10.3 Phosphorus-Containing Compounds

Question 1

phosphoric acid structure

Answer 1

sometimes referred to as a “phosphate group” or “inorganic phosphate Pi”

Question 2

inorganic phosphate at physiological pH

Answer 2

include molecule of both hydrogen phosphate (HPO4) and dihydrogen phosphate (H2PO4)

Question 3

phosphodiester bonds

Answer 3

found in the DNA backbone

link the sugars of nucleotides

Question 4

what happens when a new nucleotide is added to a growing DNA strand?

Answer 4

it releases an ester dimer of phosphate (pyrophosphate)

the release of this molecule provides the energy for the formation of the new phosphodiester bond

pyrophosphate is unstable in aqueous solution and hydrolyzed to form 2 molecules of inorganic phosphate

Question 5

organic phosphates

Answer 5

such as those in ATP, GTP, and DNA

the phosphate group is bonded to a carbon containing molecules

Question 6

phosphoric acid pkas/acidity

Answer 6

this molecule has 3 acidic hydrogens which each have their own pka value

thus, 4 forms of this molecule can exist under different pH conditions

the variety of pka value makes phosphate a good buffer

Question 7

which phosphate forms predominate at physiological pH (~7.4)

Answer 7

dihydrogen phosphate and hydrogen phosphate

Question 8

why is phosphate capable of providing so much energy?

Answer 8

adjacent phosphate groups experience a large amount of repulsion (they each have a negative charge) = unstable

when a phosphate is cleaved, a large amount of energy is released