ANAT242 Lecture 2 - Cellular Regulation Flashcards
what is a ligand?
the chemical nature of a signal molecule
what are 6 examples of ligands?
proteins amino acids steroids peptides amines gases
what determines how a ligand works?
whether it is water-soluble or lipid-soluble
where are water-soluble signals stored?
water-soluble signals are stored within phospholipid vesicles within the signalling cell
what composes water-soluble molecules?
water-soluble signals
what is exocytosis?
active transport where molecules are secreted out of the cell
how are water-soluble molecules transported in the blood and enter the target cell?
water-soluble molecules are carried in the blood bound to a carrier but cannot enter the target cell therefore the message must be transduced through the cell surface receptors
are lipid-soluble molecules made on-demand or not and why?
lipid-soluble signals cannot be stored in lipid vesicles as they would leak out of the cell therefore they are made on command
what is an advantage and disadvantage of lipid-soluble molecules being produced on command?
production on command is a slower response however the response is long-lasting as it travels the blood bound to a carrier protein and can enter the target cell
what is the relationship between a lipid-soluble molecule and the target cell?
lipid-soluble molecules can enter the target cell directly and act on intracellular receptors to directly regulate gene expression
what is the function of a carrier protein?
to provide protection for molecules to prevent them from being broken down by enzymes
what are the 4 major forms of signalling between cells?
juxtacrine
autocrine
paracrine
endocrine
what is juxtacrine cell signalling?
involves direct cell to cell contact of the same cell and is mediated by gap junctions
what are gap junctions?
bi-directional channels made up of proteins called connexins that allow the transport of ions and small molecules between cells for rapid communication between cells like cardiac muscle cells or groups of neurons
what is autocrine signalling?
involves signalling between nearby cells of the same type and requires the release of a chemical message as one cell signals to many other cells of the same type
when is autocrine cells signalling used?
used to coordinate activity between a group of similar cells
what is paracrine cell signalling?
used for local signalling between different cell types and requires the release and detection of a chemical message
what is an example of paracrine signalling?
endothelial cells communicate with nearby vascular smooth muscle via nitric oxide to regulate blood pressure
what is endocrine cell signalling?
involves the signalling between distant cells in the body through chemical signals called hormones which are transported in the blood
where are the hormones used in endocrine cell signalling produced?
produced in discrete endocrine glands, tissues and isolated cells
how is specificity achieved in juxtacrine cell signalling?
achieved by receptor expression and direct contact. The signalling between adjacent cells involves gap junctions or receptors but unlike other forms of the receptor-mediated cell to cell communication the signalling message is not released
what is the notch pathway?
delivers more complex information to the target cell compared to gap junctions and is involved in the development and cancer
how is endocrine specificity achieved?
achieved by receptor expression being limited to only target cells
how is neuronal specificity achieved?
achieved by precise contacts of rapid removal of neurotransmitters to prevent unwanted diffusion
how is autocrine specificity achieved?
achieved by receptor expression and rapid ligand degradation. The signals do not travel as they are broken down by enzymes
how is paracrine specificity achieved?
achieved by receptor expression and rapid ligand metabolism
