Question 1

Which structure allows direct cytoplasmic exchange between adjacent plant cells, facilitating coordinated cellular activities?

Accepted Answer

Plasmodesmata

Question 2

In animal tissues, which structure forms continuous protein channels between adjacent cells, allowing the flow of small molecules?

Accepted Answer

Gap junctions

Question 3

Which of the following best describes the role of hormones in long-distance cell communication?

Accepted Answer

Hormones are information-carrying molecules that circulate and act on distant target cells.

Question 4

A steroid hormone enters a cell and binds to its receptor. Where is this receptor most likely located?

Accepted Answer

Inside the cell, in the cytoplasm or nucleus

Question 5

Which step in long-distance cell signaling involves the conversion of an extracellular signal into an amplified intracellular message?

Accepted Answer

Signal transduction

Question 6

Enzyme-linked receptors, such as receptor tyrosine kinases, propagate signals by which mechanism?

Accepted Answer

By phosphorylating themselves and other proteins, creating a phosphorylation cascade

Question 7

Which of the following is TRUE about G proteins in signal transduction?

Accepted Answer

G proteins are activated when they bind GTP.

Question 8

Second messengers in cell signaling are advantageous because:

Accepted Answer

They amplify the hormone signal and activate protein kinases.

Question 9

Which of the following best explains why signal deactivation is important in cell signaling?

Accepted Answer

It allows the cell to remain sensitive to small changes in hormone concentration.

Question 10

A mutation prevents the hydrolysis of GTP to GDP in a G protein. What is the most likely consequence for the cell?

Accepted Answer

The G protein will remain active, leading to prolonged or excessive signaling.

Question 11

Which of the following is a correct sequence of steps in long-distance cell signaling?

Accepted Answer

Signal reception → Signal processing → Signal response → Signal deactivation

Question 12

If a cell lacks the appropriate receptor for a hormone, what will happen when the hormone is present?

Accepted Answer

The cell will not respond to the hormone.

Question 13

Which of the following is a real-world example of direct cell-cell communication in humans?

Accepted Answer

Gap junctions allowing ions to pass between cardiac muscle cells for synchronized contraction

Question 14

Which equation best represents the activation of a G protein?

Accepted Answer

$$G_{protein} + GTP \rightarrow G_{protein}-GTP$$

Question 15

A researcher adds a molecule that blocks phosphorylation events in a cell. Which signaling pathway will be most directly affected?

Accepted Answer

Enzyme-linked receptor signaling

Question 16

Which of the following is a multi-step process that amplifies an extracellular signal inside the cell?

Accepted Answer

Phosphorylation cascade

Question 17

In the secretin signaling system, which second messenger is produced to stimulate phosphorylation cascades?

Accepted Answer

Cyclic AMP ($$cAMP)$$

Question 18

Which of the following is NOT a function of second messengers?

Accepted Answer

Forming direct cell-cell junctions

Question 19

A cell receives a signal via a membrane-bound receptor, which then activates a G protein. What is the next step in the signaling pathway?

Accepted Answer

The G protein activates an enzyme that produces a second messenger.

Question 20

Which of the following best describes the integrated whole-organism response to hormonal signaling?

Accepted Answer

It coordinates activities across cells, tissues, and organs in response to changing conditions.

BIO181- 2.4 Cellular signaling (Unit2: Cellular Basis of Life)

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