Chapter 9 Cellular
Respiration
Mitochondrion
Electrons carried in NADH
Pyruvic
acid
Glucose
Glycolysis
Krebs
Cycle
Electrons
carried in
NADH and
FADH2
Electron
Transport
Chain
Mitochondrion
Cytoplasm
Ms. Martinez
Athletes get the energy they need
from the breakdown of glucose during
cellular respiration.
Respiration Overview
Living things get most of the
energy they need from glucose.
Autrotrophs make glucose using
photosynthesis
Heterotrophs get glucose from food they
eat
How? Cellular Respiration.
Cellular respiration is the process that
releases energy by breaking down
glucose and other food molecules in the
presence of oxygen.
The equation for cellular respiration is:
6O2 + C6H12O6 → 6CO2 + 6H2O + Energy
Oxygen + Glucose → Carbon dioxide + Water + Energy
There are three stages of cellular
respiration:
Glycolysis
Krebs Cycle
Electron Transport
Each of the three stages captures some of the
chemical energy available in food molecules
and uses it to produce ATP.
Glycolysis—Stage #1
The process begins with a pathway
called glycolysis.
Glycolysis is the process in which a
glucose molecule is split in half.
Glycolysis takes place in the
cytoplasm of a cell.
This forms
two
molecules of
pyruvic acid,
a 3-carbon
compound.
Through
glycolysis,
the cell gains
4 ATP
molecules or
2”net”
molecules.
How? 4ATP –
2ATP= 2
“net” ATP
produced
In addition, the
electron carrier
NAD+ accepts a
pair of high-energy
electrons,
producing NADH.
By doing this,
NAD+ helps pass
energy from
glucose to other
pathways in the
cell.
Glycolysis Summary
Occurs in the cytoplasm
2 “net” ATP molecules
are produced
2 pyruvic acid, 3carbon, molecules are
produced
Does not require
oxygen to occur
Mitochondria
(plural)
The mitochondrion
(singular) is the organelle
of Cellular Respiration.
Mitochondria combine
oxygen with food
molecules to obtain
energy, ATP molecule,
for the cell.
In plant and animal cells,
the second and third
stages of cellular
respiration take place in
mitochondria.
Mitochondria contain
some DNA, the molecule
that carries genetic
information.
A mitochondrion has two
membranes.
The second stage of
cellular respiration,
the Krebs Cycle,
take place in the
matrix.
The matrix is the
inner compartment
of the mitochondrion
filled with about half
water and half
protein.
The third stage of
cellular respiration,
Electron Transport,
takes place in the
cristae.
The cristae is the
folded up inner
membrane.
Mitochondrion Summary
The mitochondrion is the only place in the
cell where oxygen can be combined with
food molecules to release the energy in
them for use by the cell.
Mitochondria contain some DNA.
The second stage of cellular respiration, the
Krebs Cycle, take place in the matrix.
The third stage of cellular respiration,
Electron Transport, takes place in the
cristae.
Krebs Cycle—Stage #2
Because the pathways of cellular
respiration require oxygen, they are
said to be aerobic.
The term cellular respiration to refer
to energy-releasing pathways within
the cell that require oxygen.
During the Krebs cycle, pyruvic acid, 3
carbon molecule, is broken down into
carbon dioxide in a series of energyextracting reactions.
The Krebs cycle is also known as the citric
acid cycle, because citric acid is one of its
first products.
The Krebs cycle occurs in the matrix.
The matrix is the inner compartment of the
mitochondrion filled with about half water
and half protein.
Here are the stages of
the Krebs cycle.
• The Krebs cycle starts
when pyruvic acid formed
by glycolysis enters the
mitochondrion.
• This step requires
oxygen.
CO2
• The pyruvic acid is
broken down into
carbon dioxide.
• The carbon dioxide is
released as a waste
product.
• The Krebs cycle
continues in a series
of reactions.
CO2
•In these reactions, two
energy carriers, NAD+
and FAD+, accept highenergy electrons.
•NAD+ is changed to
NADH, and FAD+ is
changed to FADH2.
•These molecules carry the
high-energy electrons to
the electron transport
chain.
Krebs Cycle Summary
Requires oxygen.
Pyruvic acid is the starting 3-carbon
molecule.
Carbon dioxide is the waste product.
Occurs in the matrix.
Produces some ATP.
Electron Transport—Stage #3
The electron transport
chain uses the high-energy
electrons, NADH and
FADH2, to change ADP into
ATP.
Electron Transport is
known as the Energy
Extraction phase since
many ATP molecules are
produced.
It occurs in the cristae.
In the
electron
transport
chain, high
energy
electrons
move from
one carrier
protein to
the next.
At the end of the
chain, oxygen
pulls electrons
from the electron
chain.
Oxygen is the final
electron acceptor.
These electrons
join with hydrogen
ions, H+, forming
water.
Each transfer
along the chain
releases a
small amount
of energy.
ATP synthase
uses the
energy to
produce ATP.
Electron Transport Summary
Requires Oxygen.
Uses the high-energy electrons,
NADH and FADH2, to change ADP into
ATP.
Water is produced.
Occurs in the cristae.
Produces many ATP molecules.
Cellular Respiration Flowchart
*From 1 molecule of glucose, up to 36
ATP molecules are made.
1 Glucose
(C6H1206)
+
Oxygen
(02)
Glycolysis
CYTOPLASM
Krebs
Cycle
MATRIX
Carbon
Dioxide
(CO2)
Released
Electron
Transport
Chain
CRISTAE
Water
(H2O)
Formed
36 ATP
produced
Mitochondrion
Electrons carried in NADH
Electrons
carried in
NADH and
FADH2
Pyruvic
acid
Glucose
Krebs
Cycle
Glycolysis
Mitochondrion
Cytoplasm
CO2
H2O
Electron
Transport
Chain
Respiration vs. Photosynthesis
The energy flows in photosynthesis and
cellular respiration occur in opposite
directions.
On a global level, photosynthesis and
cellular respiration are also opposites.
Photosynthesis removes carbon dioxide
from the atmosphere and puts back
oxygen.
Cellular respiration removes oxygen from
the atmosphere and puts back carbon
dioxide.