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Amino Acids and Peptides

only source of nitrogen in our bodies amino acids
a metabolic energy source amino acids; last resource for metabolic energy
amino acids are classified based on R groups
the carbon in the center of the amino acid; has an amine, R group,H, and acid group attached alpha Carbon
contains BOTH positive and negative charges at pH 7.4 zwitterionic
Amino Acids are asymmetric, except for glycine; all others have 4 different things on chiral carbon
CORN L- amino acid; COOH, R group, and NH2; COUNTING CLOCKWISE. If not in this order they are "D"
All 20 standard amino acids are "L" true/ false? true; the D forms are plants and bacteria
antibiotics derived from bacteria with D- amino acids degrade more slowly true
amino acids are broken into charged and uncharged; the 5 subclasses are? negative and positive (charged) and polar, aromatic, and non-polar (neutral)
negative amino acids (2) Aspartic; Glutamic
Positive Amino Acids (3) Arginine, Histidine, and Lysine
Polar amino acids (5) STAGC Serine, Threonine, Asparagine, Glutamine, Cysteine
Aromatic Amino acids (3) PTT Phenylalanine, Tyrosine, Tryptophan
Non- polar amino acids (7) V A L G I M P Valine, Alanine, Leucine, Glycine, Isoleucine, Methionine, Proline
Which amino acid is neither L or D? Glycine; R group is a Hydrogen; no chiral structure so cannot determine CORN
Size/ shape of R- groups determine protein topology, form hydrophobic faces Neutral, non-polar aliphatic amino acids
WHent he R group of an amino acid is attached to the amine group what happens? It causes a kink in the protein
UV absorbed by this type of amino acid Neutral aromatic; planar shape and stacking
Which amino acid R group is an SH Cysteine; can be sulfur breach protein linkage
MUST know charged amino acids by name and structure check PPT notes
an oxidized derivative of cysteine Cystine; the disulfide S-S bond makes Cystine; free cysteine molecules bond to form cystine in the extracellular space. Once transported intot he cell cystine is reduced back to cysteine
The solubility of cystine decreases when pH is? Low
Cystine causes disease under what conditions? pH imbalance, precipitates in kidney
Characteristics of CHARGED amino acids hydrophilic surfaces in proteins; salt bridges in proteins; acid/ base and covalent protein chemistry
Glucose is utilized by every cell in the body Fat not utilized by brain or RBC's
NOT biosynthesized by humans, required in the diet Essential Amino Acids
Tyrosine is biosynthesized from Phenylalanine
Bulky Aliphatics and aromatics (except Tyrosine) Esential amino acids
Short aliphatics, negative charges, amides Non-essential; also Tyrosine
Semi-essential amino acids required by children and pregnant women Histidine and Arginine
amino acids that are biosynthesized by humans non-essential
If no Phenylalinine there is also no Tyrosine
Cysteine is biosynthesized from Methionine
Essential Amino Acids (8) Iso; Leu; Lys; Meth; Phenyl; Threo; Trypto; Val
Recommended Daily Allowance of protein 0.8g "high quality"; contains all the essential amino acids (animal sources) milk, eggs, meat
Low quality protein deficient in one or more essential amino acid (vegetable proteins)
High Lysine and low Arginine is used to deter herpes outbreaks; lysine disrupts functioning of herpes because it uses high Arginine and Lysine inhibits ARginine utilization; viral replication disrupted
molecule that generates a second molecule precursor
If asked the precursor to Epinephrine we would answer Tyrosine; L- dopa; and Dopamine
Amino Acic; CNS neurotransmitter found in spinal fliud Glycine
Non- standard amino acids Hydroxylysine; HYdroxyproline: Ornithine; Citrulline; Carnitine; Creatine; Taurine; Homocysteine; NME- amino acids
Non-standard amino acid important for maintaining collagen structures Hydroylysine and Hydroxyproline
Non- standard amino acid found in natural products from microorganisms; stabilize peptide against degradation NMe amino acids (N-Methyl Glycine is sarcosine)
Non- standard amino acid; intermediates in the urea cycle Ornithine and Citrulline
Non-standard amino acid; Lys derivative; fatty acid transport Carnitine
Non- standard amino acid; Arg+ Gly derivative; accepts and donates phosphate group that can supply ATP in active muscle Creatine
Non- standard amino acid; Cys derivative; Bile salt conjugate Taurine
Non- standard; Met derivative; associated with heart disease Homocysteine
Aspartic acid and Phenyl alanine= Aspartame
Genetic defect of the lys-arg-orn-cystine transport protein in intestine and kidney; (1 in 2500-15000) Cystinuria; Cysteine is not soluble; causes kidney stones. Treatment= basifying urine (acitozolamide penicillin); conjugating the cystine with drugs and lots of water
Genetic defect of the lysosomal cystine transport system Cystinosis; Cystine accumulates in lysosomes causing increased cell death rates and organ failure (1 in 100,000- 200,000)
Genetic defect of a neutral amino acid transport protein in intestines and kidney Hartnup disease; (1 in 24,000) Prevents proper absorption/reabsorption of these amino acids including Tryptophan (precursor of Vit B6); results in niacin deficiency and PELLAGRA
Genetic defect of a homocysteine- metabolizing enzyme, cystathionine synthase. accumulation of homocysteine causes long, thin bones, lens dislocation, mental deficiencies, and HEART DISEASE. 50% respond to treatment with B6 or B12 and folic acid
Phenylketonuria PKU; 1 in 15,000; inability to breakdown phenylalanine- it builds up and is toxic to brain
Symptoms of PKU intellectual disability; seizures; nausea; vomiting; eczema- like rash; mousy body odor
what diet restriction allows normal growth for PKU? Phenylalanine; BH4 oral can also reduce blood levels of this amino acid
amino acids cause the urine to smell like maple syrup; lack of amino acid metabolizing enzymes maple syrup urine disease;Mennonite families; treatment = dialysis B1 (thiamin) injections; diet low in leucine, isoleucine, valine
lack of enzyme needed to metabolize tyrosine Tyrosonemia; dysfunctional liver and kidney
B6, B12, and Folic acid have been shown to prevent atheroschlerotic plaque in what amino acid based disorder Hyperhomocysteinemia; elevated blood homocysteine- not currently true that B vitamins help and hyperhomocysteinemia is not correlated to heart disease
pKa = -log (Ka) no answer
the point of NO net charge isoelectric point; when pH= pI there is no net charge
pH > pI means negative charge
pH < pI means positive charge
calculating pI pK1 + pK2 divided by 2 = pI
how to calculate pI when 3 pKa values given there will be 4 forms; ex: A-, A, A+, A--; the 4th form will either be 2+ or 2-
To determine what 4th form will be we need to know what? If we are told the amino acid we will know whether it is positive or negative
Ex of 4th form with Histidine A++__A+__A__A- ; fill in the blanks with the given pKa and use the 2 values to the right because they include a neutral A; p31 of notes
Low pKa= molecule likes to release H+; requires high concentration of H+ to populate molecule with H+
the pKa's surrounding the neutral species are used to calculate pI no answer p.36
amino acids react to form peptide (amide) bonds
amino acids that make up a polymer are called residues
The 1st amino's COO- binds to the 2nd amino's NH3+ H2O molecule created; H2 from amino, O from the carboxylic acid
Direction of free ends in naming a peptide always N-terminal to C-terminal; -yl replaces -ine or -ate except the C terminal(last) amino acid in the sequence
2/3 residues dipeptide/ tripeptide
A few residues Oligo
many residues polypeptide
a few residues with 2D or 3D shape, usually 40+ protein
naming example: H3N+-Gly-Asp-His-Leu-Val-Coo- glycyl-aspartyl-hitidyl-leucyl-valine; start with the H3N side and leave the last amino acid in whole name
Isoelectric points are used to determine electrophoretic mobility of amino acids, peptides, proteins, and manipulating protein solubility
When protein's pI= pH of solution, a protein is least soluble
Ligands for opioid receptors; signal for pleasant feelings that counteract pain Enkephalins and Endorphins; physiological peptides
peptide hormone; 9 amino acids (nonapeptide); released from pituitary after hypothalamus detection of lack of water Vasopressin, or ADH; promotes water retention by kidneys and induces vasoconstriction to maintain blood pressure
Lack of the physiological peptide Vasopressin can lead to diabetes Insipidus; excessive thirst and urination
Physiological peptide; doesn't cross blood- brain barrier; secreted from pituitary; uterine contractions oxytocin
advantages of peptide drugs specific, active,minimal drug interactions, less accumulation in other tissues, less toxicity, potent, diverse
disadvantages of peptide drugs low absorption (injection often required); difficult membrane transport, costly, immunological risk, cleared from body quickly
Created by: angieryx



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