Which of the following statements best describes active
transport?
a. 1o is against the concentration gradient while 2o is with the
concentration gradient and a membrane associated protein must never
be involved; each requires no expenditure of energy by the
cell
b. both 1o and 2o take place with the concentration gradient and a
membrane associated protein must be involved; each requires no
expenditure of energy by the cell
c. a member associated protein must be involved but requires no
expenditure of energy by the cell
d. both 1o and 2o take place against the concentration gradient and
a membrane associated protein must be involved; each requires input
of energy by the cell
e. none of these
Ans : d) both 1o and 2o take place against the concentration gradient and a membrane associated protein must be involved, each requires input of energy by the cell.
The active transport is governed by two basic things : 1) the transport must be against the concentration gradient and 2) the transport must require the input of energy.
Here both the conditions are fulfilled , so the transport is active. When the transport is with the concentration gradient and does not require any input of energy , it is called as passive transport.
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