Light harvesting antenna complexes (AH lect 2)

Question 1

Why are antenna systems required by phototrophs?

Answer 1

to capture light and transfer excitation energy to RC special pair
-increases how much light can be absorbed
-“funnels” energy down to RC

Question 2

What are the properties of a good antenna system?

Answer 2

-wide spectral cross section (from having different pigments)
-high pigment concentrations (for efficient FRET)
-wide spatial cross section (physical area for light capture)
-modularity (more in low light, less in high light)
-arrangement to create “energy trap” (efficient transfer to RC)

Question 3

Primary antenna complexes

Answer 3

Antenna complex directly associated to RC in fixed arrangement and stoichiometry
-can be fused (bound to same polypeptide that RC pigs are bound to) or core (separate but interacting polypeptides)

Question 4

Fused vs core primary antenna complexes

Answer 4

Fused: antenna complex and RC pigments are bound to one polypeptide
-can’t be biochemically separated

Core: antenna complex and RC pigments are bound to separate (but interacting) polypeptides to eachother
-can be biochemically separated

Question 5

Peripheral antenna complexes

Answer 5

Antenna complexes which interact with RC and primary antenna complexes to increase ability to harvest light
-mobile, present in varying amounts and in different variants depending on light intensity/conditions
-intrinsic or extrinsic to membrane