Bellringer-April 22, 2015
FILL IN THE
LETTERS
Overview of Cellular
Respiration
H. Biology
Ms. Kim
Energy Flows into ecosystems as sunlight
and leaves as heat
Light energy
ECOSYSTEM
Photosynthesis
in chloroplasts
CO2 + H2O
Cellular respiration
in mitochondria
Organic
molecules
+ O2
ATP
powers most cellular work
Heat
energy
http://wps.aw.com/bc_campbell_biology_7/
Carbon Cycle
Reminder….
Anabolic pathways (“A” for add together)
Build molecules from simpler ones (ex:
photosynthesis)
Consume energy (endergonic or endothermic)
Catabolic pathways (“C” for cut in parts)
Break down complex molecules into
simpler compounds (ex: cell respiration)
Release energy (exergonic or exothermic)
Cellular respiration
Most efficient catabolic pathway
Consumes O2 and organic
molecules (ex: glucose)
Yields ATP To keep working cells
must regenerate ATP
Catabolic pathways yield energy
by oxidizing organic fuels
The breakdown of organic molecules is
exergonic (exothermic)
One catabolic process, fermentation
Is a partial degradation of sugars that occurs
without oxygen
Another example is cellular respiration
Cellular respiration
Occurs in mitochondria
similar to combustion of gas in an engine after
O2 is mixed with hydrocarbon fuel.
Food and O2 = fuel for respiration.
The exhaust =CO2 and H2O.
The overall process is:
organic compounds + O2  CO2 + H2O + energy
(ATP + heat)
Carbohydrates, fats, and proteins can all be used as
the fuel, but most useful is glucose.
Mitochondria
• Powerhouse of the cell!
• The organelle responsible
for cellular respiration
• The Krebs Cycle and ETC
take place here  ATP is
produced here!
• It is a double membrane
with the inner membrane
highly folded (to increase
the surface area and
make the mitochondria
more efficient).
Intermembrane
Space
Mitochondrion Structure
Mitochondrion Structure
• Outer membrane – similar to plasma
membrane; contains integral proteins
• Inner membrane- NOT permeable to ions
(needs help to cross); there is a membrane
potential across the inner membrane; contains
ATP synthase
• Cristae – large surface area due to folding
• Matrix - gel-like in middle or lumen; many
contains enzymes for cellular respiration
RECALL…Redox Reactions
Catabolic pathways yield energy
Due to the transfer of electrons
Redox reactions
Transfer e-’s from one reactant to another by
oxidation and reduction
In oxidation
Substance loses e-s (it’s oxidized)
In reduction
Substance receives e-s (it’s reduced)
Examples of redox reactions
becomes oxidized
(loses electron)
Na
+
Na+
Cl
Cl–
+
becomes reduced
(gains electron)
Xe-
+
Y

X
+ Ye-
**energy must be added to remove e-
X = e- donor = reducing agent and reduces Y.
Y = e- recipient = oxidizing agent and oxidizes X.
Oxidation of Organic Fuel Molecules
During Cellular Respiration
• During cellular respiration
– Glucose is oxidized
– oxygen is reduced
– E-’s lose potential energy  energy is released
becomes oxidized
C6H12O6 + 6O2
6CO2 + 6H2O + Energy
becomes reduced
http://student.ccbcmd.edu/~gkaiser/biotutorials/cellresp/ets_flash.html
Electrons are not transferred directly to oxygen
but are passed first to a coenzyme called
NAD+ or FAD
2 e– + 2 H+
NAD+
Dehydrogenase
O
NH2
H
C
N+
CH2
O
O–
O
O P
O
H
H
–
O P O HO OH
HO
CH2
O
N
H
O
H
HO
N
H
OH
+ 2[H]
(from food)
Nicotinamide
(oxidized form)
Oxidation of NADH
NADH
H O
C
H
N
NH2
Nicotinamide
(reduced form)
NAD+ and FAD=
e- acceptor and
oxidating agent
NH2
N
N
Reduction of NAD+
2 e– + H+
H
Figure 9.4
+
2H
1/
2
+
O2
(from food via NADH)
+ 2
e–
Controlled release
of energy for
synthesis of
ATP
Free energy, G
2
H+
ATP
ATP
ATP
2 e–
2
1/
2
H+
O2
H2O
Electron Flow =
(b) Cellular respiration
food  NADH/FADH2  ETC  oxygen
Cellular Respiration – Background info
• Equation –
C6H12O6 + 6O2 → 6CO2 + 6 H2O + 36 or 38 ATP
-When food is
broken down,
energy is
released
gradually and
stored in ATP.
-Respiration is
done by BOTH
plants and
animals
The Stages of Cellular
Respiration
• Respiration is a cumulative process of 3
metabolic stages
1. Glycolysis
2. Kreb’s Cycle (The citric acid
cycle)
3. Electron Transport Chain
(Oxidative phosphorylation)
The 3 Stages
 Glycolysis
Breaks down glucose into 2 molecules of pyruvate
Makes NADH
Makes a little bit of ATP
 Kreb’s Cycle (Citric acid cycle)
Completes the breakdown of glucose
Makes NADH and FADH2
CO2 is waste product
Makes a little bit of ATP
 Electron Transport Chain (Oxidative
phosphorylation)
Driven by the electron transport chain
Generates ALOTTTTT of ATP
O2 is the final electron acceptor and gets reduced to
make WATER
General overview – Cellular Respiration
1.Glycolysis:
• In the cytosol
• Anaerobic
• Turns glucose to 2
pyruvate  net
gain of 2 ATP and 2
NADH
3. ETC → uses chemiosmosis
to make LOTS of ATP
2. Krebs:
• In the
mitochondrial matrix
• Makes little ATP,
NADH, and FADH2
(electron taxis)
• Passes e- to ETC
Exit Slip-April 22, 2015
• Draw a cycle of the ecosystem between
photosynthesis and cellular respiration.
• Include the following: photosynthesis, carbon
dioxide, light energy, heat energy, oxygen,
glucose, water, and ATP.