Photosynthesis An overview 1

Objectives SWBAT describe the process of photosynthesis SWBAT relate producers to photosynthesis 2

Review Vocabulary Chemical reaction Carbohydrate Enzyme Chloroplast – where photosynthesis takes place. 3

Vocabulary Photosynthesis Producers Chlorophyll Thylakoid Light-dependent reactions Light-independent reactions 4

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. 5

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. 6

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. 7

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 8

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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). 10

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. 11

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. 12

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. 13

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

Light-Dependent Reactions 15

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 16

Light Independent Reactions 17

Photosynthesis The equation for the overall process is: 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 granum (stack of thylakoids) thylakoid sunlight 1 six-carbon sugar 6H 2 O 6CO 2 6O 2 chloroplast energy stroma (fluid outside the thylakoids) 18

Photosynthesis 19