Photosynthesis

Process uses the sun’s energy to make glucose Photosynthesis Process uses the sun’s energy to make glucose Carried out in green plants and some bacteria Purpose is to trap sun’s energy and store it in glucose (food for the plant) Photosynthesis occurs in the chloroplast SUN photons 6CO2 + 12H2O  C6H12O6 + 6O2 carbon dioxide + water  glucose + oxygen 2

6CO2 + 12H2O  C6H12O6 + 6O2 carbon dioxide + water  glucose + oxygen 3

Pores in a plant’s cuticle through which Stomata (stoma) Pores in a plant’s cuticle through which water and gases are exchanged between the plant and the Oxygen (O2) Carbon Dioxide (CO2) & Water Guard Cell Guard Cell

Organelle where photosynthesis Chloroplast Organelle where photosynthesis takes place. Stroma: gel filled space Outer Membrane Inner Membrane Thylakoid: green disks Granum: stack of thylakoids Inter Membrane Space 6

Thylakoid Grana make up the inner membrane Thylakoid Membrane Granum Thylakoid Space (Lumen) Granum Grana make up the inner membrane 7

Why are plants green?

Pigments Pigments are light-absorbing compounds. Pigments appear colored because they absorb light of certain wavelengths and reflect that of others. Chlorophyll a and b are the primary pigments in green plants that absorbs red and blue/violet light and reflects green light.

Light and Dark Reactions

Photosynthesis Steps 1. Light reaction (Light-dependent reaction) Chlorophyll traps sunlight and makes electrons and ATP to run the dark reaction. 2. Dark reaction (Light-independent reaction) Calvin Cycle uses ATP and electrons from the light reaction and carbon dioxide from the air to make glucose.

All organisms require energy for: ATP All organisms require energy for: Active transport Cell division Movement Production of proteins 17

NADPH NADP+ is an electron acceptor NADP+ + 2e- + 2 H+  NADPH + H+

LIGHT REACTION Requires light Pigments absorb photons of light and excite electrons Occurs in two photosystems in the thylakoid membranes Photosystem: a unit of several hundred chlorophyll molecules and associated acceptor molecules

Light Reaction Summary Input: light energy H2O Output: ATP NADPH O2 20

Dark Reaction (Calvin Cycle) American scientist Melvin Calvin Occurs in the stroma. Uses ATP and NADPH from light reactions. Uses CO2 to produce glucose (C6H12O6). To produce 1 glucose: it takes 6 turns of the cycle and uses 18 ATP and 12 NADPH.

Input: Output: Dark Reactions Summary ATP NADPH CO2 ADP NADP+ H2O Sugars (glucose) 22

Rate of Photosynthesis The rate at which a plant can carry photosynthesis is affected by its environment. 1. Temperature – enzymes directly impacted 2. Light intensity – no light = no photosynthesis 3. Water - required 4. [CO2]- Calvin (Dark) cycle requirements

The End!