lesson 8 - absorption of light energy

Question 1

what are photons and what do they do

Answer 1

• when any form of mattter absorbs light energy, the light is absorbed in the form of packets of energy called photons.
• photons carry specific amoutns of energy
• each wavelength/colour of visible light is associated with photons of one distinct amount of energy
• lower wavelength photons have smaller energy
  shorter wavelengths have larger

Question 2

what is wavelength absorption

Answer 2

the nature of the atom or molecule determines the enrgy levels of the electrosn in that atom or molecule
- electrons can absorb a particular photon (colour of light) only if it carries exactly enough energy to allow the elctron to move up to another allowed energy level

Question 3

what are photsynthetic pigments

Answer 3

• photosynthetic pigments is a compound that traps light energy and passes it on to other compounds.
• examples: chlorphyll a and b
  main plant pigments and reflect off green light
• cartenoids
  accesorry plant pigments
  that reflect yellow, orange and red

Question 4

absorbance spectrum

Answer 4

leaves appear green because chlorophyll molecules in leaf cells reflect off green and yellow wavelengths of light and absorb others such as red and blue

Question 5

what are photosystems

Answer 5

-in the thylakoid membranes, chlorophyll and accessory pigments are organized, along with proteins, into two photosystems (i and ii)
- a photosystem is a protein based complex that absorbs light energy
made up of a reaction centre and an antenna complex

Question 6

what are the two major things in photosystems

Answer 6

antenna complex consists of proteins and 250 to 400 pigment molecules
the reaction centre has a small number of proteins and a pair of specialized chlorophyll a molecules
this is the PRIMARY ELECTRON ACCEPTOR

Question 7

whats the antenna complex

Answer 7

• when any pigment molecule absorbs a photon, the moelcule passes the energy unil it reaches the reaction center

Question 8

whast the reaction centre

Answer 8

• when the reaction centre has recieved the energy form the antenna complex, an electron in chlorophyll a becomes excited and has enough energy to burst/passed on to a primar yelectron acceptor.
  this is what begins the light dependent reactions!

Question 9

what is photosystems i and ii

Answer 9

the reaction centre chlorophyll a of photosystem i is called p700 because it has an absorption peak. of 700nm
the reaction centre of chlorophyll a of photosystem ii is called p680 because it has an absoprtion peak of 680nm