Exam 1 Flashcards
Which of the following is not a serine protease?
Collagenase
In order to find planets that may host life, astrophysicists analyze distant solar systems using light emission spectrometry in which light is scattered through a prism and distinct spectral lines reveal the elements from which these lines are generated. If trying to find potential life-hosting worlds, which elements would you expect astrophysicists are looking for in highest abundance in these distant solar systems?
O, C, N, H
The strongest non-covalent intermolecular forces are:
Ionic interactions
Which of the following assembles by association of multiple protofilaments?
Tubulin
What is the sign of the entropy change when dry ice sublimates?
Positive
Which of the following proteins contain a high percentage of a modified Pro residue?
Collagen
In SDS gel electrophoresis
proteins are separated based on their molecular weight.
(T/F) The tertiary structures of myoglobin, alpha hemoglobin and beta hemoglobin are nearly identical and are therefore nearly identical in primary structure.
False
Using what you have learned about acidic functional groups, which form of this compound is likely to predominate int he cell at pH 7.4?
Pyruvate
Which of the following techniques is useful in determining the primary structure of peptides?
Mass spectrometry and Edman sequencing
Under what conditions would an amine group be mostly charged?
pH
Which of the following is NOT an element of protein secondary structure?
Peptide bond
Which of the following statements is TRUE about the way that hemoglobin and myoglobin bind oxygen?
Hemoglobin has SIGMOIDAL curve;
Myoglobin has a HYPERBOLIC curve
What is the [H+] for saliva (pH~6.6)?
2.5x10^-7
Which of the following would represent the reaction coordinate for an ENDERGONIC reaction?
The one where the end point of the coordinate is higher that the start end point.
Which of the following amino acids could bind to the specificity pocket of Trypsin?
Lys
Which amino acid would most likely associate with the inner part of the lipid bilayer?
Valine (V)
Isozymes are ______.
multiple enzymes that share the same catalytic function
Which of the molecules below contains a carboxylate group?
(A) (C) and (D)
or any with a COO-
O || C - O- | R
Which of the following could be unicellular?
Either prokaryotes or eukaryotes
Which of the following contain polypeptide chains that associate in a coiled-coil interaction?
Keratin and Myosin, not Actin
What type of interaction are responsible for the characteristic strength of keratin fibers?
vdW and disulfide bonds, not h-bonds
The reaction catalyzed by G3P dehydrogenase is given below. To which class does the enzyme belong?
Oxidoreductase
Rank the following compounds with increasing solubility in water. **
Note the amount of O and N atoms there are. The more = the more soluble
The following structure is an amino acid derivative found in collagen structures. Based on you knowledge of amino acid structure, what is the name of this derivative? **
Hydroxyproline (bc of the 5 bond ring with N and the OHs)
Collagen molecules contain cross-links of the amino acid side chains of __.
K
The structure of acetylsalicylic acid (asprin) is shown below. Is asprin more likely to be absorbed (pass through a lipid membrane in the stomach (pH=2) or in the small intestine (pH~8)?
Stomach,
Hundreds of hemoglobin variants are known, but one of the better known is the sickle cell Hb (Hb S). It is the aggregation of deoxy-Hb S that results in the sickling of the cell. The protozoan that causes malaria slightly decreases the pH of the red blood cells it infects. Are the malaria infected cells more or less likely to undergo sickling in individuals with the Hb S variant?
More likely
How many H-bond ACCEPTOR ATOMS are present in the molecule below ? ** (atoms not groups)
5
The enzyme that catalyzes the reaction below would be classified as a(n) ___
2-phosphoglycerate -> phosphoenolpyruvate
lyase.
(T/F) Biphosphoglycerate promotes the oxy-state of hemoglobin.
False
(T/F) Movement of the oxyanion further into the active site, where t can be preferentially bound, stabilizes the transition state of the chymotrypsin mechanism.
True
In the following reaction of succinate to form fumarate _____.
Succinate is oxidize and FAD is reduced.
What is the pH of a solution of 1.0e-10 NaOH?
7
What types of bonds are present in DNA?
Phosphodiester and glycosidic bonds
Beta sheets consists of tight, right hand turns with causes the protein to fold back onto itself and allows for the characteristic hydrogen bonding. Which amino acids would likely be found at these turning points?
G and P
Given the information below, which protein will migrate to the cathode at pH 8?
Cytochrome c
Calculate the ratio of imidazole to the imidazolium ion (pK = 7) in a solution of pH 7.4.
2.5 to 1
What is the net charge on the following peptide at pH 5?
VERYHARMFYL
+2
Based on the reaction below, how would the enzyme catalyzing this reaction be classified?
alpha-ketoglutarate -> oxaloacetate
Transferase
Hexokinase undergoes a large conformational change in order to exclude water from the active site. Would chymotrypsin undergo such a change upon binding its substrate?
No
According to the table below, which of the listed elements would likely be the strongest H-bond acceptor?
Flourine (F)
For marine mammals that spend a significant amount of time under water, retaining sufficient oxygen in muscle tissue is essential for their survival. Based on your understanding of the oxygen binding functions of myoglobin (Mb) and hemoglobin (Hb), how would you expect the ratio of Mb to Hb to compare between humans and marine mammals?
The ratio of myoglobin to hemoglobin would be higher in marine mammals than in humans.
In the reaction mechanism of the glycolytic enzyme aldolase, an active site tyrosine residue accepts a proton from the substrate. In this form the side chain of Tyr must be _________ and it is acting as a(n) __________ catalyst.
deprotonated; base
You are given data that shows the ΔG of the reaction below to be approximately -31.5 kJ/mol. In the laboratory, you measure an enthalpy value of -4.3 kJ/mol and an entropy value of +73.4 J/mol. At what temperature must this reaction take place in order to reach the experimentally determined ΔG value?
Phosphoenolpyruvate + ADP + Pi –> Pyruvate + ATP
371 K
Why is it important that the heme prosthetic group be buried in a hydrophobic pocket in O2-binding
proteins?
The heme iron is readily oxidized to Fe3+, which cannot bind O2.
In humans, Sporatic Fatal Insomnia (sFI) is a disease characterized by difficulty falling asleep, difficulty walking, gradual weight loss and excessive tear production. sFI rapidly progresses to the loss of consciousness and eventually death. sFI is thought to result from the aggregation of misfolded proteins in the cell. Which of the following interactions contributes the most to the aggregation of these protein structures?
vdW
- Enkephalin is an endogenous opioid peptide neurotransmitter. Based on the structure of the peptide at physiological pH (below), what is the sequence of the peptide?
YGGFL
What level of protein structure contains the information needed for proper protein folding?
PRIMARY
The molecule shown below is a substrate for trypsin. Which bond will be hydrolyzed?
4
Phosphoric acid (H3PO4) has 3 ionizable protons (pK1 2.15, pK2 6.82, pK3 12.38). Which two phosphate species would be used to prepare a buffer solution at pH 11?
HPO4^2- AND PO4^3-
About 24 His residues in hemoglobin (Hb) are involved in binding protons produced by cellular metabolism. In this manner, Hb contributes to buffering in the blood. One important contributor is His146 on the β chain of Hb, whose side chain is in close proximity to the side chain of Asp94 in the deoxy form of Hb but not in the oxy form. What kind of interaction occurs between Asp94 and His146 in deoxy-Hb? In what way does the proximity of Asp94 alter the pK of His?
Asp94 & His146 form an ion pair; Asp94 increases the pK of His146
One liter of 0.150 M Tris buffer (pK 8.30) is prepared and adjusted to pH 8.40. What is the pH when 2.00 mL of 3.00 M HCl is added to this buffer?
8.29
Phosphoenolpyruvate donates a phosphate groups to ADP to produce pyruvate and ATP. The ΔG value
for this reaction at 25oC is -63 kJ/mol and the value of ΔS is 190 J/K-mol. What is the value of ΔH and is the reaction exothermic or endothermic?
-6.4 kJ/mol, exothermic
Rnase A is a digestive enzyme that hydrolyzes RNA into its component nucleotides. The pK values of the catalytic His residues are 5.4 and 6.4. The first step in the mechanism is shown below. Assign the appropriate pK values. What is the pH optimum for this reaction?
His12 pK 5.4; His119 pK 6.4; pH optimum ~5.9
