Exam 2: Chemical Components of Cells

An ionic bond between two atoms is formed as a result of the

Cells contain buffers that help maintain a neutral pH.Which of the following statements is not relevant to how buffers work?

Eukaryotic cells have their DNA molecules inside their nuclei.However, to package all the DNA into such a small volume requires the cell to use specialized proteins called histones.Histones have amino acid sequences enriched for lysines and arginines. A.What problem might a cell face in trying to package DNA into a small volume without histones, and how do these special packaging proteins alleviate the problem? B.Lysine side chains are substrates for enzymes called acetylases.A diagram of an acetylated lysine side chain is shown in Figure 2-78.How do you think the acetylation of lysines in histone proteins will affect the ability of a histone to perform its role (refer to your answer in part A)? Figure 2-78

The pH of an aqueous solution is an indication of the concentration of available protons.However, you should not expect to find lone protons in solution; rather, the proton is added to a water molecule to form a/an __________ ion.

You are trying to make a synthetic copy of a particular protein but accidentally join the amino acids together in exactly the reverse order.One of your classmates says the two proteins must be identical, and bets you $20 that your synthetic protein will have exactly the same biological activity as the original.After having read this chapter, you have no hesitation in staking your $20 that it will not.What particular feature of a polypeptide chain makes you sure your $20 is safe and that the project must be restarted?

Which subatomic particles contribute to the atomic number for any given element?

Your lab director requests that you add new growth medium to the mammalian cell cultures before heading home from the lab on a Friday night.Unfortunately, you need to make fresh medium because all the premixed bottles of medium have been used.One of the ingredients you know you need to add is a mix of the essential amino acids (those that cannot be made by the cells, but are needed in proteins).On the shelf of dry chemicals you find the amino acids you need, and you mix them into your medium, along with all the other necessary nutrients, and replace the old medium with your new medium.On Sunday, you come in to the lab just to check on your cells and find that the cells have not grown.You are sure you made the medium correctly, but on checking you see that somebody wrote a note on the dry mixture of amino acids you used: "Note: this mixture contains only ᴅ-amino acids." A.What is the meaning of the note and how does it explain the lack of cell growth in your culture? B.Are there any organisms that could grow using this mixture? Justify your answer.

__________ play an important role in organizing lipid molecules with long hydrocarbon tails into biological membranes.

There are 90 naturally occurring elements on the earth, __________ of which compose 96% of the mass of living organisms.

You have a concentrated stock solution of 10 M NaOH and want to use it to produce a 150 mL solution of 3 M NaOH.What volume of water and stock solutions will you measure out to make this new solution?

Table 2-14 -Table 2-14 indicates the number and arrangement of electrons in the first four atomic electron shells for selected elements.On the basis of the information in the chart and what you know about atomic structure, which elements form stable but reactive diatomic gases?

The cell is able to harvest energy from various processes in order to generate ATP molecules.These ATPs represent a form of stored energy that can be used later to drive other important processes.Explain how the cell can convert the chemical energy stored in ATP to generate mechanical energy; for example, changing the shape of a protein.

Table 2-14 -Table 2-14 indicates the number and arrangement of electrons in the first four atomic electron shells for selected elements.On the basis of the information in the chart and what you know about atomic structure, which elements will form ions with a net charge of +1 in solution?