9.2 LESSON Photosynthesis Overview

9.2 Photosynthesis: An Overview

Learning Objectives

▪ Explain the role of pigments in the process of

photosynthesis.

▪ Describe the role of electron carrier molecules.
▪ Identify the reactants and products of photosynthesis.

Chlorophyll and Chloroplasts

• Light energy from the sun must be captured for photosynthesis

to occur.

• Sunlight is “white” light—actually a mixture of different

wavelengths.

• Photosynthetic organisms capture energy from sunlight with

pigments—principally with chlorophyll.

Drag and Drop

Photosynthetic organisms capture energy from sunlight with ​

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, primarily ​

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pigments

chlorophyll

melanin

solar panels

Chloroplasts

Photosynthesis takes place inside organelles called chloroplasts.

Plant Cell

Chloroplast

Multiple Choice

Where does photosynthesis take place?

• chloroplasts

• mitochondria

• lysosomes

• ribosomes

Chloroplast Structure

In plants, photosynthesis takes place inside chloroplasts.

​liquid filling of chloroplast

stack of thylakoids

chlorophyll in the membrane traps sunlight

Labelling

Label the diagram.

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thylakoid

stroma

chloroplast

granum

Electron Carriers

The high-energy electrons produced by chlorophyll are
highly reactive and require a special “carrier.”

Multiple Select

Electrons made by chloroplasts need special carriers. Why?

Which TWO describe the electrons produced by chloroplasts.

• high-energy

• low-energy

• highly reactive

• nonreactive

Electron Carrier

• An electron carrier is a compound that can accept a pair

of high-energy electrons and transfer them, along with
most of their energy, to another molecule.

• NADPH can carry the high-energy electrons that were

produced by light absorption in chlorophyll to chemical
reactions elsewhere in the cell.

Multiple Choice

What is the carrier that takes electrons away from chlorophyll?

(It's like D PAN you might use to carry hot coals)

• ATP

• NADPH

• thylakoid

• stroma

An Overview of Photosynthesis

Photosynthesis uses the energy of sunlight to convert water and
carbon dioxide (low-energy reactants) into high-energy sugars and
oxygen (products).

Carbon dioxide + Water → Sugars + Oxygen

light

Labelling

Label the equation for photosynthesis.

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6CO₂

6H₂O

C₆H₁₂O₆

6O₂

Photosynthesis and Light

Photosynthesis involves two sets of reactions:
▪ Light-dependent reactions
▪ Light-independent reactions

Labelling

Label the two parts of photosynthesis that happens in a chloroplast.

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light-dependent

light-independent

Light-Dependent Reactions

Light-dependent reactions require the direct involvement of light
and light-absorbing pigments.

Water

Oxygen

Energy from sunlight is

used to make

NADPH

and
ATP

in light-dependent

reactions.

Categorize

Options (6)

water

NADP⁺

ADP

oxygen

NADPH

ATP

Organize these options into the right categories for a

light-dependent reaction.

Inputs

Outputs

Light-Independent Reactions

Light-independent reactions use ATP and NADPH molecules
produced in the light-dependent reactions to produce high-energy
sugars from carbon dioxide

Sugars and
Other carbohydrates

Carbon Dioxide

Categorize

Options (6)

sugar

NADP⁺

ADP

carbon dioxide

NADPH

ATP

Organize these options into the right categories for a

light-independent reaction.

Outputs

Inputs

Interdependence of Reactions

Light-dependent and light-independent reactions have an
interdependent relationship.

Drag and Drop

In the light ​

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reaction, ​ NADPH is made in the ​

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.

In the light ​

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reaction, ​

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is made in the ​

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.

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dependent

thylakoid

independent

sugar

stroma

ATP