Exam 3: Protein Structure and Function

Figure 3.4 -The figure above represents a reaction with a fixed enzyme concentration.As the concentration of substrate increases,the graph eventually levels off and reaches a plateau.Which of the following statements best describes the reason for this?

Refer to the following paragraph and figure 3.1 to answer the following questions. Figure 3.1 Since structure correlates so well with function, biochemists are constantly looking for new ways to probe the complex structure of proteins in order to understand what they do and how they do it. One of the most powerful techniques in existence today is X-ray crystallography. The main difficulty with this technique is getting the protein to crystallize. Once crystallized, the protein is bombarded with X-rays to create a pattern that can be analyzed mathematically to determine the three-dimensional structure of the protein. This analysis has been performed by Krzysztof Palczewski on the protein rhodopsin, which is a light-sensitive protein found in species ranging from ancient bacteria (archaea)to humans. The structure (schematically shown above, where each letter represents an amino acid)is characterized by a single polypeptide chain with several α-helical segments that loop back and forth across the cell membrane. Another notable feature is the disulfide bond (-S-S-)that can be seen at the bottom of the third transmembrane segment. [Figure adapted from K. Palczewski et al., Science 289 (2000): 739.] -Refer to Figure 3.1.Which level of structure is being maintained by the disulfide bond?

In experiments that successfully simulate chemical evolution,why must at least some small,reduced molecules be present?

When polymerization of a protein is complete,but the protein is still completely linear,what is the highest level of structure that has been completed?

You've discovered an enzyme that can catalyze two different chemical reactions.Which of the following is most likely to be correct?

Which of the following involves an increase in entropy?

In cells,the activity of enzymes is often regulated by other molecules.Why is this necessary?

Figure 3.2 -Which of the following answers best describes the above metabolic pathway?

You've just sequenced a new protein found in mice and observe that sulfur-containing cysteine residues occur at regular intervals.What is the significance of this finding?

In interstellar space,millions of ice-encrusted dust particles contain simple carbon-containing compounds.When particles like these are exposed to solar radiation,more complex organic molecules form on the surfaces of the dust.What is the significance of these findings?

HIV is the virus that causes AIDS.In the mid-1990s,researchers discovered an enzyme in HIV called protease.Once the enzyme's structure was known,researchers began looking for drugs that would fit into the active site and block it.If this strategy for stopping HIV infections were successful,it would be an example of what phenomenon?

How does the structure of an amino acid enable it to play its most important roles in cells?

Which of the following metabolic pathways is Anabolic

Amino acid side chains (R groups)with what characteristic(s)dissolve best in water?