1. Bell work
Do you think photosynthesis could be considered the primary source of energy for life? Explain your answer.

2. 7.1 Sunlight powers life Life on earth is solar-powered.
Biologists classify organisms according to how they obtain food.
Autotrophs
“self-feeder”, also name producers
They convert inorganic compounds to organic compounds.
Plants use the sun’s energy to convert water and carbon dioxide into sugars.
Heterotrophs
Organisms that cannot make their own food
Also known as consumers
Depend on producers

3. 7.2 Food stores chemical energy
Energy is the ability to perform work.
There are different forms of energy:
Kinetic energy
Potential energy
Thermal energy
Chemical energy – depends on the structure of molecules; energy stored in bonds

4. Energy Endergonic or endothermic reactions
Photosynthesis: CO2 + H2O glucose
Absorbs energy
Feels cold to the touch
Exergonic or exothermic reactions
Cellular respiration: glucose CO2 + H2O
Release energy
Feels warm to the touch

5. Calories
The amount of energy required to raise the temperature of 1 gram (g) of water by 1 degree Celsius (°C).
1 kilocalorie = 1000 calories = 1 Calorie
food calorie
Energy required to
raise the temperature
to 26 °C
25 °C
1 gram

6. Photosynthesis

7. Figure 8-2 Photosynthesis takes place in cellular organelles called chloroplasts. In this sunflower, the greatest numbers of chloroplasts are located in the leaves. Chlorophylls give the chloroplasts—and in turn the leaves—their green color.

8. Chloroplast
Disc-shaped structures are called grana, which are surrounded by the stroma.
Each disc-shaped structure is called a thylakoid.
In the thylakoid is the chlorophyll and other pigments needed for photosynthesis

9. Chlorophyll
Pigment
Photoreceptor
Absorbs the energy from the sun

10. Electromagnetic Spectrum
Figure 8-5 Different forms of electromagnetic energy have different wavelengths. Shorter wavelengths have more energy than longer wavelengths.

11. Types of Chlorophyll
These two kinds of chlorophyll complement each other in absorbing sunlight.
Plants can obtain all their energy requirements from the blue and red parts of the spectrum, however, there is still a large spectral region, between nm, where very little light is absorbed.
This light is in the green region of the spectrum, and since it is reflected, this is the reason plants appear green.

12. Figure 8-7 The laboratory technique of paper chromatography can be used to analyze the pigments in a leaf.

13. Figure 8-4 This "road map" shows the two main stages of photosynthesis: the light reactions, which occur in the thylakoids, and the Calvin cycle, which occurs in the stroma.
Double membrane
Stroma
Grana
Thylakoid

14. Light-dependent Reactions: Photosystems I and II
Figure 8-8 When light strikes the chloroplast, pigment molecules absorb the energy. This energy jumps from molecule to molecule until it arrives at the reaction center.

15. Excited electrons

16. Light-dependent reactions
Hydrolysis =
Break water
Steps of e-:
Water
Photosystem I
Electron Transport Chain
Photosystem II
NADPH
Movement of e- powers ATP formation

17. Figure 8-11 In this "construction analogy" for the light reactions, the input of light energy is represented by the large yellow mallets. The light energy boosts the electrons up to their excited states atop the platform in each photosystem. The energy released as the electrons move down the electron transport chain between the photosystems is used to pump hydrogen ions across a membrane and produce ATP.

18. Light-dependent Reactions Overview
What do I need?
water, sunlight
What do I get?
ATP, NADPH (energy molecules)
oxygen

19. Light-independent reaction: Calvin Cycle
3PGA = 3-phosphoglyceric acid
G3P = glyceraldehyde phosphate

20. Calvin Cycle NADPH and ATP give the energy to be stored in glucose.
What do I need?
ATP, NADPH and 6 carbon dioxide molecules
What do I get?
Glucose (1 glucose for every 6 CO2)

21. Photosynthesis Overview
C6H12O6
Figure 8-14 The light reactions and the Calvin cycle together convert light energy to the stored chemical energy of sugar. The plant can use the sugar to build other organic molecules.

22. Photosynthesis Chemical Reaction
Overall formula:
6CO2 + 6H2O + sunlight  C6H12O6 + 6O2