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Human Anatomy & Physiology
4/29/2017
05C.6 ATP & ATP Regeneration
ATP! ATP! Cell energy is great for me!
What happens if a muscle cell is lacking ATP or the components to make more
ATP? …they let us know by cramping, burning, fatigue, and sometimes ‘aching’
us into helping them
No ATP….no power stroke…fatigue or lack of contraction! No ATP….the
myosin head cannot release….cramp
A. ATP…what is it anyway?
ATP is the molecule that is known as ‘cell energy’. The cell uses this
molecule to do work…
ATP = real name…Adenosine Triphosphate
Adenosine is the base molecule that three phosphates are going to
attach to. Now….this is easier said than done because these
phosphates have a negative charge and really are not fond of being
next to one another.
First part of the molecule begins as A + P- = AMP (Adenosine
Monophosphate)
This molecule does not have a great amount of energy, because it did
not take a lot of energy to bond one phosphate to adenosine.
Second part of the molecule continues as another phosphate is added
to AMP. Now, this is going to require more energy for this to happen
because both phosphates are negative.
A + P- ~ P- = ADP (Adenosine Diphosphate)
Notice how the symbol ~ is used to show that a high-energy bond
was used to get these two phosphates together.
ADP has more energy stored than AMP because it took more energy
to make this molecule.
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Third part of the molecule finishes by adding another phosphate bond
to the group. This is going to take some work, because two negatives
want to repel the next negative phosphate group to be added. Because
of this obstacle, the MOST ENERGY will be used to get the third
phosphate group on!
A + P- ~ P- ~ P- = ATP or ADP ~ P- = ATP
The third phosphate bond contains the MOST ENERGY of the
bonds!
*When a muscle uses ATP, it only releases the third
phosphate…because it has the most energy!
*Muscles do not want to release all the phosphates and have to
start all over…so it only releases the phosphate that has the most
energy! Also, it easier and faster for the cell to regenerate ATP
starting with ADP instead of AMP!
ATP example (can & snake)
B. Three way to get ATP Regeneration
1. Creatine Phosphate (CP):
This is a quick and easy way to turn ADP into ATP!
Creatine Phosphate is found in the cytoplasm. It will easily give up its
phosphate to ADP!
CP + ADP = ATP + Creatine
(Which is now a waste product, will be discarded by the cell and
filtered out by the kidney’s into the urine.)
This quick and easy way to regenerate ADP into ATP does not require
O2 (oxygen) and is considered anaerobic.
Some sport supplements exploit this regeneration by providing a
higher dosage of creatine. The idea is to load the muscles with more
CP and increase the muscle’s ability to convert ADP into ATP at a
greater rate. Some athletes report having increased muscle stamina
using this type of product. (Which begs the thought that too much of a
good thing can become a bad thing…especially for the kidneys who
have to clean out all the extra creatine.)
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2. Glycolysis
Break glycolysis down into glycol = glucose; lysis = to break apart
and we have the concept of this cycle: BREAK GLUCOSE APART!
Why would we break it apart?
“To get a little bit of energy, but more importantly, glucose is too big to get into
the mitochondria.”
Glycolysis cycle:
The process of splitting glucose occurs outside of the mitochondria in the
cytoplasm and requires no oxygen (anaerobic).
Leave ~ 5 lines & room on the
right side for the rest of this diagram.
Think of NAD as a taxi or carrier for Hydrogen.
Aka “acceptor”
NAD only has ‘one seat’ for hydrogen.
When carbons are split or pulled off a molecule, these taxis or
acceptors can pick up hydrogens.
Notice:

that only enough energy was created to make 4 ATP’s, but it takes 2
ATP’s to split glucose. The net gain out of glycolysis is 2 ATP’s.
 Also note that 2 NADH were formed.
The pyruvic acid is still too big to go into the mitochondria. It will now need to
loose one more carbon before it will be small enough to go in through the
mitochondria’s membrane.
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Pyruvic acid (C3) will loose a carbon, which will be picked up and
removed by oxygen to become CO2 and hydrogen (NADH). The
new C2 molecule is Acetyl CoA and can easily go through the
membrane and fall into the Citric Acid Cycle also known as the
Kreb’s cycle.
Notice that oxygen (O2) is a carbon acceptor after glycolysis is
finished and is the beginning of the aerobic breakdown of Pyruvic
acid.
WHAT HAPPENS IF NO OXYGEN IS AVAILABLE?
a
Remember that oxygen HAS TO BE AVAILBALE for Pyruvic acid
to loose a carbon.
After about 15-20 seconds of activity (depending on how ‘in shape’
the person is), oxygen is depleted and is no longer there to accept
the carbon.
What does Pyruvic acid do if no oxygen is around? It gives up! It
becomes a nasty molecule of Lactic Acid!
Lactic acid is a ‘dead end’ molecule for muscles. Because no
oxygen is available and the citric acid cycle isn’t being fed acetic
acid, every thing comes to a halt and ATP diminishes and the muscle
fatigues and can even cramp.
The build up of lactic acid gives the muscle a ‘burning’ feeling. Some
athletes use the term ‘feel the burn’ to know that they are pushing the
endurance of the muscle metabolism to its limit.
Lactic acid has a bad rap, because it has a positive purpose to protect the
muscles from working to a point of damage. Also, pushing a muscle into fatigue
only causes the muscle to adapt by chemically stimulating more blood vessels to
grow (increase O2 delivery) and mitochondrial division to increase the number of
mitochondria (match needed ATP formation to match the workload being
demanded of the muscles).
The ability of the muscle to adapt to increased energy demands and workloads is
known as conditioning or ‘getting into shape’.
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3. Citric Acid Cycle (Kreb’s cycle)
The purpose of this cycle is to GRAB HYDROGENS! This cycle goes through a
process of taking carbons off molecules, which need oxygen to pick them
up…making this cycle AEROBIC!
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As we know, when a carbon is pulled off, hydrogens come with it. So…the ‘oneseater taxi’ NAD will be there to grab up hydrogens along with another taxi that
can carry two hydrogens. This taxi or acceptor is known as FAD.
Remember that one glucose molecule made two Pyruvic acid
molecules, so the cycle below is doubled.
Citric Acid Cycle (Kreb’s)
Leave ~ 10 lines below
this diagram for the rest.
Notice:


the citric acid cycle only makes 2 ATP’s (count it twice for both pyruvic
acids and we get a whopping 4 ATP’s!).
Not a whole lot of ATP for this cycle to make, but remember that the main
purpose of this cycle is to GET THOSE HYDROGENS!


with each turn of the cycle, 6 NADH’s and 2 FADH2’s are created!
(This is a total of two pyruvic acids.)

that oxygen must be present for the cycle to continue. Oxygen is not
used to create ATP, but instead is needed as a Carbon acceptor =
CO2.
Again…the main objective here is to pull carbons to get hydrogens!

What to do with ALL THOSE HYDROGENS?
Why are they SO IMPORTANT?
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Let’s keep this simple.
Notice the cristae of the mitochondria (it is how they recognize this organelle).
With in the cristae, hyrdrogens will have their electrons taken from them.
The electrons will be taken (pumped) to a higher gradient and then dropped
down to a lower gradient, where the hydrogens should be ‘hanging out’ so they
can get their electron back.
When the electrons are dropped, they release energy! This energy
is used to regenerate ADP back into ATP!
Electron Transport Chain
Leave ~ 8 lines below
this diagram for the rest.
Notice:
 that the electron ‘falls’ and releases energy that is
transferred into bonding a third phosphate onto ADP.
(ADP ~ P- = ATP)
 that the hydrogen, now with a positive charge (H+), gather
at the end of the gradient in order to get their electron back.
 oxygen then picks up the hydrogens, that are no longer
needed here, and forms H2O. The ETC is an AEROBIC
cycle.
 Here, oxygen is a hydrogen acceptor and forms water as a
‘waste product’.
 In the ETC, NADH from the Citric Acid Cycle will generate
enough energy to regenerate 3 ADP’s into 3 ATP’s and
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FADH2 will generate energy to regenerate 2 ADP’s into 2
ATP’s.
NADH = 3 ATP FADH2 = 2 ATP
Let’s count our ATP production:
*2 NADH from Glycolysis x 2 ATP =
2 NADH from Pyruvic Acid to Acetyl CoA
6 NADH from Citric Acid Cycle_________
8 NADH x 3 ATP =
2 FADH2 x 2 ATP =
Total for the ETC:
4 ATP
24 ATP
4 ATP
32 ATP
95 % of ATP production comes from the Aerobic part of glucose metabolism
(CitricAcid Cycle and ETC)!
If we add in the 2 ATP from Glycolysis and the 2 ATP from the Citric
Acid Cycle to our 32 ATP’s , we get a total of 36 ATP from one
glucose molecule.
*(These NADH molecule had to be ‘escorted’ into the mitochondria, so they
will only generate 2 ATP’s)
The ability of a person to raise their aerobic pathways to meet workload can
lead athletes to use this means of ATP regeneration for hours of physical
activity.
Reduce, Recite, Reflect, & Review!
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