Biology Unit 4 Exam: Cell Membrane & Transport

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

Mitochondrion

Cell membrane

Chloroplast

Channel proteins

The cell membrane and cell wall are the outer boundaries of the cell.

Explanation

The cell membrane and cell wall are the outer boundaries of the cell.

2. Which means of particle transport requires energy from the cell?

Diffusion

Osmosis

Facilitated diffusion

Active transport

Active transport requires energy. Diffusion, osmosis, and facilitated diffusion are all passive.

Explanation

Active transport requires energy. Diffusion, osmosis, and facilitated diffusion are all passive.

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

Breaks down lipids, carbohydrates, and proteins from foods

Stores water, salt, proteins, and carbohydrates

Keeps the cell wall in place

Regulates which materials enter and leave the cell

The cell membrane maintains homeostasis by controlling/regulating cell transport.

Explanation

The cell membrane maintains homeostasis by controlling/regulating cell transport.

4. Passive transport is the movement of molecules from

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

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

An area of equilibrium to an area of high concentration.

An area of low concentration to an area of equilibrium.

Passive transport is where molecules spread out from high concentration to low concentration. Diffusion, Osmosis, and Facilitated Diffusion are all types of Passive Transport.

Explanation

Passive transport is where molecules spread out from high concentration to low concentration. Diffusion, Osmosis, and Facilitated Diffusion are all types of Passive Transport.

5. The process by which organisms keep their internal conditions fairly constant is called

Homeostasis.

Osmosis.

Metabolism.

Exocytosis.

Homeostasis is maintaining stable internal conditions.

Explanation

Homeostasis is maintaining stable internal conditions.

6. Which of the following is NOT a part of the cell membrane?

Phospholipids

Proteins

Carbohydrate chains

Nucleic acids

Nucleic acids are contained within the nucleus of eukaryotes and the cytoplasm of prokaryotes. Nucleic acids are not found in the cell membrane.

Explanation

Nucleic acids are contained within the nucleus of eukaryotes and the cytoplasm of prokaryotes. Nucleic acids are not found in the cell membrane.

7. The diffusion of water across a selectively permeable membrane is called

Osmotic pressure.

Osmosis.

Facilitated diffusion.

Active transport.

Osmosis is the diffusion of water.

Explanation

Osmosis is the diffusion of water.

8. Diffusion takes place

Only through a lipid bilayer membrane.

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

Only in liquids.

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

Diffusion is the movement of any type of molecule from an area of high concentration to an area of low concentration.

Explanation

Diffusion is the movement of any type of molecule from an area of high concentration to an area of low concentration.

9. Which of the following does NOT use energy?

Diffusion

Endocytosis

Active transport

A sodium-potassium pump

Diffusion is passive and does NOT use energy.

Explanation

Diffusion is passive and does NOT use energy.

10. Pure water is always hypotonic to cells. An animal cell that is surrounded by pure 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.

Water moves from where there is the most water (high) to where there is the least water (low). This means that because the fresh water is hypotonic to the cell, water will move into the cell, causing it to burst.

Explanation

Water moves from where there is the most water (high) to where there is the least water (low). This means that because the fresh water is hypotonic to the cell, water will move into the cell, causing it to burst.

11. When scientists stain natural cell membranes with a heavy metal, they can view the membranes with an electron microscope. The heavy metal stains the polar hydrophilic heads of phospholipid membranes. When viewed under a microscope, would appear stained? (Note: Shading represents stains.)

The polar heads of the phospholipids are on the outside and the nonpolar tails are on the inside (like an oreo cookie).

Explanation

The polar heads of the phospholipids are on the outside and the nonpolar tails are on the inside (like an oreo cookie).

12. Equilibrium is maintained through diffusion. Which of the following would represent equilibrium?

The concentration always remains greater inside a membrane.

The concentration eventually becomes balanced on both sides of a membrane.

The concentration always remains greater on the outside of a membrane.

The concentration becomes imbalanced on both sides of a membrane.

Equilibrium is where the concentration is the same on both sides of the membrane.

Explanation

Equilibrium is where the concentration is the same on both sides of the membrane.

13. Which of the following is NOT characteristic of facilitated diffusion?

It requires a protein channel.

It moves substances with (down) a concentration gradient.

It requires no energy input.

It is a type of active transport.

Facilitated diffusion is a type of PASSIVE transport where materials diffusion through a protein channel.

Explanation

Facilitated diffusion is a type of PASSIVE transport where materials diffusion through a protein channel.

14. The diagram shows a cell membrane composed of a phospholipid bilayer with a channel protein. Each x represents the same type of molecule inside or outside the cell. Facilitated diffusion moves these molecules across the cell membrane.

In what direction do these molecules move and through which structure?

Into the cell through the channel protein

Into the cell through the phospholipid bilayer

Out of the cell through the channel protein

Out of the cell through the phospholipid bilayer

Facilitated diffusion is a type of passive transport where molecules move from high concentration to low concentration through a protein channel.

Explanation

Facilitated diffusion is a type of passive transport where molecules move from high concentration to low concentration through a protein channel.

15. Food molecules and bacteria that are too large to be moved through the membrane can be transported INTO the cell by

Osmosis.

Endocytosis.

Lipid carriers.

Diffusion.

Endocytosis transports large molecules and fluid into the cell, but it requires energy.

Explanation

Endocytosis transports large molecules and fluid into the cell, but it requires energy.

16. Diffusion takes place

Only through a lipid bilayer membrane.

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

Only in liquids.

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

Diffusion is a type of passive transport. That means molecules move from where they are crowded (high concentration) to where they are uncrowded (low concentration) without needing energy.

Explanation

Diffusion is a type of passive transport. That means molecules move from where they are crowded (high concentration) to where they are uncrowded (low concentration) without needing energy.

17. The dispersal of ink in a beaker of water is an example of

Diffusion.

Osmosis.

Active transport.

Endocytosis.

Diffusion is the spreading out of any type of molecule from high concentration to low concentration.

Explanation

Diffusion is the spreading out of any type of molecule from high concentration to low concentration.

18. Proteins are produced by ribosomes, modified by rough ER, and then packaged by the Golgi apparatus. By what process do these packaged proteins exit a cell through the cell membrane?

Active transport

Exocytosis

Facilitated diffusion

Osmosis

Proteins are too large for any other transport, so they are packaged in a vesicle which fuses with the cell membrane. This is called exocytosis.

Explanation

Proteins are too large for any other transport, so they are packaged in a vesicle which fuses with the cell membrane. This is called exocytosis.

19. The sodium-potassium pump is an example of

Contractile vacuoles

Osmosis

Active transport

Facilitated diffusion

The sodium-potassium pump is a protein pump that moves sodium and potassium ions against the concentration gradient. This requires energy in the form of ATP.

Explanation

The sodium-potassium pump is a protein pump that moves sodium and potassium ions against the concentration gradient. This requires energy in the form of ATP.

20. Placing a plant into a hypertonic environment will

Cause turgor pressure to increase because water is moving into the cell.

Cause the vacuole to swell.

Have no effect.

Cause turgor pressure to decrease because water is moving out of the cell.

A plant cell has a cell wall, which maintains the shape of the cell. Turgor pressure (the pressure inside the cell) decreases because the cell loses water in a hypertonic solution.

Explanation

A plant cell has a cell wall, which maintains the shape of the cell. Turgor pressure (the pressure inside the cell) decreases because the cell loses water in a hypertonic solution.

21. Red blood cells have a salt content of 0.9%. When a microbiologist places red blood cells in pure water, osmosis occurs. Where do the molecules move in this instance of osmosis?

Water molecules move out of the cells.

Water molecules move into the cells.

Salt ions move out of the cells.

Salt ions move into the cells.

Water is always hypotonic to cells. The water will move into the cell causing it to swell.

Explanation

Water is always hypotonic to cells. The water will move into the cell causing it to swell.

22. 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.

If a cell is placed in a hypotonic solution, water will move into the cell. This would explain the increase in mass.

Explanation

If a cell is placed in a hypotonic solution, water will move into the cell. This would explain the increase in mass.

23. When the concentration of molecules on both sides of a membrane is the same, 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.

Molecules are constantly in motion. At equilibrium, molecules are moving in both directions at the same rate.

Explanation

Molecules are constantly in motion. At equilibrium, molecules are moving in both directions at the same rate.

24. The cell membrane contains channels and pumps that help move materials from one side to the other. What are these channels and pumps made of?

Carbohydrates

Lipids

Bilipids

Proteins

The transport channels and pumps in the cell membrane are made out of protein.

Explanation

The transport channels and pumps in the cell membrane are made out of protein.

25. Active transport is the movement of molecules from

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

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

An area of high concentration to an area of equilibrium.

An area of low concentration to an area of equilibrium

Active Transport is the opposite of Passive Transport. Active Transport forces molecules to move against the gradient. This means they are moving from low concentration (uncrowded) to high concentration (crowded). This requires energy.

Explanation

Active Transport is the opposite of Passive Transport. Active Transport forces molecules to move against the gradient. This means they are moving from low concentration (uncrowded) to high concentration (crowded). This requires energy.

26.

Refer to the illustration above. The process shown is called

Osmosis.

Facilitated diffusion.

Active transport.

Diffusion.

The solid cube is dissolving in the liquid. The molecules are spreading out from high concentration to low concentration so this is diffusion

Explanation

The solid cube is dissolving in the liquid. The molecules are spreading out from high concentration to low concentration so this is diffusion

27. Sugar molecules are large and cannot go through the lipid bilayer. If there is a high concentration of sugar outside the cell, these molecules can ENTER cells through the process of

Exocytosis.

Facilitated diffusion.

Osmosis.

Ion pumps.

If the sugar is moving from high concentration to low concentration but cannot pass the lipid bilayer, it will move through a protein channel. This is called facilitated diffusion.

Explanation

If the sugar is moving from high concentration to low concentration but cannot pass the lipid bilayer, it will move through a protein channel. This is called facilitated diffusion.

28. Match the description with the correct term.

a form of passive transport that uses transport proteins

the diffusion of water through a cell membrane

when the molecules of one substance are spread evenly throughout another substance to become balanced

when molecules move from high concentration to low concentration; no energy is required

when molecules move from low concentration to high concentration; energy is required

If you miss it, write out the description and the term.

Explanation

If you miss it, write out the description and the term.

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29. A Paramecium lives in an environment that is hypotonic to its cytoplasm. How does the Paramecium maintain homeostasis under these conditions?

It expels (pumps out) excess water using contractile vacuoles.

It expels (pumps out) excess sodium using the sodium-potassium pump.

It absorbs additional water through osmosis.

It absorbs additional sodium through facilitated diffusion.

Because it is in a hypotonic solution, water moves into the cell (paramecium). To keep the cell from swelling, it pumps the water out using a contractile vacuole. This allows it to keep internal conditions the same (homeostasis).

Explanation

Because it is in a hypotonic solution, water moves into the cell (paramecium). To keep the cell from swelling, it pumps the water out using a contractile vacuole. This allows it to keep internal conditions the same (homeostasis).

30. Match the description with the correct term.

This type of solution is at equilibrium with the cell so the cell size will not change.

This type of solution will make an animal cell swell and possibly burst. It will increase turgor pressure in a plant cell.

This type of solution will make an animal cell shrivel up. It will decrease turgor pressure in a plant cell.

This organelle is used to help maintain homeostasis in a paramecium.

This is the structure that is formed to transport substances during both endocytosis and exocytosis

If you miss it, write out the description and the term.

Explanation

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31. Match the description with the correct term.

a vesicle membrane fuses with the cell membrane and the contents are released into the extracellular fluid

the cell membrane wraps around a food particle and forms a vesicle to transport the food to the lysosome

the cell membrane forms a vesicle to transport a substance into the cell

the cell membrane wraps around fluid and forms a vesicle to transport the fluid to the lysosome

this is how ions such as sodium and potassium are transported across the cell membrane against the concentration gradient

If you miss it, write out the description and the term.

Explanation

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