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Adam T.
Tutor for five years; Teachers Assistant for 3 years
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Biochemistry
TutorMe
Question:

What are the differences between the four different structures of proteins?

Adam T.
Answer:

The four structures are: primary, secondary, tertiary and quaternary. All of these structures add on one another. Primary structure is the most simple structure. It is simply the sequence of the polypeptide chain in a denatured protein. Secondary structure is the how the backbones of those amino acids interact. When I say backbones, I am referring to the a-carbon and its adjacent carboxyl and amino groups, NOT the R-groups. The interactions between the R-groups are what make up the tertiary structure, and it accounts for much of the diversity between proteins. The bonds that hold this structure together are; hydrogen bonds, hydrophobic interactions, disulfide bonds and ionic bonds. Lastly, quaternary structure is the interaction between two or more polypeptide chains to form a functional unit. Not all proteins have a quaternary structure.

Basic Chemistry
TutorMe
Question:

If you allow 16 grams of O2 to react with 8 grams of H2, how many moles of water will you expect to gain?

Adam T.
Answer:

First you need to write out the balanced equation: 2H2 + O2 --> 2H2O Next you have to convert grams to moles of products that you have: 16 grams O2 / (32 grams O2/1 mole O2) = .5 moles O2 8 grams H2/ (2 grams H2/ moles H2)= 4 moles H2 The limiting reactant in this equation is O2 because it will be the one that is used up first. Lastly, you multiply the amount of moles of O2 you have with the ratio between O2 to H2O, to get how much water you will create. .5 moles O2 * (2 mole H2O/ 1 mole O2) = 1 mole H2O

Biology
TutorMe
Question:

If an E. coli has a mutation in the promoter of the Lac operon, such that RNApII cannot bind, will lactose be readily broken down within that bacterium?

Adam T.
Answer:

The short answer is No. This is because RNA polymerase (RNApII) binds to the promoters of the genes that it is going to transcribe. If the mutation causes RNApII to not bind to the promoter, the genes within the lac operon will not be transcribed, so there will be less transcripts of the genes. The lac operon consists of three genes that code for B-galactosidase (LacZ), a permease (LacY) and a transacetylase (LacA). The job of B-galactosidase is to break down lactose within a cell. Therefore, if there is B-galactosidase to break down the lactose, the lactose will not be readily broken down within the bacterium.

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