MT 6310 LECTURE UNIT 2 PROTEINS Flashcards
Proteins that are the chief constituents of skin, bone, hair, and nails
Collagen and Keratin
Agents of catalyzing
Enzymes
Proteins involved in muscle movement
Myosin and Actin
Protein that transports oxygen from the lungs to cells, other
proteins transport molecules across cell membranes.
Hemoglobin
Two types of proteins
Fibrous & Globular
A compound that contains both an amino group and a carboxyl group
Amino Acid
Term used to describe the un-ionized form of an amino acid
Zwitterion
TRUE OR FALSE
The most important aspect of the R groups is their polarity.
TRUE
TRUE OR FALSE
With the exception of Cysteine, all protein-derived amino acids have at least one stereocenter and are chiral.
FALSE (Glycine exists naturally with the D-configuration)
TRUE OR FALSE
The vast majority of alpha amino acids have the D-Configuration at the alpha carbon.
FALSE (most have the L-configuration)
TRUE OR FALSE
Each of the amino acids with one stereocenter exists as 2 enantiomers.
TRUE
TRUE OR FALSE
For the 19 of 20 amino acids, the alpha amino group is secondary while for proline it is tertiary.
FALSE (19 of 20 have a primary alpha amino group, proline has a secondary alpha amino group)
TRUE OR FALSE
Isoleucine (I) and Threonine (T) contain a second stereocenter.
TRUE
TRUE OR FALSE
Amino acids are zwitterions not only in the water solution but also in the solid form.
TRUE
The addition of ____ to an amino acid to lower its pH to 0.0 donates a proton to the COO- group of the zwitterion turning it into a positive ion.
strong acid (such as HCl)
The addition of a strong base such as NaOH to raise its pH to 14, a proton is transferred from the _____ group to the base turning the zwitterion into a _____ ion.
NH3+; negative
The pH at which the majority of molecules of a compound in solution have no net charge.
Isoelectricpoint, pI
TRUE OR FALSE
The -SH (sylfhydryl) group of cysteine is easily oxidized to an -S-S- (disulfide)
TRUE
The three amino acids that possess an aromatic ring
Phenylalanine (Phe, F)
Tyrosine (Tyr, Y)
Tryptophan (Trp, W)
Tryptophan is the precursor to what neurotransmitter?
Serotonin
The precursors of norepinephrine and epinephrine are?
Phenylalanine and Tyrosine
TRUE OR FALSE
The oxidation of Phenylalanine results in a molecule of Tyrosine.
TRUE
The peptide bond refers to the amide bond between what two groups of two amino acids?
alpha carboxyl group and the alpha amino group
A biological macromolecule containing at least 30-50 amino acids joined by peptide bonds.
Protein
In 1902, who proposed that proteins are long chains of amino acids joined by amide bonds.
Emil Fischer
He discovered that there is about 40% double bond character to the C-N bond and that a peptide bond between two amino acids is planar.
Linus Pauling
TRUE OR FALSE
Peptides are written from the left to right, beginning with the free -NH3+ group and ending with the free -COO- group.
TRUE
At what condition will proteins are least soluble in water at their isoelectric points and can be precipitated from a solution?
pH = pI
TRUE OR FALSE
A dipeptide refers to 2 amino acids and 1 peptide bond
TRUE
Myoglobin has how many polypeptides?
One
Hemoglobin carries oxygen with how many polypeptide chains?
Four
TRUE OR FALSE
Resonance is high proton delocalization.
FALSE (it is ELECTRON delocalization)
What do you call polypeptides that are more than 3 but less than 10?
Oligopeptides
In human insulin, what is the 30th amino acid found in the beta chain?
Threonine, Thr
In the alpha chain of human insulin, what are the amino acids found in positions 8, 9, and 10 in order?
Threonine, Serine, Isoleucine
A nonapeptide that is an antidiuretic hormone.
Vasopressin
Nonapeptide that affects the contractions of the uterus during childbirth and the muscles of the breast that aid in the secretion of milk.
Oxytocin
Vasopressin has what amino acids that make it different from oxytocin?
Arginine and Phenylalanine
Oxytocin has what amino acids that make it different from Vasopressin?
Leucine and Isoleucine
TRUE OR FALSE
The primary structure of a protein determines to a large extent the native secondary and tertiary structures.
TRUE
TRUE OR FALSE
Vasopressin also stimulates uterine contractions however to a much lesser extent.
TRUE
What are the conditions in which the alpha helix cannot form in the secondary protein structure?
- ) the presence of proline
2. ) if a chain possesses an ALL POSITIVE/ ALL NEGATIVE/ ALL HYDROPHOBIC amino acid sequence
Globular proteins that contain all three kinds of secondary structures in different parts of their molecules (alpha helix, beta pleated sheet, random coil)
Motifs
TRUE OR FALSE
The secondary structure can define specific patterns in the domain or functional part of the protein.
TRUE
In an alpha helix structure, where does the side chains point toward to?
outward the helix
TRUE OR FALSE
The shape of the alpha helix is maintained by numerous intermolecular hydrogen bonds.
FALSE (it is held by INTRAmolecular bonds)
TRUE OR FALSE
The shape of the beta pleated sheet is maintained by either intramolecular or intermolecular hydrogen bonds
TRUE
In all secondary structures, the hydrogen bonding is between what groups?
-C=O and H-N groups
Another repeated pattern classified as a secondary structure that can be seen in collagen
Extended Helix/ Triple Helix
In the tertiary structure of proteins, in what ways is it stabilized?
- ) Covalent bonds
- ) Hydrogen Bonds
- ) Salt Bridges
- ) Hydrophobic interactions
- ) Metal ion coordination
In tertiary structures, what groups interact to form different types of bonds?
R-groups (this makes it different from the secondary group because there it is the C=O and N-H group that bonds.)
The arrangement o polypeptide chains into a noncovalently bonded aggregation is called
Quaternary Structure of proteins
In the quaternary structure of proteins, the individual chains are held together by?
- ) hydrogen bonds
- ) salt bridges
- ) hydrophobic interactions
TRUE OR FALSE
Fetal hemoglobin contains 2 alpha chains and 2 beta chains.
FALSE
Fetal hemoglobin contains 2 alpha chains and 2 gamma chains and they have greater affinity for oxygen than adult hemoglobin.
The process of destroying the native conformation of a protein by chemical or physical means.
Denaturation (some are reversible and others can permanently damage the protein)
This denaturing agent can disrupt hydrogen bonding. In globular proteins, it can cause unfolding of polypeptide chains with the result that coagulation and precipitation may take place.
Heat
This denaturing agent disrupts hydrogen bonding
6 M aqueous urea
2- Mercaptoethanol cleaves disulfide bonds by reducing -S-S- groups to -SH groups. It acts as what type of denaturing agent?
Reducing Agent
What type of denaturing agent have transition metal ions that form water-insoluble salts with -SH groups
Heavy Metal ions
The Denaturing agent that penetrates bacteria and kill them by coagulating their proteins.
Alcohols
How many amino acids are there in a turn of an alpha helix structure?
3.6 amino acids
