Review Questions

Which of the following best describes the role of cell signaling?
A) To produce ATP for energy
B) To allow cells to detect and respond to signals in their environment
C) To replicate DNA before cell division
D) To maintain chromosome structure

Fill in the blank: A molecule that binds to a receptor and triggers a response is called a __________.

Which of the following is an example of a G-protein coupled receptor (GPCR)?
A) Insulin receptor
B) β-adrenergic receptor
C) Estrogen receptor
D) Epidermal growth factor receptor (EGFR)

True or False: GPCRs typically activate intracellular signaling through the binding and hydrolysis of GTP.

Match the receptor type (Column A) with its main characteristic (Column B):

1. Column A

   1. GPCR (G-protein coupled receptor)

   2. RTK (Receptor Tyrosine Kinase)

   3. Steroid receptor

   4. Ligand-gated ion channel

2. Column B
   A. Located inside the cell; activated by small hydrophobic ligands like hormones
   B. Opens to allow ions to pass through membrane when ligand binds
   C. Crosses membrane 7 times; activates G-proteins
   D. Dimerizes and autophosphorylates tyrosine residues

Fill in the blank: When steroid hormones bind their receptors, the receptor-ligand complex acts as a __________ factor.

Explain the difference between endocrine, paracrine, autocrine, and synaptic signaling.

Which of the following is a second messenger commonly used in cell signaling pathways?
A) cAMP
B) DNA
C) RNA
D) ATP synthase

Short answer: Why is signal amplification important in cell communication pathways?

Fill in the blank: RTKs, once activated, phosphorylate __________ residues on themselves and other proteins to propagate the signal.

Which of the following receptors directly alters gene expression without the need for second messengers?
A) GPCR
B) RTK
C) Steroid receptor
D) Ligand-gated ion channel

Describe the role of phosphatases in signal transduction.

Application: If a mutation prevents a GPCR from binding GTP, what would happen to the downstream signaling pathway?

What is apoptosis, and why is cell signaling important in regulating it?

Short answer: Compare how hydrophilic and hydrophobic signaling molecules differ in their receptor locations and mechanisms of action.