Biology Unit 2-3 Test

What is diffusion?

• The net movement of a substance traveling down its concentration gradient

• The net movement of a substance moving from low to high concentration to reach equilibrium

• The net movement of a substance traveling against the concentration gradient

• The net movement of a substance straight through the cell membrane, without using any ATP energy

Answer explanation

Diffusion is defined as the net movement of a substance traveling down its concentration gradient, meaning it moves from areas of higher concentration to lower concentration until equilibrium is reached.

True or false: Passive transport requires ATP energy

• True

• False

Answer explanation

False. Passive transport does not require ATP energy; it relies on the natural movement of molecules down their concentration gradient.

True or false: When molecules keep moving after equilibrium is reached it is called dynamic equilibrium

• True

• False

Answer explanation

True. Dynamic equilibrium occurs when molecules continue to move and react, but their overall concentrations remain constant, indicating a balance between forward and reverse processes.

True or false: When molecules are still after equilibrium is reached it is called dynamic equilibrium

• True

• False

Answer explanation

False. Dynamic equilibrium occurs when molecules are in constant motion, even though their overall concentrations remain constant. If molecules are still, it indicates that equilibrium has not been reached.

When a substance moves from high to low concentration it...

• Requires ATP energy

• Requires no ATP energy

• Requires protein pumps

• Requires cell signaling

Answer explanation

When a substance moves from high to low concentration, it occurs via passive transport, which does not require ATP energy. This process relies on the natural tendency of molecules to spread out evenly.

When a substance moves from low to high concentration it...

• Requires ATP energy

• Requires no ATP energy

• Requires protein pumps

• Requires cell signaling

Answer explanation

When a substance moves from low to high concentration, it requires energy input, specifically ATP, to overcome the concentration gradient. This process is known as active transport.

Where is there a low concentration of dye?

• at the bottom of cup

• in the color

• at the top of cup 

• no concenteraion gradient

Answer explanation

The dye concentration is lowest at the bottom of the cup because it tends to settle there, while the higher concentration is found at the top where the dye is more dispersed.

Tags

NGSS.HS-PS1-5

The movement of particles from an area of high concentration to an area of low concentration

• active transport

• osmosis

• diffusion

• random movement

Answer explanation

The movement of particles from an area of high concentration to an area of low concentration is called diffusion. This process occurs naturally without the need for energy, unlike active transport, which requires energy.

This picture shows molecules of red dye that have moved. What is this type of movement called?

• Osmosis; the water molecules are moving from high concentration to low

• Diffusion; the dye molecules are moving from low to high concentration

• Diffusion; the dye molecules are moving from high to low concentration.

• Facilitated diffusion; because the molecules are moving through a protein channel.

Answer explanation

The correct answer is diffusion; the dye molecules are moving from high to low concentration. This process occurs as molecules spread out to evenly fill the available space, which is characteristic of diffusion.

Diffusion is the movement of molecules from

• an area of equilibrium to an area of high concentration.

• an area of low concentration to an area of high concentration.

• an area of high concentration to an area of high concentration.

• an area of high concentration to an area of low concentration.

Answer explanation

Diffusion is the process where molecules move from an area of high concentration to an area of low concentration, seeking to equalize concentrations. Thus, the correct answer is 'an area of high concentration to an area of low concentration.'

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-4