Understanding Cellular Transport Mechanisms

What is the primary function of ATP in active transport?

• To provide energy for passive transport

• To supply energy for moving substances against their concentration gradient

• To facilitate osmosis

• To maintain isotonic conditions

Answer explanation

The primary function of ATP in active transport is to supply energy for moving substances against their concentration gradient, which is essential for maintaining cellular functions and homeostasis.

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DOK Level 1: Recall

Which of the following is an example of passive transport?

• Endocytosis

• Exocytosis

• Diffusion

• Active transport

Answer explanation

Diffusion is a type of passive transport where molecules move from an area of higher concentration to an area of lower concentration without the use of energy. In contrast, endocytosis, exocytosis, and active transport require energy.

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DOK Level 1: Recall

Explain how osmosis differs from diffusion.

• Osmosis involves the movement of solutes, while diffusion involves the movement of water.

• Osmosis requires energy, while diffusion does not.

• Osmosis is the movement of water across a semipermeable membrane, while diffusion is the movement of solutes from high to low concentration.

• Osmosis occurs only in hypertonic solutions, while diffusion occurs in isotonic solutions.

Answer explanation

Osmosis specifically refers to the movement of water through a semipermeable membrane, while diffusion describes the movement of solutes from areas of high concentration to low concentration.

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DOK Level 2: Skill/Concept

What happens to a cell placed in a hypertonic solution?

• It swells and bursts.

• It remains unchanged.

• It shrinks as water moves out.

• It becomes isotonic.

Answer explanation

In a hypertonic solution, the concentration of solutes outside the cell is higher than inside. This causes water to move out of the cell, leading to cell shrinkage.

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DOK Level 1: Recall

Describe the role of concentration gradients in cellular transport.

• They prevent the movement of substances across the membrane.

• They provide the energy required for active transport.

• They drive the movement of substances from areas of high concentration to low concentration.

• They are only relevant in isotonic solutions.

Answer explanation

Concentration gradients are crucial in cellular transport as they drive the movement of substances from areas of high concentration to low concentration, facilitating passive transport processes like diffusion.

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DOK Level 2: Skill/Concept

Which process involves the engulfing of large particles by the cell membrane?

• Exocytosis

• Endocytosis

• Osmosis

• Diffusion

Answer explanation

Endocytosis is the process where the cell membrane engulfs large particles, allowing them to enter the cell. This distinguishes it from exocytosis, which is the expulsion of materials, and other processes like osmosis and diffusion.

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DOK Level 1: Recall

How does the cellular membrane contribute to homeostasis?

• By allowing all substances to freely enter and exit the cell

• By selectively allowing substances to pass through, maintaining a stable internal environment

• By preventing any substances from entering the cell

• By only allowing water to pass through

Answer explanation

The cellular membrane maintains homeostasis by selectively allowing substances to pass through, ensuring a stable internal environment. This selective permeability is crucial for regulating what enters and exits the cell.

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DOK Level 2: Skill/Concept

What is the main difference between active and passive transport?

• Active transport requires energy, while passive transport does not.

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

• Both require energy but in different forms.

• Active transport only occurs in plant cells.

Answer explanation

The main difference is that active transport requires energy to move substances against their concentration gradient, while passive transport occurs naturally without energy input, allowing substances to move down their gradient.

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DOK Level 1: Recall

Predict the effect of placing a cell in a hypotonic solution.

• The cell will shrink.

• The cell will swell and may burst.

• The cell will remain the same size.

• The cell will become isotonic.

Answer explanation

In a hypotonic solution, the concentration of solutes outside the cell is lower than inside. Water enters the cell to balance the concentration, causing it to swell and potentially burst.

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DOK Level 2: Skill/Concept

How does the process of exocytosis help maintain homeostasis in cells?

• By bringing in large molecules from the outside

• By expelling waste materials and toxins from the cell

• By allowing water to enter the cell

• By preventing the entry of all substances

Answer explanation

Exocytosis helps maintain homeostasis by expelling waste materials and toxins from the cell, ensuring that the internal environment remains stable and free from harmful substances.

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DOK Level 2: Skill/Concept