4.2 Overview of Photosynthesis TEKS 4B, 9B

The student is expected to:

4B investigate and explaincellular processes, includinghomeostasis, energy conversions, transport of molecules, and synthesis of new molecules and9B compare the reactants and products of photosynthesis and cellular respiration in terms of energy and matter

4.2 Overview of Photosynthesis TEKS 4B, 9B

KEY CONCEPTThe overall process of photosynthesis produces sugars that store chemical energy.

4.2 Overview of Photosynthesis TEKS 4B, 9B

Photosynthetic organisms are producers.

• Producers make their own source of chemical energy.

• Plants use photosynthesis and are producers.

• Photosynthesis captures energy from sunlight to make sugars.

4.2 Overview of Photosynthesis TEKS 4B, 9B

• Chlorophyll is a molecule that absorbs light energy.

chloroplast

leaf cell

leaf

• In plants, chlorophyll is found in organelles called chloroplasts.

4.2 Overview of Photosynthesis TEKS 4B, 9B

Photosynthesis in plants occurs in chloroplasts.

• Photosynthesis takes place in two parts of chloroplasts.– grana (thylakoids)– stroma

chloroplast

stroma

grana (thylakoids)

4.2 Overview of Photosynthesis TEKS 4B, 9B

• The light-dependent reactions capture energy from sunlight.

– take place in thylakoids– water and sunlight are needed– chlorophyll absorbs energy– energy is transferred along thylakoid membrane then to

light-independent reactions– oxygen is released

4.2 Overview of Photosynthesis TEKS 4B, 9B

• The light-independent reactions make sugars.

– take place in stroma– needs carbon dioxide from atmosphere– use energy to build a sugar in a cycle of chemical

reactions

4.2 Overview of Photosynthesis TEKS 4B, 9B

• 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

2

43

energy

stroma (fluid outside the thylakoids)