2. Essential Questions
• What if the sun quit shining?
• Is the process of photosynthesis dependent
on light?
• What is photosynthesis?
• What organisms undergo photosynthesis?
• How do plants make food?
• What adaptations does a leaf have to
undergo photosynthesis?
• What are the raw materials needed for
photosynthesis?
3. Essential Questions
• What are the inputs and outputs of
photosynthesis.
• How do the light dependent reactions
occur?
• How do the light independent reactions
occur?
• What is the Calvin Cycle?
• What factors affect photosynthesis?
• Why is photosynthesis important to the
environment?
4. Important Vocabulary
• chlorophyll
• Accessory pigment
• Stomata
• Guard cell
• Spongy layer
• Palisade layer
• Epidermis
• CHLOROPLAST
– GRANUM
– THYLAKOID
– STROMA
• NADP & NADPH
• Photosystem II and I
• ATP synthase
• Carbon Fixation
• Rubp
• Rubisco
• G3P
• ATP & ADP
7. The Nature of Light
• Visible light is the component
of the Electromagnetic
spectrum of energy that a
plant uses for photosynthesis.
• Photon – particle of light!
8.
9. What Colors do we see?
• Why do leaves of plants look green?
– Leaf pigments….like chlorophyll.
• Pigments can absorb, reflect, or transmit the
light energy.
• An object that absorbs all colors is BLACK.
• An object appears that color when it reflects
that color----- GREEN PLANTS!
10.
11. Photosynthetic pigments
Found in the Chloroplast.
• Chlorophyll a – absorbs less blue and more
red light. It is directly involved in
photosynthesis.
• Chlorophyll b – absorbs more blue and less
red light. It is an accessory pigment – assists
chlorophyll a.
Other accessory pigments:
• Carotenoids – absorb blue light. Reflect
yellow, red, orange light.
19. Photosynthesis – an overview
(the absolute minimum you must know!!!
• 6CO2 + 6H2O light
C6H12O6 + 6O2
• Light energy needed - Capture LIGHT - PHOTO
• ATP used and generated
• NADP+
:the electron carrier, that combines with 2 electrons
and one hydrogen ion.
• NADP+
becomes reduced into NADPH, when it receives the
electrons.
• Glucose (SYNTHESIS) and oxygen are made.
NADP : nicotinamide adenine dinucleotide phosphate
25. PHOTOSYSTEM II (PII)
• Chlorophyll pigments (purple circles) in thylakoid membrane absorb light
energy.
– The energy is absorbed by electrons…passed to ETC.
PHOTOLYSIS
• During this process, H2O is broken down, and O2 is released.
• Electrons from hydrogen replace electrons in chlorophyll.
• H+ begin to create a positive gradient in the THYLAKOID.
26. • Electrons lose energy as they pass down the ETC.
• Energy lost “pumps” more H+ into the Thylakoid thru membrane
by active transport.
PHOTOSYSTEM I
• Light energy re-energizes electrons
• Electrons combine with NADP and H+ to form NADPH – an
electron carrier
• NADPH moves into the stroma for Light Independent Rxns.
27. Production of ATP
• The concentration of H+
ions inside the thylakoid membrane
becomes much higher than the concentration outside.
• H+
ions rush out through membrane protein called ATP
synthase.
• The ATP synthase spins like a turbine and the energy is
used to bind ADP and P together to form ATP.
28. Summary of the Light
Reactions
• Input:
• Light
• Water
• ADP
• NADP+
Output:
• 18 ATP
• 12 NADPH
• Oxygen
What do you need for more light
reactions to occur?
29. Summary of the Light
Reactions
• Input:
• Light
• Water
• ADP
• NADP+
Output:
• 18 ATP
• 12 NADPH
• Oxygen
ADP, and NADP+
30. Summary of the Light
Reactions
• Input:
• Light
• Water
• ADP
• NADP+
Output:
• 18 ATP
• 12 NADPH
• Oxygen
What is the waste product of
photosynthesis?
31. Summary of the Light
Reactions
• Input:
• Light
• Water
• ADP
• NADP+
Output:
• 18 ATP
• 12 NADPH
• Oxygen
Oxygen
37. Light Independent reactions
Carbon Fixation
• 6CO2 enter the cycle and bonds
with 6 – 5 carbon molecules
(Rubp)
– Catalyzed by enzyme Rubisco.
• These molecules split into 12 – 3
carbon molecules.
38. Light Independent reactions
Reduction:
• Each 3 carbon molecule is REDUCED
by 12 NADPH (oxidized).
• 12 ATP IS NEEDED!
• Result: G3P the 3 – carbon molecule
that will become glucose.
– 2 – G3P exit the Calvin Cycle to become
Glucose
42. Calvin Cycle Reactions
• Importance of the Calvin Cycle
– G3P (glyceraldehyde-3-phosphate) can be
converted to many other molecules
• The G3P can form:
– Fatty acids and glycerol to make plant oil
– Glucose phosphate (simple sugar)
– Fructose (which with glucose = sucrose)
– Starch and cellulose
– Amino acids
46. Rate of Photosynthesis
• What is a rate?
• It is the activity per unit time.
• What factors can affect the photosynthetic rate?
• Light intensity
• Temperature
• Oxygen
• Carbon Dioxide Concentration
• Sometimes these factors are called
LIMITING FACTORS.
47. The Effect of Light Intensity on
Photosynthetic Rate
