Question

which of the following is a characteristic of active transport?
it requires the use of transport proteins and cellular energy.
it moves substances down their concentration gradient.
it only involves the movement of water molecules.
it does not require energy input from the cell.

protein pumps are involved in ______ transport because they move molecules against their concentration gradient.
passive
facilitated
osmotic
active

the selective permeability of the cell membrane is crucial for maintaining cellular ______, a stable internal environment.
your answer

how does the cell membrane help maintain homeostasis with respect to the concentration of ions inside and outside the cell?
by actively transporting specific ions against their concentration gradients.
by allowing all ions to move freely across the membrane.
by preventing the movement of all ions across the membrane.
by relying solely on diffusion to balance ion concentrations.

Explanation:

First Question:

To determine the characteristic of active transport, recall: Active transport moves substances against their concentration gradient, requires energy (ATP) and transport proteins. Analyze options:

• "It requires the use of transport proteins and cellular energy" matches active transport (needs energy for against - gradient movement, uses proteins like pumps).
• "It moves substances down their concentration gradient" is passive transport (diffusion, facilitated diffusion).
• "It only involves the movement of water molecules" is osmosis (passive, water movement).
• "It does not require energy input from the cell" is passive transport.

Protein pumps move molecules against their concentration gradient. Active transport is defined as movement against concentration gradient, requiring energy (protein pumps use ATP). Passive transport (including facilitated, osmotic) is down the gradient, no energy. So protein pumps are in active transport.

The cell membrane's selective permeability helps maintain cellular homeostasis (a stable internal environment). Homeostasis is the cell's ability to regulate internal conditions (like ion, nutrient, waste levels) via membrane transport (selective what enters/exits). So the blank is "homeostasis".

Answer:

It requires the use of transport proteins and cellular energy.

Second Question: