Download - Capturing and using solar energy
PhotosynthesisCapturing and using solar energy
• Does photosynthesis:
• create energy?
• use energy?
• “store” energy?
• release energy?
No
Yes
Yes
No
Quick, think! WORK
TOGETHER
• Plants do photosynthesis but not cellular respiration.
• Photosynthesis is a plant’s way of creating ATP for its cells.
• Plants make sugar and other carbon compounds so that animals can eat.
False
False
False
True or False? WORK
TOGETHER
Photosynthesis
• What photosynthesis does:
• Converts sunlight into stored chemical energy.
• Makes carbon compounds that can be broken down for energy or used to build tissue.
Photosynthesis is an ___ process.
1 2
0%
100%
1. Endergonic2. Exergonic
Photosynthesis is endergonic because:
1 2 3
80%
20%
0%
1. Energy is consumed by the process.
2. Energy is given off by the process.
3. Energy is made by the process.
Remember this?energyinput
C6H12O6(glucose)
O2(oxygen)
6 CO2(carbondioxide)
6 H2O(water)
+
+
Photosynthesis is an endergonic process.Photosynthesis takes in energy and uses it to build
carbon compounds.
Inorganic mineral nutrients(nitrate, phosphate) areabsorbed from soil andused in plant tissues.
Energy iscapturedfromsunlight.
Oxygen isreleased.
Sugar issynthesizedand used inplant tissues.
planttissues,growth
Carbon dioxideis absorbedfrom the air.
Water is absorbedfrom soil, used inphotosynthesis, andstored in cells.
photosynthesis
This diagram shows that photosynthesis is
an endergonic reaction because it takes in energy.Carbon for making carbon compounds
(such as sugar) comes from the atmosphere.
Oxygen, hydrogen, and minerals are needed also.
Oxygen and hydrogen come from water.
Minerals comes from the soil
photosynthesis
cellularrespiration
(mitochondrion)
O2ATP sugar CO2H2O
(chloroplast)
Plants make carbon-based molecules from raw inorganic compounds.
Plants use the organic carbon compounds as “food” and to build cell parts.
Organic molecules are:
1 2 3 4
20% 20%
40%
20%
1. Natural, not man-made.
2. Molecules that contain carbon.
3. Molecules that contain carbon AND hydrogen.
4. Any molecule from a living organism.
Internal leaf structure
cuticleupperepidermis
mesophyllcells
lowerepidermis
chloroplastsstoma
bundlesheath
vascular bundle(vein)
Chloroplast
channelinterconnectingthylakoids
stroma
thylakoid
outer membrane
inner membrane
The function of the chloroplast is to:
1 2 3
0% 0%
100%
1. Produce energy.2. Gather light
energy and convert it to chemical energy.
3. Break sugars down for energy.
O2
energy fromsunlight
chloroplast
Light-independentreactions(C3 cycle) occurin stroma.
Light-dependentreactions areassociated withthylakoids.
CO2
NADP+
G3P
NADPH
ADP
ATP
H2O
Light energy is “captured” by
chlorophyl, which is embedded in the
thylakoid membranes.
Energy from the light-dependent reactions drives
the reactions where carbon
compounds are produced.
CO2
LIGHT-DEPENDENTREACTIONS(in thylakoids)
LIGHT-INDEPENDENTREACTIONS(in stroma)
DEPLETEDCARRIERS
(ADP, NADP+)
ENERGIZEDCARRIERS
(ATP, NADPH)
H2O
G3P
O2
ATP and NADPH are used to move energy from one
part of the chloroplast to
another.
ATP made in the chloroplast is ONLY
used to power production of carbon compounds. It is not available to the rest
of the cell.
Overall, the light-dependent reactions do what?
1 2 3 4
0% 0%
20%
80%
1. Make energy.2. Capture energy.3. Make carbon
compounds.4. Break down
carbon compounds.
Overall, the light-independent reactions do what?
1 2 3 4
20% 20%
60%
0%
1. Make energy.2. Capture energy.3. Make carbon
compounds.4. Break down carbon
compounds.
• Suppose for a moment that the ATP made in the chloroplast was available to the cell, and was the ONLY source of ATP for the cell. Could the plant survive? (Remember that ATP is an unstable molecule that cannot be stored longer than a few minutes.)
WORK
TOGETHER
NADPH
H2O2e–
2H+
reactioncenter
photosystem II
electron transport chain
energy to driveATP synthesis
ener
gy le
vel o
f ele
ctro
ns
photosystem I
sunlight
electrontransport chain
2e–
1/2 O2
H+
NADP+
2e–
2e–
2e–
9
Light-dependent reactions convert light energy into temporary chemical energy.
The electron transport chain produces NADPH and drives ATP synthesis.
C3cycle
PSII PSIETCstroma
ETC
thylakoid space
Energy fromenergizedelectrons powersNADPH synthesis.
Flow of H+ downconcentration gradientpowers ATP synthesis.
Energy from energizedelectrons powers activetransport of H+ by ETC.
High H+ concentrationgenerated by activetransport.
H+ channel coupledto ATP-synthesizingenzyme.
Energy-carriermolecules powerthe C3 cycle.
ATP synthase uses energy from the diffusion of H+ to drive ATP synthesis.
• The ETC uses light energy to produce NADPH.
• Energy from the ETC concentrates H+ ions. The energy released as they diffuse through ATP synthase makes ATP.
• ATP and NADPH are used to power the light-independent reactions.
What’s important in the light-dependent (“photo”) reactions:
In photosynthesis, water is split in order to:
1 2 3 4
40%
0%0%
60%
1. Release oxygen.2. Get protons and
electrons.3. Make energy.4. Make chlorophyll.
In photosynthesis, light energy is captured by:
1 2 3 4
20%
0%
80%
0%
1. Protons2. Oxygen3. Chlorophyll4. ATP
The membrane protein that makes ATP is:
1 2 3 4
60%
0%
20%20%
1. ATP synthase2. Chlorophyll3. ADP4. Oxygen
ATP
ADP
NADPH
NADP+
12
12
12
1212
G3PATP
ADP
6
6
66 RuBP
6 CO2
12PGA
2 G3Psynthesisuses energy.
C3 cycle(Calvin-Benson cycle)
glucose(or other molecules)
3 RuBPsynthesisuses energyand 10 G3P.
1 CarbonfixationcombinesCO2 withRuBP.
4 G3P available for synthesis of carbon compounds such as glucose.
Light-independent reactions. Notice where ATP and NADPH are used up.
• Energy carried by ATP and NADPH is used to power synthesis of G3P.
• G3P can be used to make glucose as well as other monomers.
• These monomers can be used to build polymers, or may be broken down to make ATP for the cell.
What’s important in the light-independent (“synthesis”) reactions:
The source of carbon to make carbon compounds in photosynthesis is:
1 2 3 4
0% 0%
100%
0%
1. Glucose2. G3P3. Carbon dioxide4. Water
Which of these happens in the C3 cycle?
1 2 3
20% 20%
60%1. ATP is made from
ADP and P.2. ATP is broken down
to power molecule synthesis.
3. ATP becomes the monomer of other compounds.
Plant cells need ATP to run cell processes. Where does that ATP come
from?
1 2 3 4
20%
80%
0%0%
1. Sunlight.2. The light-dependent
reactions of photosynthesis.
3. The light-independent reactions of photosynthesis.
4. Cellular respiration
IMPORTANT!!!
• Photosynthesis does NOT supply energy to the cell. Photosynthesis USES light energy to make organic compounds.
• To get energy for the cell, plant cells must use cellular respiration to break down glucose and make ATP.
An analogy:• Photosynthesis is like going to the
grocery store and buying food to store in your cupboard. The food and the energy in it is stored.
• Cellular respiration is like eating the food when you are hungry and need energy. The energy in food is released only by eating the food.
photosynthesis
cellularrespiration
(mitochondrion)
O2ATP sugar CO2H2O
(chloroplast)
While animals can only do cellular respiration, plants make “food” using photosynthesis and break the “food” down for energy in cellular
respiration.
DayNight
PhotosynthesisCellular Respiration
Cellular Respiration
DayNight
Cellular Respiration
Cellular Respiration
Animals Plants
Photosynthesis supplies the “food” that plants need to carry out cellular respiration.
CO2
C3 plants use the C3 pathway
bundle-sheathcells
In a C3 plant, mesophyll cellscontain chloroplasts; bundle-sheath cells do not.
Much photorespirationoccurs under hot, dryconditions.
Little glucoseis synthesized.
rubisco
G3P
CO2
PGA
O2
RuBP
glucose
within mesophyll chloropaststoma
C3Cycle
C3 plants are at a disadvantage in hot, dry climates.
within mesophyllchloropast
within bundle-sheathchloropast
CO2rubisco
G3P
CO2
PGA
O2
RuBP
glucose
pyruvate
4-carbonmolecule
PEP
CO2
ATP
AMP
C4 plants use the C4 pathway
bundle-sheathcells
stoma
CO2 is captured witha highly specific enzyme.
In a C4 plant, both mesophylland bundle-sheath cells containchloroplasts.
Lots of glucose is synthesized.
Almost nophotorespirationoccurs in hot, dryconditions.
C3Cycle
C4Pathway
C4 plants essentially store carbon for hot times of the day. Guess what pathway many weeds use?
• Fill in the blanks in this generalized diagram showing what goes into and what comes out of the chloroplast.
Chloroplast
WORK
TOGETHER
Recap
• Think of photosynthesis as an energy “storing” process, not an energy-making or energy-releasing process.
• The products of photosynthesis can be:
• used to build cell parts.
• broken down to make ATP for the cell.
Photosynthesis animations
• Electron transport chains• Light-dependent and light-indepen
dent reactions