Paramecium contain specialized organelles called contractile vacuoles which expel excess water from the inside of the cell, decreasing the risk of lysis. Explain the high fluid output of the paramecium exposed to freshwater.

• The freshwater is significantly hypotonic to the cell, causing an influx of water via osmosis.

• The freshwater is significantly hypertonic to the cell, causing the dehydration of the cell.

• The freshwater has a higher solute concentration than the cell, causing the cell to swell.

• The freshwater has a lower solute concentration than the cell, causing the cell to shrivel.

Tags

NGSS.HS-LS1-3

What is not true of endocytosis and exocytosis?

• They move solute from low to high concentration.

• They are a form of active transport.

• They involve the formation of lipid vesicles for the transport of polar molecules.

• They do not require an input of energy to perform.

What is true of this protein pump?

• If it becomes defective, molecules will flow through it from high to low concentration.

• If the ATP supply runs out, the pump will move molecules at a slower rate.

• The pump is powered by the hydrolysis of ATP into ADP.

• If the pump breaks, molecules will begin flowing through the phospholipid bilayer instead.

Na+/H+ antiporters can be found in cells lining the stomach. Sodium (Na+) is allowed to flow from high to low concentration into the cells while protons (H+) are pumped from low to high concentration to lower stomach pH. Which of the following best describes this form of transport?

• This is passive transport because sodium is flowing from high to low concentrations.

• The hydrolysis of ATP is power the movement of these ions across the cell membrane.

• This is an example of active transport because materials are entering the cell via endocytosis.

• The flow of sodium down its electrochemical gradient is powering the active transport of protons out of the cell.

The pump pictured is called Na+/K+ ATPase. What would most likely occur if an ATPase inhibitor was introduced to the cell?

• Na+ would build up inside the cell.

• K+ ions would build up inside the cell.

• Charged ions would begin diffusing through the phospholipid bilayer from high to low concentration.

• Na+ and K+ would begin flowing through the pump in the opposite direction (high to low).

Tags

NGSS.HS-LS1-3