Answer:
The type of protein that binds a ligand on the cell surface or within cells are transmembrane receptors. These proteins have 3 domains: an extracellular part that does the binding, a hydrophobic domain that extends through the membrane, and an intracellular region that transmits the signal. The most common membrane-anchored receptors are: G protein-coupled receptors, receptor tyrosine kinases, and ligand-gated ion channels.
Answer:
Option A, accumulate sulfur as intracellular granules.
Explanation:
Purple sulfur bacteria belong to the group of Proteobacteria. These probacterias are anaerobic in nature and yet are able to photosynthesise. They are usually found in water environments such as hot springs, stagnant water etc. They use sulphur (either in the form of sulfide, or thiosulfate) as an electron donor in their photosynthetic activity to oxidise sulfur thereby producing granules of elemental sulfur.
while filamentous sulfur oxidizers use nitrate instead of oxygen to oxidize sulfide thereby producing granules.
Hence, option A is correct.
