An Overview of Photosynthesis

The Big Picture All organisms need energy to carry out essential functions (growth, movement, maintenance, repair, reproduction). The ultimate source of energy is the sun. Energy flows from the sun to autotrophs, then to organisms that eat autotrophs (heterotrophs), and then to organisms that feed on other organisms (heterotrophs).

Autotrophs vs. Heterotrophs Organisms are classified by how they obtain their energy Organisms are classified by how they obtain their energy 1. Autotrophs- organisms that make their own food / use solar energy to power the production of food (plants, some kinds of protists and bacteria) (plants, some kinds of protists and bacteria) 2. Heterotrophs- organisms that must get energy from food instead of directly from sunlight / get energy by eating other organisms or organic wastes (all animals, all fungi, most protists, many bacteria) (all animals, all fungi, most protists, many bacteria)

The Six Kingdoms HeterotrophicAutotrophic EubacteriaXX (chemosynthesis or photosynthesis) ArcheabacteriaXX(chemosynthesis) ProtistaX(phagocytosis)X(photosynthesis) FungiX (secrete digestive enzymes into the environment) PlantaeX(photosynthesis) AnimaliaX(phagocytosis)

Autotrophs: Chemosynthesis vs. Photosynthesis Photosynthesis- the conversion of light energy from the sun into chemical energy in the form of organic compounds. Photosynthesis- the conversion of light energy from the sun into chemical energy in the form of organic compounds. 6CO 2 + 6H 2 O + (light energy)  C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + (light energy)  C 6 H 12 O 6 + 6O 2 Chemosynthesis- the use of energy stored in inorganic molecules (CO 2 ) to produce carbohydrates (organic molecules) / chemicals are used as the energy source rather than sunlight Chemosynthesis- the use of energy stored in inorganic molecules (CO 2 ) to produce carbohydrates (organic molecules) / chemicals are used as the energy source rather than sunlight 6CO 2 + 6H 2 O + (chemical energy-3H 2 S)  C 6 H 12 O 6 + 3H 2 SO 4 6CO 2 + 6H 2 O + (chemical energy-3H 2 S)  C 6 H 12 O 6 + 3H 2 SO 4

Which Organisms use Photosynthesis? Which Organisms use Chemosynthesis? Photosynthesis – takes place on land and in shallow waters where sunlight can reach plants and seaweed Photosynthesis – takes place on land and in shallow waters where sunlight can reach plants and seaweed Chemosynthesis – takes place around hydrothermal vents and methane seeps in the deep sea where there is no sunlight. It is performed by bacteria living on the sea floor or within animals. Chemosynthesis – takes place around hydrothermal vents and methane seeps in the deep sea where there is no sunlight. It is performed by bacteria living on the sea floor or within animals.

Overview of Photosynthesis 6CO 2 + 6H 2 O + (light energy)  C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + (light energy)  C 6 H 12 O 6 + 6O 2 (Reactants) (Products) (Reactants) (Products) Autotrophs use photosynthesis to produce organic compounds from carbon dioxide and water. Autotrophs use photosynthesis to produce organic compounds from carbon dioxide and water. The Two Stages of Photosynthesis: The Two Stages of Photosynthesis: Light Reactions (Light Dependent Reactions) Light Reactions (Light Dependent Reactions) Calvin Cycle (Light Independent Reactions) Calvin Cycle (Light Independent Reactions)

Stage 1: Light Reactions Series of steps in which: Series of steps in which: Light energy is absorbed from the sun and converted into chemical energy (ATP and NADPH) Light energy is absorbed from the sun and converted into chemical energy (ATP and NADPH) Water (H 2 O) is the first reactant used, and O 2 is the first byproduct produced. Water (H 2 O) is the first reactant used, and O 2 is the first byproduct produced. Chemical energy is temporarily stored as ATP and NADPH (energy carrier molecule) Chemical energy is temporarily stored as ATP and NADPH (energy carrier molecule)

Stage 2: Calvin Cycle Series of steps in which: Series of steps in which: Carbon Dioxide (CO 2 ) is the second reactant used, along with the chemical energy from the light reactions (stored in ATP and NADPH) Carbon Dioxide (CO 2 ) is the second reactant used, along with the chemical energy from the light reactions (stored in ATP and NADPH) Organic compounds (glucose – C 6 H 12 O 6 ) are formed. Organic compounds (glucose – C 6 H 12 O 6 ) are formed.

Structure and Function of a Leaf

Structure and Function 1. Upper Epidermis- structure, support, protection 2. Cuticle- waxy coating, helps prevent water loss 3. Palisades Layer- where majority of photosynthesis takes place 4. Chloroplast- site of photosynthesis 5. Phloem- transports sugars in any direction 6. Xylem- transports water upward only (roots  shoots) 7. Guard Cells- specialized cells that border a stoma and regulate gas exchange 8. Stomata- gas exchange 9. Vein- transport tissue (vein= xylem + phloem) 10. Lower Epidermis- structure, support, protection 11. Spongy Layer- photosynthesis, air exchange 12. Mesophyll- air exchange and photosynthesis (3 +11)

Stomata – please sketch on your lab Guard Cells Stomata