Writing Homework Help

I’m stuck on a Biology question and need an explanation.

1. Refer to the gallery of lipid molecules below to answer the questions that follow.

   a) Which of the molecules represented in the lipid gallery is sphingosine?
   b) Which is cortisol, an anti-inflammatory steroid hormone?
   c) Which is the diterpene trans-retinal?
   d) Which is the compound sphingomyelin?
   e) Which is an example of a cerebroside?
   f) Which is phosphatidic acid?

2. Describe in your own words how K+-selective ion channels are able to discriminate for transport of K+ only and not any other dissolved ions.
3. Sketch one complete reaction cycle of the Na+/K+ ATPase.  Include the name, number, and direction of the ions transferred.  Summarize your diagram with the complete balanced chemical equation.  [Hint: use the symbols E1 and E2 in your diagram to designate the two conformations of the Na+/K+ ATPase]
4. Imagine you are a cellular neurobiologist studying the transport of sodium across the membrane of a newly isolated cell type.  You measure the rate with which sodium enters the cell as a function of increasing sodium concentration and plot the data on the graph below (curve 1).  Then you use a microelectrode to depolarize the electrical potential across the membrane and perform the experiment again and plot the data (curve 2).  Finally, you perform the experiment a third time by measuring the rate of sodium transport in the presence of a constant concentration of the amino acid glycine and plot the data (curve 3).

   a) By what mechanism (simple diffusion, faciliated diffusion, primary active transport, or secondary active transport) does sodium enter the cell in experiment 1?
   b) By what mechanism does sodium enter the cell in experiment 2?
   c) By what mechanism does sodium enter the cell in experiment 3?
   d) What is the likely consequence of depolarizing the membrane in experiment 2?
   e) What role does Glycine play in experiment 3?