High School Biology : Cell Structures and Organelles

Study concepts, example questions & explanations for High School Biology

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Example Questions

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Example Question #1 : Understanding Plant Cell Differences

Which of the following is present in plant and fungal cells, but not in animal cells?

Possible Answers:

Chloroplast

Plasma membrane

Cell wall

Mitochondrion

Correct answer:

Cell wall

Explanation:

Both plant cells and fungal cells have cell walls; animal cells do not. Plant cells have chloroplasts, but neither fungal cells nor animal cells do. Fungal, plant and animal cells all have plasma membranes and mitochondria.

Example Question #1 : Understanding Plant Cell Differences

Which of the following characteristics is not true for animal cells?

Possible Answers:

Gap junctions allow for communication between cells

Tight junctions hold cells together, restricting the passage of materials

The extracellular matrix functions in support, adhesion, movement, and regulation between cells

Plasmodesmata allow for communication and eschange of materials between cells

Desmosomes fasten cells together

Correct answer:

Plasmodesmata allow for communication and eschange of materials between cells

Explanation:

All of the options are true for animal cells except for the existence of plasmodesmata, which are found in plant cells. Plasmodesmata are small gaps in the cell walls. They are like gap junctions in animal cells, allowing for communication between cells and the exchange of minerals throughout the plant. 

Example Question #1 : Understanding Plant Cell Differences

Which of the following best explains why salad sometimes appears wilted instead of fresh and crisp after being doused in salad dressing?

Possible Answers:

The vacuole has shrunk due to being in a hypotonic solution

The vacuole has shrunk due to being in a hypertonic solution

None of these

The vacuole swells in a hypertonic solution

The turgor pressure remains the same

Correct answer:

The vacuole has shrunk due to being in a hypertonic solution

Explanation:

Hypertonicity and hypotonicity are both relative terms. A hypertonic solution has more dissolved solutes than the cell that is submerged within it. In other words the solution has less water than the cell in the solution. A hypotonic solution is one that has less dissolved solutes (i.e. more water) than the cell or membrane within it. Water follows its concentration gradient: it flows to where it is least concentrated.

A plant's vacuole is a large membrane bound compartment within the cell that plays a structural role when it has the proper turgor pressure. It is also used as storage for various molecules. Salad generally becomes wilted in salad dressing—or other liquids with many dissolved solutes—because the water in the plant cells tends to flow outward or down its concentration gradient. Hence the salad leaves wilt because they are in a hypertonic solution. In other words, there are more dissolved solutes and non-water molecules outside the cells than there are inside. In terms of water, there is less water outside the cell than in it and so the water flows down its concentration gradient and out of the cell to equalize the gradient. This causes the vacuole to shrink, which reduces pressure on the cell wall and gives the wilted appearance.

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