+

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)

Trophic Levels Autotrophs, Heterotrophs, Primary

Consumers

Organelles of Plant Cells Nucleus, Cell Wall, Chloroplast,

Mitochondria

Energy Source for Cells ATP

Cellular Respiration CO2 is released into the

atmosphere

+In this lesson we will learn:

Sources of Oxygen

Autotrophs

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.

+Autotrophs and Photosynthesis

Called “self feeders” or

”producers”.

Organisms that can produce their

own food using light, water,

carbon dioxide, or other

chemicals.

Examples of autotrophs: green

plants, some algae, few bacteria.

Most autotrophs use

photosynthesis to make their

food.

+✔ For Understanding

Class Discuss: Where does most of the O2 we breathe come from? Did the answer surprise you? What is the difference between heterotrophs and autotrophs?

Think-Pair-Share: How do you think photosynthesis happens? What is needed for the process?

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 light

Gives leaves their green color

Membrane Envelope

Protects 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.

Granum

Dense layered stacks of thylakoids

Sites of conversion of light energy to chemical

energy.

Stroma

Dense fluid within the chloroplast

Lies inside the envelope but outside the thylakoid

membrane

Site 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 pigment absorbs light energy?

Think-Pair-Share: Do you think photosynthesis happens when its dark outside? Why or why not?

Light Dependent Reactions Light Independent Reactions

Location Thylakoid Membrane

Reactants

1. Sunlight

2. Water (H2O)

End Products

1. ATP

2. NADPH

3. Oxygen (O2)

Location Stroma

Reactants

1. ATP

2. NADPH

3. Carbon Dioxide

(CO2)

End Products 1. Sugar (glucose)

Summary and Photosynthetic Equation

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=eo5XndJaz-Y