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… Can we test this? Photosynthesis in (green plants) is more effective at the ends of the spectrum than in the middle

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?

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? Getting Started

What will it look like? 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

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 Resulting mixture absorbances mixture

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:4 th major line from bottom as 2.0 abs X-axis: each major line is 100nm; plot 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