Chapter 9 Flashcards
cell communication
- cells require this to survive
- known as cell signaling
- incoming and outgoing signals
- cells live in an environment: body is a huge environment and cells need to know how to talk to each other and outside world. Blood cells live in an environment, its important for BC to know whats going on around it
Cell communication; Plasma membrane
- PM isolates the cell
- a cell cannot survive if it cannot sense and respond to environmental changes
- PM is a boundary layer btw the cells and environment
- need a message from outside world for activity to take place
- thirsty
Why do cells need to respond to signals?
1.
- need to respond to a changing environment
- adaptation or a cellular response is critical for survival
- cells need to adapt to the change
- yeast cell- single cell, proteins inside
- glucose comes in and binds to the receptors and tells the cell something about the environment. enough glucose biding to cells present, cell responds by making glucose transporters
Why do cells need to respond to signals?
2.
- cells need to communicate with each other
- cell to cell communication
- coordinate cellular activities in multicellular organisms
Phototropism
- cells in the growing shoot tip sense light and send a signal (auxin) to cells on the nonilluminated side of the shoot.
- cells located below the growing tip receive this signal and elongate, thereby causing a bend in the shoot. In this way, the tip grows toward the light
5 methods of cell to cell communication; 1. Direct intercellular signaling
-cell junctions allow signaling molecules to pass from one cell to another
5 methods of cell to cell communication: 2. contact dependent signaling
-some molecules are bound to the surface of cells and serve as signals to cell coming in contact with them
5 methods of cell to cell communication; 3. autocrine signaling
-cells secrete signaling molecules that bind to their own cell surface and/or neighboring cells of the same type
5 methods of cell to cell communication; 4. Paracrine signaling
- signal does not affect cell secreting the signal but does influence cells in close proximity
- neuronal signaling, blood clotting
5 methods of cell to cell communication; 5. endocrine signaling
- signals (hormones) travel long distances
- hormones are released into the bloodstream
- can travel virtually anywhere in the body/organism
- usually slower acting, but longer lasting; estrogen, insulin etc
Stage one of cell signaling; 1. receptor activation
- signaling molecule (ligand) binds to its cellular receptor (protein)
- receptor undergoes a conformational/ structural change
Stage two of cell signaling; 2. signal transduction
- activated receptor stimulates sequence of cellular changes
- a group of proteins form a signal transduction pathway
- often a multi-step process
Stage three of cell signaling; 3. cellular response
- activation of a cellular response
- a huge range of responses
- alter activity of enzymes; alter cellular structure, gene expression
Ligand
- signaling molecule (key)
- steroid, peptide or protein
- hydrophilic and/or large; cannot cross the membrane easily
- binds noncovalently to receptor (lock) with high degree of specificity
- binding and release between receptor and ligand is relatively rapid
Ligand- Botex
- binding and release is not always rapid
- Clostridium botulinum
- produces most potent toxin known to human kind as a defense mechanism
- inhibits muscle cell receptors
ligand cont.
-ligands alter receptor structure 0conformation change; different structure= different function -ligand-receptor complex is activated -can initiate a cellular response -unbound receptor is not activated
