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Flashcards in Pigments in plants Deck (27)
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1
Q

What are pigments?

A

-They’re molecules that absorb light energy in the visible range

2
Q

What are Photons?

A
  • A particle of light

- They act like a discrete bundle of energy

3
Q

What type of wavelengths have higher energy?

A

-Shorter wavelength photons have higher energy vs the longer wavelength photons which have lower energy

4
Q

What is the Photoelectric Effect?

A
  • 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
5
Q

What is the strength of the Photoelectric effect dependent on?

A
  • It depends on the wavelength of light

- SO shorter wavelengths are much more effective bc they have higher energy than longer wavelengths

6
Q

How do Chloroplasts act like photoelectric devices during photosynthesis?

A

-They absorb sunlight & transfer the excited electrons to a carrier

7
Q

What happens when a photon strikes the molecule w/ the amount of energy needed to excite an electron?

A

-The molecule will absorb the photon= raising the electron to a higher energy level

8
Q

What 2 things does whether or not the photon energy is absorbed depend on?

A

-How much energy it carries (defined by wavelength) & the chemical nature of the molecule it hits

9
Q

Why can atoms only absorb specific light photons?

A

-Bc atoms have a certain amount of available energy levels= only certain light photons can fill those remaining energy levels

10
Q

What is the Absorption Spectrum?

A
  • A characteristic that each molecule has

- Which is the range & efficiency of photons it is capable of absorbing

11
Q

What are the 2 types of pigments used in green plant photosynthesis?

A
  • Chlorophyll

- Cartenoids

12
Q

What are the 2 kinds of Chlorophylls found in plants?

A
  • Chlorophyll a

- Chlorophyll b

13
Q

What kind of light does chlorophyll a &b absorb?

A
  • Violet-blue & red light

- But NEITHER of them absorb photons w/ wavelengths between 500 & 600 nm bc these are actually reflected as green

14
Q

What is Chlorophyll a ?

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
15
Q

What is Chlorophyll b?

A
  • 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
16
Q

What is the structure of Chlorophylls?

A
  • They contain a complex ring structure= Porphyrin Ring w/ alternating single & double bonds
  • It has a hydrocarbon tail that anchors the molecule to hydrophobic regions of proteins embedded within the thylakoid membrane
  • At the center of the ring is a magnesium atom
17
Q

What is the difference between the structures of Chlorophyll a & b?

A

-Is the substitution of –CHO (aldehyde) group in chlorophyll b for –CH3 (methyl) group in chlorophyll a

18
Q

What happens when photons excite the stucture of Chorophyll?

A
  • So the photons excite the electrons in the Porphyrin ring which are then channeled away through the alternating carbon single & double bond system
  • BUT electrons that ARE NOT associated w/ single atom/ bond are delocalized
19
Q

What 2 factors is the Absorption Spectrum in the Porphyin ring influenced by?

A
  • Influenced by the association of chlorophyll w/ different proteins
  • And the different side groups attached to the outside of the ring
20
Q

What is Action Spectrum?

A
  • The relative effectiveness of different wavelengths of light in promoting photosynthesis
  • It corresponds to the absorption spectrum for chlorophylls
21
Q

Why do plants only rely on chlorophyll instead of retinal pigment in our eyes?

A

-Bc chlorophyll absorbs in only 2 narrow bands w/ higher efficiency= greater energy capture rates

22
Q

What is the structure of Cartenoids?

A

-They consist of carbon rings linked to chains w/ alternating single & double bonds

23
Q

What are Cartenoids?

A
  • They are a pigment that can absorb photons w/ a wide range of energies
  • BUT aren’t always highly efficient in transferring the energies
  • They are found in many organisms including in all the 3 domains of life
24
Q

What is the role of Cartenoids in photosynthesis?

A
  • They capture light energy from light composed of wavelengths that are not efficiently absorbed by chlorophylls
  • They also play a protective role by acting as general-purpose antioxidants to lessen the damage done by redox reactions that generate destructive free radicals
25
Q

How would it be possible for carrots to enhance our vision?

A
  • If carrots were to have a high content of Beta-carotene
  • Bc Beta-carotene consists of 2 Vitamin A molcules joined together, the oxidation of 1 of the vitamin A would produce retinal= pigment used in vertebrate vision
26
Q

What are Phycobiliproteins?

A
  • They are accessory pigments found in cyanobacteria & some algae
  • They can be organized to form a light-harvesting complex that can absorb green light= helps the cyanobacteria in low-light situations in oceans
27
Q

What is the structure of Phycobiliproteins?

A

-They contain a system of altenating double bonds & molecules that transfers electrons