Review Questions
What property prevents the ligands of cell-surface receptors from entering the cell?
- The molecules bind to the extracellular domain.
- The molecules are hydrophilic and cannot penetrate the hydrophobic interior of the plasma membrane.
- The molecules are attached to transport proteins that deliver them through the bloodstream to target cells.
- The ligands are able to penetrate the membrane and directly influence gene expression upon receptor binding.
Hint:
B
The secretion of hormones by the pituitary gland is an example of _______________.
- autocrine signaling
- paracrine signaling
- endocrine signaling
- direct signaling across gap junctions
Hint:
C
Why are ion channels necessary to transport ions into or out of a cell?
- Ions are too large to diffuse through the membrane.
- Ions are charged particles and cannot diffuse through the hydrophobic interior of the membrane.
- Ions do not need ion channels to move through the membrane.
- Ions bind to carrier proteins in the bloodstream, which must be removed before transport into the cell.
Hint:
B
Endocrine signals are transmitted more slowly than paracrine signals because ___________.
- the ligands are transported through the bloodstream and travel greater distances
- the target and signaling cells are close together
- the ligands are degraded rapidly
- the ligands don't bind to carrier proteins during transport
Hint:
A
A scientist notices that when she adds a small, water-soluble molecule to a dish of cells, the cells turn off transcription of a gene. She hypothesizes that the ligand she added binds to a(n) ______ receptor.
- Intracellular
- Hormone
- Enzyme-linked
- Gated ion channel-linked
Hint:
C