Pigments in plants Flashcards
What are pigments?
-They’re molecules that absorb light energy in the visible range
What are Photons?
- A particle of light
- They act like a discrete bundle of energy
What type of wavelengths have higher energy?
-Shorter wavelength photons have higher energy vs the longer wavelength photons which have lower energy
What is the Photoelectric Effect?
- It occurs when a beam of light is able to remove electrons from certain molecules= creating an electrical current
- SO when photons transfer energy to electrons
What is the strength of the Photoelectric effect dependent on?
- It depends on the wavelength of light
- SO shorter wavelengths are much more effective bc they have higher energy than longer wavelengths
How do Chloroplasts act like photoelectric devices during photosynthesis?
-They absorb sunlight & transfer the excited electrons to a carrier
What happens when a photon strikes the molecule w/ the amount of energy needed to excite an electron?
-The molecule will absorb the photon= raising the electron to a higher energy level
What 2 things does whether or not the photon energy is absorbed depend on?
-How much energy it carries (defined by wavelength) & the chemical nature of the molecule it hits
Why can atoms only absorb specific light photons?
-Bc atoms have a certain amount of available energy levels= only certain light photons can fill those remaining energy levels
What is the Absorption Spectrum?
- A characteristic that each molecule has
- Which is the range & efficiency of photons it is capable of absorbing
What are the 2 types of pigments used in green plant photosynthesis?
- Chlorophyll
- Cartenoids
What are the 2 kinds of Chlorophylls found in plants?
- Chlorophyll a
- Chlorophyll b
What kind of light does chlorophyll a &b absorb?
- Violet-blue & red light
- But NEITHER of them absorb photons w/ wavelengths between 500 & 600 nm bc these are actually reflected as green
What is Chlorophyll a ?
- So it is the main photosynthetic pigment in plants & cyanobacteria
- It is the only pigment that can act directly to convert light energy to chemical energy
What is Chlorophyll b?
- It acts as an accessory pigment= complements & adds to the light absoprtion of chlorophyll a
- BUT it has an absorption spectrum towards the green wavelengths= can absorb photons that chorophyll a cannot= greatly influences the proportion of photons in sunlight that plants harvest