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20 Cards in this Set
- Front
- Back
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Cell-Cell communication
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Essential for multicellular and single-celled organisms
Usually via chemical messengers called Ligands Ligands are called alpha factors |
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What is local signalling?
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A signal that travels short distances (only a few cells)
Cells may communicate via direct contact Animal and plant cells have cell junctions that directly connect the cytoplasm of adjacent cells cells communicate using local regulators |
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What is long distance signalling?
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signals travel long distances through many cells, throughout the body.
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What is Paracrine Signaling?
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A signaling cell releases messenger molecules into the extracellular fluid. These local regulators influence nearby cells.
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What is synaptic signaling?
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a nerve cell releases neurotransmitter molecules into the narrow synapse separating it from its targe cell.
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What are Hormones?
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Chemical signals that travel to more distant cells. In hormonal or endocrine signalling the circulatory system transports hormones throughout the body to reach target cells with appropriate receptors. Transmission of signals through the nervous system is also a type of long-distance signaling.
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What are the 3 stages of cell signaling?
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1. Receiving (reception)
2. Transduction (the signal has been transformed) 3. Response |
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Receiving/Reception
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A signal molecule binds to a receptor protein causing it to change shape
The protein and the signal molecule both change shape The receptor must change shape Binding between signal molecule (ligand) and receptor is highly specific Receptors may be either inside the cell (intracellular) or on the external plasma membrane |
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Intracellular receptors
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are cytoplasmic or nuclear proteins
steroid hormones bind to intracellular receptors |
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Receptors in the External Plasma Membrane
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There are 3 main types of membrane receptors
1. G-protein linked receptors (proteins) 2. Receptor Tyrosine Kinases (enzymes) 3. Ligand-Gated Ion Channel Receptors(gate) |
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Signal Transduction
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Cascades of molecular interactions relay signals from receptors to target molecules
At each step in a pathway, the signal is tranduced into a different form, commonly a conformational change in a protein |
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What are multistep pathways?
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Can amplify a signal
Provide more opportunities for coordination and regulation |
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What are Protein Phosphorylation Cascades?
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Requires energy (use of ATP)
Is an example of signal transduction pathway In this process A series of protein kinases add a phophate to the enxt one in line, activating it Phosphatase enzymes then remove the phosphates |
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What are Scaffolding Proteins?
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Scaffolding proteins link relay proteins together like a scaffold so that they stay together.
Increase the signal transduction energy External signal molecule maybe local or long distance. Is the first messenger then messages goes between relay proteins called secondary messengers. |
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Secondary Messengers
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Carry message inside cell ("first messenger" carries messages between cells)
Are small, non-protein, water-soluable molecules or ions Examples cAMP (cyclic adenosine monophosphate) Ca++ IP3 (inositol triphosphate) DAG (diacylgycerol |
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What is Cyclic AMP (cAMP)
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ATP is made into cAMP by the enzyme adenylyl cyclase
Made up of 3 ATP, 2 ADP and 1 Phosphate Acts as a second messenger in cellular pathways eg of second messenger - Calcium (cation 2) May be received by calmodulin receptor Often activates protein kinase A which phosphorylates other proteins. |
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What happens in Cytoplasmic and Nuclear Responses?
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Signaling pathways regulate a variety of cell activities
Metabolism, including enzyme functino might change Changes in the membrane permeability Cytoskeleton changes Cell growth and reproduction EG's Hormone Epinephorine and glucose release |
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What do Nuclear responses do?
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regulate genes by turning genes on or off
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What is Specificity of Cell Signaling
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The different combinations of proteins in a cell
Give the cell great specificity in both the signal it detects and the responses it carries out |
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What are scaffolding proteins?
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Large relay proteins to which other relay proteins attach, increasing the efficiency of signal transduction in a pathway.
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