Pigments and Chromatography Video

How does wavelength relate to the color of light?

  • Electromagnetic Spectrum: wavelengths of light admitted from the sun

  • visible light is a part of the EM spectrum —> R.O.Y.G.B.I.V.

  • includes wavelengths 400-750 nm (range that human eyes can detect)

  • Violet has shorter wavelengths —> Red has longer wavelengths

Pigments: molecules that absorb light

Describe how absorption and reflection are related:

  • wavelengths that are NOT absorbed are reflected —> those are the colors we perceive

3 Pigments:

  • Chlorophyll: major photosynthetic pigment of the three

  • Xanthopyll —> accessory pigment

  • Carotenoids —> accessory pigment

Identify which colors of light chlorophyll absorbs and which colors of light it reflects?

  • Two types of Chlorophyll: a/b

  • reflects green light & absorbs most other colors of light (wavelengths)

    • causes chloroplasts/leaves to appear green & absorbed lights to photosynthesize

    • main pigment in plants

Absorption Spectrum: shows the different wavelengths of light absorbed by a particular pigment/substance

  • peaks: high absorption

  • each line represents ONE TYPE of pigment

How does light absorption relate to the rate of photosynthesis:

  • plants have several different types of pigments, so the overall rate of photosynthesis is a result of a combination of ALL the pigments absorbing light

  • more light absorption by pigments = higher rate of photosynthesis

Describe how the absorption spectrum differs from the action spectrum:

  • Absorption spectrum graphs are only ONE pigment, but the Action spectrum takes into account ALL the pigments present w/in the chloroplasts

Paper Chromatography: lab technique used to separate mixtures of substances as they move up the paper

  • substances: pigments extracted from plants

  • AKA thin paper chromatography

Outline how pigments are separated during paper chromatography:

  • pigments are dissolved in a solvent & will separate based on their solubility

    • the more soluble the pigment, the further it will travel up the paper

  • as the solvent travels, the pigments travel w/ it

Retention Factor (Rf): ratio of the distance moved by a pigment to the distance moved by the solvent

  • unique to each pigment in each solvent

  • Rf = distance traveled by sample/distance traveled by solvent

  • does not have units bc mm/mm cancels out

  • measure between the middle of the band

  • Plants in plant houses that use colored light must use a color besides green bc chlorophyll reflects green, color/light needs to be absorbed to perform photosynthesis