Homework 1. Due at 11:59 pm 9/18/2022
All answers must be in complete sentences and typed (unless otherwise noted). You do not have
to type labels on figures or calculations – that information can be handwritten, but any
explanation of a figure must be typed. Handwritten answers that should be typed will receive 0
points.
Do NOT include the questions in your submitted answers or it will get flagged for plagiarism and
you will lose 10% of the points.
All drawings must be made by YOU. You may hand draw these or produce them digitally using a
drawing program, but you may NOT copy an image from the internet, book, or other source.
Please cut and paste the drawings into the document where they belong (with the appropriate
question number – NOT at the end of the document). Your answer to the question (typed text)
should be immediately before or after your drawing. If you are doing this all digital, just be sure
your drawings are with the appropriate answer.
Be sure to accurately number all answers with the corresponding question number and turn them
in, in order, in ONE file.
I suggest submitting the assignment as a PDF to avoid format and loss of information issues.
Whichever format you submit, I will only grade what is submitted. Your submission must be
readable by TurnItIn for any credit. If TurnItIn gives a gray flag, you will earn a 0 on the
assignment.
Don’t forget to check what you turn in. If you turn in the wrong document or there are issues with
your document, you will not earn credit. You may upload replacement files. I will only read / grade
the LAST document you turn in.
- Which technique would you use to determine the following? You can use each technique only once.
Not all techniques will be used. There may be multiple correct answers for a question. Only include
one correct answer for each. If you write multiple options, I will only grade the first answer. Explain
your answer – how would that specific technique show you what you are trying to determine.
techniques available:
• SDS-PAGE and Western blot
• TLC
• freeze-fracture
• lactoperoxidase labeling
• FRAP/photobleaching
• photoactivation
• immunofluorescence
• hydropathy plot
a. You want to determine how many times a single protein crosses the mitochondrial membrane.
b. You want to determine which cell type expresses the Na+/K+ pump.
c. You want to determine which membrane sample contains cholesterol.
d. You want to determine if a cell is expressing a peripheral protein on the cytoplasmic or
extracellular side of the plasma membrane.
e. You want to determine the rate of protein movement in the cytoplasm under different conditions.
2
- Based on the following description, draw the membrane described. For the membrane and
transport image, you can just draw a general phospholipid bilayer, representing the lipids, like in
Figure 7-15 of the textbook, but be sure to indicate the differences in saturation of the fatty acids
(straight lines or kinks). Then include the required proteins and indicate how the molecule
transport is happening (chapter 8 info.). You also must show relative concentrations of the
molecules (so I know you know how the molecules are moving). It does not matter how many
phospholipids you draw – just a few on each side of a protein if required. Finally, to the side of each
membrane, draw one accurate representation of the specific phospholipids for each membrane
(please see example below). Put the different fatty acids tails on the same phospholipid.
Your problems to answer:
a. This membrane is made up of phosphosphingolipids (sphingosine + 18:3 fatty acid chain). This
membrane has an antiporter that moves molecules X and Y through active transport at a 1:1 ratio
(X into the cell and Y out of the cell).
b. This membrane is made up of linoleic acid and docosapentaenoic acid (yes – you need to look up
these types of fatty acid tails). The membrane has transporters for molecules A and B. The active
transport of A to the outside of the cell, drives the movement of A and B back across the membrane
and into the cell through a second transporter.
c. This membrane is made up of 22:0 and 16:0 phospholipids. This membrane also contains
cholesterol. The membrane has a channel protein for the movement of molecule Z out of the cell.
- Based on the membranes described in question 1 (parts a – c) draw a single Tm graph (like Figure
7-12b) showing the relative (not actual values – we don’t know these) transition temperatures of
each membrane and explain your reasoning. Be sure to label the peaks a, b, c,
corresponding to the membranes a, b, c, in question 2. Use the information in Figure 7-13 to
help you estimate Tm values. (A single Tm graph means all 3 Tm values on one graph. I only want
one Tm per membrane – just guesstimate. This is also illustrated in the Transition Temperature
video.)