Transcript What do we have?

Sit with last week’s group
Turn in…
• Dilutions worksheet
Goals
• Consider implications of plants being
‘green’
• Use O2 creation as a measurement of
photosynthesis
• Test a common claim from textbooks
Here’s an assertion…
Photosynthesis in
(green plants) is more
effective at the ends of
the spectrum than in
the middle
Can we test this?
HOW can we test it
• What did we do with leaves last week?
– Leaf assay
– Graph of absorption spectrum
• How did that happen?
• How can you make your data
meaningful?
• How might we subject leaves ONLY to
certain wavelengths?
Getting Started
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Groups 1 & 2: liquid permitting red
light
Groups 3 & 4: liquid permitting green
light
Groups 5 & 6: liquid permitting blue
light
All: make enough to share (yours + 2
others)
Final exp. 20 mLs, so how much to
make?
What will it look like?
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Need to place disks in at same time?
What do you time?
Does concentration matter?
How can you make comparisons valid?
Consider…
• What is the mechanism by which we
are ‘removing’ some wavelengths of
light?
• Implications for volumes of beakers?
• Consequences if red sits waiting while
you work with blue and green
• Again, when should we start extracting
O2?
Buffers
• Ca++ and PO4--  precipitate
• So, TWO different 10X buffer
components
• Add ONE of the them last or get a solid
A tool for making dyes:
Plotulence
Plotulence
Plotulence
Absorbance values
Plotulence
Concentration (_X)
Absorbance values
Plotulence
Concentration (_X)
Absorbance values
Resulting mixture
Your Goal
• Let in as much light as possible for your
‘region’ of the spectrum
– Red: include both 630 & 660
– Blue: 350 & 430
– Green: 500 & 590
• Given the above, block as much as
possible at other wavelengths
• Absorbance no more than .2 at your
wavelengths and no greater than 2 at
other waves
Plotulence
• Use ‘Plotulence’ to develop your dye cocktail
• Again, sliders indicate how much more
concentrated than last week
• Check with other group of same color
• We’re not making artificial hearts or sending
a probe to Mars
Open Plotulence
• On desktop
Plotulence
• ‘Start Table’
• Enter your data
• Use sliders
Red = 630 and 660
Blue = 350 and 430
Green = 500 and 590
Absorbance no more than 0.2 at your wavelength and
no greater than 2 at other wavelengths!!!!
Plotulence
Concentration ( e.g., 1.35X )
Absorbance values
mixture
Resulting mixture
absorbances
What do we have?
• Starting concentration of dyes/buffers?
What do we have?
• Starting concentration of dyes/buffers?
– 10X
What do we have?
• Starting concentration of dyes/buffers?
– 10X
• Final volume?
What do we have?
• Starting concentration of dyes/buffers?
– 10X
• Final volume?
– 100 mLs (how much of it is buffer?)
What do we have?
• Starting concentration of dyes/buffers?
– 10X
• Final volume?
– 100 mLs (how much of it is buffer?)
• Desired dye concentrations?
What do we have?
• Starting concentration of dyes/buffers?
– 10X
• Final volume?
– 100 mLs (how much of it is buffer?)
• Desired dye concentrations?
– Yes, we have that, too! – slider values
What do we have?
• Starting concentration of dyes/buffers?
– 10X
• Final volume?
– 100 mLs (how much of it is buffer?)
• Desired dye concentrations?
– Yes, we have that, too! – slider values
• What are we missing?
What do we have?
• Starting concentration of dyes/buffers?
– 10X
• Final volume?
– 100 mLs (how much of it is buffer?)
• Desired dye concentrations?
– Yes, we have that, too! – slider values
• What are we missing?
– Indv. dye volumes
What do we have?
• Starting concentration of dyes/buffers?
– 10X
• Final volume?
– 100 mLs (how much of it is buffer?)
• Desired dye concentrations?
– Yes, we have that, too! – slider values
• What are we missing?
– Indv. dye volumes
• What makes up the rest?
What do we have?
• Starting concentration of dyes/buffers?
– 10X
• Final volume?
– 100 mLs (how much of it is buffer?)
• Desired dye concentrations?
– Yes, we have that, too! – slider values
• What are we missing?
– Indv. dye volumes
• What makes up the rest?
– Distilled water
Mix It
• Remember there are TWO ‘buffers’
– Do not place at same time – ONE goes last
• Compare your plan to other group’s
• Mix your color
• Trade ‘colors’ with your friends; collect all
three!!!!
• Get your disks
• Float ‘em
• Controls?
What if one ‘color’ is darker?
• What can we do to account for differences in
the AMOUNT of light allowed through the
solution? HOW?
What if one ‘color’ is darker?
• Test your color using specs
• Graph (from lab manual) your data using
smoothed curves
• Cut out the graph ABOVE line
• Weigh it; record it; compare it
• What does that number represent?
• Y-axis:4th major line from bottom as 2.0 abs
• X-axis: each major line is 100nm; plot 300700 nm
• Give your graph weight to ‘sharing’ groups!
What Now?
• Did you find what you expected?
• Stones left unturned?
• Differences in graph weights?
– Red, graph 3g, floated in 5 min
– Blue, graph 2g, floated in 7 min
• Adjusted time?
This is a critical part of your experiment.
Failure to explain and deliver this
calculation = loss of points on write up