Download 6 Energy

Energy and Metabolism
GLYCOLYSIS
1 GLU + 2ATP + 2NAD = 2PYR + 4ATP + 2NADH2
NET GAIN = 2 ATP
Glycolysis takes place in the cytoplasm. It converts glucose, fructose, or galactose into 2 molecules of
pyruvate plus 2 ATP. This process uses 2NAD (an electron acceptor), which becomes reduced to
NADH. We need to get it back to NAD or glycolysis will stop. The pyruvates are then taken to the
mitochondria to go through the Kreb’s (TCA) cycle to generate ATP.
Glycolysis is like a gumball machine in the cytoplasm. You put one sugar molecule in, add 2 pennies
(ATP) and get out two gumballs (pyruvate). The gumball machine also gives your two pennies back,
plus an additional two pennies! It takes money to make money, right?
So now you have a net profit of 2 pennies to spend on energy, plus the two gumballs that you can take
to the mitochondria to convert to 2 more special pennies (GTP) that can only be used for certain games
in the body (protein synthesis and gluconeogenesis).
During glycolysis, we generate hydrogen (H+), which is a waste product that we have to get rid of, but
almost no one wants to carry that burden.
There is a guy named NAD who is willing to accept this burden. When he takes on the H+, he is
reduced. If his H+ burden is removed by someone else, he feels good, and is oxidized!
All of NAD’s brothers are also named NAD. It takes 2 NAD brothers to come to the glycolysis gumball
machine and take on the burden of the H+. They are now called NADH.
Right now, you need to take your 2 gumballs (pyruvate) to the mitochondria so you can use the Kreb’s
Cycle to convert them into special pennies.
The two NADH brothers will wait for you to complete the Kreb’s Cycle, so you can escort them to the
Electron Transport Chain, where their H+ burdens will be lifted.
Kreb’s Cycle or Citric Acid Cycle or Tricarboxylic Acid Cycle (TCA)
Acetyl CoA + 3NAD + 1 FAD + 1GTP = 3 NADH + 1FADH2 + GTP + CO2
MULTIPLY THE ABOVE BY TWO
TOTAL GAIN: 8 H+ and 2 GTP
PYRUVATE ACTIVATION
2 PYR + 2NAD + 2CoA = Acetyl CoA + 2NADH2 + 2CO2
The Krebs Cycle occurs in the mitochondria, and requires oxygen. It takes pyruvate from glucose, and
acetate (in the form of Acetyl CoA) from carbohydrates, fats and proteins, and generates 2 GTP
(similar to ATP). The waste product is carbon dioxide.
Like glycolysis, it uses NAD and reduces it to NADH. The NADH is then sent to the Electron
Transport System so it can be converted back to NAD so glycolysis can continue.
Now you have taken your two gumballs from glycolysis (pyruvate) and entered the mitochondria.
You see your neighbor, who does not use sugar. He uses another process which breaks down
carbohydrates, fats and proteins elsewhere in the body, and generates Acetyl CoA instead of pyruvate.
You put one of your pyruvate gumballs into a Kreb machine, along with one of his Acetyl CoA
molecules.
Three more NAD brothers, plus their cousin FAD have to come in to bear the burdens of the four H+
that will be generated per pyruvate gumball (8 H+ for both pyruvates are generated).
For all this, you will get only one special penny (GTP) per gumball. Since you have two gumballs you
get 2 GTP.
You will now have two special pennies, but you now have 8 new people who are carrying your H+
burden, in addition to the 2 people who are waiting for you at the door from the gumball machine.
You need to take all of them to the Electron Transport Chain so someone else can lift their burden and
they can get back to work at the gumball machine again.
Electron Transport System /Oxidatibe Phosphorylation or Cellular Respiration
16 NADH from glycolysis need to be reduced.
The Electron Transport System (aka oxidative phosphorylation, or cellular respiration) also takes place
in the mitochondria. Here, the NADH molecules from glycolysis and the TCA cycle are oxidized back
to NAD so glycolysis can continue. It also generates 3 more ATP. When this system is performing in
the presence of oxygen, oxygen is consumed and the waste product is water. When it is done
anaerobically (such as in some bacteria), sulfate is used as the H+ acceptor and the waste product is
hydrogen sulfide (will show a black precipitate on culture media). If the bacteria does not have sulfate,
it will use nitrite as the electron acceptor, and the waste product is ammonia, which causes a color
change if there is a pH indicator in the culture media.
When the NADH brothers enter this area of the mitochondria, there is a hallway lined with several
people. The first NADH brother gives his H+ burden to the first person (FMN). That makes him
oxidized to NAD again, but the person that took the H+ is now reduced, and he does not want that
burden either, so he passes it to the next person in line (FeS). Now FMN becomes oxidized and the
second person is reduced. FeS passes the burden to CoQ and so on, to the end of the line.
When they finally get to the end of the line, they are greeted by the heavenly oxygen angel. She is so
strong, she can take and hold 2 burdens at once. When she takes the H+ burden from two NADH
brothers, she becomes water. The water will be exhaled. We need to inhale some more heavenly oxygen
angels to keep this process going. Now the NAD brothers have been oxidized. They feel so good, they
want to go back to work to help again with bearing the H+ burden.
• The summary equation for cellular respiration is:
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
glucose + oxygen → carbon dioxide + water
FERMENTATION PATHWAYS
 What if there is no more oxygen?
 Some bacteria, molds, and yeasts can still use the ETC when there is no oxygen. At the end of
the hand-shaking line, they have either sulfate or nitrite.
 If they have sulfate, instead of taking the H+ and turning into water to be exhaled, it turns into
hydrogen sulfide (H2S), a waste product which shows up as a black color on a Petri dish.
 If they have nitrite, they will turn into ammonia, a waste product which has a high pH.
 Humans do not have sulfate or nitrite. They can only use oxygen as the final electron acceptor
in the electron transport chain (cellular respiration).
 Muscle cells use a lot of energy, so they are able to run out of oxygen yet still carry out cellular
respiration by using fermentation to take the H+ burden off the NAD brothers so they can go
back to work for the gumball glycolysis machine and the Kreb’s machine. Muscles are the only
human cells that can do this.
 When no oxygen is present (such as in muscles during sprinting), the NADH molecules that
were generated from glycolysis and the TCA cycle cannot use the electron transport chain to be
converted back to NAD. Instead, they use one of three fermentation pathways.

Homolactic

Ethanolic

2, 3, Butanediolic
HOMOLACTIC FERMENTATION PATHWAY
In the homolactic pathway (used by humans), the H+ from NADH is donated to pyruvate, converting it
to the waste product: lactic acid. The NAD has now been regenerated so glycolysis can continue. By
breathing heavily, oxygen is added to lactic acid, converting it to glucose. The lactic acid could also be
carried by the bloodstream to the liver, where it is converted back to pyruvate. Therefore, increasing
circulation and oxygen helps eliminate lactic acid build-up (ultrasound or massage therapy for sore
muscles helps).
ETHANOL FERMENTATION PATHWAY
Ethanolic Fermentation
PYR + NADH
Acetaldehyde + NAD + CO2
ETOH + NAD
NET GAIN = 2 NAD
+NADH
The ethanol fermentation pathway also uses glycolysis, but the pyruvate is then converted to ethanol
and carbon dioxide.
Yeasts use this pathway to create beer, and cause the rising of bread dough.
2, 3 BUTANEDIOLE FERMENTATION PATHWAY
2, 3 Butanediolic Fermentation
2PYR + 2NADH
Acetoin + NAD + 2 CO2 +2NADH
2, 3 Butanediol + 2NAD
NET GAIN = 4 NAD
Butanediol fermentation uses 2 pyruvate molecules and the waste product is 2, 3, butanediol. Use of
this pathway is typical for Enterobacter (a type of coliform bacteria) and is tested for by using the
Voges–Proskauer (VP) test. If the unknown culture has a positive VP test, we know it might be this
organism.
ATP
 Adenosine triphosphate (ATP) is used in cells as a coenzyme. It is often called the "molecular
unit of currency" of intracellular energy transfer.
 ATP transports chemical energy within cells for metabolism. It is one of the end products of
phosphorylation and cellular respiration and used in many cellular processes, including muscle
contraction, motility, and cell division.
 One molecule of ATP contains three phosphate groups which provide energy. When ATP is
used, it loses a phosphate and is reduced to ADP (diphosphate).
 Metabolic processes that use ATP as an energy source convert it back into its precursors. ATP is
therefore continuously recycled.
 Guanosine triphosphate (GTP) is similar to ATP but can only be used for is used as a source of
energy for protein synthesis and gluconeogenesis.
OH
OH
OH
Pyruvate
GLUCOSE
OH
ATP
ADP
Kinase
CH2O(P)
Homolactic
Homolactic Fermentation
PYR + NADH 
Lactic Acid + NAD
NET GAIN = 1 NAD
Lactic Acid
H
CH3-C-COO-
CH3-C-COO-
O
OH
CO2
NADH NAD+
NADH NAD+
O
OH
OH
CH3-C-COO
Acetaldehyde
H
CH3-C
O
O
Pyruvate
Ethanolic
OH
NADH NAD+
-
GLUCOSE-6-P
CH3-CH2-OH
Ethanolic Fermentation
PYR + NADH 
Acetaldehyde + NAD + CO2 
+NADH 
ETOH + NAD
NET GAIN = 2 NAD
OH
2, 3 Butanediolic
Isomerase
Pyruvate
Pyruvate
-
CH3-C-COO
CH2O(P)
FRUCTOSE-6-P
CH2OH
O
O
O
CO2
CO2
OH
OH
ATP
ADP
Kinase
CH3-C-COO-
+
C-CH3
CH3-C
O
2, 3 Butanediolic Fermentation
2PYR + 2NADH 
Acetoin + NAD + 2 CO2 
+2NADH 
2, 3 Butanediol + 2NAD
NET GAIN = 4 NAD
O
2NADH
O
CH2O(P)
FRUCTOSE-1,6
Di-Phosphate
CH2O(P)
2NAD+
OH
OH
OH
CH3-C-C-CH3
OH
Adolase
Acetoin
2NADH
2NAD+
DiOH Acetone Phosphate (3C)
P-Glyceraldehyde (3C)
OH OH
H H
1 GLU + 2ATP + 2NAD =
2PYR + 4ATP + 2NADH2
Kinase
2, 3, Butanediol
CH3-C-C-CH3
GLYCOLYSIS
1, 3, P-Glyceric acid
NAD+
ADP + Pi
NADH2
ATP
NET GAIN = 2 ATP
TCA
Acetyl CoA + 3NAD +
1 FAD + 1GTP =
3 NADH + 1FADH2 +
GTP + CO2
2 P-Glyceric acid
x2
Isomerase
Pyruvate
Acetyl CoA
CH3-C-COOH
CH3-C-S-CoA
O Dehydrogenase CO2
Oxaloacitic Acid (4C)
COO- -CH2-C-COO-
O
CO2
ά Ketoglutarate Acid (5C)
Citric Acid
Coenzyme
A
NAD+ NADH2
NAD+
NADH2
Isocitric Acid
(6C)
Enol Pyruvate
ADP + Pi
ATP
Kinase
x2
ETOH
COO- -CH2-CH2-C-COONAD+
CO2
O
NADH
2
Tricarboxylic Acid Cycle
(TCA/ Krebs Cycle)
PYRUVATE
ACTIVATION
GDP+
GTP
Succinate
NAD+
NADH2
FAD+
FADH2
Fumorate Acid
ELECRON TRANSPORT SYSTEM (RESPIRATION / OXIDATIVE PHOSPHORYLATION
H
16 NADH from
glycolysis
need to be
reduced.
H
Ox
Red
+3
+2
FMN
Fes
CoQ
+2
+3
H2
RedADP ATP Ox
ATPase
*First energy-producing
step
Malate Acid
2 PYR + 2NAD + 2CoA =
Acetyl CoA + 2NADH2 + 2CO2
ETS
TOTAL GAIN:
8 H+
2 GTP
Succinyl CoA
O
PYRUVATE ACTIVATION
MULTIPLY THE
ABOVE BY TWO
Ox
Red
Ox
Red
Ox
Anaerobic phosphorylation
end-products (instead of H2O)
H
H2O
Cyt b
Cyt c
Red
ADP ATP Ox
Red
Cyt a1
H2S
NH3
SO4
NO2
Cyt a3
O2
ATPase
Ox
Red
ADP ATP
ATPase