Chapter 13 Part II

Transphosphorylation reactions

What three enzymes are involved in the transfer of phosphoryl groups?  You should know the reactions that each catalyzes and the approximate value of  delta G'for each reaction.  You should also know the significance of each reaction.

What is inorganic polyphospate?  Where is it found?  What reaction (including the enzyme) is it involved in.  Why is it thought that prebiotic organisms may have used it as fuel?

Chemical vs Biochemical equations

The last section on page 506, states the difference between balanced chemical equations and biochemical equations that are used for thermodynamic determinations.  What is missing from biochemical equations?  When are chemical equations used in biochemistry?

Redox Biochemistry

The flow of electrons from one molecule to another supplies all of the energy for the work that is done by living organisms.  What is the source of electrons for nonphotosynthetic organisms?  What is the the chemical species in plants that absorbs photons and then is involved in electron transfer reactions.

Terms:

Review your general chemistry and make sure that you can write two half reactions if given a redox equation.  Also be sure you can assign oxidation numbers.     Figure 14-3 shows the number of electrons "owned" by a central carbon atom in a number of representative molecules.  This is slightly different from my Gchem book, but the net result is the same.  The most reduced form of carbon is methane and the most oxidized form is carbon dioxide. Table 13-7 gives the standard reduction potentials for several biochemical half reactions.(problems 18-22)

What are the four ways that electrons are transferred in biological redox reactions?

What is a reduction potential?  How are standard reduction potentials measured?   What is the difference between E' and E?  How is delta G' related to delta E'?  To calculate delta E you must calculate E for each redox pair (equation 13-4) and then subtract the oxidation E value from the reduction E value.  Then, delta G for the reaction can be calculated using the relationship between delta G and delta E.   (problem 19)

What biological molecules serve as electron carriers?  What is the main difference between the nucleotide carriers and the flavin carriers?

Where do the electrons go to on NAD?  Where do they go on FAD?  Are the reduction potentials for all FAD containing enzymes the same?  Why or why not?

 

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