Chapter 11 - Cell Communication Flashcards
The three steps in cell communication
1) Signal reception
2) Signal transduction
3) Cellular response
__________ are converted to responses within the cell
External signals…
Cells _____, ____, and ___ to signals
receive, send, and respond
Definition of Epinephrine (adrenaline)
A hormone secreted by the brain into the blood that stimulates the breakdown of stored polysaccharide glycogen within liver cells & skeletal muscle
Cells in a multicellular organism communicate via ____ targeted for cells that may or may not be adjacent
…signaling molecules…
Local signaling
animal cells communicate by direct contact (w/ cell junctions & cell-surface molecules)
Many animal and plant cells have cell junctions that ____ ____ to the cytoplasm’s/adjacent cells
directly connect
Plasmodesmata definition
Channels that connect plant cells and water & small solutes (and proteins & RNA) pass from cell to cell
Gap junctions provide ___ ___ btwn adjacent cells
cytoplasmic channels
Paracrine signaling
Another method animal cells use to communicate.
- uses secreted messenger molecules that travel only short distances
- ex: Growth factors (stimulate nearby target cells to grow & divide)
Synaptic signaling definition
- neurotransmitters released in response to electric signal
- occurs in animal nervous system
Long distance signaling
Uses hormones (plants & animals)
In ___ ___ (in animals) specialized cells release hormones, which travel to target cells via the circulatory system (bloodstream)
…endocrine signaling…
The ability of a cell to respond to a signal depends on whether it has a ___________
…receptor specific to that signal
3 stages of cell signaling
-Reception, transduction, and response
-A series of steps by which a signal on a cell’s surface is converted into a specific cellular response
Signal reception (general)
The target cell detects a signaling molecule (ligand) coming from outside the cell that binds to a receptor protein on the cell surface
Signal transduction (general)
The binding of the signaling molecule alters the receptor and initiates a signal transduction pathway
Cellular response (general)
The transduced signal triggers a specific response in the target cell
A signaling molecule binds to a receptor protein, causing it to _____ ______
…change shape
The binding btwn a ligand and receptor is _____ ______
highly specific
_______________ is generally the initial transduction of the signal
A shape change in a receptor…
Most signal receptors are _____ _______ proteins, but others are located inside the cell
…plasma membrane…
The 3 main types of plasma membrane:
-G protein-coupled receptors
-Receptor tyrosine kinases (growth factors)
-Ion channel receptors
G protein-coupled receptors (GPCRs)
-Cell-surface transmembrane receptors that work w/ G protein
-Largest family of human cell-surface receptors
-G proteins bind energy-rich GTP (Guanonsine-5’-triphosphate)
-Most water-soluble signal molecules bind to specific sites on receptor proteins that transmit info from extracellular environment to inside of cell
Receptor tyrosine kinases (RTKs)
-Membrane receptors that catalyze the transfer of phosphate groups from ATP to another protein
-Can trigger multiple signal transduction pathways at once
-Abnormal functioning of RTKs associated w/ many types of human cancers
Ion Channel Receptors
-Ligand-gated ion channel receptor acts as gate that opens & closes when the receptor changes shape
-Allows specific ions to flow through channel after ligand binds to receptor
Intracellular Receptors
-Only in target cells (cytoplasm or nucleus)
-Small/hydrophobic chemical messengers
-Activated hormone-receptor complex can act as transcription factor (turn on/off specific genes)
-Ex: Aldosterone (lipid soluble) is steroid hormone that can cross the membrane to get to the target intracellular receptor & main role is to regulate salt & water in body, influencing blood pressure
(signal transduction) Cascades of molecular interactions transmits signals…
…from receptors to relay molecules in the cell
(signal transduction) Activated receptor activates another protein, which activates another, and so on till…
…the protein producing the response is activated
(signal transduction) at each step, the signal is transducted into a different form, commonly a…
…shape change in a protein
Many relay molecules in signal transduction pathways are _______, creating a phosphorylation cascade
…protein kinases…
What do protein kinases do
They add a phosphate group to activate/inactivate other proteins
Phosphorylation & dephosphorylation or proteins are commonly used in cells to _______ (molecular switch that turns activities on/off)
regulate protein activity
Second messengers
-small, nonprotein, water-soluble molecules/ions that spread thru a cell via diffusion
-Cyclic AMP (made from ATP) & calcium ions common second messenger
-Participate in pathways initiated by GPCRs and RTKs
(Cellular response) Cell signaling leads to regulation of one or more _________
…cellular activities
(Cellular response) Many signaling pathways regulate the __________/other proteins usually by turning genes on/off in the nucleus
synthesis of enzymes
(Cellular response) Response may occur in ______
nucleus/cytoplasm
