CHAPTER 7
CELLULAR RESPIRATION
Where does the energy
of life come from?
Photosynthesis
Radiant
energy
Respiration
Chemical
energy
CELL ACTIVITIES
R
E
S
P
I
R
A
T
I
O
N
The release of chemical
energy for cellular use
*Takes place in small
steps.
Occurs in the
MITOCHONDRIA
Done by
HETEROTROPHS and
some AUTOTROPHS
Why ATP? An analogy to
money…
Glucose in our food is a great source of energy! ($100 bill)
However, individual cell processes may only require a small
amount of energy ($1 bill)
Analogy: most vending machines do not accept $100 bills!
We need a smaller form of “currency” for these processes.
ATP (adenosine triphosphate) is this important cellular
“currency” for life.
ATP releases more appropriate amounts of energy for the
individual cellular processes that require energy.
CELLULAR RESPIRATION
• Molecules are broken down inside the
cell to release energy
C6H12O6 + oxygen  CO2 + H2O + energy
2 Types
1. Aerobic:
• oxygen is present
2. Anaerobic:
• no oxygen present
CYTOPLASM
Alcoholic
Fermentation
Anaerobic
Lactic Acid
Respiration
Fermentation
glucose
Ethyl
Alcohol
and Carbon
Dioxide
Lactic
Acid
2 Pyruvic
Acids
MITOCHONDRIA
Aerobic
Respiration
Acetyl
Co-A
Krebs
Cycle
Etransport
chain
CO2
H2O
ATP
Cellular Respiration
1. Glycolysis
-Doesn’t require oxygen
-Takes place in the cytoplasm
-Main function is to take 1
C6H12O6 and make PYRUVIC
ACID
A. Glucose is phosphorylated by
2ATP molecules forming a new
6C molecule (very unstable)
B. Molecule splits into 2, 3C, PGAL
C. Each PGAL gains a “P” group,
floating in the cells
environment.
D. At the same time NAD+
removes two H+ atom to form
NADH + H+
E. The PGAL ATP
Glucose
loses 2 “P”
groups each ADP
to ADP
P
PGAL
PGAL
4ADP4 ATP
NAD
PGAL is
converted toNADH
PGAL
PGAL
PYRUVIC
ACID
2 ADP
H2O is lost
2ATP
H2O
+P
Pyruvic
Acid
ATP
ADP
P
NAD
NADH
+P
2 ADP
Pyruvic
Acid
2ATP
OVERALL ENERGY
RESULTS
OF GLYCOLYSIS
Used 2 ATP’s
Made 4 ATP’s
NET GAIN:
2 ATP’s
2. Gained 2 NADH+ H+
3. 2 (3C) Pyruvic Acid’s
1.
1. Anaerobic Respiration
Fermentation
- The breaking down of Pyruvic Acid
without oxygen
- Occurs in the CYTOPLASM
- NO ATP produced
- Pyruvic Acid Regenerates NAD+ to
be used in glycolysis
lactic acid fermentation
alcoholic fermentation
A. Lactic Acid
Fermentation:
Alternative pathway that converts
Pyruvic acid  lactic acid
During exercise breathing rates
increase to supply more O2
Enough for Aerobic Exercise (EX:
Walking, swimming, jogging)
Anaerobic exercise will result in O2
debt (Ex: Weight lifting, sprinting)
Feel the Burn…
If there is not enough O2 available
lactic acid will begin to accumulate in
the muscles
Burning sensation is the result of
lowering the muscle pH
Blood takes the lactic acid to the liver
and breaks it down to pyruvate
B. Alcoholic Fermentation:
Without O2 NADH gives H+ to pyruvic acid
pyruvic acid  ethyl alcohol + CO2 + NAD+
Wine Formation:
Sugar in grapes is broken down with
glycolysis
Dry Wine: Fermentation until all
sugar is used up
Sweet Wine: Alcohol inhibits
fermentation before all sugar is used
up
To Glycolysis
NAD
NADH+H
Pyruvic
Acid
Lactic
Acid
Fermentation
Carbon Dioxide
Pyruvic
Acid
Fermentation
Ethyl
Alcohol
NADH+H
To Glycolysis
NAD
Energy Yield
Kilocalories:
• A measurement of energy
• 1 kcal = 1,000 calories (cal)
•
Efficiency of glycolysis= Energy required to make ATP
__________________________________________________________
Energy released by oxidation of glucose
2 ATP x 12 kcal (energy required to make ATP)
= ___________ X 100% = 3.5%
686 kcal (Glucose energy)
• Conclusion: only 3.5% of energy available from the oxidation
of glucose is transferred to ATP
2. Aerobic Respiration
Glycolysis followed by the
breakdown of pyruvic acid using
oxygen
Occurs inside the MITOCHONDRIA
Pyruvic acid formed in the
cytoplasm diffuses across the
membrane into the MATRIX
1. Conversion of Pyruvic Acid 2.
Krebs Cycle 3. Electron transport
chain
The Mitochondrion
A. Conversion of Pyruvic Acid
Pyruvic Acid
CO2
NAD
NAD
H +H
CoA
CO A
ACETYL CoA
1. Pyruvic acid loses a C to form CO2 and a
H that is picked up by NAD +
Forming an Acetyl group & NADH + H+.
2. Acetyl group then picks up COENZYME
A to form Acetyl-CoA.
NAD
Pyruvic Acid
CoA
NADH + H
CO2
Acetyl –
CoA
CoA (2C)
Oxaloacetic Acid (4C)
Citric Acid (6C)
NADH + H
NAD
NAD
Malic Acid (4C)
FADH
The Krebs
Cycle
FAD
Succinic Acid
(4C)
NADH + H
ATP
ADP
NADH + H
CO2
Ketoglutaric Acid
(5C)
NAD
CO2
B. Kreb’s Cycle or Citric
Acid Cycle
Discovered by Hans Krebs
Releases CO2 and hydrogen ions
and results in the formation of ATP
Steps of the Kreb’s
1. Acetyl CoA gives up the CoA and
binds with (4C) Oxaloacetic Acid to
form CITRIC ACID (6C)
2. Citric Acid (6C):
releases H ion to NAD+ to form
NADH + H+
C to form CO2 - this results in
KETOGLUTARIC ACID (5C)
3. Ketoglutaric Acid (5C):
H ion to NAD+ to form NADH + H+
C to form CO2
phosphate group to ADP to form
ATP
this results in SUCCINIC ACID (4C).
4. Succinic Acid:
gives up H to FAD to create
FADH2 –
results in MALIC ACID (4C)
5. Malic Acid:
H+ ion to NAD+ to form NADH
+ H+
this results in OXALOACETIC
ACID (4C) - the starting and
stopping part of the Kreb’s
Cycle
Pyruvic Acid
CO2
CoA
Oxaloacetic Acid
NADH + H
NAD
Malic Acid
FADH
NAD
CoA
NADH + H
Acetyl CoA
Citric Acid
NAD
NADH + H
CO2
Krebs
Cycle
FAD
Succinic Acid
NADH + H
ATP
ADP
Ketoglutaric Acid
NAD
CO2
Overall Results Of Krebs Cycle
From one C6H12O6 molecule the following is
formed…..
•
6 NADH + H+ (3 each pyruvic acids)
•
4 CO2 (2 each pyruvic acid)
•
2 ATP (1 per pyruvic acid)
•
2 FADH (1 per pyruvic acid)
Overall Results: Glycolysis + Kreb’s
Cycle
•
•
•
4 ATP (2 from glycolysis, 2 from Kreb’s)
10 NADH +H+  30ATP
2 FADH2  4 ATP
C. Electron Transport Chain
-Occurs across the inner membrane of the
mitochondria
-Consists of enzymes, carrier molecules
Steps of Electron Transport
1. NADH + H+ and FADH2 from the
Krebs cycle arrives at the electron
transport chain
e- are released and move down the
chain, releasing energy.
Oxygen is the final e- acceptor
2. At the same time…
NADH+ H+ and FADH2
deliver H+, Across the inner
membrane out of the matrix.
This Creates a concentration
gradient
3. Ions want to diffuse across
the membrane down their
concentration gradient.
4. Hydrogen move across the
membrane through
ATPsynthase… ATP is made.
CHEMIOSMOSIS
5. The diffused hydrogen ions are
picked up by incoming oxygen to
form water.
*This is a continuous process,
oxygen removes H+ while
NADH+H+ and FADH2 replace it.
MATRIX
NADH +
H+
e-
MATRIX
ATP
Synthetase
FADH2
O2
H2O
MATRIX
H+
H+
H+
ATP
ADP + P
ENERGY RESULTS
Scientists have determined….
-After Krebs and Glycolysis• 10 NADH give 3 ATP’s each and total 30
ATP’s
• 2 FADH give 2 ATP’s each and total 4 ATP’s
34 ATP’s/ glucose
Total ATP/glucose
Glycolysis 2 ATP
Krebs
2 ATP
e- transport 34 ATP
38 ATP/glucose
2ATP
Glycolysis
2PGAL
2 P.A.
2 NADH + H+
2 NADH + H+
2 Acetyl Co-A
ADP
2ATP
2ATP
KREB’S
6 NADH + H+
2 FADH2
E-.Transport Chain
34 ATP
38 ATP’S
Respiration Overview
The Chemistry…
The chemical reactions of
photosynthesis and respiration
are opposites
Photosynthesis
CO2 + H2O + ENERGY  (C6H12O6) + O2
Respiration
C6H1206 + O2  CO2 + H2O + ENERGY