CELL ENERGY
4.1 Chemical Energy & ATP
4.2 Overview of Photosynthesis
4.3 Photosynthesis in Detail
4.1 Chemical Energy & ATP
• Key Concept:
• All cells need chemical energy.
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
ATP transfers energy from the breakdown of
food molecules to cell functions.
• Energy is released when a phosphate group is removed.
• The breaking of this chemical bond releases energy.
• ADP is changed into ATP when a phosphate group is added.
phosphate removed
Organisms break down carbon-based molecules
to produce ATP.
• Carbohydrates (details) are the molecules most commonly
broken down to make ATP.
• Not stored in large amounts (so it needs to be made all the time)
• Up to 36 ATP can come from one glucose molecule
adenosine
triphosphate
tri=3
adenosine
di=2
diphosphate
Organisms break down carbon-based molecules
to produce ATP.
• Lipids (details) store the most energy.
• 80% of the energy in your body
• About 146 ATP from one triglyceride
• Proteins (details) are the least likely to be broken down to
make ATP.
• Amino acids are not usually needed for energy
• Have about the same amount of energy as a carbohydrate
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 (deep in
the ocean for example).
• Chemosynthesis is…
• chemical energy
is used to build carbon-based
molecules.
• Similar to photosynthesis
• Uses chemical energy instead of
light energy
4.2 Overview of Photosynthesis
• Key Concept:
• The overall process of photosynthesis produces sugars that
store chemical energy.
4.3 Photosynthesis in Detail
• Key Concept:
• Photosynthesis requires a series of chemical reactions.
Photosynthesis
• The process of photosynthesis captures energy from
sunlight and converts it into sugar.
• This process happens in organisms called autotrophs
or producers. (Need to make their own food)
• This process takes place in and organelle called the
chloroplast.
• The chloroplast has a green pigment in it called
chlorophyll that is responsible for capturing the light
energy.
Photosynthesis in plants occurs in chloroplasts.
• Photosynthesis takes place in two parts of the
chloroplast.
grana (thylakoids)
• Grana (thylakoids)
chloroplast
• Light-dependent reactions
(aka Light Reactions)
• Stroma
• Light-independent reactions
(aka Dark Reactions;
stroma
aka Calvin Cycle)
How does photosynthesis work?
• The first stage of photosynthesis is called the
Light-Dependent Reactions/ Light Reactions.
1. (Sun) light is captured by the chlorophyll in the
thylakoid.
2. Energy is transferred along the thylakoid membrane
and water is broken down. Oxygen (from the broken
apart water) is released.
3. Energy is transferred to ATP and NADPH. (Both are
energy carrying molecules that will transfer energy to
the second stage of photosynthesis.)
How does photosynthesis work?
• The second stage of photosynthesis is called the
Light-Independent Reactions/ Calvin Cycle/
Dark Reactions.
1. ATP and NADPH carry energy from the thylakoid to
the stroma to begin the next reaction.
2. Carbon dioxide is added from the atmosphere to
help make sugar.
3. A molecule of glucose is formed. This molecule
stores some of the energy captured from the sun.
1
2
3
5
4
6
Contains: chlorophyll
and other lightabsorbing molecules
9
7
8
Light-independent
reactions
(Calvin Cycle)
Photosynthesis Equation
6CO2 + 6 H2O + sunlight
C6H12O6 + 6 O2
granum (stack of thylakoids)
1
chloroplast
6H2O
6O2
2
thylakoid
energy
stroma (fluid outside the thylakoids)
6CO2
1 six-carbon sugar
C6H12O6
3
4
Photosynthesis Inputs
• Sunlight
• Needed for Light Reactions
• Splits apart water
• Water (H2O)
• Needed for Light Reactions
• Hydrogen from water becomes the hydrogen in
glucose
• Carbon dioxide (CO 2)
• Needed for Dark Reactions (Calvin Cycle)
• Becomes the carbon and oxygen in glucose
Photosynthesis Outputs
• Oxygen (O2)
• Given off from Light Reactions
• Comes from water splitting apart
• Glucose (C6H12O6)
• Given off from Dark Reactions (Calvin Cycle)
• Comes from putting CO2 and H (from water)
together
• Photosynthesis Song
Enzymes control the process of photosynthesis.
• Factors like temperature will make the rate/ speed of
photosynthesis drop.
• This happens because change in temperature denatures enzymes
(changes their shape) and makes them not able to function.
• Draw a graph of what temperature does to the rate of
photosynthesis:
• How does this relate to the change of seasons?