biochemistry Flashcards
amino acids have _ groups attached to a central carbon
four
_ groups include:
1. amino group
2. carboxylic acid group
3. hydrogen atom
4. R group
amino acid
determines chemistry and function of amino acid
what is the R group?
there are _ amino acids that appear in proteins of eukaryotic organisms
20
stereochemistry for central carbon in eukaryotes will always be
L
_ amino acids can exist in prokaryotes
D
all amino acids have S configuration except _
cysteine
_ is the only achiral amino acid
glycine
glycine has R group: _
H atom
what do these amino acids have in common?
- glycine
- alanine
- valine
- leucine
- isoleucine
- methionine
- proline
these amino acids are nonpolar and nonaromatic
what do these amino acids have in common?
- tryptophan
- phenylalanine
- tyrosine
these amino acids are aromatic
what do these amino acids have in common?
- serine
- threonine
- asparagine
- glutamine
- cysteine
these amino acids are polar
what do these amino acids have in common?
- aspartate
- glutamate
these amino acids are acidic and negatively charged
what do these amino acids have in common?
- lysine
- arginine
- histidine
these amino acids are basic and positively charged
amino acids with long alkyl chains are _ while amino acids with charges are _
hydrophobic; hydrophilic
amino acids can both accept and donate protons, which means they are _
amphoteric
pH at which half of the species is deprotonated
what is pKa?
amino acids exist in _ forms at different pH values
different
amino acids are fully protonated at _ pH
low/acidic
amino acids are fully deprotonated at _ pH
high/alkaline
when the pH is near the pI of an amino acid, it is called _
zwitterion
isoelectric point (pI) can be calculated by averaging two pKa values for amino acids _ a charged side chain
without
amino acids can be _ (method)
titrated
titration curve is mostly _ at pKa value and _ at pI value (of amino acids)
flat; vertical
isoelectric point (pI) can be calculated by averaging two pKa values (protonation and deprotonation) for amino acids _ a charged side chain
with
pI of amino acids without charged side changes …
= 6
pI of ACIDIC amino acids …
below 6
pI of BASIC amino acids …
above 6
dipeptides have _ AA residues; tripeptides have _ residues
2; 3
amino acid subunits
what are residues?
oligopeptides have _ residues while polypeptides have _ residues
few (less than 20); many (over 20)
the release of one water molecule
what is dehydration (condensation)?
_ reaction forms the peptide bond
condensation (dehydration)
amide bonds are rigid due to _
resonance
nucleophilic amino group attacks _ of another amino acid
electrophilic carbonyl group
breaking a peptide bond is a _ reaction
hydrolysis
linear sequence of amino acids a in peptide
what is primary structure?
primary structure is stabilized by _
peptide bonds
local structure of neighboring amino acids
what is secondary structure?
secondary structure is stabilized by _ between amino groups and nonadjacent carboxyl groups
hydrogen bonding
clockwise coils around central axis
what are alpha helices?
rippled strands that can be parallel or antiparallel
what are beta pleated sheets?
_ can interrupt secondary structure due to rigid cyclic structure
proline
3D shape of single polypeptide chain
what is tertiary structure?
_ structure is stabilized by _ hydrophobic and acid-base interactions, hydrogen bonding, and disulfide bonds
tertiary
push hydrophobic R groups to interior of a protein
what are hydrophobic interactions?
hydrophobic interactions _ entropy and creates _ Gibbs free energy
increases; negative
forms when 2 cysteine molecules are oxidized and forms cystine (covalent bond)
what are disulfide bonds?
interaction between peptides in protein that contain multiple subunits
what is quaternary structure?
proteins with covalently attached molecules
what are conjugated proteins?
attached molecules that can include metal ions, vitamin, lipid, carbohydrate, nucleic acid
what are prosthetic groups?
loss of a 3D protein structure due to heat and increasing solute concentration
what is denaturation?
