Download 2.1 – Energy and ATP

2.1 – Energy and ATP
What is energy and what is ATP?
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.
ENERGY
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:
Light
Heat
Sound
Electrical
Magnetic
Chemical
• Energy can be changed from one form to another:
Chemical
Electrical
• 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.
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.
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
Metabolism
Movement
Energy is needed for:
Thermoregulation
Cell Maintenance/Repair
Molecular Synthesis
ATP
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.
Amino Acid 1
Amino Acid 2
Bond
• Do you think this energy comes directly from the breakdown of
glucose?
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.
ENTER:
ATP!!
• 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’.
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.
glucose
Why would you ‘spend’ a whole
glucose, when you can spend a single
ATP?
Think of glucose as
your life-savings
Think of the money as
ATP, of which the
correct amount can be
used to buy your phone
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
STRUCTURE AND SYNTHESIS OF ATP
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
Releasing energy from ATP
• So when a reaction requires energy, ATP is broken down:
ATP
+
adenosine
triphosphate
(H2O)
ADP
water (for
hydrolysis)
adenosine
diphosphate
+
Pi
+
inorganic
phosphate
E
energy
• 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!
ADP
+
Pi
+
E
ATP
+
H2O
• Notice how this is a condensation reaction, that requires energy!
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
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!
3.
2.
In respiration, ATP is
produced in a process called
OXIDATIVE
PHOSPHORYLATION.
Within mitochondria electrons are
transported, releasing energy to add Pi
SUBSTRATE-LEVEL PHOSPHORYLATION
This is when a reaction has occurred, releasing
enough energy, to combine any nearby Pi and ADP
together!
SUMMARY QUESTIONS
1.
2.
3.
4.
5.
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.
6. Give the 6 main functions that energy is needed for.
7. Explain why glucose is not a good source of immediate
energy.
8. Draw and label an ATP molecule.
9. Write two equations to show the break down and
reformation of ATP.
10. State the three methods of synthesising ATP.