Final- 11 Flashcards
Types of local signaling
Gap junctions
Plasmodesmata
Cell-cell recognition
Gap junction
Cytoplasm is directly connected. Allows molecules to directly pass through a gate from one cell to another
Plasmodesmata
Connecting cell walls to exchange material
Cell-cell recognition
Not directly connected. Receptors of cells connect
Local regulators
Messenger molecules that travel short distances. Influence cells in the area
Long distance signaling
Hormones travel through circulatory system
Ligand
Messenger. Binds to specific receptor
Types of water soluble receptors in the plasma membrane
G protein coupled receptors
Receptor tyrosine kinases
Ligand gates ion channels
G protein coupled receptors
Works with the help of a G protein. Spans the membrane. G protein switches the receptor on and off. Activated when G bonds to it. GTP released. Phosphorylation. Does Not work if GDP is bound
Receptor tyrosine kinases
Only fully activated when two ligands bind
Activation is a phosphorylation event
Membrane receptors attach phosphates to tyrosine
Can trigger multiple events
Acts as an enzyme upon substrates, transfers phosphate groups
Ligand gates ion channels
Acts as a gate type receptor
Allows passage of specific ions (ca+, na+)
Ligand binds to receptor to open gate, conformational change
Transduction
Cascade of molecular events to relay message
Usually involves multiple steps to amplify signal, larger cellular response
Signal transduction pathways
Relay message from receptor to response
Mostly proteins do this
First messanger
Ligand
Second messanger
Small non protein water soluble molecules or ions that spread throughout a cell by diffusion
Small molecules and ions
What are second messanger important for
GCPR and RTK
Common second messengers
Ca2+ and cAMP
cAMP
Activated by enzyme adenylyl cyclase. Usually activated protein kinase A
Ca2+
Regulated through changes in concentration. Ex: muscle cells
ER stores calcium ions and releases them for signal transduction
Response
Cell signaling leads to regulation of many activities
Output response
Nucleus or cytoplasm, cells response to an extracellular signal
What do signals do
act to regulate activity of transcription factors (control gene expression), enzymes (activity and synthesis), cell behavior and cell shape
Four aspects of fine tuning the response
- Amplification of signal
- Specificity
- Enhancement by scaffolding proteins
- Signal termination
Amplification of signal
Elaborate enzyme cascade Increases response (at each step, the number of activated products is much greater than the proceeding step)
Specificity
Based on different protein connections in the cell, different proteins allow cells to detect and respond to signals
Enhancement of scaffolding proteins
Large relay proteins
Increase signal efficiency by grouping together different proteins involved in the same pathway
Signal termination
Inactivation of signal
Drop in ligand concentration-termination
Can be reversible
Apoptosis
programmed cell death
How is apoptosis carried out
component of cell are chopped up and packed into vesicles, prevents enzymes from leaking out of the dying cell and affecting other cells
What happens to the cell shape during apoptosis
characteristic morphology
What is a protease
Something that cuts up proteins
What acts as a protease in apoptosis
Caspases
What triggers apoptosis
- Extracellular death signal
- DNA damage in the nucleus
- Protein misfolding
What diseases is apoptosis involved with
Parkinsons, Alzheimers
Interpherence with apoptosis may cause cancer
