Question

which of the following processes requires a cell to expend energy?
osmosis
protein pump (active transport)
diffusion
facilitated diffusion
question 14
1 pts
the plasma membrane is described as being selectively or semi - permeable, which means:
it has a permanent structure
only certain things can pass through it
nothing can pass through it
everything can pass through it

Explanation:

• For the first question: Osmosis is the movement of water across a semi - permeable membrane from an area of high water concentration to an area of low water concentration. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration. Facilitated diffusion is a type of passive transport where molecules move across the membrane with the help of transport proteins (but still down the concentration gradient). Active transport (protein pump) moves molecules against the concentration gradient and requires energy (usually in the form of ATP).
• For the second question: The plasma membrane is made up of a phospholipid bilayer with embedded proteins. It is not a rigid, permanent structure. It is not impermeable (so “nothing can pass through it” is wrong) and it is not freely permeable (so “everything can pass through it” is wrong). The term “selectively or semi - permeable” means that only certain substances (based on size, charge, solubility etc.) can pass through it.

Answer:

• First question: protein pump (active transport)
• Second question: only certain things can pass through it