BIOL 365 (Animal Phys) Flashcards
What is the difference between a conformer and a regulator?
A conformer allows its internal parameters to change with the external environment; a regulator responds to environmental change to maintain its internal parameters within a set range.
What is the difference between direct and indirect cell signalling?
Direct signalling transfers molecules from the cytoplasm of one cell to the cytoplasm of a neighbouring cell (via gap junctions); indirect signalling requires the release of chemical messengers into extracellular space.
What is a gap junction?
An aqueous channel formed between adjacent cells with aligned hemichannels made of connexins; used for direct cell signalling.
What is a chemical messenger?
A molecule that is released by a cell in response to some stimulus and transported to a target cell receptor to effect some change in the body.
What are connexins?
The protein subunits that make up the hemichannels forming each half of a gap junction between neighbouring cells.
What can be transferred via a gap junction?
Ions and chemical messenger molecules.
What is paracrine signalling?
A form of short-distance, indirect signalling in which a chemical messenger released by a cell is transported to a receptor on a different cell.
What is autocrine signalling?
A form of short-distance, indirect signalling in which a chemical messenger released by a cell is transported to a receptor on the same cell.
What are the two main mechanisms for short-distance, indirect cell signalling?
Autocrine and paracrine signalling.
What are the two main mechanisms for long-distance, indirect cell signalling?
Endocrine and nervous signalling.
What type of chemical messengers are used by the endocrine system?
Hormones.
What type of chemical messengers are used by the nervous system?
Neurotransmitters.
What triggers the release of neurotransmitters in the nervous system?
Action potentials.
What are the 7 classes of chemical messengers?
- Peptides
- Steroids
- Amines
- Lipids
- Purines
- Gases
- Amino acids
What structural property of a chemical messenger most significantly affects its signalling mechanism?
Hydrophobicity.
What are peptide hormones?
Hydrophilic chemical messengers composed of amino acids.
Where are peptide hormones synthesized?
On the rough ER.
In what form are peptide hormones usually produced initially?
Preprohormones (an inactive form).
In what form are peptide hormones usually stored?
Prohormones (an inactive form).
How are hydrophilic chemical messengers transported to target cells?
In vesicles.
What is usually cleaved off of an inactive peptide hormone during the transition from preprohormone to prohormone?
A signal peptide directing it to the appropriate vesicle.
Where is melatonin secreted?
Pineal gland.
What kind of hormone is melatonin?
Amine.
What does melatonin do?
Regulate circadean/seasonal rhythms.