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12 Cards in this Set
- Front
- Back
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Proteins - Polymers of Amino Acids linked through peptide bonds and with molecular weight higher than 5000 Daltons
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Functions of Proteins-
Structural Catalytic Hormonal Defense Transport Storage Biological Fuel Molecular Signaling |
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Amino Acid- an organic chemical compound with at least one amino acid and one acid group
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Poteinic Amino Acid- All amino acids used as building blocks of Proteins and encoded in DNA structure
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Functions of Proteinic Amino Acids-
Building blocks of Proteins Biological Fuel Only source of metabolic nitrogen |
Proteinic Amino Acids
There are only 20 19/20 are alpha amino acids (imino acid) Proline is a secondary alpha amino acid All have L-configuration All bipolar in sold state (zwitterion) Chiral center is alpha carbon; except Glycine |
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Classification of Proteinic Amino acids
according with the characteristics of side chain (R) Non-polar, aliphatic Aromatic Positively charged (diamino monocarboxylic) Negatively charged (monoamino dicarboxylic) Polar, uncharged |
Non- polar aliphatic
Glycine Proline Alanine Leucine Valine Methionine Isoleucine |
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Aromatic
Tyrosine Phenylalanine Tryptophan |
Positively charged
Lysine Histidine Arginine |
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Negatively charged
Aspartate Glutamate |
Polar, uncharged
Serine Asparagine Threonine Glutamine Cysteine |
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Classification of Proteinic Amino acids
according with side chain polarity Non-polar, neutral Glycine Alanine Valine Leucine Isoleucine Phenylalanine Methionine Proline |
Polar, neutral
Cysteine Serine Threonine Asparagine Glutamine Tyrosine Tryptophan |
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Polar, acidic
Glutamate Aspartate |
Polar, basic
Lysine Arginine Histidine |
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Solubility of Amino Acids
They are water soluble but solubility changes according to side chain |
Polar Amino Acids are highly soluble in water
Non-Polar Amino Acids are less soluble in water and more soluble in apolar solvents |
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Electrical Charge and Chemical Properties of Amino Acids and Proteins
They are amphoteric and can act as buffers resistant to pH change Amphoteric- can act as either an acid or a base (i.e. can donate/accept a proton) |
Isoelectric Points of Amino Acids
Is the pH value in which one amino acid, (in water solution and under the influence of an electric field) does not migrate neither anode nor cathode because its electric net charge is equal to zero |
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Neutral Amino Acids have pI values ranging from 5.05 to 6.30
Acidic and Basic Amino Acids have pI values on the acidic and basic sides of that range. |
Ionic Species of Neutral Amino Acids
pI= pKa1 + pKa2 ________________ 2 |
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Characteristics of Amino Acids at Physiological pH
Physiological pH= 7.4 All carboxyl and amino groups, including those on side groups of all alpha amino acids are charged at physiological pH The neutral alpha amino acids exist as bipolar ions with zero overall charge at physiological pH The acidic and basic alpha amino acids have overall charges of 1- and 1+ respectively |
Ionic Species of Alanine
[Base] pH= pKa + log ______ [Acid] |
