Chapter 9 Summary: Cell respiration
Why do all cells require food and carry out cell respiration?
1 Organic molecules are molecules made of Carbon, along with H, O, N, P, and
S.
2 The covalent chemical bonds in organic molecules store large amounts of
energy.
3 Autotrophs (producers) are the only organisms that can capture the energy of
sunlight to produce organic compounds out of inorganic CARBON DIOXIDE
AND WATER during photosynthesis.
4 So, ultimately, the chemical potential energy of covalently bonded electrons in
all organic compounds originates from sunlight.
5 Heterotrophs (consumers) use the organic compounds formed by plants as
their food_.
6 Through a process called cell respiration all cells carry out chemical reactions
that break the covalent bonds in the organic molecules that are their food_ .
7 Types of food include glucose and other carbohydrates, as well as proteins
and fats or lipids. These molecules provide the chemical building blocks for
growth, as well as a source of energy.
8 The goal of cell respiration is to transfer the energy of food’s electrons into
the chemical bonds of a special energy carrying molecule for cells. It is called
adenosine tri phosphate (ATP).
What happens during cell respiration to allow the energy of food’s
electrons to be transferred into energy of ATP?
9 The process of cellular respiration includes 3 stages.
1st glycolysis
2nd kreb’s cycle
3rd electron transport chain
10 The first stage does NOT require oxygen, so it is termed anaerobic. The
first stage occurs in the cytoplasm. It occurs in every organism on earth,
including bacteria which do not contain mitochondria.
11. The second and third staged DO require oxygen, so they are termed
aerobic. These stages occur inside organelles called mitochondria.
11. The three stages of cell respiration are interdependent, because the
products of each stage become the reactants for the next stage! If no oxygen is
available, then glycolysis must be followed by a different process, called
fermentation, in order to recycle the reactants to repeat glycolysis.
12. When oxygen is present, then the final stage called electron transport
recycles the reactants for the first staged, called glycolysis. The products of
glycolysis are 3C long sugars called pyruvate
13 When the covalent bonds are broken during the chemical reactions of cell
respiration the electrons released from the broken bonds carry their chemical
potential energy along with them.
14 During cell respiration, the electrons and their chemical potential energy
are accepted by molecules of NAD+ or FAD, called empty electron carriers
To produce the filled electron carriers called NADH and FADH2.
15. At the end of cell respiration, a special enzyme called ATP synthase is able
to use the electron’s stored energy for the energy absorbing chemical reaction:
energy from electrons in food’s bonds + ADP + Phosphate  ATP
The phases of cell respiration
16. During glycolysis and Kreb’s cycle, phases 1 and 2, the chemical bonds of
glucose are broken to donate electrons from the broken bonds to load the
electron carriers NAD+ and FAD. So, the electron carriers store most of the
energy from the food by the end of phase 2, but a few molecules of ATP are
made during glycolysis and Krebs cycle
17. The final phase, the electron transport chain is where most ATP is made.
Then, the electron carriers deliver their electrons to proteins that convert their
energy to a form that can be used by a special enzyme called ATP synthase.
18 The reason that oxygen is required as a reactant in cell respiration is that it
is the final member of the electron transport chain.
19. The ATP synthase carries out this reaction: ADP + phosphateATP
ATP synthase makes up to 32 ATP!
20 The balanced chemical equation for the entire, multistep process for cell
respiration is
Glucose C6H12O6 + oxygen 6O2  carbon dioxide 6CO2 + water H2O
21 It looks the same as the balanced chemical reaction for combustion, which
releases only heat (fire), but instead of releasing heat in a one step chemical
reaction, cell respiration occurs in MANY steps.
Name of stage
Aerobic or anaerobic
Cell location
What happens
How much
ATP energy is
harvested?
Only 2 (a few)
glycolysis
anaerobic
cytoplasmic
Glucose is split in half
at its center chemical
bond & these electrons
are gathered up by
electron carriers
Krebs cycle
aerobic
mitochondria
All the other C to C
bonds are broken,
releasing CO2 to the
air & delivering all the
released electrons to
electron carriers
Only 4 (a few)
Electron
transport chain
aerobic
mitochondria
All the electron carriers
deliver the electrons
and their energy to an
electron transport
chain which converts
the energy to a form
that an enzyme, called
ATP synthase which
makes ATP!
Lots (30+
ATP)
The empty electron
carriers are returned to
the cytoplasm to allow
a repeat of the
process!
Fermentation
anaerobic
cytoplasm
If electron transport
can’t happen to
regenerate the
electron carriers, then
fermentation
regenerates them
instead, allowing
repeated glycolysis.
none