1. Photosynthesis

2. All we know in science began with a question….
In 1634, Jan Baptist van Helmont had a question:
Where do plants get their mass when they grow?

3. Plants get their mass from water. Plants get their mass from soil.
Three Hypotheses:
Plants get their mass from water.
Plants get their mass from soil.
Plants get their mass from air.
Choose the ONE you think is the accurate answer and write it in your notebook. We will refer back to this question periodically.

4. Scientists then design an experiment for testing the hypothesis.
Jan Helmont wanted to test the idea that plants gained mass from consuming soil in some way. Think of a way you could test this idea and be prepared to share it with the class.

5. Helmont’s Experiment
1. Measure the mass of soil placed in a pot
2. Measure the mass of a young willow plant.

6. 3. Plant was watered and placed in sunlight.
4. 5 years later, the mass of the soil and the mass of the willow was determined.

7. Important Data - Helmont Experiment
Mass at Start
Mass After 5 Years
Soil
90 kg
89.9 kg
Plant
2.25 kg
76.1 kg
Based on the data, was his hypothesis that plants consumed soil accurate?
Where did the mass of the plant come from?

8. Plants get their mass from water. Plants get their mass from soil.
Which hypothesis did Helmont eliminate?
Plants get their mass from water.
Plants get their mass from soil.
Plants get their mass from air.
If “B” was your hypothesis, choose either A or C as a new hypothesis and write this in your notebook. With the person sitting next to you, develop an experiment to test your new hypothesis (either A or C). Create a sketch of your design and be prepared to share it with the class. ~ minutes.

9. Though we don’t have time to look at all of the historical experiments, scientists finally realized that air and water were necessary for plants to grow in mass.
The Law of Conservation of Matter - matter cannot be created or destroyed it just changes forms.

10. Conservation of Energy
Bozeman 4 min

11. The Law of Conservation of Energy
-cannot be created or destroyed, it can change form.
-can be transferred from one form to another.
SOLAR → CHEMICAL

12. Pause and Reflect 1. What do plants need to grow in mass?
a) light b) water c) air d) soil
2. How did Helmont show that soil did not contribute to the mass of the plant?
a) weighed the soil b) watched the plant grow c) measured water
3. Energy from the sun is converted to chemical energy such as that stored in:
a) soil b) apples c) air
4. Why was the law of conservation of matter important to Helmont’s experiment?

13. The Simple Story of Photosynthesis and Food

14. How is energy from the sun converted to chemical energy?
Photosynthesis is the process in which plants
1) use energy (sunlight) 2) to convert water and carbon dioxide 3) into glucose and oxygen.
Glucose O2

15. The Photosynthesis Equation
6CO2 + 6H2O → C6H12O6 + 6O2
carbon dioxide + water → sugar + oxygen

16. Chloroplasts - where photosynthesis occurs
Pigments in chloroplasts absorb light.
The main pigment is CHLOROPHYLL, which absorbs most colors of light except for green.

17. Structure of Chloroplast
Stacks of thylakoids
Stroma = space between
Draw this chloroplast and label it in your notes.

18. Absorption Spectrum of Chlorophyll A
Green is not absorbed very well, and is REFLECTED, this is why plants appear green.

19. Bill Nye the Science Guy Light and Color
23 min

20. Why do leaves turn red and yellow in the fall?
Carotenoids!

21. Let’s watch this TED Video to review.

22. How does
SUNLIGHT
WATER
CARBON DIOXIDE
become
CARBOHYDRATES
(glucose)

23. How does this conversion of light to glucose happen?
Stage 2
Light-Independent
Stage 1: Light Dependent
Light + Water
Releases Oxygen
(Thylakoid)
CO2 in
Glucose out
(Stroma)
“How Does Photosynthesis Work” Handout

24. Energy All living things need energy to survive
Autotrophs (plants) make food from the sun
Heterotrophs (animals) consume food

25. ATP - an energy carrying molecule
Adenosine Triphosphate
-produced by the mitochondria
- requires glucose & oxygen
- breaking bonds of ATP releases energy

26. How Can the Rate of Photosynthesis Be Measured?
Examine the diagram, try to explain what you see with regard to plants and photosynthesis.

27. What factors could affect the rate of photosynthesis?
Interpret these graphs….