Transport in Cells Revision

Movement of molecules from an area where they are in high concentration to an area where they are low in concentration is called ?

• Active Transport

• Osmosis

• Diffusion

• Currents

Answer explanation

Which type of solution has an equal water potential ?

• Isotonic solution

• Hypotonic Solution

• Hypertonic Solution

• Saline Solution

Answer explanation

A cell in an isotonic solution is in equilibrium with its surroundings, meaning the solute concentrations inside and outside are the same (iso means equal in Latin).

In this state there is no concentration gradient and therefore, no large movement of water in or out.

Water molecules do freely move in and out of the cell, however, and the rate of movement is the same in both directions.

The movement of water molecules from an area of high concentration to an area of low concentration through a semi-permeable membrane until equilibrium is reached is called ?

• Active transport

• Osmosis

• Chemotaxis

• Diffusion

Answer explanation

Two identical solutions contained in narrow beakers are separated by a semi-permeable membrane. If salt is added to one beaker, increasing its tonicity, what will happen to the volume of water in the beaker?

• It will decrease first and then increase

• It will stay the same

• It will decrease

• It will increase

Answer explanation

The solutions start out identical, or isotonic compared to each other. When you add salt to one side of the system, the concentration of salt is higher in that side. The water molecules can travel freely between the beakers, and tend to balance the concentration gradient. To do this, more water must move into the beaker with salt added.

Substances move from an area of low concentration to an area of high concentration (i.e against the concentration gradient) energy is required. This is an example of ?

• Osmosis

• Diffusion

• Active Transport

• Endocytosis

Answer explanation

What will happen to a cell if it is placed in a hypertonic solution ?

• It will shrink and shrivel

• It will swell and burst

• It will get rigid

• Nothing will happen

Answer explanation

All are examples of diffusion except:

• Gaseous exchange in a leaf

• Gaseous exchange in the the lungs

• Water uptake by plant roots

• Digestion of glucose in the small intestines

Answer explanation

Diffusion is a natural and physical process, which happens on its own, without stirring or shaking the solutions. Liquid and gases undergo diffusion as the molecules are able to move randomly. The molecules collide with each other and change their direction.

Potato wedge (A) was placed in 200 ml of distilled water. Potato wedge (B) was placed in 200 ml of distilled water with 4 tablespoons of salt was added. What will happen to each potato wedge ?

• Potato A & B will stay the same

• Potato A will shrink and Potato B will swell

• Potato A & Potato B will swell

• Potato A will swell and Potato B will shrink

Answer explanation

Why did the potato wedges in the glass with plain distilled water become bigger?

The potato wedges expand and become bigger because of osmosis. Potatoes are made of millions of cells and the cell walls act as a semipermeable membrane. The water molecules move into the potato through this membrane to balance the concentration levels. The water moving inside the potato cells causes it to expand and become bigger. 

Why did the potato wedges in the glass with salt water shrink?

Again it’s because of osmosis. The salt solution has a higher concentration and the water inside the potato moves through the cell walls to balance the concentration in the saltwater. Since the water moves out of the potato wedge, it shrinks and becomes smaller. This is also the reason why the potato wedge in the salt solution becomes less rigid and bends easily.

Which solution has the greatest water potential ?

• 5 ml of 100% distilled water

• 5ml of saline water

• 5 ml of glucose water

• 5 ml of lake water

Answer explanation

Which of the following factors affects the rate of diffusion ?

• Temperature

• Size of Particles

• Concentration Gradient

• All the above

Answer explanation