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Teaching (and learning) Photosynthesis Doesn't Need to be Hard!

When teaching photosynthesis keep it simple until basic concepts are mastered.

What do you need to know about photosynthesis?

Plants are the producers of the biosphere

Chloroplasts are the site of photosynthesis in plants

The light reactions and the Calvin cycle cooperate in converting light energy to the chemical energy in food

Light reactions convert sunlight to ATP and NADPH

The Calvin cycle uses ATP and NADPH to convert CO2 to Sugar

The plant uses that sugar for metabolic processes

Before getting to the details of photosynthesis it is a good idea to review the basic structure of a plant cell:

Major differences in a plant cell vs. an animal cell are the chloroplasts, the central vacuole, and the cell wall.

Chloroplasts are a type of plastid. They are also the site of photosynthesis and contain the thylakoid where the light reactions take place.

The central vacuole is a place of chemical storage, macromolecule breakdown, and participates in plant growth.

The cell wall is fundamentally different than the plasma membrane in animal cells. This cell wall provides structure and protects the cell from damage.

Most of the other organelles are the same for both plant and animal cells - mitochondria make energy, though plant mitochondria are not as much a part of that process as are the mitochondria in animal cells

Plants use carbon Dioxide (CO2), Water (H2O), and Sunlight to make energy.

A simplifies version of photosynthesis is pictured below:

The equation states:

Six molecules of water plus six molecules of carbon dioxide produce one molecule of sugar plus six molecules of oxygen

What this diagram says: The light reactions (left) use sunlight to make ATP and NADPH. The Dark Reactions or Calvin Cycle take the ATP and NADPH created by the light reactions PLUS CO2, and make sugar. That sugar is then used for cellular energy. The difference between ATP in a plant cell and ATP in an animal cell is that in a plant cell ATP is used to drive the Calvin Cycle and not for direct energy.

The reactants are:

H2O (water)

CO2 (carbon Dioxide)

The Products are:

O2 (Oxygen)

CH2O (A Sugar building block)

H2O (Water)

You will see that we have accounted for all the molecules from our original equation:

6CO2 + 12H2O + Sunlight -----> C6H12O6 + 6O2 + 6H2O

Do you remember what a sugar molecule looks like? Don't let that CH2O trick you - that is but a component of glucose - our ultimate product.

Need more info? Simple Schooling will be coming out with a high school biology workbook this summer. In the meantime - Take a look at these awesome video tutorials:

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