Environmental perception Flashcards
(96 cards)
1
Q
What is autocrine signaling?
A
A type of signaling where a cell targets itself with signaling molecules.
2
Q
What is paracrine signaling?
A
A type of signaling where a cell targets nearby cells.
3
Q
What is juxtacrine signaling?
A
A type of signaling where the signaling cell and the target cell are in direct contact.
4
Q
What is endocrine signaling?
A
A type of signaling where signals are sent through the bloodstream to distant cells.
5
Q
What is a receptor?
A
A protein that receives and responds to a signal molecule.
6
Q
What is signal transduction?
A
The process by which a cell converts a signal into a specific response.
7
Q
Give examples of cellular responses to signal transduction.
A
Gene expression, enzyme activation, cell movement.
8
Q
Give examples of different types of receptors.
A
G-protein coupled receptors, ion channel receptors, enzyme-linked receptors.
9
Q
How can stimulus perception be amplified?
A
Through enzyme cascades, such as activation of multiple secondary messengers.
10
Q
How can stimulus perception be desensitized?
A
By receptor internalization or feedback inhibition.
11
Q
What is cross-talk between signaling pathways?
A
Interaction between different signaling pathways to integrate cellular responses.
12
Q
Give an example where receptor activation opens an ion channel.
A
Nicotinic acetylcholine receptor in neuromuscular junctions.
13
Q
What is channelrhodopsin?
A
A light-gated ion channel used in optogenetics.
14
Q
How does channelrhodopsin work?
A
It opens in response to light, allowing ion flow and cell depolarization.
15
Q
What is the nicotinic acetylcholine receptor?
A
A ligand-gated ion channel activated by acetylcholine.
16
Q
How does the nicotinic acetylcholine receptor work?
A
Binding of acetylcholine opens the channel, allowing Na+ influx.
17
Q
Give an example where receptor activation activates enzyme activity.
A
Insulin receptor activating tyrosine kinase activity.
18
Q
What is a bacterial 2-component histidine kinase system?
A
A signaling system with a sensor kinase and response regulator.
19
Q
How does a bacterial histidine kinase system work?
A
Kinase autophosphorylates and transfers phosphate to response regulator to trigger response.
20
Q
Give functions of mammalian TGFβ.
A
Regulates cell growth, differentiation, and immune responses.
21
Q
How is TGFβ synthesized and activated?
A
Produced as a precursor, cleaved and activated in extracellular space.
22
Q
Describe the TGFβ receptor structure and mechanism.
A
Heterotetrameric complex with intrinsic serine/threonine kinase activity.
23
Q
What is the role of SMAD proteins in TGFβ signaling?
A
They transduce signals from TGFβ receptors to the nucleus.
24
Q
What mutations are found in some cancer tumors related to TGFβ?
A
Mutations in TGFβ or SMAD proteins.
25
Give an example of a receptor that recruits a kinase after activation.
Erythropoietin receptor recruiting JAK kinase.
26
How does erythropoietin initiate signaling?
Binding causes receptor dimerization and JAK kinase recruitment.
27
How are STAT proteins activated by JAK kinase?
JAK phosphorylates STATs, which dimerize and translocate to the nucleus.
28
Give an example of ligand binding initiating transcription.
Estrogen binding to its receptor.
29
What is the function of estradiol and how does it enter cells?
Regulates gene expression; diffuses through the cell membrane.
30
What is the structure and mechanism of the estrogen receptor?
Nuclear receptor that binds DNA and regulates transcription.
31
What is the relationship between estrogen receptors and breast cancer?
Estrogen receptors drive growth in some breast cancers; tamoxifen blocks them.
32
What is photomorphogenesis?
Developmental changes in plants in response to light.
33
Give examples of plant photoreceptors.
Phytochromes (red/far-red), cryptochromes (blue), UVR8 (UV-B).
34
What is the function of UVR8 photoreceptor?
Detects UV-B light and initiates protective responses.
35
What is the role of HY5 in light responses?
A transcription factor promoting photomorphogenesis.
36
How does phytochrome function in light perception?
Switches between active/inactive forms depending on red/far-red light.
37
How does phytochrome regulate PIFs?
Active phytochrome induces PIF degradation.
38
What is the function of PIF transcription factors?
Suppress photomorphogenesis; degraded in light.
39
What are the roles of rods and cones?
Rods detect dim light; cones detect color.
40
What is the structure of rods and cones?
Outer segment with photopigments, inner segment with cell organelles.
41
How does rhodopsin detect light?
Light activates rhodopsin, activating transducin and cGMP phosphodiesterase.
42
How is rhodopsin excitation amplified and desensitized?
Amplified by G-protein cascade; desensitized via phosphorylation and arrestin.
43
How do cones achieve color vision?
By using different opsins sensitive to different wavelengths.
44
What is the function of melanopsin?
Regulates circadian rhythms by detecting ambient light levels.
45
What is a circadian rhythm?
A roughly 24-hour cycle in physiological processes driven by an internal biological clock.
46
What are the defining properties of circadian rhythms?
Persistence in constant conditions, temperature compensation, and ability to entrain to environmental cues.
47
Why do organisms need to measure time?
To anticipate environmental changes, which provides a Darwinian fitness advantage.
48
What is a Zeitgeber?
An external cue like light or temperature that synchronizes the internal clock.
49
What organism is commonly used to study circadian rhythms?
Drosophila melanogaster (fruit fly), due to its well-characterized genetics.
50
What experimental method measures rhythmic activity in flies?
Drosophila Activity Monitor using infrared beam breaks.
51
What is a common method to visualize rhythmic gene expression?
Luciferase reporter fused to a circadian promoter.
52
What defines a “clock” versus a simple timer?
Clocks repeat cycles and are adjustable; timers (e.g., hourglasses) count down once.
53
What type of genetic feedback loop drives the circadian oscillator?
Transcription-translation negative feedback loop with delay.
54
What are PER and CRY in the mouse clock?
Proteins that inhibit their own transcription by repressing CLK/BMAL1.
55
What is the role of the SCN in mammals?
The Suprachiasmatic Nucleus acts as the master circadian clock.
56
What happens if the SCN is ablated in mammals?
Loss of rhythmic behavior, showing its central role.
57
What is the function of protein kinases?
Protein kinases transfer phosphate groups from ATP to specific amino acids in target proteins, regulating their activity.
58
What are the main types of kinases studied in humans?
Serine/Threonine kinases and Tyrosine kinases are the most well-studied.
59
What are the main roles of kinases in cell signaling?
Kinases function as signal amplifiers and/or key control steps in various cellular processes, including metabolism.
60
How are kinases activated?
Kinases are activated through mechanisms like binding of regulatory proteins, phosphorylation of activation loops, and removal of pseudosubstrate domains.
61
What is the role of ATP in kinase function?
ATP binds to the active site of a kinase, providing the phosphate group that is transferred to the target protein.
62
What does phosphorylation of a target protein typically result in?
Phosphorylation can change the target protein’s activity, localization, interactions, stability, and sensitivity to signals.
63
How does the pseudosubstrate domain regulate kinase activity?
The pseudosubstrate domain mimics a substrate sequence but lacks the phosphorylation site, preventing kinase activation until conditions change.
64
What is the significance of consensus motifs in kinase targets?
Consensus motifs in target proteins allow kinases to specifically recognize and phosphorylate certain amino acid sequences.
65
How do kinases like PKA and Protein Kinase C function?
PKA is activated by cAMP, regulating processes like glycogen metabolism, while Protein Kinase C is activated by DAG and calcium, regulating cell growth and differentiation.
66
What does the process of kinase regulation involve?
Kinase regulation includes the interaction with regulatory proteins, activation loop phosphorylation, and pseudosubstrate domain displacement.
67
What are Tyrosine Kinases?
Tyrosine kinases are a specialized subset of kinases involved in cell signaling, particularly in growth, cell division, and metabolism.
## Footnote
Tyrosine kinases play a critical role in various cellular processes.
68
What is the role of the insulin receptor in tyrosine kinase signaling?
The insulin receptor is a tyrosine kinase that auto-phosphorylates specific tyrosine residues upon insulin binding, recruiting signaling molecules like IRS-1.
## Footnote
IRS-1 is an important adaptor protein in insulin signaling.
69
How does ligand binding activate the insulin receptor?
Ligand binding causes receptor dimerization, activating the intrinsic tyrosine kinase and triggering autophosphorylation on specific tyrosines.
## Footnote
Dimerization is crucial for receptor activation.
70
What is the importance of receptor dimerization in receptor tyrosine kinase (RTK) activation?
Dimerization is essential for activating the kinase domain of the receptor, allowing for trans-phosphorylation and activation of downstream signals.
## Footnote
This process is fundamental for initiating signaling cascades.
71
What is the role of SH2 domains in tyrosine kinase signaling?
SH2 domains bind phospho-tyrosine residues, allowing the recruitment of specific signaling proteins to the receptor.
## Footnote
SH2 domains are key for mediating protein-protein interactions.
72
How do SH2 domains recognize phospho-tyrosine residues?
SH2 domains recognize phospho-tyrosine in the context of specific surrounding sequences, ensuring precise signaling.
## Footnote
This specificity is important for accurate signal transduction.
73
What is the significance of SH2 domain specificity?
SH2 domains exhibit specificity in binding phospho-tyrosine, determining which tyrosine residues in receptors are recognized, enabling tailored signaling responses.
## Footnote
This specificity allows cells to respond appropriately to various signals.
74
How does activation of PLC-γ occur via RTKs?
PLC-γ is recruited to the receptor by SH2 domains, then phosphorylated by the receptor’s kinase domain, leading to its activation.
## Footnote
PLC-γ plays a role in generating second messengers.
75
What is the MAPK cascade, and how is it activated?
The MAPK cascade involves the G-protein Ras, which is activated by phosphorylation and triggers a series of kinase activations for signal amplification.
## Footnote
The MAPK pathway is crucial for various cellular responses, including proliferation.
76
What happens when a ligand binds to a receptor tyrosine kinase?
Ligand binding induces receptor dimerization, activation of the kinase domain, autophosphorylation, and recruitment of SH2 domain-containing proteins.
## Footnote
This process is fundamental for initiating cellular responses to external signals.
77
What are G Protein-Coupled Receptors (GPCRs)?
GPCRs are a large, ancient family of membrane proteins involved in signal transduction, targeted by ~25% of clinically employed medicines.
## Footnote
GPCRs play a key role in numerous physiological processes and are significant in pharmacology.
78
What is the crystal structure of the β2-adrenoceptor?
The β2-adrenoceptor is a GPCR that interacts with G proteins to induce signal transduction across the plasma membrane. This receptor is the target for beta-blockers and anti-asthma medicines.
## Footnote
Understanding the structure aids in drug design and development.
79
Who won the Nobel Prize for their work on GPCRs?
Robert Lefkowitz and Brian Kobilka won the 2012 Nobel Prize in Chemistry for their work on GPCRs.
## Footnote
Their research has significantly advanced our understanding of receptor biology.
80
What happens when a GPCR is activated?
Upon ligand binding, GPCRs undergo conformational changes, activating associated G proteins and triggering signal transduction across the plasma membrane.
## Footnote
This activation is crucial for cellular communication.
81
What is the role of G proteins in GPCR signaling?
G proteins act as guanine nucleotide exchange proteins, providing a GTP-and time-dependent signaling mechanism, controlling various cellular responses.
## Footnote
They are key mediators in the signaling pathway.
82
How are GPCRs classified?
GPCRs are divided into families based on the G proteins they interact with, which include:
* G proteins that stimulate or inhibit adenylyl cyclase
* G proteins that control ion channels
* G proteins that stimulate phospholipase C
* G proteins that regulate cytoskeleton and Ca2+ levels.
## Footnote
This classification is based on functional characteristics.
83
What is the role of adenylyl cyclase in GPCR signaling?
Adenylyl cyclase converts ATP to cyclic AMP (cAMP), a second messenger that activates protein kinase A (PKA) to initiate a cascade of cellular events.
## Footnote
This process is vital for transmitting the signal within the cell.
84
Why is cAMP regulation important?
cAMP must be rapidly broken down by phosphodiesterases to return levels to basal and stop signaling, as cAMP cannot cross the plasma membrane.
## Footnote
Proper regulation is essential for maintaining cellular homeostasis.
85
What is the significance of GPCRs in drug development?
GPCRs are major molecular targets for many medicines, including treatments for asthma, hypertension, and other conditions.
## Footnote
This makes them critical in therapeutic interventions.
86
What happens when cAMP levels are not regulated?
Without proper regulation, elevated cAMP levels could prevent cells from knowing when a signal has been terminated, disrupting normal cellular processes.
## Footnote
This can lead to pathological conditions.
87
What is the Lineweaver-Burk plot used for?
To analyze enzyme kinetics and determine Vmax and Km by plotting enzyme activity as a straight line.
88
What is plotted on the X-axis of a Lineweaver-Burk plot?
1 / [S] (the inverse of substrate concentration)
89
What is plotted on the Y-axis of a Lineweaver-Burk plot?
1 / v (the inverse of reaction rate)
90
What is the equation for the Lineweaver-Burk plot?
1/v = Km/Vmax * 1/[S] + 1/Vmax
91
What does the Y-intercept of the Lineweaver-Burk plot represent?
1/Vmax
92
What does the X-intercept of the Lineweaver-Burk plot represent?
-1/Km
93
What is the slope of the Lineweaver-Burk plot?
Km/Vmax
94
Why use the Lineweaver-Burk plot instead of the Michaelis-Menten curve?
Because it gives a straight line, making it easier to find Vmax and Km from experimental data.
95
How does a competitive inhibitor affect the Lineweaver-Burk plot?
Increases the slope and shifts the X-intercept to the right; Y-intercept stays the same.
96
How does a non-competitive inhibitor affect the Lineweaver-Burk plot?
Increases the Y-intercept; X-intercept stays the same.
