Photosynthesis and Cellular Respiration Lab

“Photosynthesis and Cellular Respiration Lab” PHOTOSYNTHESIS PART I: THE SUN AND LIGHT Not all of the light from the Sun makes it to the surface of the Earth. Even the light that does make it here is reflected and spread out. The little light that does make it here is enough for the plants of the world to survive and go through the process of photosynthesis. Light is actually energy, electromagnetic energy to be exact. When that energy gets to a green plant, all sorts of reactions can take place to store energy in the form of sugar molecules. PART II: THE CHLOROPLAST Photosynthesis happens in the chloroplast. Within this cell organelle is the chlorophyll that captures the light from the Sun. We'll talk about it in a bit, but the chloroplasts are working night and day with different jobs. The molecules are moved and converted in the area called the stroma. PART III: THE MOLECULES Chlorophyll is the magic compound that can grab that sunlight and start the whole process. Chlorophyll is actually quite a varied compound. There are four (4) types: a, b, c, and d. Chlorophyll can also be found in many microorganisms and even some prokaryotic cells. However, as far as plants are concerned, the chlorophyll is found in the chloroplasts. The other big molecules are water (H2O), carbon dioxide (CO2), oxygen (O2) and glucose (C6H12O6). Carbon dioxide and water combine with light to create oxygen and glucose. That glucose is used in various forms by every creature on the planet. Animal cells require oxygen to survive. Animal cells need an aerobic environment (one with oxygen). PART IV: LIGHT AND DARK REACTIONS The whole process doesn't happen all at one time. The process of photosynthesis is divided into two main parts. The first part is called the light dependent reaction. This reaction happens when the light energy is captured and pushed into a chemical called ATP. The second part of the process happens when the ATP is used to make glucose (the Calvin Cycle). That second part is called the light independent reaction. CELLULAR RESPIRATION Respiration is a three-step process that includes glycolysis, the Krebs cycle, and a bunch of electrons being pushed around the membranes of mitochondria. Together they take that energy out of the sugar-related molecules. Glucose is combined with oxygen and releases usable energy, carbon dioxide, and water. C6H12O6 + O2--> Usable Energy (ATP) + CO2 + H2O Cells can use that extra energy to power their functions. The energy isn't just floating around. It's stored in an excitable compound called ATP (adenosine triphosphate). ATP is the power molecule used by all the cells of an organism to power the secondary reactions that keep us alive. You may also hear about other power molecules like NADH, NADPH, or FADH. These are equally important as ATP, but they are used less often. We exhale carbon dioxide when we breathe. That CO2 comes from the breakdown of glucose in our mitochondria. As we just told you, plants can take in that carbon dioxide and use it to make sugars. Did you know that plants also create CO 2? They might not breathe it out the way we do, but plants need energy too. They break down sugars in their cells and release CO2 just like us. Prelab Questions 1. Write out the chemical equations for photosynthesis and cellular respiration. Examine both equations and note any similarities and differences you see. 2. In which organelles do photosynthesis and cellular respiration occur? 3. What gases do we inhale and exhale? What gases do plants take in and release? 4. Predict what would happen to a snail if we sealed it in a test tube. Experimental Question: What nutrients and reactants are needed for plants and animals to carryout photosynthesis and/or cellular respiration? Hypothesis: Procedure 1. 2. 3. 4. Obtain glass test tubes or vials and label with the appropriate letter (A,B,C,D, E, F, G, H). Add the assigned quantity of snails and/or piece of aquatic plant. Fill your test tube ¾ full of water from the aquarium. Add 10-15 drops of BTB solution to your test tube. 5. Place your test tubes in the appropriate conditions where they will remain for a couple days. Data Photosynthesis and Respiration in Various Conditions Tube Tube A: BTB only with light Tube B: BTB only without light Tube C: BTB, 1 inch piece of plant, with light Observations Tube D: BTB, 1 inch piece of plant without light Tube E: BTB, 1 inch piece of plant, 2 snails with light Tube F: BTB, 1 inch piece of plant, 2 snails without light Tube G: BTB, 2 snails with light Tube H: BTB, 2 snails without light Conclusions 1. Compare and contrast the tubes placed in the light and dark conditions. Explain the changes observed and be sure to make reference to photosynthesis and cellular respiration in your response. 2. How do plants and animals rely on each other to perform photosynthesis and cellular respiration? 3. Do plants and animals carry out cellular respiration and/or photosynthesis. Support your response with data from the experiment. 4. Propose any sources of error that may have affected the outcome of the experiment. Extension 1. If all the mitochondria in the world stopped functioning, how would the Earth’s atmosphere change? 2. If all chloroplasts in the world stopped functioning, how would the global ecosystem change?