Question

10. Compare and contrast the following types of signaling. Give specific examples:

            -endocrine

            -paracrine

            -synaptic

11. Compare and contrast the structure and function of the following receptors:

            -intracellular receptor

            -GPCR

            -RTK

12. Calcium is the most versatile second messenger found inside the cell. Identify three different targets for calcium found inside the cell and describe briefly their corresponding functions.

Answer 1

paracrine	synaptic	endocrine
cells in the same location or tissue	Transmission occur only in the cells with the synapse.	cells in separate organs and tissues
Release of chemical messenger	Release of neurotransmitters	hormones are produce by an endocrine gland.
Communicate over relatively short distances	Communicate over relatively short distances	Transmit signal over long distances
Allow cells to coordinate with neighbouring cells	Allow cells to coordinate with neighbouring nerve cells	cells in separate organs and tissues
signaling molecule does not enter the blood stream	Does not require bloodstream	requires the blood stream to transport the signaling molecule between organs
Spinal cord development . In this case the signaling molecule is a neurotransmitter	Nerve cells conduction of an electric signal from one nerve cell to another or to a muscle cell	progesterone testosterone, thyroid hormones

g

Intracellular receptor	GPCR	RTK
Found inside the cell(cytoplasm or nucleus). Belong to nuclear receptor superfamily	Cell surface receptor Transmit signal to intracellular target	Enzyme linked receptor
ligand must pass through the plasma membrane via passive diffusion. Ligands then bind with the receptor, pass through the nuclear membrane into the nucleus, regulating gene expression	Requires guanine nucleotide binding proteins called G-proteins.	Autophosphyration of tyrosine residue are required for signal transduction.
thyroid and steroid hormones expression	embryonic development and sensory reception, vision, smell, and taste , bacterial infections	Cell proliferation and differentiation
N- terminal activation domain, central DNA binding domain and a C-terminal binding domain	Single polypeptide with multimass nature, cross lipid bilayer 7 times. Linked to trimeric G proteins(GTPase switch proteins.)	Extracellular domain, plus ligand binding site, a single hydrophobic transmembrane alpha helix and cytosolic domain with protein tyrosine kinase activity. They are monomeric.
Receptors for steroid hormones , thyroid hormones, vitamin D and retinoid.	Receptors for neurotransmitter, neuropeptides and peptide hormones	Receptor are insulin , epidermal growth factor , transforming growth factor etc..

1. Ca2+ signaling in the ?-cells of the pancreas leads to the release of insulin.
2. Ca2+ signaling in muscle cells leads to muscle contraction.
3. Ca++ effects includes exocytosis of secretory vesicles or the inducement of mitosis in fertilized eggs. nuclear envelope breakdown and reformation, cleavage furrow formation and growth, and cell plate formation. Ca²⁺ transients trigger the onset of anaphase