1. Chapter 6: Photosynthesis
Mrs. Stewart
Honors Biology
Central Magnet

2. Standards
CLE Investigate the relationship between the processes of photosynthesis and cellular respiration.
SPI Compare and contrast photosynthesis and cellular respiration in terms of energy transformation.

3. Objectives Summarize the reactants and products of photosynthesis.
Describe the reactants and products of the light reactions.
Describe the reactants and products of the Calvin Cycle (dark reactions).
Summarize how the light reactions and Calvin cycle work together to create a continuous cycle of photosynthesis.

4. Q: Where does the energy come from in each stage of the food chain?
Think – Pair - Share
Q: Where does the energy come from in each stage of the food chain?

5. Autotrophs
Make their own food

6. Heterotrophs
Cannot make their own food

7. WHAT is the energy?
Much of the energy used by living organisms is in the form of ATP

8. Chemical Energy and ATP
The principal chemical compound that cells use to store and release energy is called ATP (adenosine triphosphate)

9. Storing Energy
ATP stores energy in the bond between the second and third phosphate group
ATP is like a fully charged battery
Energy

10. Releasing Energy Think – Pair - Share
Q: How is the energy in ATP released? A: Break bond between the second and 3rd phosphates 2
ADP

11. ATP vs. ADP ATP – has all 3 phosphate groups
Fully charged battery
Brief energy storage
Can remove a phosphate group to release energy and form ADP
ADP – has only 2 phosphate groups
Partially charged battery
Can add a phosphate group to make ATP

14. ATP Availability
Most cells only have enough ATP for a few seconds of activity
Why?
Not good at storing energy over the long term
Glucose stores 90 times the chemical energy of ATP
Cells generate ATP from ADP as needed by using the energy in foods (like glucose)

15. 6-1: Photosynthesis

16. Photosynthesis
The process in which plants use the energy of sunlight to convert water and carbon dioxide into high energy carbohydrates – sugars and starches – and oxygen as a waste product

17. Photosynthesis 6CO2 + 6H2O C6H12O6 + 6O2 LIGHT (Carbon Dioxide)
(Water)
(Sun)
(Glucose)
(Oxygen)

18. Photosynthesis

19. The Visible Light Spectrum

20. Pigments Absorb different wavelengths of light (colors)
Reflect (transmit) what they do not absorb
We see what is reflected back.

21. Chlorophyll The plant’s principal pigment absorbs light energy
blue-violet
red

22. Chlorophyll a and Chlorophyll b
Absorption of Light by
Chlorophyll a and Chlorophyll b
Absorption of Light by
Chlorophyll a and Chlorophyll b
Chlorophyll b
Chlorophyll a V B G Y O R

23. Think – Pair - Share
Q: Why are leaves green?
A: because chlorophyll absorbs the blue-violet and red light and reflects the green back.

24. Because light is a form of energy…
Anything that absorbs light also absorbs the energy from that light
When chlorophyll absorbs light, much of the energy is transferred to electrons in the chlorophyll molecule, raising the energy level of these electrons
These high-energy electrons make photosynthesis work

25. Photosynthesis Basics
Where does photosynthesis take place?
In organelles called chloroplasts.

27. Thylakoids
Sac-like photosynthetic membranes arranged in stacks

28. Grana
Stacks of thylakoids
Granum – singular
Grana - plural

29. Stroma The region outside the thylakoid
The watery region in a chloroplast
Similar to the cytoplasm in the cell

31. Photosynthesis occurs in two parts:
Light – dependent reactions (takes place in the thylakoid membranes)
Light – independent/Calvin Cycle reactions (takes place in stroma)

32. ANALYZE THE PICTURE List the reactants and products for
The light dependent reactions
The Calvin Cycle (light independent) reactions
List the location where each reaction occurs

33. Pg. 123

34. Light Dependent Reactions
“photo” part of photosynthesis
Reactants:
H2O, energy from light (photons) NADP+, ADP+ and phosphate group
Products:
Oxygen gas, ATP, NADPH

35. Think – Pair – Share
Q: Where did the Oxygen, produced by the light dependent reactions come from?
A: H2O

36. What you need to know: Where do the light reactions occur?
What is needed (reactants)?
What is created (products)
In the thylakoids.
Light (photons)
water
ATP & NADPH - go on to Calvin cycle
Oxygen - that is released

37. Carrier Molecule
Compound that can accept a high energy electron and transfer it along with most of its energy to another molecule
Ex.) NADP+ + H  NADPH

38. The Calvin Cycle The “synthesis” part of photosynthesis
These reactions don’t require light, therefore these reactions are called Light – Independent or Dark reactions

39. The Calvin Cycle
Reactants: ATP and NADPH (from light – dependent reactions) and CO2
Products: high energy sugars (C6H12O6) and NADP+ and ADP+ (which will go back to light dependent reaction for reuse)

40. Carbon Fixation The incorporation of CO2 into organic compounds
The Carbon in CO2 is “fixed” into the usable energy form of sugar
6 CO2 molecules will go into the cycle to produce each organic molecule of 6-Carbon sugar. (C6H12O6 )

42. Factors Affecting Photosynthesis
Not enough water
Temperature
Light intensity
CO2 levels

43. Objectives (Did we…)
Summarize the overall reactants and products of photosynthesis.
Describe the reactants and products of the light reactions.
Describe the reactants and products of the Calvin Cycle (dark reactions).
Summarize how the light reactions and Calvin cycle work together to create a continuous cycle of photosynthesis.