C2.1 Chemical Signaling Flashcards
What are receptors?
Proteins with binding sites for specific signaling chemicals
Receptors bind to ligands, allowing cells to communicate through chemical signals
What is quorum sensing?
A method used by bacteria to assess population density through intercellular communication
It involves the secretion of signaling molecules that trigger changes in gene expression when a critical level is reached
Name examples of functional categories of signaling chemicals in animals.
- Hormones
- Neurotransmitters
- Cytokines
- Calcium ions
Each category plays a distinct role in cell signaling
What distinguishes hormones from neurotransmitters?
Hormones are produced in small amounts and transported through the bloodstream, while neurotransmitters transmit signals across synapses
Hormones can affect distant cells, whereas neurotransmitters have localized effects
What is the role of calcium ions in cell signaling?
They play a crucial role in muscle contraction and neurotransmitter secretion
Calcium ions are released upon receiving a nervous impulse and trigger various cellular responses
Fill in the blank: Signaling molecules can have ______ effects and can be transported over long distances.
distant
Hormones are examples of signaling molecules that have distant effects
What are the differences between transmembrane receptors and intracellular receptors?
- Transmembrane receptors are located in the plasma membrane
- Intracellular receptors are found in the cytoplasm or nucleus
This distinction is based on the ability of signaling chemicals to enter target cells
What initiates signal transduction pathways?
Binding of a signaling chemical to a receptor
This can lead to various cellular responses depending on the type of receptor and signaling chemical
What happens when neurotransmitters bind to their receptors?
They open membrane channels, altering membrane potential
This can either stimulate or inhibit a nerve impulse or muscle contraction
What are G-protein-coupled receptors (GPCRs)?
A diverse group of transmembrane receptors that transmit signals into cells using G proteins
GPCRs play a key role in mediating various physiological responses
What is the mechanism of action of epinephrine receptors?
Epinephrine binds to a receptor, activating G protein and stimulating adenylyl cyclase to produce cAMP
cAMP acts as a secondary messenger, initiating rapid cellular responses
What is tyrosine kinase activity?
The transfer of phosphate from ATP to the amino acid tyrosine in proteins
This process is crucial for signal transduction, as seen in insulin receptors
How do steroid hormones affect gene expression?
They bind to intracellular receptors and form a hormone-receptor complex that interacts with DNA
This can lead to activation of specific gene expression
What is the role of oestradiol in human reproduction?
Regulates the release of reproductive hormones and affects the brain
Oestradiol influences the hypothalamus, impacting the menstrual cycle
What is positive feedback in cell signaling?
Amplification of the starting point of a pathway, leading to increased product creation
An example is calcium-induced calcium release in muscle cells
What is negative feedback in cell signaling?
An increase in the end-product inhibits its own production
Testosterone production is regulated through negative feedback mechanisms involving GnRH and LH
What is cell signaling?
A process by which messages are sent to cells. Allows multicellular organisms to control and coordinate their bodies and for responding to their environment.
What are ligands?
Chemical signals
What are protein receptors?
They have ligand binding sites to which the ligand binds.
How is enzyme-substrate binding different from ligand-protein receptor binding?
- the ligand molecule can remain bound to the protein receptor for a long period of time before it’s released
- unlike enzymes
How is enzyme-substrate binding similar to ligand-protein receptor binding?
- both bind due to shape and chemical properties
- they both are unchanged by binding
What is an example of quorum sensing?
Bioluminescence in a marine bacterium known as Vibrio fischeri
Explain cell signalling by bacteria in quorum sensing.
Signalling molecules/chemicals are made/secreted at low rates by all cells. The signalling molecules diffuse freely and bind to protein receptors on each cell. As population density increases cells get more signalling chemicals and this leads to a collective change in gene expression when a quorum is sensed.
What does quorum sensing exemplify?
Interaction and interdependence as its effects require multiple cells participating together.
