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Cellular Respiration
Biology 11
A. Allen
1
http://fusionanomaly.net/mitochondria.html
Cellular Respiration
• Cellular respiration is…
The process by which a cell breaks down sugar or
other organic compounds to release energy used for
cellular work; may be anaerobic or aerobic,
depending on the availability of oxygen. Aerobic
respiration can be summarized by the following
formula:
C6H12O6 + 6O2  6H20 + 6CO2 + energy (36 ATP)
2
Glycolysis
• Glycolysis is the first stage of cellular respiration.
• Glycolysis has two parts; Glycolysis I & Glycolysis II. In order to
‘kick-start’ glycolysis I, activation energy is required (ATP).
Sugar is split into two PGAL’s. In glycolysis II, PGAL is
oxidized and ATP is produced. The overall pathway gets its name
from this sugar splitting (glyco = sugar, lysis = split).
• Glycolysis occurs in the cytosol (The fluid portion of the
cytoplasm, outside the organelles ).
3
An overview of Aerobic Cellular Respiration
Can you find
Glycolysis?
4
Glucose
6-C
Glycolysis I
1
•
ATP
ADP
2
Glycolysis I is a series of endergonic
reactions
Glucose ~P
“glucose-6-phosphate”
6-C, 1 Phosphate
1. Glucose enters the cell by diffusion
3
2. ATP donates a phosphate to the substrate.
(1 ATP used) Glucose-6-phosphate is
produced.
Fructose~P
“fructose-6-phosphate”
6-C, 1 Phosphate
3. Glucose-6-phosphate is rearranged to
fructose-6-phosphate (another 6-C sugar)
ATP
4
4. another ATP donates its phosphate (1 ATP
used). Fructose 1,6-bisphosphate is
produced.
ADP
P~ Fructose ~P
“Fructose 1,6-bisphosphate”
6-C, 2 Phosphates
PGAL
AKA G3P
X2
PGAL
AKA G3P
5
(3-C, 1 phosphate)
Animation
5. The fructose 1,6 bisphosphate molecule is
split into 2 PGALs
(phosphoglyceraldehyde), a 3-carbon
compound. Note PGAL is also known as
glyceraldehyde 3-phosphate (G3P)
**Glycolysis I …**
•2 ATP (2 ATP’s are used.)
5
Glycolysis II
PGAL (G3P)
(3-C, 1 phosphate)
NAD+
1
Pi
NADH
(3-C, 2 phosphates)
bisphosphoglyerate (BPG) is formed
ATP
2. ADP is phosphorylated to ATP (x2) as it
(3-C, 1 phosphate)
2-phosphoglycerate
(3-C, 1 phosphate)
3
H2O
phosphoenolpyruvate
(PEP)
ADP
ATP
4
Pyruvate (Pyruvic Acid)
(3-C, 0 phosphates)
Animation
(NADH is formed). The oxidized PGAL then
accepts a Pi from the cytosol. 1,3
ADP
3-phosphoglycerate (PGA)
X2
In Glycolysis II, each PGAL (2 from 1
molecule of glucose) is oxidized to release
energy. This process is exergonic.
1. PGAL is oxidized. NAD takes electrons
1,3 bisphosphoglycerate (BPG)
2
•
removes the phosphate from the substrate.
3-phosphoglycerate (PGA) is formed.
(substrate level phosphorylation: when
ADP removes Pi from the substrate to form
ATP)
3. 3-phosphoglycerate is rearranged to 2phosphoglycerate which is then rearranged
to phosphoenolpyruvate (PEP). Water is
given off in this process.
4. PEP gives a phosphate to ADP to make ATP.
Pyruvate (AKA Pyruvic acid) is formed.
**Glycolysis results in a net gain of …**
•2 ATP (2 ATP’s are used and 4 are produced)
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•2 NADH These hydrogens are transported
to the mitochondria for more ATP production
Substrate Level Phosphorylation
• The direct phosphate transfer of
phosphate from an organic molecule to
ADP.
IMPORTANT!
7
Think Together!
Partners `A` and `B` take turns answering the
questions below.
A. What is the basic difference between Glycolysis I and
Glycolysis II?
B. What is the role of NAD?
A. Using your notes, describe glycolysis to your partner
using the terms reduce, oxidize & phosporylation
B. How is substrate-level phosphorylation involved in
glycolysis? Where?
8
Coenzyme
• A substance that enhances or is
necessary for the action of enzymes. They
are generally much smaller than enzymes
themselves. NAD is a coenzyme that
serves and an electron carrier.
9
Vocabulary GAME!
•
•
•
•
•
•
•
•
•
Glucose
fructose
PGAL
Pyruvate
phosphate
Glucose-6 phosphate
NADH
ADP
endergonic
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11
Circle the end products of glycolysis. Where do they go next?
Pyruvate Oxidation (Pyruvic Acid Oxidation)
Pyruvate
(pyruvic acid)
(3-C)
NAD+
NADH
1
CO2
Acetate
(Acetic acid )
(2-C)
2
X2
Coenzyme A
(or ‘CoA’)
acetyl coenzyme A
(or ‘acetyl coA’)
Remember, in glycolysis, glucose was
oxidized to 2 pyruvate molecules.
Therefore, the above biochemical pathways
run twice for every molecule of glucose!
Pyruvate Oxidation ONLY HAPPENS IF O2
is present!
1.
The two pyruvate from glycolysis
diffuse into the mitochondrion’s
matrix. Here, it is oxidized by NAD+
(which is reduced to NADH) to make
acetate, a 2-carbon compound. (The
carbon is lost in the form of CO2)
2.
Animation
Acetic acid combines with coenzyme
A to form acetyl coenzyme A.
**Pyruvate Oxidation results in a net gain of …**
•2 NADH. These hydrogens are transported to the
Electron Transport Chain for more ATP production
12
Stop & Think!
• Under what conditions would the rate of
pyruvate oxidation in the muscle cells of
an athlete slow down?
13
Can you find Pyruvate oxidation? Where does it occur?
14
Krebs
Cycle
1.
Animation
acetyl coenzyme A
(or ‘acetyl coA’)
Coenzyme A
(or ‘CoA’)
1
2.
Oxaloacetate (4-C)
3.
Citrate (6-C)
2
Isocitrate (6-C)
X2
NAD
3
4.
NADH
CO2
α -ketoglutarate (5-C)
Co-A
CO2
Co-A
Succinate
5
(4-C )
NAD
Succinyl-CoA
(4-C )
GTP GDP + Pi
NADH
4
5.
Acetyl coenzyme A enters the
Krebs cycle and combines with
Oxaloacetate (4-C), to make
citrate (6-C). Coenzyme A is
recycled for further use.
Citrate is rearranged to isocitrate
(6-C)
NAD accepts hydrogens from
isocitrate which is therefore
oxidized. One molecule of CO2 is
given off as isocitrate loses one
carbon. α-ketoglutarate (5-C) is
formed.
α -ketoglutarate (5-C) is oxidized
to succinyl Co-A (4-C). A CO2 is
removed, coenzyme A is added,
and 2 hydrogen atoms reduced
NAD to NADH. Succinyl C0-A is
produced.
Succinyl Co-A (4-C) is converted
to succinate (4-C). A Pi from the
matrix displaces C0-A from
succilyl Co-A. The phosphate is
then tansfered to GDP (guanosine
diphosphate) to make GTP. Then
the Pi is transferred to ADP to
make ATP!
ADP + Pi
ATP
15
Krebs
Cycle
6.
Animation
acetyl coenzyme A
(or ‘acetyl coA’)
Coenzyme A
(or ‘CoA’)
1
8
7.
Oxaloacetate (4-C)
Citrate (6-C)
NADH
7
8.
2
NAD
malate (4-C)
Isocitrate (6-C)
X2
H20
NAD
3
NADH
CO2
fumarate (4-C)
α ketoglutarate (5-C)
6
FADH2
FAD
Co-A
CO2
Co-A
Succinate
5
(4-C )
NAD
Succinyl-CoA
(4-C )
GTP GDP + Pi
ADP + Pi
ATP
4
Succinate (4-C) is oxidized to
fumarate (4-C). Not enough
energy is released to reduce
NAD, so FAD is instead
reduced to FADH2.
Fumarate (4-C) is converted
to malate (4-C).
Malate is oxidized to
oxaloacetate (4-C). 2
hydrogens are reduced NAD
to NADH. Oxaloacetate has
been restored, so the cycle can
continue! Yahoo!
Only 2 ATP’s have been
produced from Krebs
cycle. 
NADH
Final products of Krebs Cycle per molecule of glucose:
3 x 2 = 6 NADH  (to electron transport chain to make ATP)
1 x 2 = 2 FADH2  (to electron transport chain to make ATP)
1 x 2 = 2 ATP
16
Think Together!
• Why is there a “X2” on the diagram of the
Krebs Cycle?
• Krebs cycle only yields 2 ATP per
molecule of glucose, but it also results in 6
NADH and 2 FADH2 produced. What do
you think NADH and FADH2 is for?
17
18
Oxidative Phosphorylation (Electron Transport Chain)
Animation #1
Animation #2
• The electron transport chain is located on the inner membrane of the mitochondrion.
It consists of several electron carriers which accept electrons from NADH and
FADH2 (from glycolysis and Krebs cycle). It requires O2!
19
…Oxidative Phosphorylation (Electron Transport Chain)
Animation #1
Animation #2
1
2
[1] Energized electrons from Glycolysis and Krebs cycle are carried to the electron
transport chain via NADH...
[2] ...and FADH2
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…Oxidative Phosphorylation (Electron Transport Chain)
Cytochrome c oxidase complex (H+ pump)
3
4
Animation #1
Animation #2
NADH Dehydrogenase
(H+ pump)
1
2
Cytochrome bc1 complex (H+ pump)
[3] Electrons are passed through a series of electron carriers which become reduced/oxidized
as they pass off the electrons [complexes I -IV]. At different places along this chain, the
energy released from the electrons is used to ‘pump’ protons (H+) across the inner
membrane of the mitochondrion into the intermembrane space
[4] This creates a concentration gradient in the intermembrane space.
21
…Oxidative Phosphorylation (Electron Transport Chain)
Cytochrome c oxidase complex (H+ pump)
3
4
Animation #1
Animation #2
7
NADH Dehydrogenase
(H+
pump)
1
2
5
6
Cytochrome bc1 complex (H+ pump)
[5] The H+ ions are allowed to pass back into the matrix through ATP synthase.
[6] Using the energy from the flow of protons, ADP is united with Pi to form ATP.
Note that because NADH and FADH2 enter the electron transport chain at different locations,
they yield different amounts of ATP; NADH yields 3 ATP and FADH2 yields 2 ATP.
[7] The electrons unite with protons (H+) and oxygen at the end of the ETC to form water.
If insufficient O2 is available in the cell, the ETC will not work! What happens then?......
22
Electron Transport and
Chemiosmosis
CoQ
NADH
H+
NAD+
H+
H+
H+
23
Electron Transport and
Chemiosmosis
Fig. 9.15
H+
Cyt C
CoQ
NADH
H+
NAD+
H+
H+
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Electron Transport and
Chemiosmosis
Fig. 9.15
H+
H+
Cytochrome c
oxidase complex
Cyt C
CoQ
NADH
H+
NAD+
H+
25
Electron Transport and
Chemiosmosis
Fig. 9.15
H+
H+
H+
Cytochrome c
oxidase complex
Cyt C
CoQ
NADH
H+
NAD+
2 H+ + ½ O2
Electron transport chain
H20
26
chemiosmosis
Electron Transport and
Chemiosmosis
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
ADP + P
ATP
H+
H+
NADH
H+
NAD+
2 H+ + ½ O2
H20
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Smokin’ Chemiosmosis & Electron
Transport Animations
• http://vcell.ndsu.nodak.edu/animations/atp
gradient/movie.htm
• http://vcell.ndsu.nodak.edu/animations/etc/
movie.htm
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Can you see why FADH2 & NADH end in different ATP yields?
29
Cyanide Blocks the Electron
Transport Chain
• Cyanide is a poison that inhibits
cytochrome oxidase activity. Why can
cyanide cause death?
30
Cyanide Blocks the Electron
Transport Chain
• Cyanide is a poison that inhibits
cytochrome oxidase activity, preventing
oxygen from acting as the final electron
acceptor in the electron transport chain.
This disruption virtually shuts down ATP
production resulting in coma and death.
That is why cyanide is a poison. However,
it is not poisonous to all organisms.
Anaerobic bacteria, called MIT-13 actually
live on cyanide – they use it the same way
aerobes use oxygen.
31
Summary of Aerobic Cellular Respiration
32
33
Structural Formula of ATP
34
• Label the diagram
35
36
Net Energy Yield of Aerobic
Respiration
ATPs
NADHs
FADH2s
ATPs From
ETC
Total ATPs
Glycolysis
A
2
B2
C0
D4
E6
Pyruvic Acid
Oxidation
F0
G
2
H0
I6
J6
Krebs Cycle
2
K
L6
2
M
22
N
24
O
Total
P4
Q
10
R2
S
32
T
36
37
Anaerobic vs. Aerobic Respiration
•
NOTE: What happens after glycolysis depends on whether or not
oxygen is present…
If O2 is absent….
If O2 is present….
Pyruvate Goes to the Kreb’s
cycle in the mitochondria
(aerobic
respiration) for complete
oxidation.
Pyruvate
(Pyruvic Acid)
(3-C)
NADH
NAD+
X2
Lactate
(Lactic acid)
(3-C)
This process is
called …
lactate
(lactic acid)
fermentation
Lactic acid
(animals)
Once thought to
make muscles
fatigued after
Strenuous exercise)
38
Think Together!
With your partner, discuss:
• Does lactic acid fermentation yield any
energy?
• Assume the energy demands within a cell
greatly exceeds the body’s ability to
deliver oxygen. What is the point of
pyruvic acid being converted to lactic
acid? HINT: NAD is a limited commodity in
the cell.
39
Alcoholic Fermentation (in yeast)
•
An anaerobic step that yeast use after glycolysis that breaks down pyruvate to
ethanol (aka ethyl alcohol) and carbon dioxide.
Pyruvate
(Pyruvic Acid)
(3-C)
C02
Acetaldehyde
(2-C)
NADH
X2
NAD+
Ethanol
(the alcohol found in beer, wine, etc.)
(2-C)
40
Alternate Pathways
• Carbohydrates are your body’s nutrient of choice.
• Proteins lipids and nucleic acids can also be used.
41
Protein Catabolism
• Proteins are made of different
types of amino acids.
• The amino groups of amino
acids are removed
(deamination).
• What remains of the amino
acids tar ether converted to
various components of
glycolysis or Krebs i.e
pyruvate, acetyl CoA, alpha
ketoglutarate.
• You know the rest!
42
Lipid Catabolism
• Triglycerides are made of
glycerol and fatty acids.
Your digestive system breaks
triglycerides into these
components.
• Glycerol may be converted
into glucose via
gluconeogenesis or to DHAP
(what’s next…?)
• The fatty acids enter the
matrix and undergo beta
oxidation (acetyl groups are
removed from the fatty acids
and combine with CoA to form
Acetyl CoA…
43
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References
•
•
•
http://cwx.prenhall.com/bookbind/pubbooks/mcmurrygob/medialib/media_portfolio/21.html
http://members.aol.com/BearFlag45/Biology1A/LectureNotes/lec10.html
Nelson Biology 12
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