Exam 4: Protein Structure and Function

Complete the sentence with the best option provided below.The secondary structures of a protein are the

The variations in the physical characteristics between different proteins are influenced by the overall amino acid compositions, but even more important is the unique amino acid

Which of the following is FALSE about molecular chaperones?

Lysozyme is an enzyme that specifically recognizes bacterial polysaccharides, which renders it an effective antibacterial agent.Into what classification of enzymes does lysozyme fall?

Two or three α helices can sometimes wrap around each other to form coiled-coils.The stable wrapping of one helix around another is typically driven by __________ interactions.

Which of the following is NOT a feature commonly observed in β sheets?

Cyclic AMP (cAMP) is a small molecule that associates with its binding site with a high degree of specificity.Which types of noncovalent interactions are the most important for providing the "hand in a glove" binding of cAMP?

The Ras protein is a GTPase that functions in many growth factor-signaling pathways.In its active form, with GTP bound, it transmits a downstream signal that leads to cell proliferation; in its inactive form, with GDP bound, the signal is not transmitted.Mutations in the gene for Ras are found in many cancers.Of the choices below, which alteration of Ras activity is most likely to contribute to the uncontrolled growth of cancer cells?

Protein families arise when a protein sequence that generates a stable fold diverges over many generations and acquires new functions.One example of this can be seen in the globin family.Myoglobin is a stable monomeric protein that can help carry oxygen using a heme molecule.Hemoglobin is stable as a tetramer.It also carries oxygen through the use of heme groups, but it is useful over a much more dynamic range of oxygen than myoglobin.The "globin fold" is structurally conserved across these proteins, but the ability to tetramerize arose through genetic drift and natural selection.Provide an explanation for how the globin sequence can change and still produce the same overall fold.Support your explanation by suggesting the location and type of sequence alterations that might have little effect on the overall protein fold, but may favor the formation of a multi-subunit protein.

Determining a protein's sequence, site of covalent modification, or entire three-dimensional structure requires the careful analysis of complex data sets.Which of the data sets below would you have to interpret to solve the structure of a protein by using X-ray crystallography?

Proteins can assemble to form large complexes that work coordinately, like moving parts inside a single machine.Which of the following steps in modulating the activity of a complex protein machine is LEAST likely to be directly affected by ATP or GTP hydrolysis?

In some cases, small molecules are integral to the function of enzymes, and are dubbed "coenzymes." Which of the following is a coenzyme for the enzyme carboxypeptidase?

Use your knowledge of amino acid characteristics to order the peptides below according to the net charge contributed by their side chains at physiological pH (~pH₇).Each peptide contains eight amino acids.Use the single-letter amino acid designations to generate your list, placing the most negatively charged peptide on the left and the most positively charged peptide on the right.In addition, for each peptide, list the total number of positive and negative charges.Remember that, at neutral pH, the amino terminus carries a positive charge and the carboxyl terminus carries a negative charge. A.YGAKKRA B.ARRKSTRK C.DERKQNST D.DDAEIYSA E.NQSTYEEG

The sequences for three different tripeptides are written out below.Indicate whether you expect to find them in the inner core or on the surface of a cytosolic protein, and explain your answer. A.serine-threonine-tyrosine B.alanine-glycine-leucine C.proline-serine-alanine

Complete the sentence with the best option provided below.The primary structure of a protein is the

Antibody production is an indispensable part of our immune response, but it is not the only defense our bodies have.Which of the following is observed during an infection that is NOT a result of antibody-antigen interactions?

The correct folding of proteins is necessary to maintain healthy cells and tissues.The presence of unfolded proteins are associated with some neurodegenerative disorders as Alzheimer's disease, Huntington's disease, and Creutzfeldt-Jakob disease (the specific faulty protein is different for each disease).What happens to these disease-causing, unfolded proteins?

In an attempt to define the protein domains of protein X, you treat it with a protease and use polyacrylamide gel electrophoresis to analyze the peptides produced.In the past, you have used chymotrypsin to perform this experiment, but the stock of this enzyme has been used up.You find a stock of elastase and decide to use it instead of waiting for a new stock of chymotrypsin to arrive. A.Give two reasons why elastase is a good substitute for chymotrypsin in this assay. B.Why might proteolysis of the same substrate by chymotrypsin or elastase yield different results?

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase should be used only once. composition irreversible reversible covalent lowest sequence denatured noncovalent stable highest renatured unstable A newly synthesized protein generally folds up into a __________ conformation.All the information required to determine a protein's conformation is contained in its amino acid __________.On being heated, a protein molecule will become __________ as a result of breakage of __________ bonds.On removal of urea, an unfolded protein can become __________.The final folded conformation adopted by a protein is that of __________ energy.