Energy and Life
• What is energy? Energy is the ability to do work!
• Sunlight is the main energy source for life on Earth.
1. Cells use chemical energy in the form of a chemical compound called
ATP, or adenosine triphosphate.
a. ATP contains:
i. ____________________________________________
ii. ____________________________________________
iii. ___________________________________________
b. The bonds between the _____________________________________________ store and release energy
• ATP transfers energy from the breakdown of food molecules to cell functions.
• Energy is released when a phosphate group is_________________
• ADP is changed into ATP when a phosphate group is added
_________________ is the basic energy source of all cells
• Organisms break down carbon-based molecules to produce ATP.
• ________________________________are the molecules most
commonly broken down to make ATP.
• not stored in large amounts
• up to _____________________________ from one glucose
molecule
Storing Energy
• Energy is stored in ATP, ADP, adenosine diphosphate, is similar to ATP but has _______________ phosphate
groups instead of three. When a cell has energy available, it can store small amounts by adding a
______________________________________ to ADP making ATP
1. When a chemical bond between the 2nd and 3rd phosphates of ATP is broken, _________________________________
2. ATP has enough energy to power a variety of cellular activities
A. active transport across the selectively permeable cell membrane
B. protein synthesis
4. ATP is a good short term energy storage that is recycled between ADP and ATP. Cells have only a small amount of ATP.
a. It is more efficient for cells to store energy as glucose.
b. When cells need energy they make ATP from ADP using energy from glucose.
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____________________________________ store the most energy.
– 80 percent of the energy in your body
– about 146 ATP from a triglyceride
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____________________________ 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
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What is photosynthesis? The process in which plants use the energy of the sun to convert
________________________________________________________________into high-energy carbohydrates
(sugars and starches) and oxygen (a waste product).
______________________ is a molecule that absorbs light energy.
In plants, chlorophyll is found in organelles called ______________________________________
Photosynthesis takes place in two parts of chloroplasts.
– ________________________
– ________________________
The light-dependent reactions capture energy from sunlight.
– take place in_________________________________________
– water and sunlight are needed
– chlorophyll absorbs energy
– energy is transferred along thylakoid membrane then to light-independent reactions
– ____________________________ is released
The light-independent reactions make ____________________________________.
– take place in stroma
– needs ________________________________________ from atmosphere
– use energy to build a sugar in a cycle of chemical reactions
The equation for the overall process is: 6CO2 + 6H2O  C6H12O6 + 6O2
Light and Pigments
• Photosynthesis requires:
– _______________________________,_____________________________ and ____________________
– chlorophyll (a pigment molecule in chloroplasts; two types)
• chlorophyll a
• chlorophyll b
Factors affecting photosynthesis
_____________________________, _________________________________, _____________________
Inside a Chloroplast
• Photosynthesis takes place inside ________________________________
• Chloroplasts contain:
– ______________________________ saclike photosynthetic membranes containing pigments
– ______________________________ (singular: granum): stacks of thylakoids
– _____________________________: region of chloroplasts outside of the thylakoid membranes
– inner membrane
– outer membrane
Photosystem II captures and transfers energy.
• _________________________ absorbs energy from sunlight
• __________________________________ enter electron transport chain
• ___________________________ molecules are split
• ____________________________ is released as waste
• hydrogen ions are transported across _______________________________________
Electron Carriers
• Sunlight excites electrons in chlorophyll, causing them to gain energy.
• An excited electron is like a hot coal, and cannot be easily carried from one place to another- a protein called an
___________________________________________ is required to transport excited electrons.
Electron transport: An electron carrier molecule can accept a pair of high-energy electrons and transfer them to
another molecule.
– Electron transport chain: Series of electron carriers
– Example: NADP+ (nicotinamide adenine dinucleotide phosphate)
NADP+ + 2 electrons + H +  NADPH
__________________________ can carry high-energy electrons to other chemical reactions in the cell that need energy
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Photosystem I captures energy and produces energy-carrying molecules.
chlorophyll absorbs energy from sunlight
energized electrons are used to make ________________________
NADPH is transferred to ___________________________________ reactions
Light Dependent Reactions
• The light-dependent reaction ___________________, produce ________________________ gas as waste, and
converts ADP and NADP+ into ______________________ and _______________________.
• The second stage of photosynthesis uses energy from the first stage to make __________________________.
• Light-independent reactions occur in the ________________________ and use _______________ molecules.
• A molecule of glucose is formed as it stores some of the energy captured from sunlight.
• carbon dioxide molecules enter the _________________________________
• energy is added and carbon molecules are rearranged
• a high-energy three-carbon molecule leaves the cycle
• two three-carbon molecules bond to form a _____________________________
• remaining molecules stay in the cycle
Light Dependent Reactions
1. Light hits Photosystem II in the thylakoid membranes. Two electrons are excited and these excited electrons are
passed onto the electron transport chain
a. To replace the lost electrons, the thylakoid membrane obtains low-energy electrons by splitting water
2H2O  4H+ + O2 + 2 e• The O2 is released as waste
• The hydrogen ions (4H+) are released inside the thylakoid membrane
2. Electron transport chain (ETC)
a. Electrons are passed from Photosystem II to Photosystem I from one electron carrier to the next until
they reach Photosystem I
b. Energy from the electrons is used by the electron carriers in the ETC to force H+ ions from the stroma
into the inner thylakoid space- buildup of H+ will be used to drive ATP synthase
3. Light hits Photosystem I
a. Pigments in Photosystem I use energy from light to energize two electrons, making them high-energy
b. They are passed to NADP+ Reductase which catalyzes the reaction of NADP+ take combining with the
high-energy electrons and hydrogen ions (H+) to become NADPH
4. Hydrogen Ion Movement
– The inside of the thylakoid membrane fills up with positively charged hydrogen ions (H+) as electrons
are passed from Photosystem II to I
– ATP synthesis
• The thylakoid membrane contains a protein called ATP synthase that spans the membrane and
allows H+ ions to pass through it
• As H+ ions pass through ATP synthase, the protein rotates and binds ADP and a phosphate
group to produce ATP.
Light-independent reactions (The Calvin Cycle)
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During the Calvin cycle, plants use ATP and NADPH from the lightdependent reactions to produce high-energy sugars for long-term
storage.
• The Calvin cycle does NOT require light.
• The Calvin Cycle: (4 Steps)
1. CO2 enters the cycle
– Six carbon dioxide molecules enter and combine with
six 5-Carbon molecules.
– Result: 12 3-carbon molecules
• Energy input
– The 12 3-carbon molecules are converted into high energy forms
using ATP and NADPH
• During this process, 12 ATP  12 ADP
• During this process, 12 NADPH  12 NADP+
• 6-carbon sugar produced from two 3-carbon molecules removed to produce sugar
• 5-carbon molecules regenerated
– 10 remaining 3-carbon molecules converted into six 5-carbon molecules
– This requires 6 ATP  6 ADP
– These 5-carbon molecules can be reused in step A.