UNIT V: CELL REPRODUCTION
A. Cell Recognition
➢ Mosaic-fluid model
➢ The virus binds with the cell’s receptors and gains access to the entry
➢ MHC (major histocompatibility complex)
○ More proteins allow recognition more easily.
○ Cell signaling
➢ Direct Communication:
○ by making direct contact with another cell
■ Targets a cell connected by gap junctions/ signaling across gap junctions
between animal cells
■ Plasmodesmata: binding between plant cells.
■ Cell-cell recognition
➢ Short-Distance:
○ not touching so it needs to send signals but not too bad bc it’s short-distanced
■ Neurotransmitters and received by target cell (proper receptor for proper
input)
■ Interstitial fluid
■ Quorum sensing
■ Paracrine: a cell targets a nearby cell
■ Autocrine: a cell targets itself
➢ Long Distance
○ Endocrine: a cell targets a distant cell through the bloodstream
■ Hormone travels in the bloodstream
■ Target cell specifically binds hormones through blood vessel
■
➢ Signal transduction is the process by which an external signal is transmitted to the
inside of a cell
○ 1. RECEPTION
■ Ligand (signaling molecule) binding to a specific receptor
● Ligand: signaling chemical (ions/hormone) molecule
■ Intracellular or extracellular
■ Even the same signal can have different effects in cells with different
proteins and pathways
■ Pathway branching further helps the cell coordinate incoming signals
○ 2. TRANSDUCTION
■ Activation of a signal transduction pathway
■ AMPLIFICATION
● Phosphorylation cascade
, ○ Relay molecule: each molecule can stimulate the next one
to do an action
■ one enzyme (kinase) phosphorylates another,
causing a chain reaction leading to the
phosphorylation of thousands of proteins
■ At each step, the number of activated products is
much greater than in the preceding step
○ RESPONSE
■ Able to do gene transcription
■ End result: make a protein
■ Change enzymatic activity
■ Apoptosis
● Programmed cell suicide
● Can be triggered by extracellular ligands, DNA damage, or
proteins misfolding in ER
➢ G Protein-coupled receptors
○ Most common receptor
○ Works with G proteins
A. Cell Recognition
➢ Mosaic-fluid model
➢ The virus binds with the cell’s receptors and gains access to the entry
➢ MHC (major histocompatibility complex)
○ More proteins allow recognition more easily.
○ Cell signaling
➢ Direct Communication:
○ by making direct contact with another cell
■ Targets a cell connected by gap junctions/ signaling across gap junctions
between animal cells
■ Plasmodesmata: binding between plant cells.
■ Cell-cell recognition
➢ Short-Distance:
○ not touching so it needs to send signals but not too bad bc it’s short-distanced
■ Neurotransmitters and received by target cell (proper receptor for proper
input)
■ Interstitial fluid
■ Quorum sensing
■ Paracrine: a cell targets a nearby cell
■ Autocrine: a cell targets itself
➢ Long Distance
○ Endocrine: a cell targets a distant cell through the bloodstream
■ Hormone travels in the bloodstream
■ Target cell specifically binds hormones through blood vessel
■
➢ Signal transduction is the process by which an external signal is transmitted to the
inside of a cell
○ 1. RECEPTION
■ Ligand (signaling molecule) binding to a specific receptor
● Ligand: signaling chemical (ions/hormone) molecule
■ Intracellular or extracellular
■ Even the same signal can have different effects in cells with different
proteins and pathways
■ Pathway branching further helps the cell coordinate incoming signals
○ 2. TRANSDUCTION
■ Activation of a signal transduction pathway
■ AMPLIFICATION
● Phosphorylation cascade
, ○ Relay molecule: each molecule can stimulate the next one
to do an action
■ one enzyme (kinase) phosphorylates another,
causing a chain reaction leading to the
phosphorylation of thousands of proteins
■ At each step, the number of activated products is
much greater than in the preceding step
○ RESPONSE
■ Able to do gene transcription
■ End result: make a protein
■ Change enzymatic activity
■ Apoptosis
● Programmed cell suicide
● Can be triggered by extracellular ligands, DNA damage, or
proteins misfolding in ER
➢ G Protein-coupled receptors
○ Most common receptor
○ Works with G proteins
