Cellular Respiration
Review
Cellular Respiration
1. Define cellular respiration.
A process that releases energy from food,
such as the simple sugar glucose, when
there is oxygen present.
2. Name several organisms that undergo cellular
respiration
Nearly all living things undergo cellular respiration*.
Exceptions include a few microscopic marine animals (Loricifera)
and some bacteria.
Cellular Respiration
3. Using chemical formulas, write the balanced
equation for cellular respiration.
6O2 + C6H12O6
6CO2 + 6H2O + Energy
4. Now write out the equation using words.
Oxygen + Glucose yields Carbon dioxide + Water + Energy
Cellular Respiration
5. What organelle in eukaryotes is involved in
cellular respiration?
The mitochondrion
6. What is a common analogy for mitochondria?
Mitochondria are sometimes
called “cellular power plants” or
the “powerhouses” of the cell.
Cellular Respiration
7. Where in eukaryotes are mitochondria found?
In all cells. Depending
on the organism and the
type of cell, the number
of mitochondria can
range from one to
thousands.
Mitochondria
Root tip of a corn plant.
Cellular Respiration
8. What kind of human cells contain the most
and least number of mitochondria?
Cells that require the most energy
contain the highest number of
mitochondria. The cells of the
brain, skeletal muscle, heart
muscle, and the eye contain the
greatest number (as many as
10,000 per cell) while the skin cells,
which do not require much energy,
contain only a few hundred.
Skeletal Muscle
Cellular Respiration
9. Identify the mitochondria in this micrograph of
a human pancreatic cell.
The pancreas
secretes insulin
in response to
glucose levels
in the blood.
Mitochondria
Endoplasmic
reticulum
Nucleus
Nucleolus
Pancreas
Pancreas cell
Cellular Respiration
Identify the following structures of the mitochondrion.
10
11
12
13
Cellular Respiration
Identify the following structures of the mitochondrion.
Outer
membrane
11
12
13
Cellular Respiration
Identify the following structures of the mitochondrion.
Outer
membrane
Inner membrane
12
13
Cellular Respiration
Identify the following structures of the mitochondrion.
Outer
membrane
13
Inner membrane
Inner
membrane
space
Cellular Respiration
Identify the following structures of the mitochondrion.
Outer
membrane
Matrix
Inner membrane
Inner
membrane
space
Cellular Respiration
14. What are the three main stages of
cellular respiration?
Glycolysis (Converting glucose to pyruvic acid)
Two pyruvic acid
Glucose
The Krebs cycle (Breaking down pyruvic acid into CO2)
Three
Carbon
dioxide
Pyruvic acid
Electron Transport (Making lots of ATP)
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
Cellular Respiration
15. Where in the mitochondrion does each
stage of cellular respiration occur?
Glycolysis takes
place in the cell’s
cytoplasm outside
the mitochondrion
The Krebs cycle
occurs in the matrix
The Electron Transport Chain
operates in the inner membrane.
Cellular Respiration
16. What happens during glycolysis?
Four enzymes are
used to break glucose Glucose
into two molecules of
G3P*
Five enzymes then
convert G3P into
pyruvic acid**
Two electron carriers
pick up electrons
during the process
ATP
ATP
Two
G3P
ATP
Electron
carriers
Two ATP
pyruvic
acid
ATP
Electron
carriers ATP
ATP
Two ATP are
invested to get
this done.
Four ATP are
produced.
ATP
A net of two ATP
are made.
*G3P is Glyceraldehyde-3-phosphate ** Pyruvic acid is known as pyruvate
Cellular Respiration
17. What happens in the Krebs cycle?
Pyruvic acid enters the mitochondrial matrix where
it will enter the Krebs cycle.
Matrix
Mitochondrion
Pyruvic acid
Enzymes
Electron
carriers
Cellular Respiration
17. What happens in the Krebs cycle?
Here pyruvic acid will interact with enzymes and
other molecules.
Matrix
Mitochondrion
Enzymes
Electron
carriers
Cellular Respiration
17. What happens in the Krebs cycle?
After a series of chemical reactions, three carbon
dioxide molecules are produced.
Matrix
Mitochondrion
Enzymes
Electron
carriers
Cellular Respiration
17. What happens in the Krebs cycle?
In addition, a molecule of ATP is generated…
Matrix
Mitochondrion
ATP
Enzymes
Electron
carriers
Cellular Respiration
17. What happens in the Krebs cycle?
Electron carriers* also pick up excess electrons.
Matrix
Mitochondrion
Enzymes
ATP
* Electron carriers NAD+ and FAD
Electron
carriers
Cellular Respiration
17. What happens in the Krebs cycle?
Electron carriers* also pick up excess electrons.
They then travel to the inner membrane.
Matrix
Mitochondrion
Electron
Enzymes
carriers
ATP
* Electron carriers NAD+ and FAD
Cellular Respiration
18. What do the carriers do with their electrons?
The electron carriers drop off their electrons at
the inner membrane.
Matrix
Mitochondrion
Electron
carriers
Electron
carriers
Electron
carriers
Enzymes
Electron
carriers
* Electron carriers NAD+ and FAD
Electron
carriers
Cellular Respiration
18. What do the carriers do with their electrons?
The carriers then return to the matrix to pick up
more electrons while other molecules are recycled.
Matrix
Mitochondrion
Electron
carriers
Electron
carriers
Electron
carriers
Enzymes
Electron
carriers
* Electron carriers NAD+ and FAD
Electron
carriers
Cellular Respiration
19. What happens to the electrons at the inner membrane?
At the inner membrane, the electron carriers attach
themselves to membrane proteins.
Electron
carriers
Inner
membrane
H + ions
Matrix
Inner
membrane
space
Cytoplasm
Outer
membrane
Cellular Respiration
19. What happens to the electrons at the inner membrane?
The electrons are then passed to the protein.
H + ions
Inner
membrane
Electron
carriers
Matrix
Inner
membrane
space
Cytoplasm
Outer
membrane
Cellular Respiration
19. What happens to the electrons at the inner membrane?
Some of the energy from the transfer of electrons is used to
pump hydrogen ions (H+) into the inner membrane space.
H + ions
Inner
membrane
Matrix
Inner
membrane
space
Cytoplasm
Outer
membrane
Cellular Respiration
19. What happens to the electrons at the inner membrane?
Meanwhile, the shuttle protein ubiquinone moves in to
pick up the electrons.
H + ions
Inner
membrane
Matrix
Inner
membrane
space
Ubiquinone
Cytoplasm
Outer
membrane
Cellular Respiration
19. What happens to the electrons at the inner membrane?
The shuttle will move the electrons to the next protein.
H + ions
Inner
membrane
Matrix
Inner
membrane
space
Ubiquinone
Cytoplasm
Outer
membrane
Cellular Respiration
19. What happens to the electrons at the inner membrane?
Some of the energy from the transfer of electrons will be
used to pump more H+ ions across the membrane.
H + ions
Matrix
Inner
membrane
Inner
membrane
space
Cytochrome C
Outer
membrane
Cytoplasm
Cellular Respiration
19. What happens to the electrons at the inner membrane?
The electrons will then be shuttled by cytochrome c to
their last protein.
H + ions
Matrix
Inner
membrane
Inner
membrane
space
Cytochrome C
Outer
membrane
Cytoplasm
Cellular Respiration
19. What happens to the electrons at the inner membrane?
Again, H+ ions will be pumped across the membrane.
H + ions
Inner
membrane
Matrix
Inner
membrane
space
Cytoplasm
Outer
membrane
Cellular Respiration
19. What happens to the electrons at the inner membrane?
Finally, an oxygen atom will pick up the two electrons
along with two H+ ions to form a molecule of water.
H + ions
Inner
membrane
Matrix
O2
H2O
Inner
membrane
space
Cytoplasm
Outer
membrane
Cellular Respiration
20. Where does the water molecule go?
Water will exit the mitochondrion
H + ions
Matrix
Inner
membrane
H2O
Inner
membrane
space
Cytoplasm
Outer
membrane
Cellular Respiration
21. How will the pH in the inner membrane space change?
As more H+ is pumped into the inner membrane space, the
space becomes more acidic. This causes the pH to drop.
H + ions
Inner
membrane
Outer
membrane
Matrix
pH 7.8
Inner
membrane
space
pH 7.2
Cytoplasm
Cellular Respiration
22. How does the concentration of H+ ions in the matrix
compare to that in the inner membrane space?
There are more H+ ions in the inner membrane
space, which sets up a concentration gradient.
H + ions
Inner
membrane
Outer
membrane
Matrix
Low H+ Concentration
High H+ Concentration
Inner
membrane
space
Cytoplasm
Cellular Respiration
23. In which direction is the concentration gradient?
The H+ ions will flow down their concentration
gradient from the inner membrane space toward
the matrix.
H + ions
Low H+ Concentration
Gradient
Inner
membrane
Matrix
Outer
membrane
High H+ Concentration
Inner
membrane
space
Cytoplasm
Cellular Respiration
24. Through what membrane protein will the H+ ions flow?
The H+ ions will flow through an enzyme called ATP
synthase. This flow provides the energy needed to
generate ATP from ADP.
H + ions
Matrix
Inner
membrane
ATP
P
ADP
Cytoplasm
Outer
membrane
Cellular Respiration
25. About how many ATP can be generated by cellular
respiration from one glucose molecule?
One glucose molecule yields about 36 to 38 ATP
(2 ATP from glycolysis, 2 ATP from the Krebs cycle,
and 32 to 34 ATP from the electron transport chain).
ATP
Inner
membrane
ATP
ATP
ATP
H + ions
ATP
ATP
ATP
ATP
ATP
Matrix
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
ATP
Inner
membrane
space
Cytoplasm
Outer
membrane