Cell respiration
Definition:
The series of chemical reactions in cells which oxidize
food energy (Carbohydrates, proteins, lipids) into cell
energy (ATP) and heat; may occur with or without O2
being used as the terminal electron acceptor
(aerobically or anaerobically)
General equation:
Glucose + O2  CO2 + H2O + ATP + Heat
The “bottom line” of cell respiration is the
production of ATP (cell energy)
ATP can be produced in 1 of 3 ways:
1) Substrate-level phosphorylation:
Essentially, Food-P + ADP  food + ATP
2) Oxidative phosphorylation:
Occurs as NADH2 and FADH2 relay e-’s to an
ETC, setting up an electrochemical gradient of
H+’s which is relieved by ATPase which uses
kinetic energy of proton flow to form ATP from
ADP + Pi
3) Photophosphorylation: during photosynthesis
Substrate-level phosphorylation
-occurs during the rxns of Glycolysis and the Krebs Cycle
Oxidative Phosphorylation: occurs
during the rxns of the Electron Transport
Chain along inner membrane (cristae) of
the mitochondrion
The complete oxidation of food
Aerobic respiration
Equation:
Glucose + O2  CO2 + H2O + energy
The above set of reactions occur in 4 distinct steps:
1)
2)
3)
4)
Glycolysis – splits 6-C glucose into 2 X 3-C pyruvic acids
(pyruvates)
Pyruvate oxidation – removes 1 C from each pyruvate to form 2
X 2-C acetyl groups which may enter the rxns of the Krebs Cycle
Krebs Cycle – cyclical series of rxns which break down each of
the 2-C acetyl groups into 2 CO2
Electron Transport Chain – electron carrying coenzymes relay
their e-’s to a series of electron carrying proteins to O2 setting up
an electrochemical gradient which is relieved through ATPase
which transforms the kinetic energy of proton flow into ATP
formation
During each step of the process,
energy is released!!
In Glycolysis: 4 total ATP’s are formed (yet, there is only a
net gain of 2 ATP’s) and 2 NAD coenzymes are reduced
to NADH2
In Pyruvate oxidation: 2 NADH2’s are produced
In the Krebs Cycle: 2 ATP’s are formed, 6 NADH2’s are
produced, and 2 FADH2’s
In Electron Transport: 32 ATP’s are formed as 10 NADH2’s
and 2 FADH2’s are oxidized back to NAD+ and FAD+
and recycled back to the system and re-used
4
1
ETC
2
3
The reactions of cell
respiration:
Glycolysis
The reactions of
cell respiration:
Pyruvate
oxidation
The reactions of
cell respiration:
the Krebs Cycle
the Electron Transport Chain
Overview of aerobic respiration
 General equation: glucose + O2  CO2 + H2O + energy
 Glucose is oxidized (broken down) to form 6 CO2
 E-’s stripped away from glucose are relayed to ETC by
NAD+ and FAD+ coenzymes and accepted by O2
 O2 is the terminal electron acceptor
 ETC relays e-’s and pumps H+’s (protons)
 [H+] outside of ETC membrane is relieved by ATPase
 H+’s flow through ATPase
 ATPase transforms kinetic flow of H+’s into bond
between ADP and P