Who is responsible for our current climate change? why?
a. humans, increased release of co2 from burning fossil fuels.
b. it is natural, it has happened at the same rate before.
c. we don’t know, there is no scientific evidence for it.
d. asteroids, when they burn up in the atmosphere they release chemicals that trap heat.

What is the significance of the protein-lined pits? a. protein attracts other proteins needed for atp synthesis within the cell. b. protein-lined pits are able to transport one molecule at a time down the concentration gradient within the cell. c. the polarity of proteins allows other polar molecules to attach and be transported in the cell by transport channels. d. receptors within the pits allow ligands to fuse and be transported into the cell by endocytosis.