Cell Respiration
Cell respiration

The process of using oxygen to release
usable energy (ATP) from sugar
Cell respiration starts with the
respiratory system
Breathing –everyone does it!
Respiratory system

Oxygen goes in
Carbon dioxide goes out

How does the Oxygen change to CO2 ??

In the alveoli of the lungs, Oxygen
diffuses into the capillaries and CO2
diffuses out
The circulatory system brings the
oxygen in blood to the cells
Blood pathway to cells

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Lungs  heart
Heart  arteries
Arteries  capillaries
Once O2 blood gets to the cells

In the capillaries, O2 diffuses into cells
and CO2 diffuses out
The circulatory system also brings
Sugar (glucose) to the cells
Cell Respiration

The complex process of cells “burning”
sugar (glucose) with oxygen to form
usable energy (ATP)
There are 2 types of cell respiration
Aerobic –
Anaerobic –
Aerobic cell respiration
The “Usual” process of respiration in
humans
Aerobic means “air”
Occurs with oxygen
Produces up to 38 ATP per glucose
Anaerobic respiration
Occurs without oxygen
Produces only 2 ATP per glucose
Fermentation is an anaerobic process
Fermentation


Yeast and bacteria obtain energy through
anaerobic respiration
Fermentation forms Alcohol, Vinegar and
Lactic acid
Bacteria can only use fermentation

Prokaryotes have NO Membrane
organelles  No mitochondria
Cheese


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Cheese is made by fermentation.
Hand made cheese 7 min
How its made: cheese 4 min
Lactic acid can form from over
exercise or lack of training
Not enough oxygen can cause painful
lactic acid build up in muscles
Aerobic respiration occurs in the
mitochondria

Prokaryotes have no mitochondria so they
can only perform anaerobic respiration
Cell Respiration Reaction:
Sugar + O2  CO2 + H20+ Energy (ATP)
(glucose)
Photosynthesis is the opposite of cell
respiration (except energy type)
Photosynthesis
In Chloroplasts
CO2 + H2O + SUN  Sugar + O2


Respiration
In Mitochondria
Sugar + O2
 CO2 + H2O + ATP
Cell Respiration occurs in both
plants and animals
3 Stages of Cell Respiration:

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1) Glycolysis
2) Krebs cycle
3) Electron Transport Chain (ETC)
(or Electron Transport System (ETS)
1) Glycolysis
Occurs in the cytoplasm


Glucose breaks into 2 pyruvate molecules
Some Energy products form - 2 ATP and 2 NADH
Over view
C-C-C-C-C-C  C-C-C + C-C-C + 2 ATP
+ 2 NADH
Glycolysis Energy investment

2 ATP must be used to initiate glycolysis.
Glycolysis produces 4 ATP

NET gain is 2 ATP

Enter Mitochondria

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Pyruvate then is transported into
mitochondria
Oxygen is Now needed
Each Pyruvate must become
Acetyl CoA to enter Krebs cycle

Each pyruvate forms 1 NADH = 2 per
glucose
2) Krebs Cycle (citric acid cycle)

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Occurs in the Mitochondria
Pyruvate is broken into C02 molecules
More Energy molecules form
(ATP, NADH and FADH2 )
Overview
2 C-C-C (pyruvate) + O2 6 CO2 + 2ATP +
6NADH + 2FADH2
Hydrogen Energy carriers
These molecules gain energy in Redox
reactions when electrons and hydrogen are
added (they are reduced)
These can be oxidized later to form ATP
 NAD+  NADH
 FAD+  FADH2
 (NADP+  NADPH) * only in photosynthesis
Krebs Cycle products from
1 glucose molecule
Each Acetyl CoA must
go around cycle
Two turns per
glucose molecule
(once for each acetyl
CoAs)
TOTALS From 1 glucose
 4 C02
 6 NADH
 2 ATP (substrate level
Phos.)
 2 FADH2
3) Electron Transport System
Occurs in the inner
Mitochondria membrane

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NADH and FADH2 are Oxidized
(lose electrons) to form much ATP
Oxygen is used up (reduced)
Water (H2O) is produced from the O2 and
the Hydrogen from NADH and FADH2
ETC Energy :

ETC Proteins use electrons from the NADH
and FADH2 to generate ATP in redox
reactions
ETC electron flow


Electrons flow along protein chain in inner
membrane
At end of ETC, Oxygen accepts electrons
forming water
Net ATP from aerobic respiration
Each NADH = 3 ATP
 Each FADH = 2 ATP
TOTAL = 36 ATP

Note –
NADH from glycolysis,
must use 1 ATP to get
inside mitochondria

QUIZ
What are the 3 stages of cell respiration? And
their main purpose?
1) Glycolysis
Purpose – Split glucose, form 2 ATP 2 NADH
2) Krebs Cycle
Purpose – Form CO2, form NADH, FADH2 +ATP
3) Electron transport chain
Purpose – Use NADH + FADH2 and O2
to form ATP + H2O