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Lab 7: Photosynthesis
10/27/2015
Basics of Photosynthesis
Photosynthesis: process that transforms light energy into chemical energy.
occurs on land and in water
performed by autotrophic plants, algae, and bacteria
Formula of photosynthesis
Inputs: Products:
6 O2oxygen gas
C6H12O6glucose
6 CO2carbon dioxide
6 H2Owater
Formula of cellular respiration: (from last week)Inputs: Products:
6 CO2carbon dioxide
6 H2Owater
6 O2oxygen gas
C6H12O6glucose
Nature Recycles: Photosynthesis and Cellular respiration are opposites: Each one takes the products of the others reactions and uses it for inputs.
6 O2oxygen gas
C6H12O6glucose
6 CO2carbon dioxide
6 H2Owater
Photosynthesis: Road Map
Photosynthesis can be divided into two parts:
1. Light Reactions
2. Dark Reactions
Light reactions: convert solar energy to chemical energy.
Dark reactions: convert chemical energy and carbon dioxide into sugars
Photosynthesis: light reactions(convert solar energy to chemical energy.)
Different colors of light are different wavelengths with different energies.
Inputs:Light and
Water
Products: O2
Chloroplasts are organelles that absorbs light in plant tissue. Green color in chloroplast comes from chlorophyll – light absorbing pigment. thylakoids which are membranous sacs forming stacks called grana.
Chloroplast Thylakoids form stacks called grana
So why are plants green? Chloroplasts and chlorophyll
Photosynthesis: dark reactions / Calvin cycle(convert chemical energy & carbon dioxide into sugars.)
This part is called a dark reaction because it can happen with or without light. Input:
CO2
Product:glucose
Stroma is a thick fluid within chloroplast, this is where enzymes associated with dark reactions occur.
Chloroplast
Photosynthetic PigmentsPart A: 2.
Remember: chlorophyll is a light absorbing pigment. However most chloroplasts contain 4 or more different pigments. These pigments show up as the different colors in fall leaves.
Paper Chromatography:Allows us to separate out each pigment based on molecular size. Smaller pigments travel further up the paper than larger ones. We can identify the pigments by color.
Photosynthesis: Light ReactionPart A: 3.
• As part of the light reaction, oxygen is produced from water.
Volumeter
3% sodium bicarbonate (NaCO3)
2-3 fresh Elodea sprigs, cut end up.
Beaker filled with water – heat absorber
Light source
• Mark the solution front on the glass tube initially and when you first notice movement start timing 10 minutes.
• After 10 minutes mark front again and measure the distance in mm.
water
Photosynthesis: Light ReactionPart A: 3.
• Then carefully pick up tube being sure not to disturbing the stopper or bent tube.
• Wrap the tube in aluminum foil.• Place back into the light.• Wait 10 minutes and mark where the
front is, then measure the distance in mm.
Volumeter
3% sodium bicarbonate (NaCO3)
2-3 fresh Elodea sprigs, cut end up.
Wrap in aluminum foil.
Beaker filled with water – heat absorber
Light source
water
Uptake of Carbon DioxidePart B
Blow into straw
• Add a sprig (or several) of Elodea to one of the test tubes – make sure it is alive!
• Stopper both tubes.
Beaker filled with water and phenol red (red = basic).
CO2 + H2O → H2CO3 → H+ + HCO3−
Yellow = acidic
Uptake of Carbon DioxidePart B
• Monitor any color change over time.
• Swirl the tubes occasionally.
Beaker filled with water – heat absorber
Light source
water
• Place the test tubes in the test tube rack with the tube from Part A.3
To do:• Lab reports• Visual aid for bioethics presentations will be due in 2 weeks
– “Visual aids are due before the beginning of class the week of Nov. 4. So if you have Thursday lab at 12:00 pm on Nov 7, it’s due Thurs, Nov. 7 at 11:59 am. You may email your electronic slide to [email protected]. In addition, please bring to class a copy of your visual aid on a thumb drive on the day you present.”
• Research paper topics – due next week on quiz!!• For quiz:
– What are inputs and outputs of cellular respiration? Photosynthesis? Know the formulas!
– What is the purpose of the light reactions? The dark reactions? Why are they called light and dark reactions, respectively?
– What happened to the water in the volumeter in part A 3 when the Elodea was in the light? In the dark? WHY? Be sure your answer to ‘why’ is in terms of the inputs and products of photosynthesis and respiration.
– What happened to the color of the acidified solution in part B when Elodea was photosynthesizing? WHY? Be sure your answer to ‘why’ is in terms of the inputs and products of photosynthesis.