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Photosynthesis

An overview

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Objectives

• SWBAT describe the process of photosynthesis

• SWBAT relate producers to photosynthesis

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Review Vocabulary

• Chemical reaction• Carbohydrate• Enzyme• Chloroplast – where photosynthesis takes

place.

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Vocabulary

• Photosynthesis• Producers • Chlorophyll• Thylakoid • Light-dependent reactions • Light-independent reactions

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Photosynthesis – the engine of life

• Photosynthesis is carried out by producers.– You learned about producers during our ecology

unit. Make sure you know what a producer is!– Plants, some bacteria, and some protists (like the

euglena), are able to make their own energy through photosynthesis.

– They are at the base of our energy pyramid.

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Photosynthesis – the engine of life

In an energy pyramid, the producers are the base on which all other life depends (directly and

indirectly almost all energy in ecosystems begins as sunlight). Producers are the photosynthesizers.

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Photosynthesis – the engine of life• Photosynthetic organisms are producers.

• Photosynthesis is a process that captures energy from sunlight to make simple sugars (glucose).

• There are two parts to photosynthesis: the production of ATP from ADP and then the utilization of the ATP to make glucose.

Glucose is a monomer used by the plant to make other, more complex, molecules such as cellulose, starch,

and carbohydrates.

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Chlorophyll• Chlorophyll is a molecule found in chloroplasts (the

organelle that makes ATP in plants and other photosynthesizers).– Chlorophyll absorbs visible light, which the chloroplasts are

able to turn into energy.

The chlorophyll is found in the granum

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Why are plants green?

• Plants have two main types of chlorophyll.– Chlorophyll a and – Chlorophyll b

• Together chlorophyll a and b absorb mostly red and blue wavelengths of visible light.– Plants are green because neither of them absorb

green light (it is reflected and thus we see leaves as green).

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Chloroplasts

• Chloroplasts are the membrane-bound organelle where photosynthesis takes place in plants.– Most chloroplasts are in the leaf cells, which are

specialized for photosynthesis. • Two main parts to chloroplasts:

– The grana– The stroma.

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Grana

• Grana are stacks of coin-shaped membranes enclosed in compartments called thylakoids.

• The membranes of the thylakoids contain chlorophyll.

• The grana are where light-dependent (needing sunlight) reactions take place.

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Stroma

• The stroma is fluid outside the thylakoids (it surrounds the grana inside the chloroplasts).

Stroma is where the light-independent (not

requiring light) reactions take place.

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Light-dependent reactions

– take place in thylakoids– water and sunlight are

needed– chlorophyll absorbs

energy from sunlight. – energy in the form of

ATP is made in the thylakoid membrane then transferred to light-independent reactions

– oxygen is released

• The light-dependent reactions capture energy from sunlight.

The product of the light-dependent reactions is ATP synthesized from ADP – this is called photophosphorylation.

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Light-Dependent Reactions

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The light-independent reactions make glucose (known as the Calvin Cycle) .

• take place in stroma• needs carbon dioxide from atmosphere• use energy to create glucose in a cycle of chemical

reactions

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Light Independent Reactions

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Photosynthesis• The equation for the overall process is:

6CO2 + 6H2O C6H12O6 + 6O2

C6H12O6

granum (stack of thylakoids)

thylakoid

sunlight

1 six-carbon sugar

6H2O

6CO2

6O2

chloroplastchloroplast1

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energy

stroma (fluid outside the thylakoids)

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Photosynthesis