Passive and Active Transport Practice

Explain how the sodium-potassium pump functions as an example of active transport. Include the role of ATP in your explanation.

Answer explanation

The sodium-potassium pump actively transports 3 sodium ions out and 2 potassium ions into the cell using ATP. ATP provides the energy needed for this process, allowing the pump to move ions against their concentration gradients.

Predict what would happen to a cell placed in a hypertonic solution and explain why.

Answer explanation

A cell in a hypertonic solution will lose water and shrink due to osmosis, as water moves out of the cell to balance the higher solute concentration outside. This can lead to cell dehydration and impaired function.

Tags

NGSS.HS-LS1-3

Which of the following processes is an example of passive transport?

• Endocytosis

• Osmosis

• Exocytosis

• Sodium-potassium pump

Answer explanation

Osmosis is a type of passive transport where water moves across a membrane from an area of lower solute concentration to an area of higher solute concentration, without the use of energy. The other options involve active processes.

Which of the following is a characteristic of active transport?

• Movement of molecules from high to low concentration

• Does not require cellular energy

• Utilizes transport proteins

• Involves diffusion through the lipid bilayer

Answer explanation

Active transport requires energy to move molecules against their concentration gradient, often utilizing transport proteins. It does not involve diffusion through the lipid bilayer, which is characteristic of passive transport.

Which of the following statements best describes facilitated diffusion?

• It is a type of active transport that requires energy.

• It involves the movement of water molecules only.

• It requires transport proteins to move substances across the cell membrane.

• It moves substances against their concentration gradient.

Answer explanation

Facilitated diffusion is a passive transport process that requires transport proteins to help move substances across the cell membrane, allowing molecules to cross without using energy.

What is the main difference between passive and active transport?

• Passive transport requires energy, while active transport does not.

• Active transport moves substances against their concentration gradient, while passive transport does not.

• Passive transport involves vesicles, while active transport does not.

• Active transport only occurs in animal cells, while passive transport occurs in all cells.

Answer explanation

The main difference is that active transport moves substances against their concentration gradient, requiring energy, while passive transport allows substances to move along their gradient without energy input.

What role do carrier proteins play in facilitated diffusion?

• They provide energy for the transport process.

• They form channels that allow substances to pass through the membrane.

• They bind to specific molecules and change shape to transport them across the membrane.

• They actively pump substances against their concentration gradient.

Answer explanation

Carrier proteins facilitate diffusion by binding to specific molecules and changing shape, allowing these molecules to cross the membrane. This process does not require energy, distinguishing it from active transport.

Which of the following best explains why active transport is necessary for cells?

• It allows cells to move substances along their concentration gradient.

• It enables cells to maintain homeostasis by regulating ion concentrations.

• It provides energy for cellular respiration.

• It allows cells to passively absorb nutrients.

Answer explanation

Active transport is essential for cells to maintain homeostasis by regulating ion concentrations, allowing them to control the internal environment despite external changes.

Tags

NGSS.HS-LS1-3

Why is energy in the form of ATP required for active transport processes?

• To move substances along their concentration gradient

• To maintain the structure of the cell membrane

• To move substances against their concentration gradient

• To facilitate passive transport

Answer explanation

Energy in the form of ATP is required for active transport because it enables the movement of substances against their concentration gradient, which is essential for maintaining cellular functions and homeostasis.

How does the concentration gradient affect the rate of diffusion?

• The rate of diffusion decreases as the concentration gradient increases.

• The rate of diffusion is not affected by the concentration gradient.

• The rate of diffusion increases as the concentration gradient increases.

• The rate of diffusion is constant regardless of the concentration gradient.

Answer explanation

The rate of diffusion increases as the concentration gradient increases because a greater difference in concentration between two areas drives more molecules to move from high to low concentration, enhancing diffusion.