Ap Biology Notes Cellular Communication

Topics: Signal transduction, Cell signaling, Protein Pages: 5 (1459 words) Published: February 19, 2013
Chapter 11: Cell Communication

Cell-to-cell communication is essential in multicellular organisms. They must communicate to coordinate activities such as growth and development, and reproduction. In addition unicellular organisms communicate with each other. Signals may use light, or touch but we will focus on chemical signals.

1. External signals are converted to responses within the cell a. Evolution of cell signaling
i. In yeast a cells and αcells both secrete chemicals, which can only be received by the alternate type yeast. This signals the two cells to join via fusion 1. The process by which the signal on the surface of the cell is converted to a series of steps by the cell in response is called a signal transduction pathway ii. Signal transduction pathways are very similar in yeast and in complex multicellular organisms 2. This leads scientists to believe that this pathway evolved first in ancient prokaryotes b. Local and long distance signaling

iii. Local signaling
3. Adjacent cells of plants and animals may communicate through cell junctions a. Signaling substances dissolved in the cytoplasm travel between cells i. Plants = plasmodesmata

ii. Animals = gap junctions
4. Animal cells may use the following
b. Cell-to-cell recognition
iii. Direct contact between membrane-bound cell-surface molecules iv. Important in embryonic development and immune response c. Paracrine signaling

v. Uses local regulators which are released and travel only a short distance to nearby cells vi. Ex. Growth factors target nearby cells to grow and divide d. Synaptic signaling

vii. Electrical signal along a nerve cell triggers a chemical release across a synapse to trigger response in target cell viii. Ex. Nerve cells
iv. Long- distance signaling
5. Both plants and animals use hormones
e. Animals (endocrine signaling) cells release hormones which travel in the circulatory system to target cells f. Plants hormones travel in vessels or by diffusion through the air as gas g. Hormones vary in size and shape

6. Nervous system signals can also be long distance c. The three stages of cell signaling: A preview
v. Reception: when the target cell detects a signaling molecule. The signaling molecule binds to a receptor protein on the target cell’s surface vi. Transduction: After binding the receptor protein is changed in some way, this converts the signal to a form that will bring about a specific cellular response 7. May occur in a single step or a series of changes vii. Response: The transduced signal triggers a specific cellular response. 8. Catalysis of an enzyme, rearrangement of the cytoskeleton, activation of a specific gene 2. Reception: A signaling molecule binds to a receptor protein, causing it to change shape d. To ensure signals are sent to the correct cell signaling molecules act as a ligand. viii. Ligand- molecule that specifically binds to another (usually larger) molecule ix. The receptor protein then usually changes shape x. May be located on the membrane or inside the cell e. Receptors in the plasma membrane

xi. Water-soluble signaling molecule binds to receptor on the membrane causing it to change shape or aggregate. f. Intracellular Receptors
xii. Found in cytoplasm or nucleus of target cells
9. Signaling molecule must be hydrophobic enough or small enough to pass through the plasma membrane h. Steroid hormones, thyroid hormones, nitric oxide | Examples| Pathway| Other|

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