C ELLULAR E NERGY Photosynthesis & Respiration

P HOTOSYNTHESIS It is the process that converts sunlight energy into chemical energy (in the form of glucose and other carbohydrates) Equation: Six molecules of carbon dioxide react with six molecules of water to form 1 molecule of glucose and six molecules of oxygen. Occurs in the CHLOROPLAST of plant cells The first half of the reaction occurs in the thylakoid; the second half happens in the stroma Utilized by autotrophs (plants, algae)

P HOTOSYNTHESIS : M AJOR S TEPS Light-Dependent Reactions (Light Reactions) Sunlight strikes chlorophyll Energy is used to split water (photolysis), releasing oxygen Energized electrons go through a chain of proteins in the thylakoid membrane (Electron Transport Chain) known as Photosystem I and II. ATP and NADPH are produced; these molecules act as “energy carriers” to carry the energy to the next step Light-Independent Reactions (Calvin Cycle, Dark Reactions) The ATP and NADPH produced in the first step are used Carbon dioxide is taken in from the air through openings in the leaf called stomata A series of reactions in the stroma converts these reactants into glucose (or other carbohydrates)

H OW ARE PHOTOSYNTHESIS AND RESPIRATION LINKED ?

C ELLULAR R ESPIRATION It is the process that converts the chemical energy stored in the bonds of glucose into chemical energy cells can use (ATP); produces ATP Equation: Occurs in the MITOCHONDRIA First step occurs in the cytoplasm; 2 nd and 3 rd steps occur in the mitochondria Utilized by ALL aerobic eukaryotic organisms (plants, animals)

C ELLULAR R ESPIRATION – M AJOR S TEPS Glycolysis Glucose molecules from your food are broken to make two 3- Carbon molecules of PYRUVIC ACID (pyruvate) Makes 2 ATP Occurs in the cytoplasm Krebs Cycle (Citric Acid Cycle) Pyruvic Acid is sent to the mitochondria, where it is converted through several reactions to a compound known as Citric Acid CO 2 is produced as a waste product ATP, NADH, and FADH 2 are produced – these molecules will carry the chemical energy to the last step Electron Transport Chain Products of the previous step are used Electrons are passed through a series of proteins in the inner membrane of the mitochondria The final electron acceptor is OXYGEN Approximately ATP are produced in this step! This process is AEROBIC (requires oxygen)

A NAEROBIC R ESPIRATION : F ERMENTATION Used by single-celled organisms, such as yeast cells Glucose is broken down by glycolysis Products are further broken down to make CO 2 and ethyl alcohol Only 2 ATP are made! Occurs in your muscle cells when oxygen is not available Glucose is broken down by glycolysis Products are further broken down to produce waste product of lactic acid, which causes muscle soreness Only 2 ATP are made! Alcoholic FermentationLactic Acid Fermentation Making ATP without oxygen