Week 12 Cell junctions and signalling Flashcards
What are gap junctions?
A type of communicating junction in animal cells that connect the cytoplasm of adjacent cells via pores. It is similar in the function of plasmodesmata. Gap junctions are made out of proteins called connexin.
What is connexin?
A protein that makes up gap junctions
6 connexin proteins form what?
A pore of the gap junction
What can pass through gap junctions?
There is a set limit of solutes below 1.2 kDa, therefore, ions, sugars, amino-acids, and other small molecules ca pass but proteins and viruses cannot.
What are the opening of gap junctions regulated by?
Ca2+ ions and hormones
What do gap junctions function in?
Coordinating activities of cells within a tissue such as muscle contraction
What are tunneling nanotubes? (TNTS)
Membrane tubules that contain a thin tube of cytoplas. It can connect cells over long distances but are not well understood
True or Fasle? Tunneling nanotubes are small.
False, they are really big and allow the movement of membrane lipids, vesciles, and whole organelles between cells.
Where are gap junctions usually found?
In most animal tissues
Are gap junctions involved in connecting or communicating?
Communicating
What can cells sense?
Signals using proteins calling receptors
Signalling enables what in multicellular organisms?
Co-ordination
What are the 3 processes of signalling at a cellular level?
- Signal reception 2. Signal transduction and 3. Signal response
What are mechanoreceptors?
A sense organ or cell that responds to mechanical stimuli such as touch or sound.
What are chemoreceptors?
A sensory cell or organ responsive to chemical stimuli.
What are thermoreceptors?
Thermoreceptors are specialized nerve cells that are able to detect differences in temperature
True or False? Sometimes the cell that detects a signal is the same one that responds
True
True or False? The cell that detects signals is always close to the cells that respond
False, sometimes they can be a long way away
What are the two types of direct cell to cell signalling?
Cell Junctions and Cell-Cell recognition
What are the two types of local signalling?
Paracrine signalling and Synaptic signalling (nerve cells).
What is long-distance signalling?
Also called endocrine signalling. It is a type of communication whereby a signaling molecule acts on a target cell far from the signaling cell. Mediated my hormones
How diverse can signalling molecules be?
Very diverse, they can be gas molecules, lipid soluble, water soluble, small molecules, and even proteins.
What is a signal transduction pathway?
Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events, most commonly protein phosphorylation catalyzed by protein kinases, which ultimately results in a cellular response. AKA Signal reception - Signal transduction - Signal response (Change in protein activity or expression).
What happens once a signalling molecule binds to a receptor?
It changes shape.
Why are receptors specific for certain signals?
So that only the correct cells respond, and so that the cells don’t respond to the wrong signals.
What is a ligand?
The specific signalling molecule that binds to a specific receptor.
What percentage of human proteins are cell surface receptors?
30%
What are cell-surface receptors?
Cell surface receptors are receptors that are embedded in the plasma membrane of cells. They act in cell signaling by receiving extracellular molecules.
What are cytoplasmic receptors?
Found in the cytoplasm of the cell and respond to hydrophobic ligand molecules that are able to travel across the plasma membrane. Once inside the cell, many of these molecules bind to proteins that act as regulators of mRNA synthesis