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physio lab exp#9
Luminescence
| Question | Answer |
|---|---|
| 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
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