AP BIO FINAL 1 CHAPTERS

Fight-or-Flight Response: Example of impala fleeing from a cheetah demonstrates physiological functions driven by hormones from adrenal glands.
- Rapid breathing, increased heart rate, and active leg muscles are all part of this response.
- The process involves signal reception when an epinephrine molecule binds to a receptor on muscle cells, activating a pathway that fuels the muscles for escape.

Stages of Cell Signaling:
- Signal Reception: Binding of a signaling molecule (ligand) to a receptor.
- Signal Transduction: Series of molecular interactions relay the signal inside the cell.
- Cellular Response: Activation of a cellular activity, often involving gene regulation or enzymatic action.

External Signals: Converted into cellular responses, important for communication within multicellular organisms.
Quorum Sensing: Bacteria communicate to measure cell density and coordinate behaviors, such as forming biofilms or producing toxins.
Cell Types in Communication:
- Yeast (e.g., Saccharomyces cerevisiae) uses chemical signaling during reproduction via mating factors.

Binding Anticipation: When a signaling molecule binds to its specific receptor, it causes a conformational change initiating intracellular signaling.

Relay Molecules: Proteins that transmit the signal inside the cell, often involving phosphorylation cascades.
Protein Kinases: Enzymes that add phosphate groups to other proteins, modifying their functions.
Second Messengers: Small molecules (e.g., cAMP, Ca²⁺) that rapidly disseminate signaling within the cytosol after a signaling event.

Gene Expression: Signals can activate transcription factors leading to gene expression changes and regulation of cellular activities.
Examples:
- Epinephrine activates glycogen breakdown for energy release.
- Other signaling pathways can regulate processes such as apoptosis.

Structure: Span the cell membrane and interact with G proteins.
Mechanism: When activated by a ligand, G proteins trigger various signal transduction pathways.

Function: Enzymatic receptors that add phosphate groups to tyrosine residues in proteins, initiating multiple signaling pathways simultaneously.

Action: Open or close in response to ligand binding, allowing ions to flow across membranes, crucial for quick cell signaling in nerve cells.

Endocrine Signaling: Hormones, such as adrenaline, are secreted into the bloodstream, affecting target cells throughout the body.
Effects of Hormones: Depending on the receptors present, the same hormone can trigger various responses in different tissues (e.g., epinephrine impacting muscle versus liver cells).

Cellular Responses to Signals: Involve intricate pathways where multiple signals can still lead to a cohesive cellular outcome.
Regulating Responses:
- Efficient signal propagation requires components such as scaffolding proteins, which enhance interactions among signaling molecules and maintain a coordinated response.
- Termination mechanisms ensure pathways do not remain perpetually active, allowing for new signals to be processed effectively.

Apoptosis and Signaling Pathways: Apoptotic pathways can integrate multiple signals, emphasizing the importance of regulated cell death in development and maintenance of health.

The mechanisms of cell signaling are vital for responding to internal and external cues, demonstrating how cells coordinate their activities for survival and functionality in multicellular organisms.