Phosphorus

Question 1

What are the components of phosphorus

Answer 1

1 P and 4 oxygen- atoms in the fully ionised state of

Question 2

What are the 4 major roles of phosphate

Answer 2

1- phospholipid bilayer

2- control protein/enzyme activity by phosphorylation/dephosphorylation

3- component in high energy molecules such as ATP and NAD

4- form dna and rna backbone

Question 3

What is the structure called that makes up bones from phosphate and calcium

Answer 3

Hydroxyapatite

Question 4

Explain the steps of ionisation/origination from phosphoric acid (H3PO4) to a phosphate ion (po4)3–

Answer 4

The last H is lost and the phosphate is fully ionised

A fully protonated form is phosphoric acid H3PO4

When ionisation occurs and 1 proton is lost

= dihydrogen phosphate (H2PO4)-

Another H is lost in further ionisation

= hydrogen phosphate (Hpo4)2-

Phosphate (Po4)3-

Question 5

What does a titration curve show of phosphoric acid

Answer 5

It shows the ph at which there is change in the state of the phosphate eg to dihydrogen phosphate

This is through the increased addition of OH which allows H2O to be lost at each endpoint (H is lost each time)

Question 6

What is Pka

Answer 6

The ph at which the concentration of the acid(one that is going to lose the H) is the same as the conjugate base (the next form of phosphate)

Question 7

What does the first endpoint show on the titration curve (at 2.2 pKa)

Answer 7

The concentration of phosphoric acid is equal to the conc of dihydrogen phosphate (via the addition of OH causing ionisation)

This happens at ph 2.2

Question 8

The 2nd endpoint is at 7.2 Pka (7.2 ph). What does this show

Answer 8

The equal conc of dihydrogen phosphate and hydrogen phosphate

Due to the ionisation of the dihydrogen phosphate (loses H through addition of OH)

Question 9

At what pKa (ph) is the conc of hydrogen phosphate equal to conc of phosphate ion PO43-

Answer 9

12.7 (maximum amount of OH)

Question 10

What is the Henderson hasselbach equation showing ph /Pka relationship

Answer 10

Ph = pKA + log (conc of conjugative base/ previous acid)

Question 11

What are esters/ how are they made

Answer 11

Through the condensation of an alcohol (R2OH)
And an acid (C-o-OH)

Produces an ester and H20

The H from the acid is displaced by Hydroxyl on the alcohol to form an ester link (the O left from the acid)

Question 12

How do you go from phosphoric acid to a phosphotriester (displacement via alcohol)

Answer 12

Start off with phosphoric acid H3PO4

One of the H is displaced by the OH from an alcohol to form OR1 and h20
= phosphomono ester
H2Po4 OR1

From phosphomonoester to phosphodiester another H is displaced by the OH from another alcohol = HPO4 and OR1 and OR2

Phosphodiester to phosphotriester the last H is displaced by another Oh from alcohol

= P and 3x OR1,2,3 and 1 O

Question 13

How can phosphomonoester have either -1 or -2 charge??

Answer 13

Because it has 2 hydroxyl groups, if it is protonated these can be lost

Only has 1 OR1 group

Question 14

Why can phosphodiester only have a -1 charge

Answer 14

Only has 1 hydroxyl group remaining (2 ester bonds OR1,OR2)

Question 15

Why can’t phosphotriester have a charge?

Answer 15

No ionisable groups

Lost all its hydroxyls to 3 ester bonds (OR1,2,3)

Question 16

Where is a phosphodiester bond created in DNA/RNA (from phosphomonoesters because 1 O is linked to a pentose at 5’)

Answer 16

Between the OH on the 3’ carbon on a pentode sugar

And the OH on the phosphate at 5’ carbon on the other pentode sugar

Question 17

Why is hydrolysis of a phosphodiester bond called an SN2 reaction

Answer 17

Substitution of an R2OH on the diester with an OH
N- water is a nucleophile

2- 2 bio molecules involved (phosphate and water)

Question 18

What happens in the hydrolysis of a phosphodiester bond starting from electrons being donated from oxygen on water

Answer 18

Electrons from the oxygen on H2O are donated to the phosphate group (P)

These electrons displace the OR2 group (the ester bond from phosphodiester)

This OR2 forms an alcohol with free H

And to replace the OR2 , water donated a hydroxyl OH

This forms a phosphomonoester

Question 19

What does R1OH represent

Answer 19

An alcohol which then reacts with an H on a phosphate to form an ester

Question 20

What is a phosphoanhydride bond

Answer 20

Condensation of 2 acids

C=o -OH and C=o-OH

FormsO= C-O-C = O + h20

O= P-O-P =O is phosphoanhydride

Question 21

Where are phosphoanhydride bonds found? (Condensation reaction with hydrogen phosphates)

Answer 21

In ATP

Question 22

What are the 2 types of hydrolysis of ATP?

Answer 22

Where 1 phosphate is hydrolysed leaving an ADP molecule and an inorganic phosphate

Or where 2 phosphates are hydrolysed and 1 phosphate is left(AMP) and the 2 phosphates are pyrophosphates which then later hydrolysed into 2 x Pi

Question 23

Why is the hydrolysis of atp described as exergonic

Answer 23

Because there is free energy release when phosphoanhydride bonds are hydrolysed

Question 24

Why are enzymes still needed for the hydrolysis of ATP?

Answer 24

To get it hydrolysed state, the molecules transition state needs to be lowered as not enough energy can be generated to hydrolyse it otherwise

Question 25

Name the 2 reasons hydrolysis of ATP releases free energy (exergonic)

Answer 25

1- electrostatic repulsion between -ve charges on phosphates

2- resonance stabilisation (delocalisation of electrons)

Question 26

How is electrostatic repulsion the reason for high free energy of hydrolysis

Answer 26

The negative charges repel each other on the O from the phosphates in ATP. When 1 is hydrolysed the others will move from eachother, making hydrolysis favourable

Question 27

How is resonance stabilisation a reason for hydrolysis being energetically favoured

Answer 27

Delocalised electrons which surround the oxygens on phosphate are more present when the anhydride bonds deform. This causes resonance STABILITY more than in ATP form

Question 28

True or false, the hydrolysis of ATP allows more opportunity for H2O to interact meaning its energetically favoured

Answer 28

True !

Question 29

What energy generating processes use the production of ATP from adp + pi?

Answer 29

Photosynthesis

Question 30

What energy requiring processes use the Hydrolysis of ATP coupling

Answer 30

Muscle contraction
Cell signalling
Active transport