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Lecture 3

Amino Acids

effect of hypotonic solution on RBC? solution has lower solute concentration than in the cytosol causes H2O diffusion into the cell causing it to rupture
effect of hypertonic solution on RBC? solution has higher concentration than cytosol, H2O diffuses out of the cell causing it to shrink
effect of isotonic solution on RBC? solution has the same concentration as the cytosol, H2O diffusion in and out of the cell is balanced
significance of proteins? - 20% of human body is made up of proteins - play crucial role in almost all biological processes
functions of proteins? 1. enzymes- digest, pH reg, DNA copy 2. structure- collagen, keratin 3. movement/motor proteins- actin, myosin 4. fight infection-antibody 5. hormones- insulin, glucagon, GH 6. metabolism- lipoprotein, lipase, glycogen synthesis, phosphofructokinase
what links amino acids into polypeptides? peptide bonds
what determines amino acid order or sequence? genetic code
proteins are __________ polymers of amino acids
polypeptides are _________ repeating monomers of amino acids
amino acid structure? amino group and carboxyl group attached to an alpha carbon. As well as an R group which is unique for each amino acid
what are zwitterions dipolar and charged at physiological pH amino acids are that
what are the two isometric forms of amino acids L and D are the two forms, L forms are found in natural proteins (most common)
peptide bonds covalent bonds formed between α amino group of one amino acid and α carboxyl group of another
what adds amino acids to polypeptides? ribosomes during the process translation
N terminal is the only amino acid that has _____________ and C terminal is the only one that has _________________ free amino group, free carboxyl group
direction of polypeptide? to the α-carboxyl group of the last amino acid in peptide
rotation in peptide bond? limited
configuration of peptide bonds? why? trans(R's face diff directions), due to steric clashes between R groups when Cis
why is an amino acid's sequence important? because it determines a protein's shape, and shape determines function of proteins. Mutating a single amino acid can make protein dysfunctional and lead to diseases
neutral nonpolar amino acids glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, phenylalanine
neutral polar amino acids serine, threonine, tyrosine, cysteine, asparagine, glutamine
acidic amino acids aspartate, glutamate
basic amino acids lysine, arginine, histidine
branched chain amino acids valine, leucine, isoleucine. used to build muscle
aromatic amino acids phenylalanine, tyrosine (not hydrophobic), tryptophan
amino acids that absorb light aromatic
what amino acids are responsible for the absorbance of ultraviolet light by proteins tryptophan and tyrosine
amino acid that can form disulfide bonds cysteine
why is proline considered an "imino" acid because its the only aa with a secondary amine
where would a hydrophobic amino acid be found in a cytosolic protein? in the core of the cytosolic protein contort to avoid water
where would a hydrophobic amino acid be found a transmembrane protein? would be found in the membrane-spanning regions of transmembrane protein because membrane is hydrophobic
amino acids found mostly in active sites positively charged/basic
the negative charge on acidic amino acids is on the _________ and the positive charge on basic amino acids is on the____________ carboxyl, amino
amino acids that has sulfur cysteine and methionine
what does it mean to hydroxylate an amino acid add OH to R group
what aa's can be hydroxylated? lysine and proline
what aa's can be phosphorylated? serine, threonine, and tyrosine
what aas make turns and loops? proline (for collagen) and glycine
pKa value of amino acid refers to point where protonated and non-protonated forms of the amino acid are found in equal concentrations. 50-50
If the pH is less than the value of the pKa of an aa, then the predominant form is the protonated (acid, proton donor)
If the pH is more than the value of the pKa of an aa, then the predominant form is the non protonated (base/proton acceptor)
what is an ampholyte structure that can be acidic or basic depending on the solution they're in aa's are that
Isolelectric point pH at which there is 0 net charge
what groups can ionize on aa carboxy and amino groups for all aa's some aa's have ionizable R groups as well
how to find PI (pKa1+pKa2)/2 for normal aa's average lower pKa's for acidic aa average higher pKa's for basic aa
what amino acids have ionizable side chains? aspartic acid, glutamic acid, lysine, arginine, histidine, cysteine, tyrosine (acidic+basic+cysteine+tyrosine)
what amino acid depends on the environmental pH and can bounce from neutral, to positively charged basic or negatively charged acidic histidine
why do we look for histidine when we find a protein that changes charge when pH changes? because the pKa of histidine varies depending on pH of environment
a polypeptide with a net positive charge at physiological pH (~7.4) most likely contains amino acids with R groups of what type? Basic R groups
in lysine, the pKa of the side chain is about 10.5. assuming that the pKa of the carboxyl and amino groups are 2 and 9, the pI of lysine is closest to choose 2 higher 10.5+9 divide by 2 ~9.8
Created by: rusulali97
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