Case Study Electra the Itinerant Electron

Learning Goal: I’m working on a biology case study and need the explanation and answer to help me learn.

[In the following scenario, atomic particles, elements, and molecules are given thinly disguised “people� names (e.g. Electra=an electron). For many of the questions, you will need to figure out from the clues what the actual name of the entity is (perhaps it is a molecule, or an atom of a particular element, or a part of an atom). I suggest you draw some pictures of the scenario as you read it so you can more easily interpret the clues.]

Electra began her day quietly orbiting the nucleus of an atom of a rather sedate element, Constance, which contained 6 neutrons and 6 protons. The day was much like many others Electra had passed as part of Constance. It was a little like driving through the endless wheat fields of Kansas – nothing to see but a long line of other Constance atoms, each with a few Holly atom “groupies� hanging off the side. Even though Electra knew that she and her neighbors belonged to an important macromolecule, a glycolipid sticking out of the inner plasma membrane of a mitochondrion, she longed for a more exciting life. Little did Electra know, her existence was about to undergo a dramatic change.

This day was different because the mitochondrion of which Electra was a part (by being part of an atom that was part of a molecule that helped make up the structure of the mitochondrion) finally became sufficiently “worn out� to be slated for destruction. Electra’s first warning of this was when another membrane-bound cellular organelle sidled up to the mitochondrion, enveloped (“swallowed�) it, and began breaking it down into smaller molecules and atoms. As part of this digestive frenzy, the atom of which Electra was a part collided at high speed with an atom of another element, Ollie. Ollie’s nucleus contained 8 protons. After the collision, Electra was delighted to find that she was now orbiting Ollie’s nucleus – she was finally beginning her new life! Electra soon found that her orbital path was now more interesting than previously. Ollie was bound to two atoms of Holly to create a molecule of Wally. Electra found herself splitting her time between Ollie and the two bound Holly atoms, but not equally. As the result of Electra’s preference for orbiting nearer one end of the molecule than the other, Wally had a slightly negatively charged end (pole) and a slightly positively charged end.

Because Wally was a polar molecule, he had a lot more interactions with other molecules than Electra was used to experiencing. Most commonly, Wally would form weak bonds with other Wally molecules whereby the slightly negative end of one Wally molecule would attract the slightly positive end of another Wally molecule. Electra’s favorite job, as an integral part of Wally, was to help dissolve molecules with ionic bonds into two charged atoms, called ions. Electra was happy in her new life, but realized that at any point another random collision might send her reeling off into another adventure.

Your job is to answer the following questions that arose during Electra’s journey…

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Questions (list the sources you used to answer these questions — at the end):

1. What type of atomic particle is Electra? [Hint: Look at her name.] W

1. hat element is Constance? [Think about the clues you have.]

1. How many particles of the same type as Electra are contained in an atom of the element Constance (remember to include Electra herself in the total!)?

1. What is the atomic weight of Constance (how many atomic mass units)?

1. What is the atomic number of Constance?

1. What is the charge on an atom of Constance in her elemental form (e.g. +1, -1, no charge, etc)? [Hint: One idea might be to add up all the charged particles that make up Constance and see what you get.]

1. When an atom loses one electron to another atom, does the original atom become more negatively charged by 1 or more positively charged by 1?

1. Constance atoms tend to form long chains of other Constance and Holly atoms (Constance as the “backbone� with Holly sticking out each side).
   1. Which element is Holly?
   2. Explain why this arrangement of Constance and Holly atoms is so stable (with Constance atoms always “connected�/bound to 4 other atoms)?

1. Which element is Ollie?

1. How many neutrons does Ollie have?

1. Ollie needs to bind to 2 atoms of Holly in order to be stable. It does this by sharing electrons with Holly. Which type of molecular bond is formed between the elements which make up Ollie?

1. Which molecule is Wally?

1. As she orbits around the molecule known as Wally, Electra spends more time orbiting near the end of the molecule where Ollie is (rather than near either of the 2 Hollys). That’s because Ollie is a large atom with more positively charge protons than Holly has (these positive charges are more attractive to negatively charged electrons). Does this mean that Wally is formed by a polar (asymmetrical) or non-polar (symmetrical) covalent bond?

1. Define the term ion

1. It turns out that Constance has an extroverted cousin named Callie. Callie (who goes by they/them) is also an atom, but they typically exist in charged form when dissolved in the water of the body. Callie is a key ion in bone health as well as in signaling cells to activate important pathways. That means that the concentration of Callie in the bloodstream, and bathing the cells of the body, needs to be kept at levels that are not too high or too low (or else things really start to go wrong). Would you say that the systems that keep Callie in a healthy range depend on negative or positive feedback? (Make sure you go back to see how these two types of feedback differ). Please explain why you chose the answer you did.

1. [Extra credit] What is the term for the membrane-bound organelle such as the type that digested the mitochondrion of which Electra was a part?