5.2 Photosynthesis

Chloroplasts

- average green plant cell contains 10-50 chloroplasts

-space between inner and outer memebrane is called the chloroplast envelope

-thylakoids are membrane discs that stack to form a granum which is part of the membrane system inside of the chloroplast called the grana

-chlorphyll is found on the thylakoid membranes

-grana are joined by lamallae which are extensions of the thylakoid membranes

-the lamallae act as a skeleton w/in the chloroplast to maintain enough distance between between the grana in order for them to get the max amount of light to function efficiently

Chlorophyll

-is a pigment made up of other cloely related pigments, inc chlorophyll a, chlorophyll b, carotenoids and a grey pigment call phaeophytin

-chlorophyll a is found in all photosynthesising plants and is the most abundant of all the pigments

-each of the pigments absorbs and captures light from different areas of the light spectrum

-meaning more the max amount of light that falls on the plant can be used

Absorption spectra and action spectra

-absorption spectra= range of the amount of light of different wavelengths that a photosynthetic pigment absorbs

-action spectra= a graph shpwing rate of phtotosynthesis against the wavelength of light

-action spectra show us that the rate of photosynthesis is closely related to the absorption spectra of all of the different types of pigments

Chromatography

-grinding up plant material with propanone then placing it on chromatography paper with a solvent on a seeing the different pigments travel up the paper

-seperates the photosynthetic pigments

-Rf vale= distance travelled by photsynthetic pigment/distance travelled by solvent

-the Rf value should always be somewhere between 0 and 1

Photosystems

-the pigments carry out the absorption of light in 2 chlorophyll complexes

-PS1 and PS2

-PS1 absorbs w.l. @ 700nm and PS2 absorbs w.l of light @ 680nm

-they are different sized particles attached to the membranes in the chloroplast

-PS1 are mainly on the intergranal lamallae while PS2 are mainly on the actual grana

Light-Dependent stage of photosynthesis

-takes place on the thylakoid membranes

-has 2 main funtions…