Review Problems week 7
1) Outline the process for protein digestion starting with a protein in the lumen of the
intestine and ending with amino acids in the blood.
2) What is the basic cell signal for protein degradation? What is the energetic
requirement for attachment of this signal? Describe the structure of the attachment.
3) How many protein activities are required to tag a protein for degradation? Show the
reactions these catalyze. (Fig 23.3)
4) What is the effect of multiple ubiquitinylation? What property is displayed in
multiple ubiquitinylation steps?
5) In general, what does E3 recognize (read) to determine whether a protein should be
degraded?
6) What cellular assemblage degrades proteins that are ubiquitinylated? Describe the
mechanism of this process.
7) What is the first step in amino acid breakdown?
8) What cofactors/cosubstrates are required for this activity?
9) In most vertebrates, what is the ultimate fate of the nitrogen in amino acids that
undergo degradation? Which organ is responsible for this transformation? When amino
are broken down in peripheral tissues, how does the nitrogen reach this organ?
10) Draw the mechanism for a pyridoxal-dependent transamination.
11) What are ketone bodies (structures)? Describe how they are formed.
12) Under what conditions would you expect ketone body formation? Why?
13) How does the brain adapt to starvation?
14) What are the three basic levels at which fatty acid synthesis and breakdown are
regulated.
15) Which enzyme of fatty acid synthesis is regulated? Describe this regulation.
16) How is citrate used for fatty acid synthesis? How is citrate synthesized and
mobilized? Describe what happens to the remnant after the citrate is utilized to provide
carbons for fatty acid synthesis.
17) What are the two major methods for supplying NADPH for fatty acid synthesis?