Cell Communication and Signaling

Study Notes

Cell Communication

Cell Signaling Steps: Reception (receiving the signal), Transduction (passing the signal inside the cell), Response (cell reacts to the signal)
Cell Communication Methods:
- Autocrine: Cell signals itself
- Juxtacrine: Cells communicate by touch
- Paracrine: Cells signal nearby cells
- Endocrine: Signals travel long distances
Reception Details:
- Ligands: Signal molecules (hydrophobic or hydrophilic)
- Hydrophobic ligands cross membranes directly
- Receptor proteins bind to signal molecules
Signal Specificity: Signals bind specific receptors; same signal can trigger different responses in different cells
Receptor Types:
- G-Protein Coupled Receptors: Found outside the cell, often targeted in cancer treatments.
- Tyrosine Kinase Receptors: Two receptors bind signals
- Ion Channel Receptors: Gates open upon signal binding, allowing specific ions through.
Signal Transduction:
- Signal changes receptor shape, activating G-protein
- Amplification: One signal activates many molecules
- Phosphorylation: Activating proteins by adding phosphate groups
- Secondary Messengers (e.g., cAMP): Speed up responses
Intracellular Receptors: Hydrophobic signals bind inside the cell
Homeostasis: Maintaining internal stability (Negative Feedback: Fixes changes to return to normal; Positive Feedback: Strengthens a process until complete)
Plasma Membrane and Cell Signaling (Chapter 5.6):
- Structure: Phospholipid bilayer
- Functions: Transport, Signal Transduction, Recognition
- Steps: Reception -> Transduction -> Response (activating enzymes or genes)
- Communication Types: Short-distance (local signals) and long-distance (hormones)
Immune System Communication: Uses local signals and chemicals
Signal Transduction Details: Links reception to cell responses, has three steps: Reception -> Transduction -> Response, amplifies signals through protein changes.
Plant Responses: Light sensors control seed growth, defenses include physical barriers and chemicals, and various responses to threats
Nervous System Communication:
- Neurons: Dendrites receive signals, cell body contains the nucleus, axon sends signals
- Signal cycle: Resting → Activation → Resetting

Cell Cycle

Cell Division Reasons: Growth, repair, reproduction
DNA Organization: DNA packaged into chromatin, copies into sister chromatids before division
Cell Cycle Phases:
- Interphase (90%):
  - G₁: Growth, normal functions
  - S: DNA replication
  - G₂: Prepares for division
- M Phase:
  - Mitosis: Nucleus divides
  - Cytokinesis: Cell splits
Mitosis Steps:
- Prophase: DNA condenses, spindle forms
- Metaphase: Chromosomes line up in the center
- Anaphase: Chromatids separate
- Telophase: Nuclei form
- Cytokinesis: Cell splits (Animal cells pinch, Plant cells build new wall)
Cell Cycle Checkpoints:
- G₁ Checkpoint: Cell ready for growth?
- G₂ Checkpoint: Correct DNA replication?
- M Checkpoint: Chromosomes attached?
External Signals: Growth factors and environment control cell division.
Cancer Cells: Grow uncontrollably, ignore checkpoints, can make their own growth signals
Apoptosis: Programmed cell death
G₀ Phase: Non-dividing cells (e.g., nerve cells)
Gametes: Do not divide like other cells

Key Vocabulary

Ligand: Signal molecule
Receptor Protein: Receives signal
G-Protein: Relays messages
Amplification: Makes signals bigger
Phosphorylation: Activates proteins
cAMP: Secondary messenger
Apoptosis: Cell self-destructs
Checkpoints: Control points in the cycle
Chromatin: DNA-protein complex
Sister Chromatids: Duplicated chromosomes
Centromere: Holds chromatids together

Description

Explore the intricate processes of cell communication, including the steps of signaling and various communication methods such as autocrine and paracrine signaling. Understand the roles of different types of receptors and how signals are transduced within cells for specific responses. This quiz will enhance your knowledge of cellular interactions and receptor functions.