section 5, chapter 2
DESCRIPTION
proteins and nucleic acidsTRANSCRIPT
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Section 5, Chapter 2Organic molecules
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Proteins
Proteins have many functions:
Proteins provide structural material.
They are a source of energy.
Some act as chemical messengers (hormones, neurotransmitters).
Many proteins are receptors.
Most enzymes are proteins.
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Synthesis reaction involving an enzyme
Enzymes catalyze reactions (increases rate), but are not consumed by the reaction (reusable).
Proteins: enzymes
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Proteins: amino acids
All amino acids consists of:An amino group (-NH2)
A Carboxyl Group (-COOH)
A single Carbon atom
An “R” group (R = rest of the molecule)1 of 20 possible “R” groups = determines amino acid
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Amino group Carboxyl group
R groupAmino Acid
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20 amino acids determined by 20 possible “R” groups
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Peptide BondsAmino Acids are joined by peptide bonds
Dipeptide = 2 amino acids joined by peptide bond
Polypeptide = several amino acids joined by peptide bond
Peptide bond (red) joins two amino acids.
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Dipeptide: two amino acids joined together
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Polypeptide: several amino acids joined together
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Primary structure is the amino acid sequence of a polypeptide chain
A protein’s shape, or conformation, determines its function. Therefore, it’s important to understand a protein’s shape at 4 levels.
4 Levels of Protein Structure
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Secondary Structure Shapes within local regions of polypeptides Includes coils (alpha helix) & folds (pleated sheets) Secondary structures are stabilized by Hydrogen bonding.
Red dots indicatehydrogen bonding
4 Levels of protein structure
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Tertiary Structure• includes the three-dimensional folding of a polypeptide
•The tertiary structure is the highest level for proteins consisting of just one polypeptide.
4 Levels of protein structure
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Quaternary Structure• The quaternary structure is the three-dimensional shape of proteins consisting of two or more polypeptides
4 Levels of protein structure
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Hemoglobin = protein with 4 polypeptide chains
Example of a protein
4 Levels of protein structure
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ConformationComplex 3 dimensional fold of a protein
Conformation determines a protein’s function
DenatureTreatment that alters the shape of a protein to make it nonfunctional
Heat, pH changes, radiation, certain chemicals may denature proteins
Protein Structure
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Deoxyribonucleic Acid (DNA)Double stranded polynucleotide
Ribonucleic Acid (RNA)Single-stranded polynucleotide
Nucleic acids: overview
Nucleic AcidsIncludes DNA and RNAGenetic informationConsists of monomers, called nucleotides
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RNAContains the sugar ribose (ribonucleic acid)RNA is a single-stranded nucleic acid.Transcribes DNA for protein synthesisRNA also may act as an enzyme
DNADNA contains a sugar, called deoxyribose (deoxyribonucleic acid)Double-stranded helixEncodes genetic information for protein synthesis.
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NucleotidesNucleotides are the monomers of Nucleic Acids
3 Components of a Nucleotide5 Carbon Sugar (S)Nitrogenous Base (B)Phosphate Group (P)
RNASugar = ribose
DNASugar = deoxyribose
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RNASingle polynucleotide strand
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DNA
2 polynucleotide strands stabilized by Hydrogen bonds Strands are anti-parallel
H bonds
Antiparallel
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Summary of organic compounds
end of section 5, chapter 2