Energy All organisms require energy to grow, reproduce, move and carry out maintenance and repairs. Energy can not be created or destroyed, but it can be converted from one form to another. The ultimate source of energy is the sun. Photo credit: NASA Heat (thermal energy) Lightning (electrical energy) The Sun is the ultimate energy source for life on Earth

Energy Producers Organisms which produce their own energy are autotrophs. Most plants are autotrophs.

Energy Consumers Heterotrophs are organisms which cannot make their own energy. All animals, fungi and some bacteria are heterotrophs.

Photosynthesis Photosynthesis is the action of transforming sunlight energy into chemical energy. It produces: Sugar (fuel) oxygen Sugar Oxygen gas Water and nutrients Carbon dioxide 6CO H 2 OC 6 H 12 O 6 + 6O 2 + 6H 2 O Chlorophyll Light Sunlight

Photosynthesis Takes place in organelles called chloroplasts. Chloroplasts are filled with a green pigment called chlorophyll.

The Chloroplast Stroma, the liquid interior of the chloroplast Thylakoid sac (disc) Grana, are stacks of thylakoid membranes containing chlorophyll Outer membrane Inner membrane

Photosynthesis There are two phases in photosynthesis: The light dependent phase (D), which occurs in the thylakoid. The light independent phase (I), which occurs in the stroma. D D I I

Photosynthesis Water Oxygen Carbon dioxide Sugar ATP NADPH + H +

Light Reactions of Photosynthesis

Light Independent Phase Calvin cycle (carbon fixation) occurs in the stroma of the chloroplast. Carbon from CO 2 is incorporated into existing organic molecules. G3P CO 2 sugars RuBP RuBisCo ADP + P i ATP ADP + P i Triose phosphate NADPH + H + NADP Ribulose phosphate

Factors Affecting Photosynthetic Rate the amount of light available. the level of carbon dioxide (CO 2 ). the temperature.