Post on 14-Apr-2018
7/27/2019 Chapter 1 Amino Acids
1/4
1.A buffer is a solution
that RESISTS change
in pH following the
addition of an acid or
base. A buffer can be
created by mixing a
weak acid (HA) withits conjugate base (A-
). If an acid such as
HCl is added to such a
solution, A- can
neutralize it, in the
process being
converted to HA.
If a base is added, HA
can neutralize it, in
the process being
converted to A-.
Maximum buffering
capacity occurs at a
pH equal to the pKa
but a conjugate
acid/base pair can
still serve as an
effective buffer when
the pH of a solution is
what?
within approximately 1 pH unit of
the pKa - (example) - solution
containing acetic acid (HA = CH3-
COOH) and acetate (A- = CH3-
COO-) with a pKa of 4.8 resists a
change in pH from pH 3.8 to 5.8,
with maximum buffering at pH =4.8. [Note: At pH values less than
the pKa the protonated acid form
(CH3-COOH) is the predominant
species. At pH values greater than
the pKa the deprotonated base form
(CH3-COO-) is the predominant
species in solution.]
2.A zwitterion is the
isoelectric form of a
molecule having an
overall charge of zero,
what else is this
called? (form)
Dipolar form
3.All amino acids found
in proteins are of the
L-configuration. So
where would the D-
amino acids be found?
Some antibiotics and in bacterial
cell walls.
4.All of the amino acids
with uncharged
POLAR side chains
are hydrophilic except
which one?
Tyrosine
5.All of the NONpolar
amino acids are
hydrophobic except?
Methionine - hydrophillic -
contains SULFUR
6.Amino acids are
classified by their side
chains (R-groups). If
the amino acid has an
even distribution of
electrons, is it polar or
nonpolar?
Nonpolar
7. Amino acids are classified by their side
chains (R-groups). If the amino acid has
an uneven distribution of electrons, is it
polar or nonpolar?
Polar - ie
Acids or Bases
8. Amino acids in aqueous solution
contain weakly acidic -carboxyl groups
and weakly basic -amino groups and
each of the acidic and basic amino acids
contains an ionizable group in its side
chain. Thus, both free amino acids and
some amino acids combined in peptide
linkages can act as what?
Buffers
9. Amino acids that have an asymmetric
center at the -carbon can exist in two
forms, designated D and L, that are
mirror images of each other. What are
the 2 forms called?
Stereoisomers,
optical
isomers, or
enantiomers
10.Are ketogenic amino acids basic oracidic? What are the ketogenic amino
acids?
Acidic1. Leucine
2. Lysine
11. Concept question: Which amino acid
will increase your respirations or
increase your potassium levels?
Leucine,
Lysine
12. Concept question: Which hormones
have a lot of cysteine?
If they have
cysteine - they
have
dissulfide
bonds
(Insulin,
inhibin,growth
hormone,
prolactin)
13. Cysteine's side chain has a -SH group
which is an important component of the
active site of many enzymes, which other
amino acid has a side chain that is an
important component of the active site
of many enzymes?
Serine
Chapter 1 Amino AcidsStudy online at quizlet.com/_bhvyh
7/27/2019 Chapter 1 Amino Acids
2/4
14. Define dissociated vs
soluble vs. bioavailable
in reference to
acid/base?
Dissociated is loss of H+ (removal
of hydrogens)
Bioavailable is neutral, can cross a
fat soluble membrane
Soluble (POLAR) has a charge and
will a ttract H2O (can not cross
BBB)
15. Describe the amino
group and carboxyl
group of an amino
acid at physiologic
pH.
CHARGED at physiologic pH -
Amino group is protonated (NH2
to NH3+) Carboxyl Group is
dissociated (COOH to COO-)
16. Explain the equation:
Ka = [H+] [A-]
-----------------
[HA]
Dissociation constant: The larger
the Ka, the stronger the acid,
because most of the HA has been
converted into H+ and A+.
Conversely, the smaller the Ka, the
less acid has dissociated and,
therefore, the weaker the acid.
17. For a base w/ pH = 7and pKa = 8, how
much is dissociated
and how much is
bioavailable?
pH = pKa - 1 = 10% dissociated(10% bioavailable)
18. For and acid w/pH = 5
and pKa = 4, how
much is dissociated
and how much is
bioavailable?
pH = pKa - 1 = 10% dissociated
(90% bioavailable)
19. If your body is acidic,
what effect does this
have on your
potassium?
Acidic = Hyperkalemic
20. In proteins found in
aqueous solutions,
where are the
nonpolar acids found?
Nonpolar (oily) - are found
clustered together in the interior of
the protein = hydrophobicity of the
R-groups - help give it, its 3-D
shape.
21. In proteins, the -SH
groups of two
cysteines can become
oxidized forming a
covalent cross-linkcalled a dissulfide
bond, this is called
what?
Cystine (a dimer)
22. Ketones are broken
down and made from
Acetyl-CoA, so what is
the building block for
ketones?
Acetyl-CoA
23. Most enzymes have
serine, threonine or
tyrosine in their active
sites, what is important
about this?
These amino acids have an
OH group that is used to make
bonds
24. N-linked glycosylation of
proteins - post
translational
modification of proteins
associated with what cell
organelle?
Endoplasmic Reticulum
25. O-linked glycosylation of
proteins - post
translational
modification associated
with which cell organelle?
Golgi Apparatus
26. Proteins located in a
hydrophobic
environment, such as a
membrane, where are thenonpolar amino acids
found?
Nonpolar R-groups are found
on the outside surface of the
protein, interacting w/the lipid
environment - they function tostabilize the protein structure
27. Substances that can act as
either an acid or a base
are defined as what and
are referred to as what?
1. Amphoteric
2. Ampholytes (amphoteric
electrolytes)
28. The alpha carbon of each
amino acid is attached to
four different chemical
groups and is therefore
considered to be a chiral
carbon or optically active
carbon. What protein is
the exception?
Glycine - its alpha carbon has
2 hydrogens attached
29. The alpha carbon of each
amino acid is attached to
four different chemical
groups and is therefore
considered to be what
type of carbon atom?
Chiral Carbon or Optically
active carbon atom
30. The amino acids (with
acidic side chains)
aspartic and glutamicacid: are they proton
donors or proton
acceptors?
Proton Donors - side chains
are fully ionized at neutral pH
containing a negativelycharged carboxylate group (-
COO) so called Aspartate and
Glutamate to emphasize that
these amino acids are
negatively charged at
physiologic pH
31. The amino acids (with
basic side chains) Lysine
and arginine: are they
proton donors or proton
acceptors?
Proton Acceptors - side chains
are fully ionized at physiologic
pH being positively charged
7/27/2019 Chapter 1 Amino Acids
3/4
7/27/2019 Chapter 1 Amino Acids
4/4
53.Which amino acid has an Inole group? Tryptophan the "Largest"
amino acid
54.Which amino acids are glucogenic and Ketogenic? 1. Phe
2. Iso
3. Thr
4. Trp
Mr. PITT
55.Which amino acids have uncharged POLAR side chains? 1. Ser2. Thr
3. Tyr
4. Asn
5. Cys
6. Glu
56.Which free amino acid is weakly basic and largely uncharged at physiologic pH? Histidine
57.Which NONpolar amino acid can form Serotonin & niacin? Tryptophan
58.Which protein is the best buffer in the body? Histidine
59.Which three amino acids have a polar hydroxyl group that can participate in hydrogen bond
formation?
1. Serine
2. Threonine
3. Tyrosine
60.Which three amino acids have side chains that can serve as a site of attachment for
oligosaccharide chains in glycoproteins?
1. Asparagine - amide grou
2. Serine or Threonine -
hydroxyl group