar-phosphate backbone
RNA & DNA
• RNA
o Single nucleotide chain
• DNA
o Double nucleotide chain
� N bases bond in pairs across chains.
o Spiraled in a double helix.
� Double helix 1st proposed as structure of DNA in 1953 by James Watson & Francis
Crick.
• Pairing of Nucleotides
o Nucleotides bond between DNA
strands
o H bonds between purine AND
pyrimidine
� A :: T
• 2 H bonds
� G :: C
• 3 H bonds
Information Polymer
• Function
o Series of bases encodes information
� Like the letters of a book
o Stored information is passed from
parent to offspring
� Need to copy accurately
o Stored information = genes
DNA Molecule
• Double helix
o H bonds between bases join the 2 strands
� A :: T
� C :: G
� Why is it important that the strands are bonded by H bonds?
• Copying DNA
o Replication
� 2 strands of DNA helix are complementary
• Have one, can build other
• Have one, can rebuild the whole
� Why is this a good system?
� When in the life of a cell does replication occur?
• mitosis
• meiosis
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Cool Beans
• Ratio of A-T::G-C affects stability of DNA molecule.
o 2 H bonds vs. 3 H bonds
• More G-C = need higher T° to
separate strands.
• High T° organisms have more G-
C.
• Parasites have many A-T (don’t
know why).
ATP Adenosine Triphosphate
• Modified nucleotide
o Adenine ribose + Pi + Pi +
Pi
Macromolecule Review
1) Carbohydrates
• Structure / monomer
o monosaccharide
• Function
o Energy
o Raw materials
o Energy storage
o Structural compounds
• Examples
o glucose, starch, cellulose, glycogen
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2) Lipids
• Structure / building block
o Glycerol, fatty acid, cholesterol, H-C chains
• Function
o Energy storage
o Membranes
o Hormones
• Examples
o Fat, phospholipids, steroids
3) Proteins
• Structure / monomer
o Amino Acids
o Levels of structure
• Function
• Enzymes, Defense, Transport, Structure,
Signals, Receptors
• Examples
o Digestive enzymes, membrane channels,
insulin hormone, actin
4)Nucleic Acids
• Structure / Monomer
o Nucleotide
• Function
o Information storage & Transfer
• Examples
o DNA, RNA