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Nucleic Acids & Proteins
Chapter 3
Biochemistry
What you need to know!
• How to recognize nucleic acids and proteins
by their structural formulas
• The cellular functions of nucleic acids and
proteins
• The 4 levels of protein structure
• The denaturing impact that heat, pH, and
other variables can have on protein structure
Nucleic Acids
• Consists of C, H, N, O, P
• 3 types: DNA – Deoxyribonucleic Acid
RNA – Ribonucleic Acid
ATP – Adenosine Triphosphate
• Different functions
– DNA: hereditary information
– RNA: production of proteins
– ATP: energy molecule
• Monomer = Nucleotide
Nucleotide
Three parts:
1. Phosphate group
2. Sugar (Deoxyribose in
DNA, Ribose in RNA
& ATP)
3. Nitrogenous base:
(Adenine, Guanine,
Cytosine, Thymine,
Uracil)
Nitrogenous Bases
Come in 2 groups:
1. Pyrimidines (single ring):
Thymine (T), Cytosine (C), Uracil (U)
2. Purines (double ring):
Adenine (A),
Guanine (G)
• Purines fit with Pyrimidines
A pairs with T
G pairs with C
(2 Hydrogen Bonds)
(3 Hydrogen Bonds)
• RNA replaces all T’s with Uracil (U)
Polynucleotides
• Nucleotide monomers can form Phosphodiester
bonds
– Phosphate-Sugar backbone of DNA and RNA
• DNA double helix
• RNA single helix
ATP
• Single nucleotide with 3 Phosphate groups (P)
instead of 1
• It can lose P to release energy
– ATP  ADP + Energy
– ADP  AMP + Energy
Proteins
1. Contain C, H, O, N, S
2. Millions of functions some of which include:
•
•
•
•
•
Enzymatic proteins regulate chemical Rxs
Structural proteins support (ex. Muscles, cartilage)
Storage proteins store amino acids
Transport proteins move substances
Hormonal proteins coordinate multicellular
organisms
• Receptor proteins respond to environmental stimuli
• Contractile and motor proteins allow for movement
• Defensive proteins protect against disease
(antibodies)
Proteins
3. Monomers: 20 different amino acids (AA)
4. Polymer = polypeptide
• Small protein = ~100 AA
• Large protein = 1000’s of AA (Titin)
5. Proteins are sensitive to
•
•
•
•
temperature
pH
Imbalanced solutions
all cause denaturizing (loss of accurate 3D
structure)
Amino Acids
• Zwitterions: molecules that have
both an amino group (NH3) and
carboxyl group (COO or COOH)
• 20 different AA
• All have the same central carbon,
amino group, and carboxyl group
• Different functional groups (R – side
chain)
• R can be:
– Polar, non-polar, charged, uncharged,
hydrophilic, hydrophobic
20 Amino Acids
Polypeptides
• Connecting multiple AAs
• Condensation Reaction forms peptide
bond
• Repetitive peptide backbone
– (NCC-NCC-NCC-NCC)
Protein structure (4 stages)
• Structure and function determined
by # and sequence of AA
1. Primary structure (AA sequence)
2. Secondary structure (Hydrogen to
Oxygen)
• Primary polypeptide coil and fold
• Due to hydrogen bonds between
adjacent peptide bonds O   H
(NOT r-side chains)
• Special: alpha-helix, beta-pleated
sheet
Protein Structure
3. Tertiary Structure (R-side interactions)
• Further coiling of secondary
polypeptide due to R interactions
• Hydrophobic vs. Hydrophilic
• Polar Molecules
• Formation of disulfide-bridge S-S
• Hydrogen bonds
• Van der Waals
4. Quaternary structure
• Some proteins will associate with
other tertiary proteins to form
quaternary proteins
• Several tertiary polypeptides connect
together; usually held together by Rside chain interactions (hemoglobin)
Structure Animation
http://www.youtube.com/watch?v=lijQ3a8yU
YQ
Mutations  Abnormal Proteins
• Gene mutations can lead to the exchange of one or
more AAs. This sometimes leads to a non-functional
quaternary structure (Structure  Function)
• Example: Sicle-Cell Anemia, 1 AA is exchanged in
the hemoglobin primary structure, resulting in
abnormal folding.