Photosynthesis

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?

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.

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.

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

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.

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?

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. ~ 5 -10 minutes.

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.

Conservation of Energy Bozeman 4 min https://www.youtube.com/watch?v=LIh9ueO9FBM

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

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?

The Simple Story of Photosynthesis and Food https://www.youtube.com/watch?v=eo5XndJaz-Y

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

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

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

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

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

Bill Nye the Science Guy Light and Color 23 min https://www.youtube.com/watch?v=XMVY33cZ9To

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

Let’s watch this TED Video to review.

How does SUNLIGHT WATER CARBON DIOXIDE become CARBOHYDRATES (glucose)

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

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

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

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

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