Cellular respiration involves the breakdown of glucose molecules through glycolysis, the Krebs cycle, and electron transport chain to release energy in the form of ATP. Glucose and oxygen are converted to carbon dioxide, water, and energy. The energy is used to produce ATP, which cells use as fuel to power their processes. Respiration takes place aerobically with oxygen or anaerobically without oxygen through fermentation.

1. Cellular Respiration
 Cells convert
carbon from
glucose molecules
into carbon dioxide
and release energy
C6H12O6 + 6 O2  6 CO2 + 6 H2O + energy

2. Cellular Respiration
 Cells convert
carbon from
glucose molecules
into carbon dioxide
and release energy
C6H12O6 + 6 O2  6 CO2 + 6 H2O + energy

3. Cellular Respiration
 Energy released used to make ATP, main
energy source for cell processes
 Primary fuel for respiration is glucose

4. Glycolysis
 Occurs in cytoplasm
 Step 1: Phosphates from 2
ATP attach to a molecule of
glucose
 Step 2: These phosphates
destabilize the molecule and it
splits into 2 molecules of G3P

5. Glycolysis
 Step 3: After another phosphate is added, G3P
“reduces” NAD+ to NADH by adding electrons to
it

6. Glycolysis
 Step 4: 2
phosphates from
each molecule are
used to convert 2
ADPs into 2 ATPs
 Result is two 3-
carbon molecules
called “pyruvic acid”
or “pyruvate”

7. Terminology
 Reactions that require oxygen to take
place = aerobic
 Reactions that do not require oxygen
= anaerobic

8. Aerobic Respiration

9. Bridge Reaction
 Pyruvate is transported into
mitochondria
 Pyruvate releases 1 carbon in the
form of CO2 to become a compound
known as Acetyl-CoA (makes an
NADH)

10. Krebs Cycle
 Step 1: Acetyl-CoA (two
carbons) is then added to
oxaloacetic acid to create a
6-carbon molecule (called
citric acid)

11. Krebs Cycle
 Step 2: 2 CO2 molecules
released and 2 NADH
molecules created in
succession
 This results in a 4-carbon
molecule
 4-carbon is recycled into
oxaloacetic acid, creating
ATP, NADH, and FADH2

12. Electron Transport
 NADH and FADH2 donate
electrons to enzymes
along inner mitochondrial
membrane
 Energy from electrons
used in electron transport
chain to pump H+ ions out
of mitochondrial matrix
• Concentration gradient created

13. Chemiosmosis
 As in photosynthesis,
energy from the
diffusion of H+ used to
make ATP from ADP
 Leftover (used-up)
electrons and H+ that
has diffused into
mitochondria combine
with O2 to create H2O,
which is released

14. Electron Transport
 Even though some ATP is produced earlier,
most is produced here
 Without oxygen present, electron transport chain
and Krebs cycle stop

15. Efficiency of Respiration
 Actual number
of ATP created
from each
glucose varies
 Active transport
of NADH
consumes about
5% of energy
 Glycolysis
without the other
steps results in 2
ATP instead of
38!

17. Anaerobic Respiration

18. Fermentation
 Recycles NADH so glycolysis (ATP production)
can continue

19. Lactic Acid Fermentation
 Occurs in eukaryotes,
specifically humans &
animals
 Pyruvate can accept
electrons from NADH
and is converted to
lactic acid
 Lactic acid buildup
causes muscle
fatigue

20. Alcoholic Fermentation
 Occurs in plants, fungi
(yeast), prokaryotes
 CO2 released, converting
pyruvate to a 2-carbon
molecule
 Electrons added from NADH
to convert 2-carbon molecule
to ethanol

21. Alcoholic Fermentation
 Used to produce
alcoholic beverages
and “biofuel”
(ethanol)
 Used to make bread
rise (CO2)

22. A REVIEW

23. Photosynthesis
 CO2 + H2O + light energy  glucose + O2
 Autotrophs ONLY!
 Occurs in chloroplasts

24. Respiration
 glucose + O2  CO2 + H2O + energy
 BOTH atuotrophs and heterotrophs
 (ATP-heavy part) occurs in mitochondria