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physio lab exp#9

Luminescence

QuestionAnswer
Luminescence light that usually occurs at low temperatures and is thus a form of cold body radiation
Luminescence can be caused by what three things? by chemical reactions, electrical energy, and subatomic motions
Incandescence: heat-driven light emissions as a result of electron displacement. EX: light bulb
How is light produced? The electron displacement (from excited electrons moving from ground state to outer orbital shells and back) emits energy in the form of visible light
What are three types of luminescence. Triboluminescence, Chemiluminescence, and Bioluminescence
Triboluminescence an optical phenomenon in which light is generated through the breaking of chemical bonds in the material. (when material is pulled apart, ripped, scratched, crushed, or rubbed)
For our experiment, triboluminescence is caused by what? the separation and reunification of electrical charges.
During the crystallization process both + and - charges are separate. When you chew on them what happens to these charges ? they come into close proximity which produces the sparks in your mouth.
Triboluminescence occurs when molecules (crystalline sugars) are crushed, forcing e- out of their atomic fields. These free electrons then do what? collide into N molecules in the air. When they collide, the electrons impart energy to the N molecules, causing them to vibrate.
In this excited state, and in order to get rid of the excess energy, these nitrogen molecules emit ultraviolet light. This ultraviolet light fluoresces when it hits the __________ ___, (methyl salicylate), and produces the visible sparks. wintogreen oil
Chemiluminescence the emission of light as the result of a chemical reaction
Luminol (C8H7N3O2) + K4Fe(CN)63H2O + H2O2 ==> Oxidized Luminol + Blue light For this reaction, what is the oxidizing agent and what is the reducing agent? H2O2 is the oxidizing agent and potassium hexacyanoferrate is the reducing agent.
OIL: Oxidation Is a Loss of electrons
RIG: Reduction Is a Gain of electrons
An atom that is itself oxidized is causing another atom or atoms to be reduced is called a _________ _____ reducing agent or reductant
An atom that is itself reduced is causing another atom or atoms to be oxidized is called an _________ _____ oxidizing agent or oxidant.
Fe + 2HCl => FeCl2 + H2: What are the oxidizing/reducing agents? Fe is the reducing agent; HCl is the oxidizing agent
Redox reaction for oxidation (Fe + 2HCl => FeCl2 + H2) Fe => Fe2+ + 2e-
Redox reaction for reduction (Fe + 2HCl => FeCl2 + H2) 2H+ + 2e- => H2
Oxidation state of Fe changes from ___ to ___ (Cl- is unchanged) 0 to +2
what are two ways to manipulate the blue light caused by chemiluminescence? to diminish (quench) the light or enhance the light
Diminish (quench) the light by doing what? adding HCl
how does this quench the light? HCl shifts the reaction to the left, disfavoring the forward reaction and hence immediately quenching the light.
Enhance the light by doing what? adding 1N NaOH
how does this enhance the light? NaOH enhances the ability of the luminol to be oxidized by H2O2, so the reaction shifts to the right favoring oxidation and hence enhancing the light.
What is the objective of Chemiluminescence II? to determine composition of each dye
What were the three unknown dyes (D, E and F) ? 1. Fluorescein (Yellow) 2. Rhodamine B (Rose) 3. Eosin Y (Orange)
To each unknown dye (D, E, and F) we add reagents C and G. What is C? luminol + DMSO (dimethylsulfoxide)
To each unknown dye (D, E, and F) we add reagents C and G. What is G? saturated NaOH(add one drop with Pasteur Pipette)
Bioluminescence light that is carried out by living organisms. Ex: Firefly mating rituals
Luciferin + O2 + ATP + Luciferase + Mg2+ => Oxyluciferin + AMP + PPi + H2O + Light Where does Luciferin come from for our experiment? Luciferin comes from firefly lantern extract
The cells of the firefly are called __________ PHOTOCYTES
The luciferase enzyme works optimally at what pH level? 7.4
Any shift in pH causes what? the visible light to quench
What two solutions did we add to quench the light? NaOH and HCl
the salt, NaCl, dims and eventually quenches the light. Since it has no effect on pH, how does this work? Chloride ions bind the Mg2+, so enzyme becomes catalytically inactive, (apoenzyme) reaction does not occur; so the light does not persist.
what must be present with the enzyme to make the enzyme catalytically active? cofactors! => Divalent metal cations (Mg2+, Zn2+, Fe2+, Mn2+)
apoenzyme enzyme without its cofactor.
Holoenzyme enzyme with its cofactor
Luminol is used by forensic investigators for what? to detect trace amounts of blood left at crime scenes as it reacts with iron found in hemoglobin.
Luminol is used by biologists in cellular assays for what? the detection of copper, iron, and cyanides.
summary: Electrons prefer to be where?? at a lower, stable energy state
summary: Sucrose causes visible sparks when what? the charges of the sugar molecule come together
summary: Acids and bases effects on bioluminescence light quenches the light
summary: Strong bases effects on chemiluminescence light. enhances the light
summary: ________ are necessary for a catalytically active enzyme. Cofactors
Created by: cmccartney2