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Lecture 3
Amino Acids
| Question | Answer |
|---|---|
| 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 |
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