Autotrophs (producers) produce organic molecules from CO 2 and other inorganic raw materials obtained from the environment. Can be categorized by source of energy that drives their metabolism. Photoautotrophs use light. Photosynthesis occurs in plants, algae & some other protists, and some prokaryotes. Chemoautotrophs (occurs in some bacteria) get energy from oxidizing inorganic substances, including sulfur and ammonia. Plants and other autotrophs are producers

Heterotrophs (consumers) live on organic compounds produced by other organisms. Herbivores  plants only Carnivores  animals only Omnivores  plants & animals Detritivores  feed on dead organisms and organic litter, like feces and fallen leaves Decomposers  break down dead organisms / absorb nutrients Almost all heterotrophs are completely dependent on photoautotrophs for food and oxygen.

Any green part of a plant has chloroplasts. Leaves = major site of photosynthesis for most plants. About half a million chloroplasts per square mm of leaf. Color of a leaf comes from chlorophyll, the green pigment in the chloroplasts. Chlorophyll absorbs light energy (usually sunlight) during photosynthesis. Chloroplasts = sites of photosynthesis in plants

O 2 exits and CO 2 enters the leaf through microscopic pores, stomata, in the leaf. Veins (xylem) deliver water from the roots and carry off sugar from mesophyll cells to other plant areas (phloem).

A typical mesophyll cell (where photosynthesis takes place) has chloroplasts. Each chloroplast has two membranes around a central watery space, the stroma. In the stroma are membranous sacs, the thylakoids that may be stacked into columns called grana. Fig. 10.2

Using glucose as our target product, the equation describing the net (overall) process of photosynthesis is: 6CO 2 + 6H 2 O + light energy -> C 6 H 12 O 6 + 6O 2 Photosynthesis Equation Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Photosynthesis is two processes, each with multiple stages. Light reactions: solar energy  chemical energy. Occur in thylakoids Calvin cycle: incorporates CO 2 from the atmosphere into an organic molecule; uses energy from the light reaction to reduce the new carbon piece to sugar. Occurs in stroma The light reactions and the Calvin cycle cooperate in converting light energy to chemical energy of food: an overview