1. What is the role of the phospholipid monolayer at the outer surface of the pa
ID: 219723 • Letter: 1
Question
1. What is the role of the phospholipid monolayer at the outer surface of the particle?
2. Why are cholesterol, cholesteryl esters, and triglycerides on the inside of the particle?
3.What is a committed step? Why do complex pathways have enzymes that are subject to regulation near the start of the pathway? Contrast committed steps to rate-limiting steps. Are all committed steps rate-limiting steps? Do all rate-limiting steps function as the committed step in a given pathway?
4. Why does it make “metabolic sense” that lower levels of ATP turn down HMG-CoA reductase activity even though ATP is not a direct substrate for the enzyme?
5. If you fed cells radioactive acetate (labeled with 14C), would you expect to make radioactively labeled mevalonate? (Hint: Look back at Figure 4.)
NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE Statins Stat Anne G. Rosenwald Department of Biology Georgetown University, Washington, DC PartI- Cholesterol Metabolism Naomi, who had just turned 50, decided it was high time to get a physical. At a preliminary visit, she exchanged brief pleasantries with her physician, Dr. Hernandez, and continued with the following conversation. Dr. Hernandez: As you get older, there are some issues you need to think about. Tell me about your eating habits. Naomi: I try to eat healthy Dr. Hernandez: Wh at kinds of food do you eat! Naomi: I try to eat fresh fruits and vegetables, I avoid refined flour and sugar, and I eat mostly chicken and fish, very little red meat. I try to exercise a few times a week. I like to walk and I go swimming when I can. grandparents, parents and siblings. Have they had any health issues? Cancer, diabetes, heart dis- Dr. Hernandez: And what about exercise? Naomi: Dr. Hernandez: You're at a good weight for your height, so no concerns there. Tell me about your family-your ease Naomi: We're mostly pretty healthy, though my father did have a heart attack a few vears agoExplanation / Answer
Answer 1
The outer surface of the particle has a monolayer of phospholipids, with their polar head groups interacting with aqueous environment on the outside, and their fatty acid tails interacting with the fully non-polar TG and CE hidden in the core, away from water. This makes the lipid particle a little more water friendly but not enough to travel freely in the watery medium of the bloody stream.
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