Adenosine Triphosphate

• Adenine

• Ribose

• 3 phosphate groups

Using enzyme ATP hydrolase in a hydrolysis reaction.

Water is added to ATP to break it down into ADP and Pi

releasing energy at the same time.

ADP (adenosine diphosphate) and Pi (inorganic phosphate).

ATP hydrolase

A condensation reaction, where a molecule of water is released.

ADP + Pi → ATP;

Both sides correct, but allow other recognised symbols or words for phosphate ion. 

Reject P unless in a circle.

Accept reversible arrow

Ignore any reference to kJ / water

ATP synthase.

ATP is resynthesised by the condensation of ADP and Pi . 

This reaction is catalysed by the enzyme ATP synthase during photosynthesis, or during respiration. 

Phosphorylates other compounds making them more reactive.

Hydrolysis (reaction)

1.      To provide energy for other reactions/named process

Reject ‘produce’ energy

2.      To add phosphate to other substances and make them more reactive/change their shape

1.      ATP cannot be stored / is an immediate source of energy

2.      ATP only releases a small amount of energy at a time

3. ADP + Pi ⟶ ATP + H2O

1.      Energy released in small / suitable amounts

1. In context of release, not storage. Ignore producing energy / manageable amounts.

2.      Soluble

2. Reject "broken down easily / readily". Reject "quickly / easily resynthesised".

3.      Involves a single / simple reaction

1.      ATP to ADP + Pi by ATP hydrolase in hydrolysis reaction

Accept ATPase for ATP hydrolase

2.      ADP + Pi to ATP by ATP synthase

Accept synthayse

3.      In condensation reaction

Adenosine triphosphate

1. and 2. Correct names of three components adenine, ribose/pentose, three phosphates

Accept for 1 mark, correct name of two components

Accept for 1 mark, ADP and phosphate/Pi

Ignore adenosine

Accept suitably labelled diagram

3. Condensation reaction Ignore phosphodiester

4. ATP synthase Reject ATPase

1. Attachment/association of inorganic phosphate to the enzyme

For ‘phosphate/Pi’ accept PO43– and P in a circle.

Accept ‘phosphate goes to the enzyme’.

Ignore named bonding or position of phosphate attaching to enzyme but reject formation of E-S complex.

2.  Released from hydrolysis of ATP

OR Released from ATP to ADP + Pi

For ATP accept adenosine triphosphate.

For ADP accept adenosine diphosphate.

Adenosine diphosphate and (inorganic) phosphate;

Accept ADP for adenosine diphosphate

Accept Pi / PO43– / P in a circle for inorganic phosphate

Reject adenine diphosphate

Reject phosphorus / P for phosphate

1. Releases energy in small / manageable amounts. Accept less than glucose

2. Broken down in a one step / single bond broken immediate energy compound / makes energy available rapidly. Accept easily broken down

3. Phosphorylates / adds phosphate makes phosphorylated substances more reactive / lowers activation energy

Do not accept phosphorus or P on its own

4. Reformed / made again rapidly

Must relate to regeneration

Human ATP synthase has a different tertiary structure to bacterial ATP synthase

OR Human ATP synthase has a different shape active site to bacterial ATP synthase

OR Antibiotic cannot enter human cells/mitochondria

OR Antibiotic not complementary (to human ATP synthase)

1. From ADP and phosphate

Reject P/Phosphorus

Reject use of water in the reaction

2. By ATP synthase

3.  During respiration/photosynthesis

1.      Releases relatively small amount of energy / little energy lost as heat

Key concept is that little danger of thermal death of cells

2.      Releases energy instantaneously

Key concept is that energy is readily available

3.      Phosphorylates other compounds, making them more reactive

4.      Can be re-synthesised

5.      Is not lost from / does not leave cells.

ATP is broken down into adenosine diphosphate (ADP) and an inorganic phosphate group (Pi ).

The reaction is catalysed by the enzyme ATP hydrolase.