Chapter 9

 Energy: the ability to do work  In cells, energy is in the chemical form  The stored chemical energy in cells is called ATP, or adenosine triphosphate  Energy is released when ATP is converted into ADP + a phosphate group

PPlants and animals obtain energy in different ways: ◦P◦Plants ONLY: make their own energy through the process of photosynthesis ◦P◦Plants and Animals: get ATP by breaking down organic compounds (proteins, carbs, etc.) through the process of cellular respiration

PPhotosynthesis: the conversion of light energy into chemical energy ◦O◦Occurs in chloroplasts ◦R◦Reactants (IN): CO 2, H 2 O, and energy ◦P◦Products (OUT): O 2 and glucose (C 6 H 12 O 6 ) ◦6◦6CO 2 + 6H 2 O + light energy → C 6 H 12 O 6 + 6O 2

 1) Light Reactions (“photo”) ◦ Occurs in thylakoid ◦ Light from sun excites electrons ◦ O 2 is released  2) Calvin Cycle (“synthesis”) ◦ Occurs in stroma ◦ CO 2 is used to make glucose (C 6 H 12 O 6 )

 Plant and animal cells make ATP by breaking down organic molecules (sugars, fats, etc.)  This process is called Cellular Respiration ◦ Occurs in the mitochondria ◦ Reactants (IN): C 6 H 12 O 6 (glucose) & O 2 ◦ Products (OUT): CO 2 & H 2 O & ATP (energy) ◦ C 6 H 12 O 6 + 6O 2 → 6CO H 2 O + 36 ATP

BBegins with Glycolysis ◦1◦1 molecule glucose is split in half into 2 pyruvate molecules IIf O 2 is present → Citric Acid (Kreb’s) Cycle & Electron Transport Chain IIf O 2 is NOT present → Fermentation

OOccurs when no O 2 is present 22 Types: ◦1◦1. Lactic Acid Fermentation: Converts pyruvate → lactic acid HHelps make yogurt & cheese CCreates burning sensation in muscles during exercise ◦2◦2. Alcoholic Fermentation: Converts pyruvate → ethyl alcohol HHelps make bread, wine & beer

OOccurs when O 2 is present BBreaks down pyruvate molecules (from glycolysis) into smaller molecules AAs chemical bonds form and break, electrons get moved around & CO 2 is released TThis releases energy, thus making ATP!