Cell Communication Flashcards
What recognizes the signal to the protein?
receptors
What is a cellular response?
the way a cells responds to a signal communicating a change
What role does glucose play in a yeast cell?
It acts as a signal that binds to the cell and tells it to increase glucose transporters to bring in glucose
What is it called when cell share information with each other?
cell-to-cell communication
Why are there different types of cell communication types?
the distance between cells
What are the 5 types of cellular signaling?
direct intercellular, contact-dependent, autocrine, paracrine, endocrine
What happens during direct intercellular signaling?
the cell junctions between adjacent cells allow them to pass ions/signaling molecules between their cytosols
What is contact-dependent signaling?
A receptor recognizes a membrane-bound signaling molecule of one cell on the surface of another cell
What is autocrine signaling?
A cell secretes signaling molecules that bind to its own cell surface and the surface of neighboring cells of the same cell type
What is paracrine signaling?
A cell secretes a signaling molecule (does not affect itself) that affects the target cells close to them
What signals do not last long?
autocrine and paracrine a
What type of signaling are neurotransmitters?
paracrine signals
What are neurotransmitters?
molecules made in neurons that transmit a signal to an adjacent cell
What is endocrine signaling?
the signals (hormones) are secreted into the bloodstream to reach target cells; can affect all cells in the body/those far away
What are the 3 steps to cell signaling
receptor activation, signal transduction, and cellular response
What happens during receptor activation?
a signaling molecule binds to a receptor of the target cells causing a conformational change to active its function
What happens during signal transduction?
the initial signal is converted into another signal inside the cell
How do cells respond to signals? (3 ways)
Altering the activity (de/activate) of enzymes, changing the function of structural proteins, and affecting transcription factors
What are transcription factors?
Proteins that regulate the transcription of genes and sometimes activate gene expression
What is a ligand?
a signaling molecule
Is the binding of receptors and the ligand very specific?
Yes very specific, so that only the receptor recognizes a specific ligand
What is a ligand-receptor complex?
noncovalent binding of the ligand and receptor
Do receptors alter the structure of ligands?
No, ligands alter the structure of receptors (conformational change) which helps that receptor initiate a cellular response
The binding of a ligand to a receptor is reversible. What does that mean?
the ligand and receptor will dissociate, deactivating the receptor
What is a cell surface receptor?
a receptor in the plasma membrane that allows the cell to respond to extracellular signaling molecules
Why do signaling molecules need cell surface receptors?
Because most signaling molecules are hydrophilic or large molecules that can’t pass the plasma membrane
What are the 3 types of cell surface receptors?
enzyme-linked receptors, G protein-coupled receptors (GPCR), and ligand-gated ion channels
How do enzyme-linked receptors work?
A signaling molecule binds to an extracellular domain and a conformational change affects the intracellular domain to become active
What is a protein kinase?
enzymes that transfer a phosphate group from ATP to an amino acid
What do most enzyme-linked receptors function as?
protein kinases phosphorylating itself or intracellular proteins
How do GPCRs work?
GPCRs interact w/ intracellular G proteins, the G protein releases GDP and binds to GTP causing the G protein to dissociate into alpha subunit and B/Y dimer
What are G proteins?
a lipid-anchored protein that binds to GTP and GDP
How do ligand-gated ion channels work?
ligands bind to the receptor allowing the ion channel to open and ions to flow through
What happens if there is an extracellular (outside cell) signaling molecule that has a receptor inside?
The signaling molecule will diffuse the plasma membrane to reach its receptor
Receptor tyrosine kinases are a type of…..
enzyme-linked receptors
What does a tyrosine kinase phosphorylate?
phosphorylates tyrosines within a specific motif (sequence of amino acids) on any protein displaying that motif
What is a growth factor?
a signaling molecule that promotes cells division
What is (EGF) epidermal growth factor?
a signaling molecule that stimulates epidermal cells to divide
What is the cell signaling process for EGF?
secreted from endocrine cells–>goes through bloodstream–> binds to receptor tyrosine kinases/ EGF receptor
What are the (3) parts of the signal transduction pathway?
relay protein activates protein kinase cascade, protein kinase cascade phosphorylates intracellular proteins, the phosphorylated transcription factors stimulate gene transcription
How is the EGF receptor activated?
2 EGF subunits each bind to a molecule of EGF, this causes the subunits to combine and phosphorylate each other in tyrosines within the receptors activating the EGF receptor
How do the relay proteins work for the EGF pathway?
the phosphorylated EGF receptor is recognized by Grb (starting pathway)–>Grb (conformation change)–>Sos (ch) activation causes Ras to release GDP and bind to GTP activating Ras
What do the relay proteins (EFG pathway) activate
the protein kinase cascade
How many proteins are in the protein kinase cascade?
3 activated Ras–>Raf–>Mek–>Erk
What is an advantage of the protein kinase cascade?
Signal amplification, greater cellular response
What is the cellular response to the EFG pathway?
Erk phosphorylates transcription factors that stimulate the transcription of genes that promote cell division
What is a first messenger?
Extracellular signaling molecules that bind to the cell surface receptors
What are second messengers?
small molecules that relay signals inside the cell, the signals are short
What is adenylyl cyclase?
an enzyme that when bound to an alpha subunit of a G protein synthesizes cAMP from ATP
What is cAMP or cyclic AMP
a second messenger synthesized from adenylyl cyclase and ATP
Explain the signal transduction pathway with GPCR and epinephrine
epinephrine binds to its receptor and activates a G protein, the alpha subunit activates adenylyl cyclase to produce cAMP which activates PKA
What is PKA?
protein kinase A, which activates a cellular response
How does PKA lead to a cellular response?
the catalytic subunit of PHA phosphorylates a cellular protein that influences the structure and function of the cell
What enzymes does PKA activate?
phosphorylase kinase and glycogen synthase
What does phosphorylase kinase do?
it phosphorylates glycogen phosphorylase, which causes glycogen to breakdown into glucose and phosphate
What does glycogen synthase do?
synthesize glycogen
What role does cAMP play in glycogen synthesis?
It inhibits synthesis
What effect does the epinephrine signal have on energy?
It stimulates glycogen breakdown and stops glycogen synthesis to provide more glucose to cells for energy
What does phosphodiesterase do?
convert cAMP to AMP
What does protein phosphatase do?
remove phosphate groups from protein reversing the effects of PKA
What are 2 advantages of second messengers?
amplifying the cellular response and it is faster because they are small and water soluble
What is crosstalk?
when one or more components of one transduction pathway affect a different signal transduction pathway
Why does a signal have diverse responses throughout the body?
genes are turned off or on in certain parts of the body leading to a different proteome (protein)
What is apoptosis?
programmed cell death
In what ways can apoptosis cause disease?
cell not dying- cancer cells dying too much- HIV and neurodegenerative disease
What is the extrinsic pathway?
A pathway for apoptosis that has a death receptor on the cells surface
What is the intrinsic pathway or mitochondrial pathway?
An apoptosis pathway stimulated by DNA damage
