Energy  in  the  Bonds  of  ATP    Instructions:  Read  through  the  background  information  and  procedure  carefully.  Answer  the  pre-­‐lab  questions.  After  I’ve  approved  them,  you  may  begin  the  lab.    Pre-­‐Lab  Questions:  Answer  in  the  lab  section  of  your  notebook.  

1. What  does  ATP  stand  for?        

2. What  is  its  main  function  in  the  cell?      

 3. What  are  some  sources  of  ATP?  

   

4. How  many  phosphate  groups  does  it  have?    

 5. What  do  the  rubber  bands  in  the  experiment  represent?    

   

6. HYPOTHESIS:  Which  rubber  band  do  you  expect  will  travel  the  greatest  distance?    WHY?        

7. HYPOTHESIS:  Which  will  travel  the  least  distance?  WHY?        Background:  Adenosine  Triphosphate  (ATP):  Adenosine  triphosphate  is  the  most  common  energy-­‐storing  molecule  in  the  cell.  ATP  is  constructed  from  a  nucleotide  called  adenine  and  a  sugar  called  ribose.  Together,  the  adenine  and  ribose  are  called  adenosine.  Adenosine  triphosphate  is  called  triphosphate  because  of  the  three  phosphates  attached  to  the  adenine  and  ribose.    

Adenine  +  Ribose  Sugar  +  3  Phosphates  =  A-­‐P~P~P.    Two  other  molecules  in  the  cell  are  related  to  ATP:  •  Adenosine  diphosphate  (ADP)  has  two  phosphate  groups  attached  to  it:  A-­‐P~P.  •  Adenosine  monophosphate  (AMP)  has  a  single  phosphate  group:  A-­‐P.    When  organisms  need  energy,  they  break  a  chemical  bond  from  the  third  phosphate  group  off  from  ATP  to  form  ADP  and  a  single  phosphate.  The  energy  from  that  is  used  to  power  many  cellular  processes.    Materials:  Rechargeable  batteries  •  Four  blocks  of  wood  of  equal  length,  one  twice  as  wide  as  the  other  three  •  Colored  markers  •  Nine  identical,  long  rubber  bands  •  Protective  eyewear  for  all  students  •  Scissors  •  Tape  measure        

 Procedure:  

1. Label  the  large  wooden  block  with  an  A  (adenosine)  and  label  each  of  the  smaller  three  wooden  blocks  with  a  P  (phosphate  group)  if  not  already  done.  

2. Use  three  rubber  bands  to  represent  the  chemical  bonds  holding  the  phosphates  to  the  adenosine  molecule.  The  first  rubber  band  goes  around  the  adenosine  block  and  one  phosphate  group.  The  second  goes  around  the  adenosine  and  two  phosphate  groups.  The  third  goes  around  the  adenosine  and  all  three  phosphate  groups.    

3. Cut  the  rubber  bands  with  scissors  to  simulate  the  breaking  of  the  bonds.  Start  with  the  band  encircling  all  three  phosphate  groups.  Measure  the  distances  the  rubber  bands  traveled,  which  represent  the  amounts  of  energy  in  the  molecule.  Record  these  results  in  cm  on  your  results  sheet.  

4. Repeat  the  above  by  cutting  the  one  circling  two  phosphate  groups.  Then  finish  with  one  circling  one  phosphate  group.  

 Safety  Note:  The  trajectory  of  a  rubber  band  can  be  totally  unpredictable.  Be  prepared!  Keep  safety  glasses  on  at  all  times.    

 TRIALS  

THIRD  PHOSPHATE  

(ATP)  

SECOND  PHOSPHATE  

(ADP)  

FIRST  PHOSPHATE  

(AMP)    1    

     

 2    

     

 3    

     

 Data  Analysis  and  Conclusion:  

1. Did  the  data  support  or  reject  your  hypothesis?      

2. How  can  you  explain  your  results?      

3.  What  sources  of  error  did  you  have  in  your  experiment?      

4. Is  there  more  or  less  energy  in  ADP  (two  phosphate  groups)  than  in  ATP?        

5. We  have  discussed  how  ATP  functions  like  a  rechargeable  battery.  Describe  how  ATP  works,  using  another  analogy  of  your  choice.