Autotrophs are organisms that make their own food (plants) Heterotrophs have to eat other organisms, they do NOT make their own food (us) Most autotrophs get E from sunlight– they use it to produce carbohydrates This process is called photosynthesis Plants change the E of sunlight into chemical E stored in the bonds of carbohydrates (sugars and starches) This chem E is called ATP, short for adenosine triphosphate Photosynthesis

Photosynthesis Occurs in chloroplasts in all green plants and photosynthetic protists Some bacteria contain chlorophyll, but not in chloroplasts (remember they don’t have organelles) Chloroplasts are filled with flattened membrane-bound sacs called thylakoids Stacks of thylakoids are called grana Grana are suspended in a fluid called stroma which contains enzymes needed for making the CH2O product of photosynthesis

Pigments are found in the thylakoid membranes, not the chloroplast membrane Chlorophyll (green)-- primary light/E absorbing molecule for photosynthesis—absorb blue-violet and red light Carotenoids— yellow/orange pigments—absorb violet to green light Anthocyanins—red pigments absorb blue- green and UV light—they act as sunscreen to protect plants PHOTOSYNTHESIS

General Steps of Photosynthesis 1. pigments capture E from sunlight (light-dependent reactions) 2. E is converted to chemical E: ATP and NADPH (nicotinamide adenine dinucleotide phosphate + H proton) 3. ATP and NADPH power the synthesis of organic molecules (food) using carbon from CO2 (light-independent reactions) Formula for photosynthesis in plants: 6CO2 + 6H2O + light E → C6H12O6 + 6O2