Energy for Cells, Photosynthesis, and Respiration Flow of Energy Energy for Cells, Photosynthesis, and Respiration

Energy for Cells: Living organisms need energy to function WHERE DO THEY GET IT? Free Energy: energy available to do biological work Ex. Energy required for muscle contraction Endergonic Reaction: chemical reaction requiring free energy

*Free energy comes from other chemical reactions: Exergonic Reactions: “Energy releasing” *Both reactions must be linked (b/c energy can’t just “wait around”) *Most free energy comes from adenosine triphosphate-- ATP ATP: A-P-P-P *the bonds between P (phosphate groups)  energy released Ex. Hydrolysis: (ATP + H20); last P breaks off  ADP ATP + H20  ADP + Pi + energy

Mini Lab Demonstration: *Can you detect energy released by a biological reaction? Half fill a test tube with 3% hydrogen peroxide. Use a thermometer– take initial temperature. Add a small piece of fresh liver to the tube. Observe what happens. After 1 min., retake temp. What evidence of a reaction did you observe? Was the reaction endergonic or exergonic?

Respiration with Oxygen: *When ATP is used, energy is released. HOW CAN ATP BE REPLENISHED??? *REJOIN ADP and PHOSPHATE to replenish supply of ATP (But need energy to do so) Cellular Respiration: some of energy released by breaking bonds of glucose converts ADP to ATP

*AEROBIC RESPIRATION: requires Oxygen *Cellular respiration is usually aerobic EXERGONIC *First steps occur in cytoplasm; last steps are in mitochondria C6H12O6 + 6O2 + 38 ADP + 38 Pi 6CO2 + 6H20 + 38 ATP *Early steps of breaking down glucose require 2 ATP Thus, a net product of 36 ATP are produced *What’s this mean? 1 glucose molecule  released little by little  lots of ATP

ATP is the cell’s currency!!!!

Anaerobic Processes *absence of oxygen *Some bacteria and muscle cells can switch between aerobic and anerobic processes Lactic Acid Fermentation: *enzymes break down glucose into 2 lactic acid molecules C6H12O6 + 4 ADP + 4 Pi  2CH3CHOHCOOH + 4 ATP Ex. Muscles build up lactic acid during excessive exercise

C6H12O6 + 4 ADP + 4 Pi  2C2H5OH + 2CO2 + 4 ATP Alcoholic Fermentation: plants/ microorganisms *enzymes break down glucose into 2 molecules of ethanol and 2 molecules of CO2 C6H12O6 + 4 ADP + 4 Pi  2C2H5OH + 2CO2 + 4 ATP Ex. Yeast  alcohol, gasoline additives, bubbles  dough rises

Both types use 2 ATP during process-- net product is only 2 ATP!!!

PHOTOSYNTHESIS REVIEW: Producers = plants, algae, & some bacteria *PRODUCERS  absorb energy from Creates chemical energy REVIEW: Producers = plants, algae, & some bacteria

Some light is absorbed; some reflected REVIEW: LIGHT = WAVELENGTHS VISIBLE SPECTRUM= ROY G BIV Some light is absorbed; some reflected Ex. White reflects all

*Light energy  chemical energy due to pigments Ex. Chlorophyll (a) appears green b/c reflects green light Other pigments: CAROTENOIDS: Yellow, orange, and red *absorb other colors/ wavelengths and pass energy to chlorophyll (a) THIS IS WHY LEAVES CHANGE COLOR!!!

PHOTOSYNTHESIS REACTION: 6CO2 + 6H20  C6H12O6 + 6O2 * “” involves enzymes, chlorophyll, and light energy *ENDERGONIC *ultimate source of energy comes from light Place Elodea in two test tubes. Fill test tubes w/ Bromothymol yellow and cover tubes with plastic. Place one tube in direct light and the other in a dark place. Compare in 24 hours. If yellow color is gone, means CO2 is no longer present. MINI LAB 2:

PHOTOSYNTHESIS: 2 PARTS: 1. LIGHT REACTIONS: Chloroplasts: electrons absorb energy/ move to higher energy levels 3 MAIN EVENTS: 1. Light energy absorbed and converted to chemical energy in bonds of ATP Water splits into H ions, O, and electrons H ions from water  attach to carrier coenzymes for later use

2. CALVIN CYCLE: *Occurs in fluid of chloroplast *Synthesizing sugars REVIEW: WHAT ELEMENTS MUST BE PRESENT FOR SUGARS TO BE MADE? Light reactions provide H ions and ATP + CO2  3 carbon sugars  6 carbon sugars  more complex

ENERGY RELATIONSHIPS Thus, a CONTINUOUS CYCLE is NECESSARY!! *PLEASE REFER TO PAGE 160 **Photosynthesis is the opposite of respiration **These processes are INTERDEPENDENT: reactants of one are products of the other *Sugars are broken down in cellular respiration (ATP used) ATP can’t be recycled– some given off as heat as well Thus, a CONTINUOUS CYCLE is NECESSARY!!

THE END!