5.
Gated channel proteins can NOT be opened by which of the
following?
a
Chemical or electrical signals
b Temperature
c Mechanical force
All of the above can open gated channel
proteins

Which of the following is a reason why early living organisms on earth could not have survived on the surface? 1. the lack of an ozone layer 2. the lack of oxygen in the atmosphere 3. the fact that these organisms were single-celled