Cell Signalling ✅ Flashcards
What are the two basic types of cell communication? What is another word for cell communication?
The two basic types of physiological signals (messengers) are:
1) electrical signals
2) chemical signals
How do cells have electrical signals? What changes for them to occur?
Electrical signals are changes in a cell’s membrane potential.
How do cells have chemical signals? What changes for them to occur?
- cells secrete molecules into the extracellular fluid
What are the cells called that receive electrical and chemical signals?
target cells
Which form of communication is most frequent?
chemical communication
What are the three basic methods of cell-to-cell communication?
- DIRECT CYTOPLASMIC TRANSFER - electrical and chemical signals through gap junctions that connect adjacent cells.
- LOCAL COMMUNICATION- by chemicals that diffuse through the extracellular fluid.
- LONG-DISTANCE COMMUNICATION- through a combination of electrical signals carried by nerve cells and chemical signals transported in the blood.
Explain direct cytoplasmic transfer.
DIRECT CYTOPLASMIC TRANSFER of electrical and chemical signals through gap junctions that connect adjacent cells.
Explain local communication.
LOCAL COMMUNICATION by chemicals that diffuse through the extracellular fluid.
Explain long-distance communication.
LONG-DISTANCE COMMUNICATION through a combination of:
- electrical signals carried by nerve cells
- chemical signals transported in the blood.
What is a gap junction? What does it form? Which type of signal passes through them?
- A gap junction is a cytoplasmic connection between adjacent cells
(Protein channels create cytoplasmic bridges between the cells)
When gap junctions are open, ions and small molecules (eg. amino acids, ATP, AMP) pass directly from one cell’s cytoplasm to the next.
- Gap junctions are the only means by which electrical signals can pass directly from cell to cell,
What happens when channels open in the gap junction?
the connected cells function like a single cell with multiple nuclei.
How do chemical signals distribute?
by diffusion through the interstitial fluid.
How is local communication accomplished?
By the diffusion of paracrines and autocrines.
What is a paracrine?
A chemical that is secreted by a cell to act on cells very near it.-
- acts short-distance
- on neighbouring cells
What is an autocrine?
A signal molecule that acts on the cell that secreted it.
- cell creates a hormone which later acts on itself
Why is the effective range of a chemical signal restricted to adjacent cells?
Because distance is a limiting factor for diffusion.
How does the nervous system communicate?
Through chemical and electrical signals.
How does the endocrine system communicate?
Through hormones.
Explain the long-distance communication endocrine system.
- Hormones are secreted by endocrine glands or cells into the blood (and distributed all around the body).
- Only target cells with receptor for the specific hormone will respond to the signal.
What type of signal is for hormones? (specific or non-specific)?
SPECIFIC.
Explain the long-distance communication nervous system.
- the electrical signal travels along a neuron until it reaches the end of a cell
- the neuron then releases chemical signals (NEUROTRANSMITTER) that diffuse across the synapse to the target cell.
What are the “chemicals” of the nervous system?
neurotransmitters
What is the synapse?
A small junction between two neurons, or a neuron and a tissue.
Explain the key steps of a signal pathway.
- RECEPTION (of the extracellular signal by the cell)
- TRANSDUCTION (of a signal from the outside of a cell to the inside of the cell (often multi-stepped))
- CELLULAR RESPONSE (is initiated and it occurs entirely within the receiving cell).
Why do cells not respond to every signal that reaches them?
The signal molecule only recognises the target cell due to its specific receptors.
A cell cannot respond to a chemical if it lack the receptors for that signal.
What are all receptors?
proteins
What are most signal molecules?
water-soluble and too large to pass through the plasma membrane.
How many molecules at a time can one receptor bind to?
one! (1)
What does binding of a molecule do to its receptor?
changes its shape
What is the specific region called at which the signal molecule joins?
the binding site
What are molecules that bind specifically to receptors called?
ligands
What is a ligand?
A molecule that binds specifically to a receptor.
What type of messenger is a ligand?
the FIRST messenger, as it brings information to the target cell.
What is an agonist?
- has an active site of similar shape to the endogenous ligand
- binds to the receptor and produces the same effect
What else circulates in the blood that is not a ligand?
agonists and antagonists
What is an antagonist?
- similar shape of the active site to the ligand
- cannot perform the reaction: takes up space and the the endogenous ligand from attaching –> inhibits the reaction from taking place
What is an intracellular receptor? Where is it located?
- a receptor for lipid-soluble hormones
- located in the cytosol or nucleus
What is a membrane receptor? Where is it located?
- a receptor for water-soluble hormones
- located on the cell membrane
What are the three steps of transferring information mediated by water-soluble substances?
- FIRST MESSENGER (ligand) recognises the receptor in the target cell membrane
- LIGAND-RECEPTOR COMPLEX activates a signal transduction system in the membrane.
an intercellular signal molecule is released (second messenger). - The second messenger TRIGGERS A SEQUENCE OF INTRACELLULAR PROCESSES, resulting in increasing or decreasing protein functions.
What are the three parts of membrane receptors?
1) AN EXTRACELLULAR PART (protrudes from the membrane and comprises the binding site for the ligand)
2) A TRANSMEMBRANE PART (consists of one or more segments that transverse the membrane and help to activate the signal transduction system)
3) AN INTRACELLULAR PART (extends into the cytosol and is involved in the activation of the signal transduction system)
What are the major classes of membrane receptors?
- ion-channel receptor
- 7-helix membrane receptor
- enzyme-linked receptors
What does the intracellular domain have sometimes?
- an enzyme or enzyme-linked receptor.
Why are G-protein receptor systems important?
- they are diverse in their function
play an important role in: - embryonic development
- sensory systems
What interferes with G-function proteins?
several diseases
Who discovered G-proteins, and their role in the signal transduction pathway?
Alfred G. Gilman and Martin Rodbell.
How is signal amplification achieved?
One extracellular ligand binds to a membrane receptor and initiates a signal cascade.
- one ligand is amplified into many second messengers (intracellular signal molecules).
What are the steps of a cascade reaction?
1) Initial STIMULUS activated the first step in the cascade.
2) In each step the activated molecule from the previous step converts an inactive molecule into an active one.
3) The final step is the CONVERSION of a SUBSTRATE into a PRODUCT.
How many responses can result from the reception of a single ligand?
MORE THAN ONE. (1+)
