1. What is energy and what is ATP?
2.1 – Energy and ATP
What is energy and what is ATP?

2. Learning Objectives To learn what energy is and why organisms need it.
To understand how the molecule ATP stores energy.
To learn how ATP is synthesised.
To understand the role of ATP in biological processes.

3. energy

4. What is energy?
Energy is something that allows ‘work to be done’ on something else – i.e. move an object or heat it up.
Energy can exist in different forms:
Energy can be changed from one form to another:
This leads us on to the point that energy cannot be created or destroyed.
Energy is measured in joules (j).
With respect to biology, most of the energy used by organisms, is stored in chemical bonds in molecules.
Light
Heat
Sound
Electrical
Magnetic
Chemical
Electrical
Chemical

5. How is energy related to living organisms?
In order to remain alive, energy is required to ‘power’ the biological processes occurring within all life forms.
This energy initially comes from the Sun.
Plants harness this solar energy, using it to combine water and CO2 into glucose – in a process called photosynthesis.
Light
Chemical
Therefore, photosynthesis is responsible for locking solar energy into molecules such as glucose.
Both plants and animals can then break down these molecules, releasing energy, which can be used in processes essential to life.

6. What do organisms do with energy?
Organisms are highly ordered, so without the constant input of energy, these organisms will eventually breakdown into disarray.
Active Transport
Movement
Metabolism
Energy is needed for:
Thermoregulation
Cell Maintenance/Repair
Molecular Synthesis

7. atp

8. So what’s ATP??
Now that we know plants are responsible for trapping solar energy into molecules such as glucose, we need to know how animals (and plants themselves) benefit from this energy.
For example:
Building a chain of amino acids (into a protein) requires energy. The bonds between each amino acid do not form spontaneously, but require energy input.
Do you think this energy comes directly from the breakdown of glucose?
Amino Acid 1
Amino Acid 2
Bond

9. ATP is therefore, an energy ‘carrier’.
NO! It doesn’t.
Although glucose stores a lot of energy, it takes time to release, via a complicated series of reactions.
This means that it is not a good source of immediate energy.
What actually happens, is that during cellular respiration, molecules such as glucose, are broken down, which releases free energy.
This free energy, is used to form chemical bonds in a molecule called ATP.
Aerobic cell respiration produces about 30 ATP molecules per glucose.
If a reaction only requires one ATP molecule, why use a whole glucose molecule to power it?
ATP is therefore, an energy ‘carrier’.
ENTER: ATP!!

10. Understanding why ATP is important
As explained on the previous slide, reactions need energy to occur, and the amount of energy required by a reaction is quite specific.
It’s usually way less than the amount of energy stored in a glucose molecule – so if you used glucose directly, you’d be wasting the excess energy released.
This is why we ‘convert’ the energy in one glucose molecule, to energy stored in many ATP molecules.
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
glucose
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
Why would you ‘spend’ a whole glucose, when you can spend a single ATP?
ATP
ATP
ATP
ATP

11. Think of glucose as your life-savings
If you wanted to go out and buy a phone, you wouldn’t take your life-savings with you
Instead you’d go to a cash machine and withdraw the correct amount of money
Think of the money as ATP, of which the correct amount can be used to buy your phone

12. Structure and synthesis of atp

13. Structure of ATP
The full name of this molecule is Adenosine Triphosphate, which as suggested by the name, has three phosphate groups.
This bond, is the one that can be broken to release energy for reactions to occur.
The bond is formed in cellular respiration, using energy released during the breakdown of glucose.
ADENINE
RIBOSE
THREE PHOSPHATES

14. Releasing energy from ATP
So when a reaction requires energy, ATP is broken down:
This hydrolysis reaction releases energy to drive other reactions.
When the terminal phosphate is removed from ATP, the leftover molecule only has TWO phosphates left, so is now called adenosine diphosphate.
The phosphate that is removed, is called an inorganic phosphate.
Yep, you guessed it. ATP can be reformed by adding Pi to ADP!
Notice how this is a condensation reaction, that requires energy!
ATP (H2O)
ADP Pi E
adenosine triphosphate
water (for hydrolysis)
adenosine diphosphate
inorganic phosphate
energy
ADP Pi E
ATP H2O

15. The conversion of ATP into ADP is a reversible reaction.
When this happens, energy is released, which can be used to do all kinds of useful biological processes
When this happens, energy is being used to reform ATP, which is then ready to drive yet another reaction.
Remember, that in the case of respiration, that energy comes from the complex breakdown of glucose

16. How and Where is ATP synthesised?
Remember that forming ATP involves adding an inorganic phosphate (Pi) to an ADP molecule.
This can happen in three ways: 1.
In photosynthesis, ATP is produced in a process called PHOTOPHOSPHORYLATION.
This is essentially where light is used to add the inorganic phosphate to ADP! 2.
In respiration, ATP is produced in a process called OXIDATIVE PHOSPHORYLATION.
Within mitochondria electrons are transported, releasing energy to add Pi 3.
SUBSTRATE-LEVEL PHOSPHORYLATION
This is when a reaction has occurred, releasing enough energy, to combine any nearby Pi and ADP together!

17. Summary questions

18. Name at least 5 ‘forms’ in which energy can exist.
State the First Law of Thermodynamics.
What is the unit energy is measured in?
To biologists, where is energy stored within molecules?
State the ‘ultimate’ source of energy in organisms, and explain how it is harnessed.
Give the 6 main functions that energy is needed for.
Explain why glucose is not a good source of immediate energy.
Draw and label an ATP molecule.
Write two equations to show the break down and reformation of ATP.
State the three methods of synthesising ATP.