Cell Structures & Organelles — Practice · Grade 7 Science

Chapter: Cells, Transport & Cellular Energy

What this practice covers

By the end of Cell Structures & Organelles you should be able to:

8 questions, written answer and multiple choice, each with a worked explanation.

Vocabulary used: organelle, cytoplasm, nucleus, ribosome, mitochondrion.

Problem 1

Why would a completely sealed boundary be a poor cell model?
Answer and explanation

It would prevent needed exchanges such as uptake of materials and removal of wastes.

Problem 2

Does a nucleus itself assemble all proteins?
Answer and explanation

No. Ribosomes build proteins using cellular instructions; the nucleus stores much genetic information in a typical eukaryotic cell.

Problem 3

Why is “mitochondria create energy” misleading?
Answer and explanation

They help transfer energy from food into usable forms; energy is not created.

Problem 4

Why is labeling organelles not a complete explanation of cell function?
Answer and explanation

An explanation also connects each structure with its role and interactions in the functioning system.

Problem 5

Illustrative cell record: the membrane is damaged and substances leak outward; ribosomes remain visible. A draft says visible ribosomes prove the whole cell functions normally. Explain the membrane’s role, evaluate the draft, and identify a useful further observation.
Answer and explanation

The membrane helps maintain regulated exchanges and internal conditions. Leakage suggests disruption even though ribosomes remain visible. Presence of one structure does not prove normal system function. Measurements of exchange, internal conditions, and cell activity would help assess the extent of damage.

Locate the exchange boundary.

Connect uncontrolled leakage with disrupted internal conditions.

Separate visible presence from measured function.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 6

A bacterium has DNA and ribosomes but no nucleus. Can it still make proteins?
Answer and explanation

Yes. Ribosomes can use cellular instructions without an enclosed nucleus; the arrangement differs from the typical eukaryotic-cell model.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 7

Which structure builds proteins?
  1. Cell wall
  2. Ribosome
  3. Scale bar
  4. Whole organ system
Answer and explanation

Ribosome

Ribosomes assemble proteins using cellular instructions.

Problem 8

Why do plant cells need usable energy even though they photosynthesize?
Answer and explanation

Building, transporting, repairing, and maintaining cellular conditions require energy transfers. Photosynthesis stores energy in food; respiration releases energy into usable forms.

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