Question 1

Humans have been described as superorganisms consisting of human cells in combination with a larger number of microorganisms. Explain. Is this a symbiotic relationship? What effect can the consumption of antibiotics have on this relationship?

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Question 2

Biological membranes are held together by weak noncovalent forces. Why is it important that weak forces hold membranes together? What would happen if membrane structure involved stronger covalent bonding?

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Question 3

What effect does macromolecular crowding have on the traditional analysis of reaction rates?

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Question 4

Eukaryotic cells are much larger cells than prokaryotic cells. What factors of internal structure make this increase in size possible?

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Question 5

Comment on the statement that the cytoplasm is just a soup containing organelles.

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Question 6

The interior of living cells is highly organized and this organization is maintained over long periods of time. Entropy, a measure of the disorder or randomness of the system, predicts that highly organized systems should become progressively disorganized. How does a living cell evade entropy?

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Question 7

The surface of the eukaryotic cell is coated with carbohydrate groups attached to protein and lipid molecules. What structural feature of the carbohydrate molecule accounts for this phenomenon?

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Question 8

Mitochondria are one of many types of organelles. What features of mitochondria argue most strongly for their descent from a free living ancestor?

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Question 9

In eukaryotes the DNA remains within the nucleus and RNA, synthesized within the nucleus, is used to transfer information to the rest of the cell. Why use RNA for this purpose and why not just use DNA directly?

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Question 10

In density gradient centrifugation the products are removed from the bottom of the centrifuge tube. Why not remove them from the top of the tube?

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Question 11

The dimensions of a prokaryotic ribosome are approximately 14 nm x 20 nm. If ribosomes occupy 20% of the volume of a bacterial cell calculate how many ribosomes are in a typical cell such as E. coli. Assume that the shape of a ribosome is approximately that of a cylinder. A typical bacterial cell volume is 1.6 um³.

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Question 12

The E. coli cell is 2 $\mu$m long and 1 $\mu$m in diameter, while a typical eukaryotic cell is 20 $\mu$m in diameter. Assuming that the E. coli cell is a perfect cylinder and the eukaryotic cell is a perfect sphere, calculate the surface-to-volume ratio for each cell type [cylinder volume V = $\pi$r²h; cylinder area A = 2 $\pi$r² + 2 $\pi$rh; sphere volume V = 4/3( $\pi$r³); sphere area 4 $\pi$r²].What do these numbers tell you about the evolutionary changes that would have to occur to generate an efficient eukaryotic cell considering that most biochemical processes depend on membrane-bound processes.

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Quiz 2: Living Cells