Question

1. when molecules diffuse across the cell membrane, do they move down the concentration or against the concentration gradient? does it need energy?
2. draw arrows in the picture below to show which way the molecules will diffuse across the cell membrane.

a)
facilitated diffusion
what is the difference between diffusion and facilitated diffusion? (hint: look at the picture below)
osmosis

1. what is osmosis?
2. does water move down the concentration gradient or against the concentration gradient?
3. look at the picture of a solution below. what type of solution is this? which way will the solute particles move?

Explanation:

Step1: Answer diffusion - related questions

Molecules move down the concentration gradient during diffusion and it does not require energy.

Step2: Draw diffusion arrows

For the given picture in question 2, arrows should be drawn from the area of higher - molecule concentration (inside the box) to the area of lower - molecule concentration (outside the box).

Step3: Differentiate diffusion and facilitated diffusion

Diffusion is the passive movement of molecules from high to low concentration directly through the membrane. Facilitated diffusion also moves molecules from high to low concentration but uses carrier proteins in the membrane.

Step4: Define osmosis

Osmosis is the diffusion of water across a semi - permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Step5: Determine water movement in osmosis

Water moves down its own concentration gradient (from higher water concentration to lower water concentration) which is equivalent to moving from lower solute concentration to higher solute concentration.

Step6: Analyze solution type and solute movement

Without seeing the full details of the solution picture in question 3, in general, if it's a hypertonic solution, water moves out of the cell and solute particles may not move across the semi - permeable membrane easily; in a hypotonic solution, water moves into the cell; in an isotonic solution, there is no net movement of water. If the membrane is permeable to solutes, they will move down their concentration gradient.

Answer:

1. Molecules move down the concentration gradient during diffusion and it does not need energy.
2. Arrows should be drawn from inside the box (higher molecule concentration) to outside the box (lower molecule concentration).
3. Diffusion is passive movement of molecules directly through the membrane; facilitated diffusion uses carrier proteins in the membrane while also moving from high to low concentration.
4. Osmosis is the diffusion of water across a semi - permeable membrane from lower solute concentration to higher solute concentration.
5. Water moves down its own concentration gradient (from lower solute to higher solute concentration).
6. Without full details of the solution picture, in general, water moves according to the tonicity of the solution and solutes move down their concentration gradient if the membrane is permeable to them.