Kreb's Cycle and Electron Transport Chain

The Kreb’s Cycle
and Electron
Transport Chain
Biology 112
The End of Glycolysis
 Only
10% of the energy available in
glucose has been used
 The rest is still contained in pyruvic acid
 The remainder of the energy needs
oxygen for the final phases of cellular
These pathways are said to be aerobic
The Kreb Cycle
 Steps
of this process:
Pyruvic acid enters the mitochondrion
One of the three carbons becomes part of
a carbon dioxide molecule
The remaining two carbon molecules
attach to a coenzyme and form citric acid
The citric acid breaks down, releasing more
carbon dioxide
Energy is released in the form of NADH
The Kreb’s Cycle - cont
 Citric
acid turns into a five carbon
molecule which then releases another
carbon atom to form more carbon
 NADH and ATP is also released
 The four carbon molecule remaining will
be picked up and used again in the cycle
NADH and FADH2 (another energy releasing
molecule) is released
The Electron Transport Chain
and FADH2 enter the electron
transport chain to be used to generate
ATP from ADP
 It is composed of carrier proteins
embedded in the mitochondria
(eukaryotes) or cell membrane
 The end of the chain releases water
Adding Up the ATP
 By
the end of cellular respiration – 36 ATP
molecules will have been produced from
one molecule of glucose
 The cell can generate energy from more
than just glucose
 Any energy not used by the cell is
released as heat
Quick and Long Term Energy
 Overall,
a small amount of ATP is
produced by cellular respiration
 After a few moments of intense activity,
for instance, lactic acid fermentation
produces necessary ATP for energy
 Lactic acid will require oxygen in order to
be broken down
 The body stores more energy in the form
of the carbohydrate glycogen
 After this is used, fats and other molecules
are utilized
Photosynthesis vs. Respiration
Requires energy
Releases energy
CO2 + H2O
C6H12O6 + O2
C6H12O6 + O2
CO2 + H2O