MCB 354 Exam 1 QUESTIONS AND
CORRECT ANSWERS
What did scientists find in the samples from the osirex sample? - CORRECT ANSWER all five
nucleotide bases and 14/20 amino acids
What could the osirex samples tell us? - CORRECT ANSWER - the first amino acids were
brought to earth by asteroids
- life outside of earth is based on dna/amino acid biology
How many acids are chiral molecules? - CORRECT ANSWER 19/20
What are the two enantiomers of amino acids? - CORRECT ANSWER L and D
Our proteins are entirely made of what kind of amino acids? - CORRECT ANSWER L amino
acids
How many of the amino acids from the osirex sample were L and D? - CORRECT ANSWER
half and half
What is unique about amino acids for possible life outside of earth? - CORRECT ANSWER
they could be based on D-amino acids instead of L-amino acids
What is insulin and what is it made up of? - CORRECT ANSWER small protein that controls
sugar levels in blood, made up of 51 amino acids
What is the function (type) of insulin? - CORRECT ANSWER signaling
What are the common structural features of amino acids - CORRECT ANSWER - alpha carbon
with four substituents
- carboxyl group
- amino group
,- H atom
- r group
What is an R group? - CORRECT ANSWER a side chain unique to each amino acids
What is the geometry of amino acids? - CORRECT ANSWER tetrahedral
What is a characteristic of the nonpolar, aliphatic amino acids? - CORRECT ANSWER
hydrophobic
What is a characteristic of the polar, uncharged amino acids? - CORRECT ANSWER
hydrophilic
What is a characteristic of the positively charged amino acids? - CORRECT ANSWER more
hydrophilic than the polar, uncharged amino acids
What is a characteristic of the negatively charged amino acids? - CORRECT ANSWER
hydrophilic
What order you do write amino acid chains? - CORRECT ANSWER N teminal to C terminal
What is the alpha carbon in an amino acid? - CORRECT ANSWER the carbon attached to the
four subsituents (carbon 2, not 1)
What amino acid is not a chiral molecule? Why? - CORRECT ANSWER glycine has two
hydrogens attached to it, does not have 4 unique groups
Since the amino acid have two possible stereoisomers, they have... - CORRECT ANSWER
enantiomers
What was the first molecule used to determine L and D configurations? - CORRECT ANSWER
glyceraldehyde
,How do you determine if something is an L or D molecule? - CORRECT ANSWER - draw
fischer molecule with carboxylic/aldheyde ON TOP
- if the OH/NH3 is on the left = L
- if OH/NH3 on right = D
What is an ionizable group? - CORRECT ANSWER a part of a molecule that can gain or lose a
proton/electron and acquire an electrical charge
How many amino acids have ionizable R groups? Which ones? - CORRECT ANSWER 7
(tyrosine, cysteine, aspartic acid, glutamic acid, arginine, histidine, lysine)
What does pKa tell you? - CORRECT ANSWER how acidic a functional group is
What does a low (1-3) pKa indicate? - CORRECT ANSWER the group is acidic and is
deprotonated easily
What does a high (9-11) pKa indicate? - CORRECT ANSWER the group does not get
deprotonated easily
amino groups have a _____ pKa than the carboxyl group - CORRECT ANSWER higher
What is an isoelectric point? - CORRECT ANSWER pI is the pH at which the net electric
charge is zero
What happens when pH = pKa? - CORRECT ANSWER half of the molecule is protonated and
the other half is deprotonated
What is a zwitterion? - CORRECT ANSWER a molecule with both a positive and a negative
charge
How do you find pI for aa without ionizable side chains? - CORRECT ANSWER average of
the two pkas
, when pH = pI, the net charge is... - CORRECT ANSWER 0
when pH > pI, the net charge is... - CORRECT ANSWER negative
when pH < pI, the net charge is... - CORRECT ANSWER positive
How do you find pI for aa with an ionizable side chains? - CORRECT ANSWER - draw all
charged molecules
- calculate average using the two pka values associated with the 0 charged molecule
What is an oligopeptide? - CORRECT ANSWER peptide with 2-20 amino acids
How many amino acids in a polypeptide vs a protein? - CORRECT ANSWER polypeptide: 20-
100
protein: more than 100
Ribosomes use information from ____ to synthesize proteins - CORRECT ANSWER mRNA
What kind of bonds are between amino acids? - CORRECT ANSWER peptide bonds
What is a peptide bond? How is it formed and broken? - CORRECT ANSWER covalent bond
between amino acids that is formed via condensation and broken through hydrolysis
What specific atoms are in a peptide bond? - CORRECT ANSWER the carbonyl carbon of one
amino acids and an amino nitrogen of the other
Where does the water come from in in the condensation reaction of peptide bond formation? -
CORRECT ANSWER OH from carboxyl of amino acid 1, and H atom from amino acid 2
Condensation reaction of a peptide bond is _________ - CORRECT ANSWER reversible
CORRECT ANSWERS
What did scientists find in the samples from the osirex sample? - CORRECT ANSWER all five
nucleotide bases and 14/20 amino acids
What could the osirex samples tell us? - CORRECT ANSWER - the first amino acids were
brought to earth by asteroids
- life outside of earth is based on dna/amino acid biology
How many acids are chiral molecules? - CORRECT ANSWER 19/20
What are the two enantiomers of amino acids? - CORRECT ANSWER L and D
Our proteins are entirely made of what kind of amino acids? - CORRECT ANSWER L amino
acids
How many of the amino acids from the osirex sample were L and D? - CORRECT ANSWER
half and half
What is unique about amino acids for possible life outside of earth? - CORRECT ANSWER
they could be based on D-amino acids instead of L-amino acids
What is insulin and what is it made up of? - CORRECT ANSWER small protein that controls
sugar levels in blood, made up of 51 amino acids
What is the function (type) of insulin? - CORRECT ANSWER signaling
What are the common structural features of amino acids - CORRECT ANSWER - alpha carbon
with four substituents
- carboxyl group
- amino group
,- H atom
- r group
What is an R group? - CORRECT ANSWER a side chain unique to each amino acids
What is the geometry of amino acids? - CORRECT ANSWER tetrahedral
What is a characteristic of the nonpolar, aliphatic amino acids? - CORRECT ANSWER
hydrophobic
What is a characteristic of the polar, uncharged amino acids? - CORRECT ANSWER
hydrophilic
What is a characteristic of the positively charged amino acids? - CORRECT ANSWER more
hydrophilic than the polar, uncharged amino acids
What is a characteristic of the negatively charged amino acids? - CORRECT ANSWER
hydrophilic
What order you do write amino acid chains? - CORRECT ANSWER N teminal to C terminal
What is the alpha carbon in an amino acid? - CORRECT ANSWER the carbon attached to the
four subsituents (carbon 2, not 1)
What amino acid is not a chiral molecule? Why? - CORRECT ANSWER glycine has two
hydrogens attached to it, does not have 4 unique groups
Since the amino acid have two possible stereoisomers, they have... - CORRECT ANSWER
enantiomers
What was the first molecule used to determine L and D configurations? - CORRECT ANSWER
glyceraldehyde
,How do you determine if something is an L or D molecule? - CORRECT ANSWER - draw
fischer molecule with carboxylic/aldheyde ON TOP
- if the OH/NH3 is on the left = L
- if OH/NH3 on right = D
What is an ionizable group? - CORRECT ANSWER a part of a molecule that can gain or lose a
proton/electron and acquire an electrical charge
How many amino acids have ionizable R groups? Which ones? - CORRECT ANSWER 7
(tyrosine, cysteine, aspartic acid, glutamic acid, arginine, histidine, lysine)
What does pKa tell you? - CORRECT ANSWER how acidic a functional group is
What does a low (1-3) pKa indicate? - CORRECT ANSWER the group is acidic and is
deprotonated easily
What does a high (9-11) pKa indicate? - CORRECT ANSWER the group does not get
deprotonated easily
amino groups have a _____ pKa than the carboxyl group - CORRECT ANSWER higher
What is an isoelectric point? - CORRECT ANSWER pI is the pH at which the net electric
charge is zero
What happens when pH = pKa? - CORRECT ANSWER half of the molecule is protonated and
the other half is deprotonated
What is a zwitterion? - CORRECT ANSWER a molecule with both a positive and a negative
charge
How do you find pI for aa without ionizable side chains? - CORRECT ANSWER average of
the two pkas
, when pH = pI, the net charge is... - CORRECT ANSWER 0
when pH > pI, the net charge is... - CORRECT ANSWER negative
when pH < pI, the net charge is... - CORRECT ANSWER positive
How do you find pI for aa with an ionizable side chains? - CORRECT ANSWER - draw all
charged molecules
- calculate average using the two pka values associated with the 0 charged molecule
What is an oligopeptide? - CORRECT ANSWER peptide with 2-20 amino acids
How many amino acids in a polypeptide vs a protein? - CORRECT ANSWER polypeptide: 20-
100
protein: more than 100
Ribosomes use information from ____ to synthesize proteins - CORRECT ANSWER mRNA
What kind of bonds are between amino acids? - CORRECT ANSWER peptide bonds
What is a peptide bond? How is it formed and broken? - CORRECT ANSWER covalent bond
between amino acids that is formed via condensation and broken through hydrolysis
What specific atoms are in a peptide bond? - CORRECT ANSWER the carbonyl carbon of one
amino acids and an amino nitrogen of the other
Where does the water come from in in the condensation reaction of peptide bond formation? -
CORRECT ANSWER OH from carboxyl of amino acid 1, and H atom from amino acid 2
Condensation reaction of a peptide bond is _________ - CORRECT ANSWER reversible
