Chp. 19 Amino Acids Flashcards
Storage protein examples?
Casein
Ferritin
Amino acids, the molecular building blocks of proteins, have a central carbon atom called the α carbon, bonded to
an ammonium group (—NH3+) and a carboxylate group (—COO−)
a hydrogen atom and an R group or side chain in addition to the carboxylate and ammonium groups.
a balance of positive and negative charge, which gives an overall zero charge (NET CHARGE = 0)
zwitterion
hydrogen, alkyl, or aromatic R groups
nonpolar (hydrophobic) amino acids
have R groups that interact with water, which makes them hydrophilic
polar amino acids
contain hydroxyl (—OH), thiol (—SH), or amide (—CONH2) R groups
polar neutral amino acids
contain a carboxylate (—COO−) R group.
polar acidic amino acids
contain an ammonium(—NH3+) R group.
polar basic amino acids
All are AAs are chiral except?
Glycine
Nonpolar AA
Glycine Alanine Valine Leucine Isoleucine Methionine Phenylalanine (F) Tryptophan (W) Proline
Polar AA
Serine Threonine Tyrosine (Y) Cysteine Asparagine Glutamine (Q)
Polar acidic AA
Aspartate
GLutamate
Polar basic AA
Histidine
Lysine (K)
Arginine (R)
an amide bond that forms when the —COO− group of one amino acid reacts with the —NH3+ group of the next amino acid
peptide bond
the particular sequence of amino acids held together by peptide bonds
primary structure
polypeptide of 50 or more amino acids with biological activity
protein
9 Essential AA
Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine
describes the structure that forms when amino acids form hydrogen bonds between the atoms in the backbone and atoms on the same or another peptide chain.
secondary structure
Common secondary structure?
Alpha helix
Beta pleaded sheet
hydrogen bonds form between the oxygen of the C=O groups and the hydrogen of N—H groups of the amide bonds
α helix
R-group is “pointed out”
hydrogen bonds form between the carbonyl oxygen atoms and hydrogen atoms in the amide groups bending the polypeptide chain into a sheet
β-pleated sheet
three polypeptide chains are woven together
hydrogen bonds hold the chains together, giving the polypeptide the added strength typical of collagen, connective tissue, skin, tendons, and cartilage
triple helix
overall three-dimensional shape formed by the interactions and repulsions of amino acid residues in different parts of the chain
tertiary structure
5 stabilizing interactions for tertiary structures…
Hydrophobic interactions Hydrophilic interactions Salt bridges HYdrogen bonds Disulfide bonds
ionic attractions between ionized Rgroups of polar basic and polar acidic amino acids
Salt bridges
covalent bonds that form between the —SH groups of cysteine residues in a polypeptide chain
Disulfide bonds
Biologically active proteins with two or more polypeptide chains or subunits have a
quaternary structure.
occurs when the interactions that stabilize secondary, tertiary, or quaternary structures are disrupted, which destroys the shape and renders the protein biologically inactive
Denaturation
occurs in the stomach when enzymes catalyze the hydrolysis of proteins to give amino acids.
breaks up the primary structure by breaking the covalent peptide bonds that link the amino acids
Hydrolysis
The loss of secondary and tertiary structures in a protein occurs when conditions change, such as
increasing the temperature.
making the pH very acidic or basic.
adding certain organic compounds or heavy metal ions.
adding mechanical agitation.
Proteins are denatured when heated above 50°C. The heat
disrupts the hydrogen bonds and hydrophobic interactions among nonpolar residues
does not change the nutritional value of proteins but make them more digestible.
Proteins can be denatured by changing the pH, which
breaks hydrogen bonds.
disrupts ionic bonds and salt bridges.
Organic compounds such as ethanol and isopropyl alcohol act as disinfectants by
exchanging the bacterial protein’s hydrogen bonds to water with their own.
disrupting the side chain intramolecular hydrogen bonding.
Heavy metal ions such as Ag+, Pb2+, and Hg2+ denature proteins by
forming bonds with ionic residues or reacting with disulfide —S—S— bonds
mechanical agitation to denature proteins.
stretches the polypeptide chains until the stabilizing interactions are disrupted
