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:
CO2
6 CO2
carbon dioxide
Products:
H2O
6 H2O
water
C6H12O6
C6H12O6
glucose
6 O2
O2
oxygen gas
Formula of cellular respiration: (from last week)
Inputs:
C6H12O6
glucose
Products:
6 O2
oxygen gas
6 CO2
carbon dioxide
6 H2O
water
Nature Recycles: Photosynthesis and Cellular respiration are opposites:
Each one takes the products of the others reactions and uses it for inputs.
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.)
So why are plants green?
Chloroplasts and chlorophyll
Inputs:
Light and Water
Different colors of light are different
wavelengths with different energies.
Chloroplast
Products:
Thylakoids form stacks
called grana
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.
Photosynthesis: dark reactions / Calvin cycle
(convert chemical energy & carbon dioxide into sugars.)
Input:
CO2
This part is called a dark reaction
because it can happen with or
without light.
Chloroplast
Product:
glucose
Stroma is a thick fluid within chloroplast, this is where
enzymes associated with dark reactions occur.
Photosynthetic Pigments
Part 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 Reaction
Part A: 3.
Volumeter
• As part of the light reaction, oxygen is
produced from water.
• 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
3% sodium bicarbonate
(NaCO3)
2-3 fresh Elodea sprigs, cut
end up.
Light source
Beaker filled with water –
heat absorber
Photosynthesis: Light Reaction
Part A: 3.
Volumeter
• 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.
water
3% sodium bicarbonate
(NaCO3)
2-3 fresh Elodea sprigs, cut
end up.
Wrap in aluminum foil.
Light source
Beaker filled with water –
heat absorber
Uptake of Carbon Dioxide
Part B
Blow into straw
Beaker filled with water and
phenol red (red = basic).
Yellow = acidic
CO2 + H2O → H2CO3 → H+ + HCO3−
• Add a sprig (or several) of
Elodea to one of the test
tubes – make sure it is
alive!
• Stopper both tubes.
Uptake of Carbon Dioxide
Part B
• Place the test tubes in
the test tube rack with
the tube from Part A.3
water
Light source
Beaker filled with water –
heat absorber
• Monitor any color change
over time.
• Swirl the tubes occasionally.
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
jerome1.wilson@umconnect.umt.edu. 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.