Photosynthesis!Photosynthesis!

Remember the 8 Characteristics of Living Things:

***All things obtain and use energy.  

Photosynthesis!Photosynthesis!

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Where does the mass come from??

Photosynthesis

• Purpose: plants, some bacteria, and some protists use energy from sunlight to convert water and CO2 into high energy carbohydrates (sugars and starches) and oxygen

1653 – Jan van Helmont

• Planted seed, 5 years later there was a small tree weighing 75grams. Soil mass was unchanged. Concluded it must all be water weight. This was partially true. He had the “hydrate” but from where did the “carbo” come from?

• CO2 in air made a major contribution to the mass of his tree. C in CO2

is used to make sugars and other carbs in photosynthesis.

1771 Joseph Priestly • Took candle and placed glass

jar over it. Flame died. Concluded something in air was necessary to keep flame going. This was/is oxygen.

• He then placed a small plant in the jar, waited several days, the

candle could then remain lit for much longer. Conclusion plants must release oxygen!

1779 Jan Ingenhousz

• Took Priestly’s experiment one step further. He showed that aquatic plants produce bubbles in light.

So…

• Helmont, Priestly and Ingenhousz laid groundwork for future understanding of photosynthesis with light, plants transform CO2 and H2O into carbohydrates and release oxygen.

Photosynthesis Equation

6 CO2 + 6 H2O 1 C6H12O6 + 6

O2

6 _______ + 6 ______ + _______ = 1 ______ (glucose) + 6 _______

carbon dioxide water

sugar oxygen

sun

Where do the reactants come from?

1. Water comes from the soil and roots2. Carbon Dioxide (CO2) comes from the air 3. Sunlight comes from the sun

How do plants capture sunlight?

• Sunlight travels to the Earth as white light (a mixture of all the different wavelengths and colors of light)

How do plants capture sunlight?

• Chlorophyll is a pigment molecule that captures light energy

• Chlorophyll absorbs blue and red light and reflects green light

Where does photosynthesis occur?

• Photosynthesis occurs in the chloroplast of a plant cell

Chloroplast Structures

1. THYLAKOID• Light collecting units

in chloroplasts• Light-dependent

reactions

Chloroplast Structures

2. GRANUM• A stack of thylakoid

discs

Chloroplast Structures

3. STROMA• Space outside of the thylakoid membrane• Light-independent reactions

Overall: Two Reactions

1. LIGHT-DEPENDENT reactions• Takes place in the thylakoid• Uses water and light energy from the sun to make oxygen and ATP

- Light strikes chlorophyll - Electrons are removed from water- Electrons get excited by light and are sent down the

ETC

- H+ removed from water move into the thylakoid space- Oxygen gets kicked out as a waste- Excited electrons are sent down the ETC

- H+ move through membrane protein out of the thylakoid

- Energy from excited electrons use the H+, ADP, and NADP+ to make ATP and NADPH

Overall: Two Reactions

2. LIGHT-INDEPENDENT reactions• the Calvin cycle• Takes place in the stroma• Uses ATP, water, and CO2 to make glucose

Things to remember about photosynthesis:

• What is the energy source for photosynthesis?

• In what part of the plant does photosynthesis occur?

• Which molecule absorbs light energy?

• Why do plants look green?

Things to remember about photosynthesis:

• What are the reactants of the photosynthesis equation?

• What are the products of the photosynthesis equation?

• Why is glucose an important product?

Warm-Up 10-5-12

Using words, symbols, or pictures, write the

equation for photosynthesis.