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Chapter 4

BIO270H1 Chapter Notes - Chapter 4: Golgi Apparatus, Autocrine Signalling, Extracellular Fluid

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Chris Garside

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Chapter 4 – Cell Signaling and Endocrine Regulation
- Communication occurs when a cell sends a signal to a “target cell” in the form of a
chemical messenger
- Most are indirect
- Messenger chemical binds to receptor it cell changing its shape and
activating it
Endocrine messengers = hormones
Gap Junctions - Channels that span the area of the membrane between adjacent cells
- Specialized proteins that connect cytoplasm of 2 cells
Neurohormone – Neutrotransmitter released into the circulation
Pheremone – Chemical messenger released into the external environment (members of
the SAME species)
- Allochemicals are for members of a DIFFERENT species
Aqueous cytoplasm  lipid membrane  aqueous extracellular
- Path of chemical messenger in cell
Indirect signaling systems:
- Specialized ways of achieving the same result
- Differ in cells involved, the way messenger is transported and signaling distance
- Autocrine and paracrine signals move by diffusion
- Slow and move over short distances
- Endocrine system use circulatory system and nervous system using synapses
- Long distance chemical communication occurs between pheromones and allochemicals 
Exocrine glands
- Exocrine glands secrete chemicals into ducts that lead to the surface of the body
- Peptide hormones are synthesized by ribosomes on the rough endoplasmic reticulum as a
pre-hormone (inactive hormone)
- Signaling sequence cleaved off and becomes pro-hormone - moves to golgi
apparatus for further processing and sorting
- Steriods can diffuse across short distances in extracellular fluid but for long distance
transports need to be bound to carrier proteins
Ligands - Any molecule that binds specifically to a protein
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