2. 4.1 Chemical Energy and ATP
The chemical energy used for most cell processes is
carried by ATP.
• Molecules in food store chemical energy in their bonds.
Starch molecule
Glucose molecule
3. 4.1 Chemical Energy and ATP
phosphate removed
• ATP transfers energy from the breakdown of food
molecules to cell functions.
– Energy is released when a phosphate group is removed.
– ADP is changed into ATP when a phosphate group is
added.
4. 4.1 Chemical Energy and ATP
Organisms break down carbon-based molecules to
produce ATP.
• Carbohydrates are the molecules most commonly broken
down to make ATP.
– not stored in large amounts
– up to 36 ATP from one
glucose molecule
tri=3
adenosine triphosphate
adenosine diphosphate
di=2
5. 4.1 Chemical Energy and ATP
• Fats store the most energy.
– 80 percent of the energy in your body
– about 146 ATP from a triglyceride
• Proteins are least likely to be broken down to make ATP.
– amino acids not usually needed for energy
– about the same amount of energy as a carbohydrate
6. 4.1 Chemical Energy and ATP
A few types of organisms do not need sunlight and
photosynthesis as a source of energy.
• Some organisms live in places
that never get sunlight.
• In chemosynthesis, chemical
energy is used to build
carbon-based molecules.
– similar to photosynthesis
– uses chemical energy
instead of light energy
7. 4.1 Chemical Energy and ATP
KEY CONCEPT
The overall process of photosynthesis produces
sugars that store chemical energy.
8. 4.1 Chemical Energy and ATP
Photosynthetic organisms are producers.
• Producers make their own
source of chemical energy.
• Plants use photosynthesis and
are producers.
• Photosynthesis captures energy
from sunlight to make sugars.
9. 4.1 Chemical Energy and ATP
• Chlorophyll is a molecule that
absorbs light energy.
• In plants, chlorophyll is
found in organelles called
chloroplasts.
chloroplast
leaf cell
leaf
10. 4.1 Chemical Energy and ATP
Photosynthesis in plants occurs in chloroplasts.
• Photosynthesis takes place in two parts of chloroplasts.
– grana (thylakoids)
– stroma
chloroplast
stroma
grana (thylakoids)
11. 4.1 Chemical Energy and ATP
• The light-dependent reactions capture energy from sunlight.
– take place in thylakoids
– water and sunlight are needed
– chlorophyll absorbs energy
– energy is transferred along thylakoid membrane then to
light-independent reactions
– oxygen is released
12. 4.1 Chemical Energy and ATP
• The light-independent reactions make sugars.
– take place in stroma
– needs carbon dioxide from atmosphere
– use energy to build a sugar in a cycle of chemical
reactions
13. 4.1 Chemical Energy and ATP
• The equation for the overall process is:
6CO2 + 6H2O C6H12O6 + 6O2
granum (stack of thylakoids)
thylakoid
6H2O
6CO2
6O2
chloroplast
1
2
C6H12O6
4
3
energy
stroma (fluid outside the thylakoids)
1 six-carbon sugar
14. 4.1 Chemical Energy and ATP
KEY CONCEPT
Photosynthesis requires a series of chemical
reactions.
15. 4.1 Chemical Energy and ATP
The first stage of photosynthesis captures and transfers
energy.
• The light-dependent
reactions include groups
of molecules called
photosystems.
16. 4.1 Chemical Energy and ATP
• Photosystem II captures and transfers energy.
– chlorophyll absorbs
energy from sunlight
– energized electrons
enter electron
transport chain
– water molecules are
split
– oxygen is released as
waste
– hydrogen ions are
transported across
thylakoid membrane
17. 4.1 Chemical Energy and ATP
• Photosystem I captures energy and produces energy-
carrying molecules.
– chlorophyll absorbs
energy from sunlight
– energized electrons
are used to make
NADPH
– NADPH is transferred
to light-independent
reactions
18. 4.1 Chemical Energy and ATP
• The light-dependent reactions produce ATP.
– hydrogen ions flow through a channel in the thylakoid
membrane
– ATP synthase attached to the channel makes ATP
19. 4.1 Chemical Energy and ATP
The second stage of photosynthesis uses energy from
the first stage to make sugars.
• Light-independent
reactions occur in the
stroma and use CO2
molecules.
20. 4.1 Chemical Energy and ATP
• A molecule of glucose is formed as it stores some of the
energy captured from sunlight.
– carbon dioxide molecules enter the Calvin cycle
– energy is added and carbon molecules are rearranged
– a high-energy three-carbon molecule leaves the cycle
21. 4.1 Chemical Energy and ATP
• A molecule of glucose is formed as it stores some of the
energy captured from sunlight.
– two three-carbon molecules bond to form a sugar
– remaining molecules stay in the cycle
22. 4.1 Chemical Energy and ATP
KEY CONCEPT
The overall process of cellular respiration converts
sugar into ATP using oxygen.
23. 4.1 Chemical Energy and ATP
Cellular respiration makes ATP by breaking down sugars.
• Cellular respiration is aerobic, or requires oxygen.
• Aerobic stages take place in mitochondria.
mitochondrion
animal cell
24. 4.1 Chemical Energy and ATP
• Glycolysis must take place first.
– anaerobic process (does not require oxygen)
– takes place in cytoplasm
– splits glucose into two three-carbon molecules
– produces two ATP molecules
25. 4.1 Chemical Energy and ATP
Cellular respiration is like a mirror image of
photosynthesis.
• The Krebs cycle transfers energy to an electron
transport chain.
– takes place in
mitochondrial matrix
– breaks down three-carbon
molecules from glycolysis
– makes a small amount of
ATP
– releases carbon dioxide
– transfers energy-carrying
molecules
2
mitochondrion
matrix (area enclosed
by inner membrane)
inner membrane ATP
energy
energy from
glycolysis
1
2
4
3
6O
and
ATP
and
6CO2
and
6H2 O
Krebs Cycle
26. 4.1 Chemical Energy and ATP
2
mitochondrion
matrix (area enclosed
by inner membrane)
inner membrane
energy
energy from
glycolysis
1
2
4
3
6O
and
ATP
and
6CO2
ATP
and
6H2 O
• The electron transport chain produces a large amount of
ATP.
– takes place in inner
membrane
– energy transferred to
electron transport
chain
– oxygen enters
process
– ATP produced
– water released as a
waste product
Electron Transport
27. 4.1 Chemical Energy and ATP
• The equation for the overall process is:
C6H12O6 + 6O2 6CO2 + 6H2O
• The reactants in photosynthesis are the same as the
products of cellular respiration.
28. 4.1 Chemical Energy and ATP
KEY CONCEPT
Cellular respiration is an aerobic process with two
main stages.
29. 4.1 Chemical Energy and ATP
Glycolysis is needed for cellular respiration.
• The products of glycolysis enter cellular respiration when
oxygen is available.
– two ATP molecules are used to split glucose
– four ATP molecules are produced
– two molecules of NADH produced
– two molecules of pyruvate produced
30. 4.1 Chemical Energy and ATP
The Krebs cycle is the first main part of cellular
respiration.
• Pyruvate is broken down
before the Krebs cycle.
– carbon dioxide
released
– NADH produced
– coenzyme A (CoA)
bonds to two-carbon
molecule
31. 4.1 Chemical Energy and ATP
• The Krebs cycle produces energy-carrying molecules.
32. 4.1 Chemical Energy and ATP
• The Krebs cycle produces energy-carrying molecules.
– NADH and FADH2 are made
– intermediate molecule with
CoA enters Krebs cycle
– citric acid
(six-carbon molecule)
is formed
– citric acid is broken down,
carbon dioxide is released,
and NADH is made
– five-carbon molecule is broken down, carbon dioxide is
released, NADH and ATP are made
– four-carbon molecule is rearranged
33. 4.1 Chemical Energy and ATP
The electron transport chain is the second main part of
cellular respiration.
• The electron transport chain uses NADH and FADH2 to
make ATP.
– high-energy electrons enter electron transport chain
– energy is used to transport hydrogen ions across the
inner membrane
– hydrogen ions
flow through a
channel in the
membrane
34. 4.1 Chemical Energy and ATP
The electron transport chain is the second main part of
cellular respiration.
• The electron transport chain uses NADH and FADH2 to
make ATP.
• The breakdown of one glucose molecule produces up to
38 molecules of ATP.
– ATP synthase
produces ATP
– oxygen picks up
electrons and
hydrogen ions
– water is
released as a
waste product
35. 4.1 Chemical Energy and ATP
KEY CONCEPT
Fermentation allows the production of a small
amount of ATP without oxygen.
36. 4.1 Chemical Energy and ATP
Fermentation allows glycolysis to continue.
• Fermentation allows glycolysis to continue making ATP
when oxygen is unavailable.
• Fermentation is an anaerobic process.
– occurs when oxygen is not available for cellular
respiration
– does not produce ATP
37. 4.1 Chemical Energy and ATP
• Fermentation allows glycolysis to continue making ATP
when oxygen is unavailable.
• NAD+ is recycled to glycolysis
• Lactic acid fermentation occurs in muscle cells.
– glycolysis splits glucose into two pyruvate molecules
– pyruvate and NADH enter fermentation
– energy from NADH converts pyruvate into lactic acid
– NADH is changed back into NAD+
38. 4.1 Chemical Energy and ATP
Fermentation and its products are important in several
ways.
• Alcoholic fermentation is similar to lactic acid
fermentation.
– glycolysis splits glucose and the products enter
fermentation
– energy from NADH is used to split pyruvate into an
alcohol and carbon dioxide
– NADH is changed back into NAD+
– NAD+ is recycled to glycolysis
39. 4.1 Chemical Energy and ATP
• Fermentation is used in food production.
– yogurt
– cheese
– bread
