Please answer all of the questions as concisely and accurately as possible.

1. (4 pts.) Which type of junction would best serve the following situations. Choose from adhesive junction, tight junction or gap junction.

a. cells which line the lumen of the blood vessels keep blood from flowing out into the tissues

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b. cells in the uterus which must undergo much mechanical stress

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c. smooth muscle cells pass on a chemical signal to surrounding cells

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d. cells in the bladder where urine is stored before excretion

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2. (20 pts.) Tell whether each of the following characteristics is true for transport of molecules into the cell by transport proteins vs. receptor-mediated endocytosis by writing YES or NO under each heading.
 
 

Characteristic	Entry into cell through transport protein	Entry into cell by Receptor-mediated Endocytosis
Can be used for bringing things into the cel
involves membrane proteins
clathrin is important
The process increases the  surface area of membrane

3. (10 pts.) You are studying movement of [H+] across the inner mitochondrial membrane. Using the following concentrations:

[H+] inside = 5 mM [H+] outside = 0.008 mM .......Membrane potential = -70mV

a. What is the DGinward for hydrogen ions at 37°C?

b. The DG' for the hydrolysis of ATP at 37°C is -7.3 kcal/mol. How many calcium ions can be transported for each ATP hydrolyzed?

a. (4 pts.) Here is a tube containing cellular components. You perform density gradient ultracentrifugation on this sample. In the empty tube, draw the expected result after strong centrifugation.

e. (4 pts.) You are studying both lysosomes and peroxisomes. You have a tube containing proteins from the lysosomes and another tube containing the proteins from peroxisomes.

a. Name a technique you could perform to tell if these samples contain any of the same proteins?

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You isolate one protein from the peroxisomes. What is a possible function of the protein (i.e. what job could it be doing in the peroxisome?)

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