Download Midterm 1 Fall 2012 ANSWER KEY

Midterm 1 Fall 2012
ANSWER KEY
SA1 Consider the following biological items: microfilament, muscle cell, plasma membrane
a. (1.5 points) Rank the three items from lowest to highest structural complexity:
Lowest: ___microfilament_____ < ______plasma memb_____ < ______muscle cell_____ : Highest
b. (1.5 points) Explain your logic for the most complex item:
Microfilaments have only one type of subunit. Plasma membranes have many different molecules, muscle cells
have plasma membranes plus many other organelles.
SA2 (4 points) In the movie of a white blood cell chasing a bacterium:
a. What motor protein was used for ameboid movement? _____myosin_____
b. What motor protein was used for flagellar movement? _______dynein_______
c. What type of endocytosis
did the white blood cell use to ingest the bacterium? _______phagocytosis________
d. What cell organelle was used to digest the bacterium? ______lysosome_________
SA3 (2 points) The circle in the diagram represents a vesicle that has just budded off the Golgi and is being
transported to the plasma membrane. It contains a new sodium-potassium pump.
a. What cytoskeletal fiber is transporting the vesicle? ____microtubule___
b. Draw a small star on the part of the pump that will be exposed to a higher
concentration of _________________ when the vesicle fuses with the plasma
membrane.
Potassium ion: Star on outside
Sodium ion: star on inside
1. Kinesin is a protein that:
a. moves vesicles from the nucleus toward the plasma membrane
b. is important in muscle contraction
c. binds to and walks toward the minus end of microtubules
2. During its synthesis on a ribosome, which of the following proteins will bind to a signal recognition particle?
a. aquaporin channels
b. tubulin
c. DNA polymerase (involved in replication of DNA)
d. myosin
e. actin
3. A researcher is testing the effects of garlic extract on white blood cells. They found that
cells treated with garlic extract showed a change in rate of lateral movement of labeled
proteins within the membrane as shown in the graph.
Which of the following statements is most likely to be true?
Midterm 1 Fall 2012
a.
b.
c.
d.
ANSWER KEY
Garlic extract increases the concentration of unsaturated phospholipids in the membrane
Garlic extract decreases the number of LDL receptor proteins in the membrane
Garlic extract decreases the concentration of cholesterol in the membrane
Garlic treated cells would travel less quickly by amoeboid movement
4. Unlike microtubules, actin:
a. Uses myosin as a motor protein
b. Has a plus and minus end
c. Is important in cell movement
d. Is made of smaller subunits
5. A membrane protein was found that was correctly shaped but was missing an important sugar group. This
error likely occurred in the:
a. Smooth ER
b. Lysosome
c. Golgi apparatus
d. Nucleus
6. If you wished to design an experiment to block a G protein-coupled receptor’s interaction with the G protein,
the block should affect which of the following?
a. the cytosolic end of the receptor
b. the extracellular end of the receptor
c. the receptor’s transmembrane domain
Cancer Research at UCI
Two UCI researchers (Longmuir and Robertson) published a report in 2009 describing a new way to deliver a cancer
drug to cancer cells in the liver. Answer the following questions related to this study.
7. The researchers placed the drug in an artificial vesicle called a liposome that can travel in the bloodstream. The
most likely configuration of this liposome is a:
a. Single layer of phospholipids with the tails facing out
b. Single layer of phospholipids with the tails facing in
c. Lipid bilayer
8. The researchers took a protein normally found on the Plasmodium parasite, and attached it to the outside of
the liposome. This protein will only bind to the heparin sulfate molecules found on liver cells. Heparan sulfate
must be a:
a. Carbohydrate
b. Phospholipid
c. Protein
9.
After delivering the drug, the amounts of the following molecules in the cancer cell were measured using
fluorescence imaging, and compared to the amounts in an untreated cell. The results are shown here:
Midterm 1 Fall 2012
Amount of DNA Amount of Ribosomes
Treated cell
Normal
Normal
Untreated cell
Normal
Normal
Which is the likely effect of the drug on the cell?
a. It blocks nuclear pores
b. It blocks transcription of DNA
c. It blocks the translation of protein
ANSWER KEY
Amount of nuclear mRNA
Reduced
Normal
10. This drug delivery system is most similar to which type of cell signaling normally seen in the body?
a. Synaptic
b. Hormonal
c. Intracellular
Water balance in Frogs
Most frogs have cells with the same salinity as mammalian cells – about 1% solute. The crab-eater, however, lives
in seawater and has cells isotonic to the sea – 3.5% saline. Cells from two frog species are placed in a three
solutions of different salinity: 1%, 2% and 3.5% saline. The results are as follows. Use this information as needed for
the following questions.
Cell Diameter (in micrometers)
Solution X
Solution Y
Solution Z
Crab-eater (saltwater)
20
30
45
Bullfrog (freshwater)
5
10
20
11. If the frogs all have a normal cell diameter of 20 micrometers, which solution is equal to 1% saline?
a. Solution X
b. Solution Y
c. Solution Z
12. When a cell from a saltwater frog is placed in a solution more dilute (fewer solutes) than the cell, the cell is:
a. Actively pumping water across the plasma membrane
b. Hypertonic to the solution
c. Undergoing a net loss of water
13. Researchers develop an inhibitor that blocks the sodium-potassium pump in the membrane of the frog cell.
Exposure of cells to this inhibitor would be most likely to cause:
a. An increase in potassium ions entering the cell
b. An increase in the activity of proton pumps
c. The inside of the cell to become more negative
d. An increase in intracellular sodium
e. An increase in ATP use in the frog cells