Unit 4: Cell Communication & Cell Cycle
Lesson 1: Cell Communication & Signal Transduction
Lesson 2: Feedback Mechanisms
Lesson 3: Cell Cycle
Lesson 4: Mitosis
Lesson 5: Checkpoints & Regulatory Proteins
Lesson 6: Cancer
Aim: How do cells communicate with each other?
Importance of cell communication
Think-Pair-Share Question: Why is it important for cells to communicate?
Consider examples to illustrate the concept.
Learning Objectives:
IST-3.A: Describe ways that cells communicate.
IST-3.B: Explain short and long-distance communication.
Describe vs Explain:
Describe: note characteristics.
Explain: delve into the "why" or "how".
Learning Objectives:
IST-3.C: Describe components of signal transduction pathways.
IST-3.D: Explain role of components in cellular response.
Learning Objectives:
IST-3.E: Role of environment in cellular response.
IST-3.F: Types of cellular responses from signal transduction pathways.
Definition: Series of steps allowing cells to respond to environmental signals.
Responses can initiate cellular activities (e.g., cell cycle initiation).
Involves ligand secretion and receptor interaction.
Three stages:
Reception: Ligand binds to receptor.
Transduction: Signal conversion occurs.
Response: Alteration of cellular processes.
Initiation of transcription of target genes leads to protein synthesis that elicits responses.
Reception: Detection of ligand by receptor in target cell.
Receptor Characteristics:
Binds signal molecules (ligands).
Involves specificity in binding.
Ligand binding induces conformational change, facilitating interaction with other cellular molecules.
May occur at plasma membrane or intracellularly.
Plasma Membrane Receptors:
Most common type; bind to polar and large ligands.
Examples: G protein coupled receptors, ligand-gated ion channels.
Intracellular Receptors:
Found in cytoplasm/nucleus; bind to hydrophobic molecules like steroid hormones.
Cell-to-Cell Contact:
Physical contact between cells for signal transmission.
Paracrine Signaling:
Short-range signaling via ligands.
Autocrine Signaling:
Cell acts on itself via secreted ligands.
Endocrine Signaling:
Hormones released into circulation for long-distance signaling.
Fastest signaling method; using gap junctions in animal cells or plasmodesmata in plant cells for rapid signal diffusion.
Transduction: Conversion of extracellular signals to intracellular signals, forming a signal transduction pathway.
Regulated by phosphorylation (activation) and dephosphorylation (deactivation) of proteins.
Shape change impacts protein function.
Amplifies the signaling response.
Common second messenger: cyclic AMP (cAMP).
Final signaling pathway molecule translates signal into a cellular response:
Alters membrane permeability.
Impacts metabolic processes.
Modifies gene expression.
Influence gene expression and cell function, modifying phenotypes or inducing cell death.
Mutations in signaling molecules/receptors can disrupt normal cellular responses, leading to diseases.
Identify the three stages of cell signaling and the nature of the signal transduced.
Answer: Reception, transduction, response; signal is a ligand.
Two main categories of membrane receptors:
G protein-coupled receptors (GPCRs)
Ion channels
Ligand binding activates GPCR and phosphorylates G proteins, initiating transduction.
Functions in sensory systems; largest receptor category.
Ligand-gated ion channels act as gates allowing ion diffusion, triggering cellular responses.
Medicines/toxins can modulate signaling pathways (e.g., Botox interferes with neurotransmitter release).
TSH initiates signal transduction in the thyroid gland;
Implications of mutations in TSH receptors in various health conditions (e.g., hypothyroidism).
Correct order of signal transduction events.
Communication among bacteria that affects gene expression based on population density.