Download HOW CELLS HARVEST ENERGY (AKA CELLULAR RESPIRATION

HOW CELLS HARVEST ENERGY
(AKA CELLULAR RESPIRATION)
CH 9
 Energy is stored in the chemical bonds of
organic molecules
 Breakdown of these large organic
molecules releases ATP which is used for
cellular work
I. Catabolism of glucose
 Cellular respiration = catabolism of
glucose to produce ATP
 3 types of cellular respiration:
o Aerobic respiration (nearly all
organisms)
o Anaerobic respiration (only a few types
of bacteria)
o Fermentation (when aerobic can’t work)
A. Aerobic Respiration
 Requires O2
 Occurs in most organisms
 In eukaryotes, most of it occurs in the
mitochondria
 Produces 36 ATP
 Occurs in 4 stages:
o Glycolysis
o Oxidation of pyruvate
o Kreb’s cycle
o Electron transport chain and
oxidative phosphorylation
1. Glycolysis
 Occurs in ALL cells
 Occurs in the cytoplasm
 Breaks down glucose to 2 3-carbon
molecules called pyruvate
RESULTS:
 ATP production
2 ATP used
4 ATP made
Net yield = 2ATP
 NADH production
2 NADH made which go to ETC to make
ATP
Only 2 of the 36 ATP has been made
THE REST OF THE ENERGY STORED IN
GLUCOSE IS NOW IN THE PYRUVATES
http://www.science.smith.edu/departments/Biology/Bio231/glycolysis.html
2. Oxidation of pyruvate
 Occurs in the mitochondria
 Converts pyruvate to acetyl CoA
 Produces NADH
 NADH produced goes to ETC to make
ATP
 Fate of acetyl CoA:
o It enters into the Kreb’s cycle to
continue aerobic respiration
3. Kreb’s cycle
 Occurs in the mitochondrial matrix
 Yield:
For EACH glucose molecule
6 NADH
2 FADH2
2 ATP
 NADH and FADH2 go on to ETC to make
ATP
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_cycle_wor
ks__quiz_1_.html
4. Electron Transport Chain
 Occurs on the inner membrane of the
mitochondria
 Uses energy in NADH and FADH2 to
make 32 ATP
 NADH and FADH2 donate e- to ETC
 As e- is moved thru ETC, the energy in eis used to actively pump protons across
the inner membrane
 NRG from the e- is now stored in the
proton gradient
 As the protons diffuse down their
concentration gradient, ATP synthase
uses the energy in the gradient to make
32ATP by chemiosmotic phosphorylation
 The e- that was hopping thru ETC goes to
O2 which acts as final acceptor of e4H+ +4e- + 202 →2H2O
http://www.science.smith.edu/departments/Biology/Bio231/etc.html
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter9/
Aerobic respiration: the big picture
B. Regulation of Aerobic Respiration
By feedback regulation
Glucose + ADP +NAD + FAD → ATP
+NADH +FADH2
 High ATP means cell has enuf ATP
and ATP acts like allosteric inhibitor
to turn off 2nd enzyme in glycolysis
(phosphofructokinase)
 High NADH means too much glucose
is being broken down and it acts as
allosteric inhibitor to the oxidation of
pyruvate
 High ADP means cell needs more ATP
and ADP acts as allosteric activator to
activate phosphofructokinase
C. Aerobic respiration, small mammals
and generation of heat
 In the cold, many small mammals will
allow the proton gradient generated in
the ETC to bypass ATP synthase
 Thus the energy in the proton
gradient is lost as heat to help
maintain body temp
D. Aerobic respiration in prokaryotes
 Almost identical to eukaryotes:
Glycolysis
Oxidation of pyruvate
Kreb’s cycle
ETC
HOWEVER:
 Since they have no mitochondria, all
of aerobic respiration takes place in
the cytoplasm, and the ETC occurs on
the cell membrane
E. Anaerobic respiration
 Occurs in certain bacteria
 Has the same stages as aerobic
respiration:
Glycolysis
Oxidation of pyruvate
Kreb’s cycle
ETC
 However, O2 is NOT the final eacceptor.
 They use another molecule as the final
e- acceptor
CO2
SO2
F. Fermentation
 Occurs when not enuf O2 is available
for aerobic respiration
 Produces limited ATP (only 2) when
compared to aerobic respiration
 NADH produced in glycolysis is
converted back to NAD to keep
glycolysis running
 2 types: lactic acid fermentation and
alcoholic fermentation
1. Lactic acid fermentation
 Occurs in muscle cells when
circulatory system can’t supply enuf
O2 for aerobic respiration
 Produces lactic acid
2. Alcoholic fermentation
 Occurs in yeast cells
 Produces alcohol and CO2
The fate of pyruvates depends on the
amount of oxygen: