C2.1 Chemical Signaling Flashcards
Why are intracellular receptors lipids?
Lipids are nonpolar and won’t dissolve in the cytoplasm.
The process of signal transduction begins with the binding of a ligand to a _________.
receptor protein
Receptors present on the outer side of the target cells are called __________ receptors.
cell surface
___________ enzyme is responsible for bioluminescence in Vibrio fischeri.
Luciferase
Autoinducers can only act on a different cell.
True or false?
False - Autoinducers can also bind to the regulatory gene in the same cell that produces it.
N-acyl homoserine lactone is the chemical that triggers
___________ in Vibrio fischeri.
bioluminescence
Calcium ions can move in and out of the cell through the ______ _____.
Calcium pump
_________ are chemical substances that carry signals from one neuron to the other or from one neuron to a target cell such as muscle cells.
Neurotransmitters
Insulin is an example of a _____ hormone.
peptide
The type of amino acids found in transmembrane receptors:
- Found on either side of the cell membrane: __________
- Spanning the cell membrane: _____
Hydrophilic, Hydrophobic
Identify the role of a ligand in initiating signal transduction pathways by receptors.
It binds to the extracellular domain of the receptor.
When a neurotransmitter binds to a receptor on the postsynaptic membrane, it can cause a change in the ________ potential, which can lead to the generation of an ______ potential.
membrane, action
Order events:
I. Secondary messengers activate protein kinase
II. Receptor gets activated
III. Ligand binds to the receptor
IV. Protein kinases phosphorylates other proteins
V. Gene expression is regulated
III, II, I, IV, V
1.) Ligand binds to GPCR on ______ membrane
2.) G protein binds to GTP and becomes active
3.) Adenyl cyclase converts ATP to cAMP
extracellular
The binding of ________ to the IRS receptor causes phosphorylation of the tyrosine kinase residue.
insulin
Identify which of the following is the first step in the mechanism of action of epinephrine (adrenaline) receptors.
Conformational change in the GPCR
The genomic signalling pathway results in the _____ of heat shock proteins once the hormone binds to the receptors.
detachment
Positive feedback causes an _____ in the signalling pathway response whereas negative feedback causes its _____.
increase, reversal/stop
Positive feedback definition:
A mechanism that amplifies the signal and increases the response
Negative feedback definition:
A mechanism that dampens the signal and decreases the response
Which type of receptor is associated with positive feedback
Transmembrane receptors with tyrosine kinase activity, Transmembrane receptors with G-protein coupling
Identify an example of negative feedback in cell signalling pathways.
Insulin signalling in response to high blood glucose levels
Outline the structure and function of receptor molecules.
Receptors are proteins, with a site to which the signaling chemical can bind.
Outline the relationship between receptor and a specific ligand.
- when a specific ligand binds with receptor protein, causes conformational change (change in shape)
-kick off series of chemical reactions
-ligand remains unchanged
Describe the process of quorum sensing in a population of bacteria, including the role of signaling molecules, receptors and a threshold for gene expression.
-used to regulate gene expression in a cell-density-dependent manner.
-Bacteria can synchronize population behavior using small molecules called autoinducers that are produced by cognate synthases and recognized by specific receptors.
Outline the process of bioluminescence in Vibrio fischeri as an example of quorum sensing in bacteria.
-luminescence of V. fischeri is activated through a quorum sensing (QS) mechanism
-the cells remain dark until their population reaches the high densities that signify colonization of the light organ of the symbiotic host.
Define quorum sensing:
a change in the behavior of a colony when its population density reaches a certain threshold
Signaling systems have evolved _________, leading to a wide range of _______ substances being used as signaling chemicals.
repeatedly, chemical
What is a ligand?
a molecule that binds to another molecule called a receptor to send signals within or between cells
Compare the structure and function of different categories of animal chemical signaling molecules, including: hormones.
Hormones -
-endocrine glands secrete hormones directly into bloodstream
-long effect time
-target cells have receptor proteins
Compare the structure and function of different categories of animal chemical signaling molecules, including: neurotransmitters.
Neurotransmitters:
- synaptic transmission (between nerves)
- Isolated to just that nerve junction
- short effect time
- removal from synapse
Compare the structure and function of different categories of animal chemical signaling molecules: cytokines
Cytokines:
-proteins that act as chemical messengers between nearby cells
-cells produce cytokines
-how cells in a tissue communicate with each other (not nerve cells)
Compare the structure and function of different categories of animal chemical signaling molecules: calcium ions
Calcium ion
- muscle fiber: during muscle contraction, calcium ions bind to a protein on actin —> allowing myosin heads to attach
- neurons: causes the release of neurotransmitters from the presynaptic neuron
Hormone examples:
insulin, glucagon, testosterone, estrogen
Neurotransmitter examples:
Go between motor neurons & muscles:
acetylcholine,
- In the brain:
dopamine, serotonin
Cytokines examples:
Interferon
- inflammation process in immune cells
-warn nearby cells of viruses
Some examples of signaling chemicals are ______, _____, ______, and ______.
hormones, neurotransmitters, cytokines, calcium ions
State the properties shared by all signaling chemicals.
- small
- soluble
- have a shape compatible with their receptor
Outline the chemical categories of hormones.
-different chemical structure but they work the same way in body:
-Amines
-Peptides and proteins
-Steroids
Outline chemical categories of neurotransmitters.
-Amines
-Amino Acids
-Esters
-Gases
Contrast the location of effect relative to the location of release between hormones and neurotransmitters.
-Hormones can have effects over large distances (travel through the bloodstream to reach target cells)
-Neurotransmitters produce a localised effect between 2 neurons (nanometers in between - small distance)
Distinguish between the structure of transmembrane receptors and intracellular receptors, including distribution of hydrophilic and hydrophobic amino acids.
Signaling molecule CAN enter cell
-Receptor protein located in cytoplasm or nucleus
-Intracellular (within cell)
-Hydrophilic amino acids (dissolved)
—> surface of receptor
—> cytoplasm + water
Signaling molecules CANNOT enter cell
- (ex. insulin)
-receptor protein located on the plasma membrane
-transmembrane proteins (middle is hydrophobic/ top and bottom is hydrophilic amino acids)
Compare the ligands ability to enter the target cell for transmembrane and intracellular receptors.
Transmembrane - molecule CANNOT enter cells
INTRACELLULAR receptor - molecule CAN enter cell
Outline the steps of a signaling pathway.
Reception- cell detects signal in environment
Transduction- activating change in cell
Response- change that occurs in cell as a result of signal
The signaling molecules are called _____________. They are _______. An example would be hormones or neurotransmitters.
first messengers, extracellular factors
Define transduction
The binding of the signaling molecules induces a change in the shape of the receptor
Define signaling cascade
Series of metabolic reactions within the cell that occur in a linear fashion
Define second messenger
The intracellular signaling molecules that are released in response to extracellular signaling molecules
Outline the three pathways that can be activated when a ligand binds to a transmembrane receptor.
- ligand binds with receptor
- receptor changes shape
- produces secondary messenger molecules
- causes changes within cell
Outline the effect of a ligand binding to an intracellular receptor.
- ligand enters cell
- binds to receptor
- complex regulates gene expression
List the general cell responses to the binding of a signaling molecule.
- change in gene expression
- change in cell metabolism
- change in cell shape/movement
Outline the mechanism by which the receptor for the neurotransmitter acetylcholine changes membrane potential in a postsynaptic cell membrane.
- neurotransmitter binds to 2 subunits outside of cell
- channel is lined with negatively charged amino acids
- allows sodium to flow into inside cell
- Na+ inside cell leads to muscle contraction
Acetylcholine receptor AKA _______ allows sodium to come into the cell, causing the postsynaptic cell to become ______.
AchR, depolarized
Describe the structure and function of the G-protein coupled receptors (GPCRs) and of the G-proteins.
- seven hydrophobic transmembrane segments
- proteins that act as secondary messengers during signal transduction
Outline activation of G-protein coupled receptors (GPCRs).
-ligand binds, allowing inactive GDP to be replaced by GTP
Outline how binding of a signaling ligand to a G-protein coupled receptor (GPCR) can cause change in the target cell.
-the cell is inactive before ligand binds
-after binding of ligand, GDP is replaced by GTP (active molecule is secondary messenger)
List example signaling ligands that target G-protein coupled receptors (GPCRs).
Neurotransmitters (Serotonin, Acetylcholine, Glucamate)
Epinephrine is secreted by ______ glands in preparation for _____ activity.
adrenal, vigorous
Describe the activation of the cAMP second messenger system by the epinephrine receptor.
- epinephrine binds with G-protein
-Cause ATP —> cAMP (2ndary messenger molecule)
-amplifies the effect
Outline the effects of epinephrine on a body.
epinephrine = adrenaline
fight or flight response
Define phosphorylation and kinase.
enzyme that phosphorylates molecules.
-gets phosphate group from ATP
and adds it to another molecule
Describe the action of receptors with tyrosine kinase activity.
enzyme transfer a phosphate group from ATP to tyrosine (amino acid) in a protein
Insulin is secreted by _____ cells when blood glucose levels are ____.
pancreas, high
Describe the cause and effect of the activation of the insulin receptor.
- insulin binds to a transmembrane receptor
- signal transduction
- glucose channels embedded within cell membrane
Describe the mechanism of steroid hormone action.
attaches to DNA in nucleus, changes gene expression
List example steroid hormones.
Cortisol, Progesterone, Estriol
Outline one example of a steroid hormone promoting transcription of a specific gene.
Cortisol is a steroid that has many effects depending on the target cell. (maintain blood glucose levels, fight or flight response in immune system cells)
______ and progesterone are steroid hormones.
Oestradiol
Describe the role of oestradiol in the regulation of the release of FSH and LH from the anterior pituitary, including the role of the hypothalamus, the oestradiol receptor, transcription factor and gonadotropin releasing hormone.
-binding of oestradiol to DNA in hypothalamus activates transcription of GnRH gene into mRNA
-The mRNA is translated into a gonadotropin releasing hormone protein
-causes pituitary to release luteinizing hormone, triggering ovulation
Describe the role of progesterone in the formation and maintenance of the endometrium, including the progesterone receptor, transcription factor and growth factor protein.
increases nutrients in the endometrium
Compare the processes and consequences of positive and negative feedback.
positive feedback - produces instability
negative feedback - reduces the effect of change/helps maintain balance
Outline one example each of hormonal regulation via positive feedback.
-muscle cells
- ligand binds with receptor(opens calcium ion channels)
- calcium-induced calcium release in muscle contraction
Outline one example each of hormonal regulation via negative feedback.
Testosterone levels are too high, the hypothalamus sends a signal to the pituitary gland to stop sending signals to the testes
