Term
Feedback:
Negative feedback |
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Definition
| These mechanisms maintain dynamic homeostasis for a particular condition (variable) by regulating physicological processes, returning the changing condition back to its target set point. |
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Term
Feedback:
Positive feedback |
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Definition
| These mechanisms amplify responses and processes in biological organims. The condition initiating response is moved farther away from the initial set-point. Amplification occurs when the stimulus is further activated which, in turn, initiates an additional response that produces system change. |
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Term
Cell-to-cell communication:
Cells send or receive inhibitory or stimulatory signals from other cells, organisms, or the environment. |
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Definition
- In single-celled organisms, it is response to its environment.
- In multicellular organisms, signal transduction parthways coordinate the activities w/in the individual cells. Ex: Epinephrine stimulation of glycogen breakdown in mammals
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Term
Cell-to-cell communication:
Cells communicate by cell-to-cell contact. |
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Definition
Example: Immune cells interact by:
- cell-cell contact
- antigenpresenting cells (APC's)
- helper T cells
- killer T cells
- Plasmodesmata b/w plant cells that allow material to be transported from cell to cell
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Term
Cell-to-cell communication:
Cells communicate over short distances by using ... |
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Definition
... local regulators that target cells in the vicinity of the emitting cell.
Example: Neurotransmitters, plant immune response |
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Term
Cell-to-cell communication:
Signals released by one cell type can travel long distances to ... |
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Definition
... target cells of another cell type.
Example: hormones |
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Term
Cell-to-cell communication:
A receptor protein recognizes signal molecules, causing...
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Definition
... the receptor protein's shape to change, which initiates transduction of the signal.
Example: G-protein linked receptors, ligand-gated ion channels, tyrosine kinase receptors |
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Term
Cell-to-cell communication:
Signal transduction |
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Definition
The process by which a signal is converted to a cellular response.
Signaling cascades relay signals from receptors to cell targets, often amplifying the incoming signals, with the result of appropriate responses by the cell. |
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Term
Cell-to-cell communication:
Second messengers inside of cells |
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Definition
| are often essential to the function of the cascade. |
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Term
Cell-to-cell communication:
Many signal transduction pathways include: |
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Definition
| Protein modifications or phosphorylation cascades in which a series of protein kinases add a phosphate group to the next protein in the cascade. |
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Term
Gene Regulation:
Prokaryotes |
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Definition
- Inducers (turn genes on) and repressors (turn genes off) are small molecules that interact w/ regulatory proteins and/or regulatory sequences.
- Regulatory proteins inhibit gene expression by binding to DNA and blocking transcription (negative control).
- Regulatory proteins stimulate gene expression by binding to DNA and stimulating transcription (positive control) or binding to repressors to inactivate repressor function.
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Term
Gene Regulation:
Eukaryotes |
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Definition
- Transcription factors bind to DNA sequences and other regulatory proteins
- Some of these transcription factors are activators (increase expression), while others are repressors (decrease expression).
- The combination of transcription factors binding to the regulatory regions at any one time determines how much, if any, of the gene product will be produced.
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Term
Immunity:
Plants, invertebrates, and vertebrates have ... |
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Definition
... multiple, nonspecific immune responses.
Example: phagocytes engult and digest pathogens w/ the help of lysosomes |
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Term
Immunity:
Mammals use specific immune responses triggered by natural or artificial agents that disrupt dynamic homeostasis. |
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Definition
The mammialian immune system includes 2 types of specific responses: cell mediated and humoral.
Cell mediated response: cytotoxic T cells (a type of lymphcytic white blood cells) target intracellular pathogens when antigens are displayed on the outside of the cells.
Humoral response: B cells (a type of lymphocytic white blood cells) produce antibodies against specific antigens.
Antigens are recognized by antibodies to the antigen.
Antibodies are proteins produced by B cells, and each antibody is specific to a particular antigen.
A second exposure to an antigen results in a more rapid and enhanced immune response. |
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Term
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Definition
| Viruses inject DNA or RNA into the host cell |
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Term
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Definition
| Viruses have highly effective replicative capabilities that allow for rapid evolution |
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Term
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Definition
| Viruses replicate via the lytic cycle, allowing one virus to produce many progeny simultaneously |
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Term
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Definition
| Virus replication allows for mutations to occur through usual host pathways |
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Term
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Definition
| RNA viruses lack replication error-checking mechanism, and thus have higher rates of mutation |
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Term
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Definition
| Related viruses can combine/recombine information if they infect the same host cell |
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Term
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Definition
| Some viruses are able to integerate into the host DNA and establish a latent (lysogenic) infection |
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Term
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Definition
| HIV is a well-studies system where the rapid evolution of a virus w/in the host contributes to the pathogenicity of viral infection. |
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Term
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Definition
| Genetic information in retroviruses is a special case and has an alternate flow of information: from RNA to DNA, made possible by reverse transcriptase (an enzyme that copies the viral RNA genome into DNA). This DNA integrates into the host genome and becomes transcribed and translated for the assembly of new viral progeny. |
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