Unit 3 Chapter 5 Energy and Life

Essential Questions 1. What is a catalyst and how is it important to living things? 2. What is the lock-and-key model? 3. How do living things get energy? 4. What is ATP? 5. What are the steps of photosythesis? 6. How does photosythesis provide energy to all living things? 7. What is cellular respiration and why is ti important to living things?

5-1 Catalysts  Catalysts: compounds that speed up chemical reactions  activation energy: activates the reactants and triggers a chemical reaction  “start-up” energy  heat can provide activation energy, but may cause other reactions

Enzymes  enzymes: biological catalysts  Proteins  they provide a way for chemical reactions to occur at normal temperature  does not supply activation energy, but it lowers the energy requirement barrier  each enzyme is specific to one reaction  Always recycled  pH and temp can affect function

How Enzymes Work  the shape of the enzyme fits the shape of only particular reactant molecules  substrate - a specific reactant acted upon by an enzyme  active site - the substrate fits into a particular region of the enzyme  can change shape slightly to fit snugly  will accept two substrates into adjacent sites

5-2 Cells and Energy  Food  Water Cycle  Climate

ATP  ATP: adenosine triphosphate  Adenosine = adenine + ribose  Triphosphate = 3 phosphates  One phosphate is lost in a chemical reaction  ATP --> ADP  The molecule that accepts the phosphate undergoes a change (for work)

5-3 Photosynthesis CO 2 + H 2 O + sunlight --> O 2 + glucose Uses the sun’s energy to make food (glucose)

Step 1: Capturing the Sun’s Energy  Takes place in the Chloroplast  thylakoids: many disk- shaped sacs  chlorophyll: chemical compound that gives green color

Step 2: Using the Sun’s Energy to Form ATP  The energy from the sun is converted to ATP molecules  Water is used to make oxygen

Step 3: Making Carbohydrates Calvin Cycle  “Light- independent reactions”  Makes sugar from CO 2  Enzymes located in stroma  ATP from light reactions provides energy

5-4 Cellular Respiration  cellular respiration: chemical process by which food molecules are broken down to provide Energy for the cell (ATP) C 6 H 12 O 6 (glucose) + O 2 --> H 2 O + CO 2 + energy

CR takes place in the Mitochondria  Mitochondria  Envelope of 2 membranes; inner and outer with space  Inner membrane encloses thick fluid (matrix)  Enzymes and other molecules built into inner membrane  Complex folding allows many sites of reactions to maximize ATP production

Stage 1: Glycolysis  “splitting of sugar”  Outside the mitochondria in the cytoplasm  One glucose molecule breaks down into 2 smaller pyruvate molecules  Also makes 2 ATP

Cellular Respiration is like a Car Engine  high chemical energy = glucose and oxygen (gasoline and oxygen)  “exhaust” = carbon dioxide and water  40% from food to work  60% thermal energy as heat = 100W light bulb

Stage 2: Oxidative Respiration  Uses oxygen to produce 34 ATP’s  Finishes breakdown of pyruvic acid molecules to CO 2 which releases more ATP  Includes Kreb’s Cycle and Electron Transport Chain

Fermentation in Animals  fermentation: process that can make ATP without oxygen (only 2 ATP)  anaerobic: environment without oxygen  Produces waste product called lactic acid  Temporary build-up results in soreness & fatigue  Eventually converts back into pyruvic acid

Fermentation in Microorganisms  Yeast is forced to ferment sugar  Produces alcohol and CO 2, not lactic acid  Some fungi and bacteria produce lactic acid  Transform milk into cheese and yogurt  Oxygen allows most energy from food  Much more efficient  38 ATP (w/oxygen) vs. 2 ATP (w/out)