8.2

8.2 Summary
LIGHT REACTION
-light energy
-electromagnetic energy travel in waves
-Wavelength- distance between 2 waves
-electromagnetic spectrum: range of type of rays (short to large)
-pigments: chemical compounds that causes color.
-chloroplast allows some to pass through and others to reflect
-green reflects, causing the color of the leaves.
-paper chromatography can be used to observe the different pigments in a leaf.
-photosystems contain hundreds of pigment molecules, which act like light gathering panels
-when energy is absorbed, electron gain and lose energy while the energy bounce from place to place and is finally trapped by the primary electron acceptors.

8.2 Vocabulary
Wavelength is the distance between 2 adjacent waves.
Electromagnetic spectrum is the range in types of electromagnetic energy from the short gamma rays to the long radio waves.
Pigments are what make a substance’s color.
Paper chromatography is a laboratory technique that can be used to observe the different pigments in a green leaf.
Photosystems are clusters within the thylakoid membrane hat chlorophylls and other molecules are arranged in.

8.2 Concept Check
1. Explain why a leaf appears green.
A leaf appears green because chloroplast pigments do not absorb green light well, causing the green light to bounce back (reflect) and not to be absorbed.
2. Describe what happens when a molecule of chlorophyll a absorbs light?
When a molecule of chlorophyll absorbs light, one of the pigment’s electrons will gain energy, but since the high energy stage is unstable, it will fall to a low energy state again, which will transfer its energy to the next electron. After a while, the energy will arrive at the center of the photosystem, which will cause the electron accepter to trap the excited electron from the chlorophyll a molecule.
3. Besides oxygen, what two molecules are produced by the light reactions?
Besides oxygen, NADPH and ATP and produced by light reactions.
4. Where in the chloroplast do the light reactions take place?
The light reactions take place in the thylakoid membranes in the chloroplast.