Cell Signals & Feedback — Practice · Grade 10 Science

Chapter: Body Systems, Signals & Homeostasis

What this practice covers

By the end of Cell Signals & Feedback you should be able to:

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

Vocabulary used: receptor, target cell, negative feedback.

Problem 1

Why might only some cells respond to a circulating hormone?
  1. They have suitable receptors and response machinery
  2. They contain no DNA
  3. Only those cells have membranes
  4. Hormones choose by cell size alone
Answer and explanation

They have suitable receptors and response machinery

Signals require a compatible detection and response system.

Problem 2

Why is a regulated range more realistic than a perfectly fixed value?
Answer and explanation

Inputs, demands, and responses fluctuate and can have delays.

Problem 3

Does “positive feedback” mean beneficial?
Answer and explanation

No. It means amplification; consequences depend on context.

Problem 4

A hormone is present, but a cell lacks its receptor. Predict the direct response through that pathway. Explain the reasoning in your own words.
Answer and explanation

The cell will not show the usual direct response through that missing-receptor pathway.

Reception is the first necessary step in the specified pathway.

Without the receptor, the signal cannot initiate that pathway's normal response.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 5

If a receptor is blocked, must the cell's DNA sequence change? Show the reasoning, not just the conclusion.
Hints

Exposure to a signal is not sufficient by itself.

Answer and explanation

No. Signaling can be disrupted without altering DNA sequence.

Problem 6

How can one extracellular signal affect gene expression?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Receptor-triggered pathways can regulate factors controlling transcription, depending on the cell and signal.

Problem 7

Opposing pathways can adjust an output under changing inputsOpposing pathways can adjust an output under changing inputsSelected output (model units)0369120123Supplied signal input (model units)Signal pathway AOpposing pathway B
Original opposing-output example, not measured hormone doses or a recommendation about substances.
Interpret the supplied visual. What must remain the same when comparing these opposing response records?
Answer and explanation

The defined output, scale and relevant conditions; otherwise an apparent opposition may compare unlike quantities.

An antagonistic pair has effects that oppose each other on a specified variable. Examples in regulation can include pathways promoting storage versus release or activation versus inhibition. The pathways do not need to be equal in strength, act at the same time or use one universal control organ. A higher signal level can cause different downstream effects depending on receptor and context. Identify the variable, direction and input conditions before calling two molecules opposites; an effect in one tissue does not define all their actions.

The defined output, scale and relevant conditions; otherwise an apparent opposition may compare unlike quantities.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 8

Two tissues reach the same response maximum, but one responds strongly at a lower signal concentration. Explain the difference and why their response does not prove identical receptor abundance.
Answer and explanation

They differ in sensitivity under the stated comparison, not necessarily maximal capacity. Binding, receptor number, downstream amplification and adaptation can differ; further controlled measurements are required.

They differ in sensitivity under the stated comparison, not necessarily maximal capacity. Binding, receptor number, downstream amplification and adaptation can differ; further controlled measurements are required.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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