Unit 2: Cell Signaling Flashcards
Cell Signaling
communication between cells to coordinate responses
Steps of cell signaling (5)
signal, reception, transduction, response, and termination.
Ligands
A molecule that binds to another specific molecule, in some cases delivering a signal
Receptors
Proteins in target cells that bind specific ligands
Signal Transduction
Process of converting extracellular signals into intracellular responses in the cytoplasm.
Response
Cellular reaction to the signal received
Termination
End of the signaling process to stop the cellular response
Types of ligands involved in signaling (2)
small hydrophobic ligands and water-soluble ligands
Small Hydrophobic Ligands are __ ligands that __ through the plasma membrane.
Lipid-soluble ligands, diffuse (steroid hormones)
Water-Soluble Ligands
Polar ligands binding to cell-surface receptors
Types of water soluble ligands
small molecules, peptides, and proteins.
We can divide receptors into two main classes,
intracellular and cell-surface receptors.
Intracellular Receptors
Proteins in the cytoplasm responding to hydrophobic ligands
When a ligand binds to an intracellular receptor a ___ occurs that exposes a ___. on the protein. The ligand-receptor complex moves into the ___then binds to specific regulatory regions of the chromosomal DNA and promotes the initiation of __.
conformational change, DNA-binding site, nucleus, transcription
Intracellular receptors can directly influence gene expression without having to
pass the signal on to other receptors or messengers.
Cell-Surface Receptors (transmembrane receptors)
Membrane proteins binding external ligands for signal transduction
Properties of a cell surface receptor (3)
extracellular, hydrophobic transmembrane, and intracellular domain
Signaling found in multicellular organisms can be divided into three main classes:
direct, paracrine, and endocrine signaling
Direct Signaling
Cell communication through direct contact between cells
Specialized types of direct signaling include (3)
juxtacrine, gap junctions, and plasmodesmata
Juxtacrine Signaling
Direct signaling between cells via direct contact between membrane-bound ligands
Gap Junctions
Connections between neighboring cell membranes
Plasmodesmata
Connections in plants between neighboring cell membranes
Paracrine Signaling
Local signals between nearby cells via diffusion through extracellular matrix
Specialized types of paracrine signaling (2)
autocrine and neuronal signaling
Autocrine Signaling
Signals produced by cells binding to released ligands, influencing self or similar cells
Neuronal Signaling
Transmission of signals between neurons and target cells through synapses
synaptic signal
a chemical signal that travels between nerve cells.
Synaptic signal process
Signals within the nerve cells are propagated by fast-moving electrical impulses. When these impulses reach the end of the axon, the signal continues on to a dendrite of the next cell by the release of chemical ligands called neurotransmitters from the presynaptic cell (the cell emitting the signal).
Endocrine Signaling
Signals from distant endocrine cells affecting target cells via hormones in the bloodstream
The ligands released in endocrine signaling are called
hormones
a signaling molecule that regulates physiology, behavior, or development
Hormone
Hormone transportation
travel the large distances between endocrine cells and their target cells via the bloodstream
Why do hormones present in low concentrations
they become diluted by the time they reach their target cell, due to their long distance of travel
Types of hormones include; (4)
amine, peptide, protein, steroid
Signal transduction
Once a ligand binds to a receptor, the signal is transmitted through the membrane and into the cytoplasm (and sometimes also the nucleus) of the cell
When a ligand binds to its receptor, ___ occur that affect the receptor’s intracellular domain
conformational changes
Signaling Pathway (signaling cascade)
Chain of events triggered by receptor activation, leading to cellular changes
Methods of intracellular signaling include; (2)
phosphorylation and second messengers
Second Messengers (2)
Enzymes and proteins in a signaling cascade interacting with specific proteins
Examples of second messengers
calcium ions and cAMP (cyclic AMP)
Calcium signaling
a calcium ion is a widely used second messenger that regulates various cellular responses
Phosphorylation
Common modification adding phosphate groups to proteins, often catalyzed by kinases
Kinase
Enzyme catalyzing the transfer of a phosphate group
Dephosphorylation
Removal of a phosphate group from a protein, reversing its activation
Cyclic AMP (cAMP)
Second messenger synthesized from ATP, activating A-kinase
Response to signal is determined by
external/internal conditions and cell type
Common responses to cell signaling include;
gene expression, increase in cellular metabolism, cell growth & death, and termination of the signal.
Gene expression is regulated by
RNA transcription or protein translation by signaling pathways
MAPK/ERK Pathway
Protein chain signaling from cell surface receptor to nuclear DNA
Cell Growth Factors
Ligands promoting cell division, binding to RTKs and activating MAP kinase pathway
Apoptosis
Programmed cell death mechanism to eliminate damaged or unnecessary cells
Termination of signal is done by
degrading ligands or reversing cellular modifications
Functions of nucleic acids
They carry the cell’s genetic blueprint and carry instructions for its functioning.
nucleic acids are the most important___ for the continuity of life
macromolecules
Main groups of nucleic acids (2)
RNA and DNA
ribonucleic acid (RNA)
a nucleic acid that is involved in gene expression and regulation
deoxyribonucleic acid (DNA)
nucleic acid that stores genetic information in its sequence of nucleotides
DNA in eukaryotic cells is not
enclosed in a membrane-bound organelle.
RNA that carries information from DNA to ribosomes to enable protein synthesis
Messenger RNA (mRNA)
ribosomal RNA (rRNA), transfer RNA (tRNA), and microRNA (miRNA) — are types of RNA involved in
protein synthesis and its regulation.
specific signal transduction pathway takes place in the__ domain
Intracellular
