Environmental Perception Flashcards
What do bacteria use to respond to environmental factors?
Flagellae for swimming and regulating gene expression
Bacteria exhibit positive and negative tactic responses.
What are the components of a 2-component system in bacteria?
Receptor histidine kinase and response regulator
These components mediate responses to various stimuli.
What is positive chemotaxis?
Movement towards a source of sugars or amino acids
It is an example of a bacterial response to stimuli.
What is channelrhodopsin?
A light-activated ion channel in unicellular green algae
Example: Functions in phototaxis of Chlamydomonas.
What happens when the receptor is stimulated in channelrhodopsin?
Activation of ion channel leading to a response
Channelrhodopsin is activated by light.
What is the role of the nicotinic acetylcholine receptor?
Involved in neural transmission
It is a ligand-gated ion channel.
What can defects in receptor/signaling mechanisms cause?
Impair metabolism/development or cause diseases
Examples include cancers, diabetes, endocrine diseases.
What is signal desensitization?
Mechanism to curtail a response if the stimulus persists
It prevents excessive responses that may waste energy.
What is the function of retinal in channelrhodopsin?
Acts as a chromophore for light absorption
Retinal absorbs blue light maximally at 480 nm.
What is the mechanism of signal amplification?
Enzyme activities amplify the level of response to stimuli
Involves protein kinase cascades that phosphorylate target proteins.
What are the types of signaling mechanisms discussed?
- Autocrine signaling
- Juxtacrine signaling
- Paracrine signaling
- Endocrine signaling
These mechanisms describe how cells communicate signals.
What is the role of the response regulator in a 2-component system?
Initiates the response after being phosphorylated
It regulates flagellar movement or gene expression.
What is the characteristic structure of channelrhodopsin?
7-transmembrane protein that forms an ion channel
It opens in response to light activation.
What does receptor activation often lead to?
Negative feedback that switches off the receptor
This is a part of the desensitization process.
What types of stimuli can cells perceive?
- Physical stimuli (light, temperature, touch)
- External chemicals
- Internal metabolites or hormones
Cells can detect a wide range of molecular signals.
What is the function of the ligand binding domain in a receptor?
Binds specific ligands, such as sugars or amino acids
This activation leads to intracellular responses.
What is the primary ligand for the nicotinic acetylcholine receptor?
Acetylcholine
It also binds nicotine.
Fill in the blank: The receptor histidine kinase activates _______ on a histidine amino acid.
Autophosphorylation
True or False: Rhodopsin functions as an ion channel.
False
Rhodopsin is involved in visual photoreception but is not an ion channel.
What are the subunits of the nicotinic acetylcholine receptor?
- 2 alpha subunits
- Beta subunit
- Gamma subunit
- Sigma subunit
Each subunit has 4 membrane-spanning helices.
What is the primary role of receptors in cells?
To detect stimuli and couple them to appropriate responses
This involves signal transduction.
