BLG 143 Study Guide - Final Guide: Signal Transduction, Enzyme Inhibitor, Signal Processing
27 Apr 2018
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8.5 How Do Distant Cells Communicate?
In plants and animals, adjacent cells are physically connected and communicate with each
other directly through openings in their plasma membranes.
Distant cells communicate by long-distance signals.
Cell-Cell Signalling in Multicellular Organisms
Hormone information carrying molecule that is secreted from a cell, circulates in the
body and acts on target cells far from the signalling cell; usually small and present in
minute concentrations; large impact on the condition of the organism as a whole
The function and chemical structure of plant and animal hormones vary widely.
Steps of Cell-Cell signalling:
1. Signal reception
• Hormone (a ligand) binds to a receptor protein
• Receptor protein is on surface of target cell if hormone is hydrophilic
• Receptor protein is within cytoplasm if hormone is hydrophobic (steroid)
• Receptor protein is expressed in only a single or few types of cell
• Receptors are dynamic, copy number can increase or decrease in a cell
depending on hormonal situation
• Receptors can be blocked (competitive enzyme inhibition)
2. Signal processing
• Direct processing when lipid-soluble signals enter a cell, the information
they carry is processed directly without any intermediate steps; diffuse
through cell membrane, bind to cytoplasmic receptor and are carried to the
nucleus
• Signal has to processed and relayed to the nucleus to elicit a response
(transcription of a gene and production of a specific protein)
• Hormones that cannot diffuse across the plasma membrane bind to
membrane receptors
• Signal transduction triggered by signal binding at the cell, the conversation
of the signal from one form to another; occurs at the plasma membrane;
conversation of the signal from one form to another
• Amplification occurs inside
• G proteins intracellular proteins that bind the guanine nucleotide GTP and
attach to a transmembrane receptor protein on the inside of the cell
• When signal is received, change in the receptor causes G protein to release
GDP and bind GTP
• G protein released from the receptor protein splits and one part carries GTP
to an enzyme
• Enzyme is phosphorylated and catalyzes production of molecules that act as
second messengers non-protein signalling molecule that elicits a response
to the first messenger
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Document Summary
In plants and animals, adjacent cells are physically connected and communicate with each other directly through openings in their plasma membranes. The function and chemical structure of plant and animal hormones vary widely. Block or enhance enzyme activity in a cell. As cells process sugar, the energy that is released is used to transfer a phosphate group to adenosine diphosphate adp, generating atp. Glucose most common fuel used by organisms; used to make atp through cellular respiration of fermentation. Metabolism all chemical reactions that occur in living cells. 9. 1 nature of chemical energy and redox reactions. Phosphorylation addition of a phosphate group to a substrate; exergonic; electrons in. Adp and the phosphate group have much less potential energy than they did in atp; of substrates or enzymes makes the reactions that occur in cell exergonic. The exergonic phosphorylation is coupled to an endergonic reaction. Redox reactions loss of electrons: oxidation or gain of electrons: reduction.
