Unit 2 Target 4: Cell Membrane And Homeostasis

1. Which of the following structures serves as the cell's boundary from its environment?

Mitochondrion

Cell membrane

Chloroplast

Channel proteins

The cell membrane serves as the cell's boundary from its environment. It is a thin, flexible barrier that surrounds the cell and separates its internal environment from the external environment. The cell membrane controls the movement of substances in and out of the cell, allowing nutrients to enter and waste products to exit. It also plays a crucial role in maintaining the cell's shape, providing support and protection.

Explanation

The cell membrane serves as the cell's boundary from its environment. It is a thin, flexible barrier that surrounds the cell and separates its internal environment from the external environment. The cell membrane controls the movement of substances in and out of the cell, allowing nutrients to enter and waste products to exit. It also plays a crucial role in maintaining the cell's shape, providing support and protection.

2. Which of the following is a function of the cell membrane?

Breaks down lipids, carbs, and proteins from food

Stores water, salt, proteins, and carbs

Keeps the cell wall in place

Regulates which materials enter and leave the cell

The cell membrane is responsible for regulating which materials enter and leave the cell. It acts as a selectively permeable barrier, allowing certain substances to pass through while preventing others from entering or leaving the cell. This function is crucial for maintaining the cell's internal environment and ensuring that necessary nutrients and molecules are able to enter, while waste products and harmful substances are kept out.

Explanation

The cell membrane is responsible for regulating which materials enter and leave the cell. It acts as a selectively permeable barrier, allowing certain substances to pass through while preventing others from entering or leaving the cell. This function is crucial for maintaining the cell's internal environment and ensuring that necessary nutrients and molecules are able to enter, while waste products and harmful substances are kept out.

3. The plasma membrane

Encloses the contents of a cell.

Allows material to enter and leave the cell.

Is selectively permeable.

All of the above.

The plasma membrane is the outer boundary of a cell that encloses its contents. It is responsible for controlling the movement of materials in and out of the cell, making it selectively permeable. Therefore, the correct answer is "All of the above" because the plasma membrane encloses the cell, allows materials to enter and leave, and is selectively permeable.

Explanation

The plasma membrane is the outer boundary of a cell that encloses its contents. It is responsible for controlling the movement of materials in and out of the cell, making it selectively permeable. Therefore, the correct answer is "All of the above" because the plasma membrane encloses the cell, allows materials to enter and leave, and is selectively permeable.

4. An animal cell that is surrounded by fresh water will burst because the osmotic pressure causes

Water to move into the cell.

Water to move out of the cell.

Solutes to move into the cell.

Solutes to move out of the cell.

When an animal cell is surrounded by fresh water, the concentration of solutes is higher inside the cell compared to the surrounding water. This creates a concentration gradient, causing water molecules to move from an area of lower solute concentration (the fresh water) to an area of higher solute concentration (inside the cell). This movement of water into the cell is known as osmosis. As a result, the cell will gain water and eventually burst. Therefore, the correct answer is "water to move into the cell."

Explanation

When an animal cell is surrounded by fresh water, the concentration of solutes is higher inside the cell compared to the surrounding water. This creates a concentration gradient, causing water molecules to move from an area of lower solute concentration (the fresh water) to an area of higher solute concentration (inside the cell). This movement of water into the cell is known as osmosis. As a result, the cell will gain water and eventually burst. Therefore, the correct answer is "water to move into the cell."

5. A scientist places a cell in a solution, and over time the cell gains mass and swells. What is the most likely explanation for the cell's gain in mass?

The solution is hypertonic to the cell.

The solution and the cell have equal concentrations of solutes.

The solution is hypotonic to the cell.

The solution and the cell have equal concentrations of water.

The most likely explanation for the cell's gain in mass is that the solution is hypotonic to the cell. In a hypotonic solution, the concentration of solutes is lower outside the cell compared to inside the cell. As a result, water moves into the cell through osmosis, causing the cell to swell and gain mass.

Explanation

The most likely explanation for the cell's gain in mass is that the solution is hypotonic to the cell. In a hypotonic solution, the concentration of solutes is lower outside the cell compared to inside the cell. As a result, water moves into the cell through osmosis, causing the cell to swell and gain mass.

6. Biochemists have created an artificial cell membrane that they hope to insert into artificial red blood cells for future dehydration and transportation into outer space.When scientists stain natural cell membranes with a heavy metal, they can view the membranes with an electron microscope. The heavy metal stains the nonpolar hydrophobic tails of phospholipid membranes. If the artificial membranes resemble natural membranes, what area(s), when viewed under a microscope, would appear stained? (Note: Shading represents stains.)

The correct answer is the hydrophobic tails of the artificial membranes.

Explanation

The correct answer is the hydrophobic tails of the artificial membranes.

7. When the concentration of molecules on both sides of a membrane is the same (Isotonic solution), the molecules will

Move across the membrane to the outside of the cell.

Stop moving across the membrane.

Move across the membrane in both directions.

Move across the membrane to the inside of the cell.

In an isotonic solution, the concentration of molecules on both sides of a membrane is the same. This means that there is no net movement of molecules across the membrane. However, individual molecules will still move across the membrane in both directions, but at equal rates. This is because the concentration gradient is balanced, resulting in an equal movement of molecules in and out of the cell. Therefore, the correct answer is that molecules will move across the membrane in both directions.

Explanation

In an isotonic solution, the concentration of molecules on both sides of a membrane is the same. This means that there is no net movement of molecules across the membrane. However, individual molecules will still move across the membrane in both directions, but at equal rates. This is because the concentration gradient is balanced, resulting in an equal movement of molecules in and out of the cell. Therefore, the correct answer is that molecules will move across the membrane in both directions.