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Photosynthesis: Converting sunlight into chemical energy

Students who demonstrate understanding can:HS-LS1-5: Use a model to illustrate how photosynthesis transforms light energy into stored chemical energy.

+✔ For Understanding

To understand the process of photosynthesis we need to build off what we already know about:

Topic Examples

Molecules Water (H2O), Oxygen (O2 ), Carbon Dioxide (CO2)

Carbohydrates Sugar (glucose)

Organelles of Plant Cells Nucleus, Cell Wall, Chloroplast, Mitochondria

Energy Source for Cells ATP

Role of Coenzymes in Chemical Reactions

NADH

+In this lesson we learn: Sources of Oxygen

Where photosynthesis happens

Structure of chloroplasts

Two reactions of Photosynthesis

Steps of Photosynthesis

Locations, Reactants and Products of the two process of photosynthesis

Photosynthetic Equation

Driving Question: How does photosynthesis happen?

Try this: Lets all take a deep breath in and then slowly exhale out. Ready go!

Think-Pair-Share: Where do you think the oxygen (O2) we breathe comes from?

O2 is produced by different kinds of bacteria, algae, and plants (including trees) during photosynthesis.

About 25% of O2 comes from land plants.

So where does the other 75% come from? Well...

Most of Earth’s O2 comes from the ocean. Released from tiny ocean

plants called, phytoplankton.

+✔ For Understanding

Class Discuss: Where does most of the O2 we breathe come from? Did the answer surprise you?

Think-Pair-Share: How do you think photosynthesis happens?

Excellent! Now lets learn about WHERE and HOW photosynthesis happens!

+Class Discuss: What organelles are unique to plant cells? Where does photosynthesis take place in the cell?

+Chloroplast Anatomy: Notice this organelle has a double membrane (inner and outer) and has special structures inside. Inside the chloroplast are the sites of the two processes of photosynthesis. We will talk more about those sites in a couple slides!

First, lets learn more about chloroplast structure and functions!

Structure Functions

Chlorophyll (pigment)Allows plants to absorb energy from lightGives leaves their green color

Membrane EnvelopeProtects and keep chloroplast structures enclosed

Thylakoid membrane Flattened sac-like membrane structures called thylakoids Thylakoids serve as the sites of conversion of light energy to chemical energy.

GranumDense layered stacks of thylakoidsSites of conversion of light energy to chemical energy.

Stroma Dense fluid within the chloroplast Lies inside the envelope but outside the thylakoid membraneSite of conversion of carbon dioxide to carbohydrates

Class Discuss: Why are plants green?

+Now lets look at HOW photosynthesis happens:The processes of photosynthesis is categorized into two different reactions. These two reactions are called, light dependent reactions and light independent reactions. Light independent reactions are also referred to as Calvin Cycle.

Steps of Photosynthesis

1. The pigment, chlorophyll, in the chloroplasts absorbs light energy provided by the sun.

2. Chloroplasts use the light energy to split water molecules into oxygen which gets released into the atmosphere for us to breathe. The light energy also starts the two reactions of photosynthesis.

3. Light Reactions: Capture light energy and uses electrons from the splitting of water to make ATP and NADPH

4. Light Independent Reactions: Use CO2, ATP, and NADPH to make glucose.

https://www.youtube.com/watch?v=g78utcLQrJ4

Summary and Location of Reactions

Class Discuss: What are the two reactions of photosynthesis? What absorbs light energy?

Think-Pair-Share: Do you think light independent reactions use light energy?

Light Dependent Reactions Light Independent Reactions

Location Thylakoid Membrane

Reactants1. Sunlight 2. Water (H2O)

End Products1. ATP2. NADPH3. Oxygen (O2)

Location Stroma

Reactants1. ATP2. NADPH3. Carbon

Dioxide (CO2)

End Products 1. Sugar (glucose)

This entire process can be summarized into a single chemical equation:

Driving Question: How does photosynthesis happen? Light energy gets converted into

chemical energy.

Chemical energy is stored in the form of glucose (sugar).

Carbon dioxide, water, and sunlight are used to produce carbohydrates and oxygen.

Occurs in two stages: Light Dependent Reactions Light Independent Reactions

Think-Pair-Share: Why is photosynthesis essential to life on Earth? https://www.youtube.com/watch?v=eo5Xnd

Jaz-Y