Question 1

Which of the following best describes the role of connexins in intercellular communication?

Accepted Answer

Connexins are plasma membrane proteins that form channels allowing small molecules to pass directly from one cell to another.

Question 2

A patient is experiencing an allergic reaction. Which chemical messenger is most likely responsible for coordinating the body's defense against allergens, and what is its classification?

Accepted Answer

Histamine; classified as a paracrine chemical messenger.

Question 3

Which of the following statements about amino acid chemical messengers is correct?

Accepted Answer

Amino acid messengers are hydrophilic and dissolve in water but do not cross the plasma membrane.

Question 4

Which of the following is TRUE regarding the synthesis and release of steroid hormones?

Accepted Answer

Steroid hormones are synthesized on demand and released immediately because they are membrane permeant.

Question 5

Which amino acid is the precursor for catecholamines, and which catecholamine functions as a hormone?

Accepted Answer

Tyrosine; epinephrine functions as a hormone.

Question 6

A cell releases a chemical messenger that acts on itself, stimulating its own secretion. What is this type of signaling called?

Accepted Answer

Autocrine signaling

Question 7

Which of the following chemical messengers is most likely to require a carrier protein for transport in the blood?

Accepted Answer

Steroid hormones

Question 8

What is the effect on hormone half-life when a hormone is bound to a carrier protein in the blood?

Accepted Answer

The half-life increases because the hormone is protected from degradation.

Question 9

Which of the following best explains why eicosanoids are released immediately after synthesis?

Accepted Answer

Eicosanoids are hydrophobic and can readily cross the plasma membrane, so they are synthesized on demand.

Question 10

Which of the following is a correct sequence for the synthesis of serotonin (5-HT) from its precursor?

Accepted Answer

Tryptophan $$\rightarrow$$ tryptophan-5-hydroxylase $$\rightarrow 5-$$hydroxytryptophan $$\rightarrow$$ aromatic L-amino acid decarboxylase $$\rightarrow 5-HT$$

Question 11

Which of the following is NOT a function of paracrine chemical messengers?

Accepted Answer

Transmitting signals across long distances via the bloodstream

Question 12

Which chemical messenger class is most likely to act via receptors located in the cytosol of the target cell?

Accepted Answer

Steroids

Question 13

A neuron releases acetylcholine at the neuromuscular junction. What type of chemical messenger is acetylcholine in this context?

Accepted Answer

Neurotransmitter

Question 14

Which of the following best describes the transport mechanism for hydrophilic chemical messengers in the blood?

Accepted Answer

They are transported in dissolved form in plasma.

Question 15

Which of the following is a correct statement about the specificity of receptors for chemical messengers?

Accepted Answer

Receptors generally bind only one specific messenger or a class of closely related messengers.

Question 16

Which process describes the increase in the number of receptors on a target cell in response to prolonged exposure to low concentrations of a messenger?

Accepted Answer

Upregulation

Question 17

Which of the following is a correct pairing of messenger class and its chemical property?

Accepted Answer

Peptides/proteins; lipophobic

Question 18

A hormone is released into the blood and binds to a carrier protein. What effect does this binding have on the hormone's availability to target cells?

Accepted Answer

It decreases the hormone's immediate availability, as only free hormone can bind to receptors.

Question 19

Which of the following is a correct statement about the synthesis of peptide/protein chemical messengers?

Accepted Answer

They are synthesized in the same way as other proteins destined for secretion.

Intercellular Communication and Chemical Messengers in Anatomy & Physiology

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