How Are They Similar?

A Metabolic Revolution

The Oxygen Revolution

Why was the development of photosynthetic lifeforms so revolutionary?

With more oxygen, life could move onto land and took on larger, more complex and more active forms

Why was this revolution ultimately mutualistic?

How Do Photosynthesis & Respiration Compare?

Comparative Functions PHOTOSYNTHESIS What: Using the energy of the sun, high potential energy glucose is built from water and carbon dioxide CELLULAR RESPIRATION What: High potential energy of glucose is transferred to the bonds of multiple ATP

Comparative Reactants & Products PHOTOSYNTHESIS –6H 2 O + 6CO 2 + Light Energy ->C 6 H 12 O 6 + 6O 2 CELLULAR RESPIRATION (Aerobic) –C 6 H 12 O 6 + 6O 2 -> 6H 2 O + 6CO 2 + ATP

Comparative Multi-Step Processes Photosynthesis –Photolysis – excite electrons with radiant energy, generating ATP and splitting water to provide hydrogen –Calvin Cycle –CO 2 is “fixed” by the leaf and combined with H to make glucose. Powered by ATP from photolysis Aerobic Respiration –Glycolysis – split 6 carbon glucose into two 3-carbon pyruvate –Krebs Cycle – breakdown further to 1-carbon CO 2 –Electron Transport Chain – use electrons from Glycolysis and Krebs Cycle to power the synthesis of ATP

Comparative Locations

Lab: Balance of Photosynthesis & Respiration Purpose: To assess the relative conditions for and rates of photosynthesis and respiration within a single organism Method: Qualitative assessment of pH using Brom-Thymol Blue (an indicator for acids)

Elodea canadensis Canadian waterweed Performs both cellular respiration and photosynthesis under the right conditions

Key Conceptual Points Aerobic respiration produces CO 2 as waste. CO 2 + H 2 O -> H 2 CO 3 (carbonic acid) The Calvin Cycle of photosynthesis effectively “fixes”/removes CO 2 from the system

Tracking The Changes If excess CO 2 enters the system, Brom- Thymol blue will turn yellow, indicating that the solution is now acidic (due to the carbonic acid produced) If CO 2 is removed, the system may shift back from acidic to neutral, indicated by the BTB returning to its normal blue color

What do the results mean? Shift to yellow? CO 2 is being produced faster than it is being removed Respiration > Photosynthesis Shift to blue? CO 2 is being removed faster than it is being produced Respiration< Photosynthesis

Protocol Place 200mL of H 2 O into two different Ehrlenmeyer flasks Obtain BTB from your instructor and add to each flask (appx. 5mL per flask). Using a straw, exhale into one of the flasks until it is acidified, indicated by a shift to yellow

Setting Up The Trials Clean and label your four test tubes Place a sprig of Elodea into test tube 1 and fill the remainder with acidified (yellow) BTB Fill test tube 2 to the top with acidified BTB. Place a sprig of Elodea into test tube 3 and fill the remainder with neutral (blue) BTB Fill test tube 4 to the top with blue BTB

Applying the Variable Lab groups 1-3 will place their bottles in the dark Lab groups 4-6 will place their bottles in the light Reassess color of tubes later.