Note
Studied by 12 people11_CELL_SIGNALING_CANVAS_STUDENTS-2
Page 1: Cell Signaling Overview
Key Components
External Environment: Cells interact with various signals.
Ligands: Molecules that convey signals, categorized as hydrophilic (water-soluble) or hydrophobic (lipid-soluble).
Receptors: Molecules on the cell surface or inside cells that bind ligands.
Signal Transduction Pathway: A series of biochemical events initiated by receptor-ligand binding, leading to a cellular response.
Page 2: Learning Outcomes
Understanding Cell Responses
Cells detect and respond to internal/external signals for functioning.
Communication is vital for coordination of development, defense, and environmental responses.
Receptors: Primarily proteins or RNA (riboswitches) that identify signals.
Different signals include chemical and physical stimuli.
Receptors localized for recognizing hydrophilic and hydrophobic signals.
Receptors connect to signal transduction pathways.
Scaffolding Proteins: Organize molecules for signal perception and transduction.
Protein Kinase Cascade: Amplifies signals for response.
Page 3: Signals That Cells Must Respond To
Biological and Environmental Signals: Includes blood pressure, cell size, food molecules, hormones, toxins, etc.
Page 4: Communication Among Cells
Importance of Cell Communication
Enables coordination of growth, repair, and responses to external factors.
Page 5: Recognizing Signals for Cellular Function
Example in Immune Response
White blood cells must identify signals from pathogens or cancer cells.
Page 6: Types of Receptors
G Protein Coupled Receptors (GPCR)
Histidine Kinase Receptors
Ligand-Gated Ion Channel Receptors
Riboswitches
Tyrosine Kinase Receptors (RTK)
Page 7: G Protein-Coupled Receptors (GPCR)
Activation Process
Signal binding activates GPCR.
Activation of G protein follows.
G protein triggers cellular response.
G protein self-deactivates to ensure normal signaling.
Page 8: Impact of Pharmaceuticals
Approximately ~30-60% modify GPCR activity.
Abnormal GPCR activation can lead to cancers.
Page 9: Tyrosine Kinase Receptors (RTKs)
Activation Steps
Two RTKs bind the signal.
Kinase activity is initiated.
Phosphorylation of each other triggers response.
RTKs are later deactivated to prevent irregular signaling.
Page 10: Cancers Linked to RTKs
Constitutive RTKs: Always active.
Excess RTKs: Increased numbers lead to abnormal cell signaling.
Page 11: Signal Molecule Properties
Hydrophilic vs. Hydrophobic Signals
Hydrophilic: Cannot cross the cell membrane; bind to surface receptors.
Hydrophobic: Pass through the membrane; bind to internal receptors.
Page 12: Signal Transduction Pathways
Initiated by activated receptors, forming biochemical sequences connecting signal recognition to cellular responses.
Page 13: Kinase Phosphorylation Cascades
Sequential activation of kinases enhancing responses (1 kinase > 5 > 25 > cellular response).
Critical for rapid immune response (e.g., against viruses).
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Page 14: Role of Scaffolding Proteins
Organize signaling proteins and receptors for effective communication.
Page 15: Study Guide Questions
Types of Signals Recognized by Cells
Biological Signals: These include hormones, toxins, and food molecules
Environmental Signals: For example, blood pressure and cell size
What Are Receptors?
Definition: Receptors are molecules located on cell surfaces or inside cells that bind to specific ligands.
Biological Molecules That Are Receptors: Primarily proteins or RNA, such as riboswitches.
Major Groups of Receptors
G Protein Coupled Receptors (GPCR)
Histidine Kinase Receptors
Ligand-Gated Ion Channel Receptors
Riboswitches
Tyrosine Kinase Receptors (RTK)
Activation and Deactivation of GPCRs and RTKs
GPCR Activation:
Signal binding activates the GPCR.
G protein is activated subsequently.
A cellular response is triggered by the G protein.
G protein self-deactivates to ensure normal signaling.
RTK Activation:
Two RTKs bind to a signal.
Kinase activity is initiated, followed by phosphorylation.
Activation triggers cellular responses.
RTKs are deactivated to prevent irregular signaling.
How Can a Defective G-Protein Cause Cancer?
Abnormal GPCR activation can lead to uncontrolled cellular responses, contributing to cancer development.
How Can Tyrosine Kinase Receptors (RTKs) Cause Cancer?
Constitutive RTKs (always active) or excessive RTKs can lead to abnormal signaling pathways that promote uncontrolled cell division and cancer.
Pharmaceuticals and G-Protein Function
Approximately 30-60% of drugs modify GPCR activity to help restore proper cell function.
Placement of Receptors for External Signals
Hydrophobic Signals: Receptors that recognize hydrophobic signal molecules are found inside the cell.
Hydrophilic Signals: Receptors for hydrophilic signal molecules are localized on the cell surface.
Importance of Signal Transduction
Essential for conveying signals from outside the cell to initiate appropriate cellular responses, facilitating coordination of various functions.
Role of Scaffolding Proteins
Scaffolding proteins organize signaling proteins and receptors spatially to enhance effective communication and facilitate proper cellular responses.
Protein Kinase Cascade Function
The protein kinase cascade amplifies the signal recognition process in cells (1 kinase activates several others, exponentially increasing the cellular response).