Communication and signalling Flashcards
Multicellular organisms signal between cells using what?
Multicellular organisms signal between cells using extracellular signalling molecules
what are steroid hormones and neurotransmitters an example of
Steroid hormones, peptide hormones, and neurotransmitters are examples of extracellular signalling molecules.
what are Receptor molecules of target cells
Receptor molecules of target cells are proteins with a binding site for a specific signal molecule
Binding changes the conformation of the
receptor which initiates what
Binding changes the conformation of the
receptor, which initiates a response within the
cell
Signalling molecules may have different effects on different target cell types due to what
Signalling molecules may have different effects on different target cell types due to differences in the intracellular signalling molecules and pathways that are involved.
Different cell types produce specific signals that can only be detected and responded to by what type of cells
Different cell types produce specific signals that can only be detected and responded to by cells with the specific receptor
In a multicellular organism, different cell types may show what
In a multicellular organism, different cell types may show a tissue-specific response to
the same signal
what can hydrophobic signalling molecules do
Hydrophobic signalling molecules can diffuse
directly through the phospholipid bilayers of
membranes, and so bind to intracellular receptors
The receptors for hydrophobic signalling molecules are what?
The receptors for hydrophobic signalling molecules are transcription factors
what are transcription factors
Transcription factors are proteins that when
bound to DNA can either stimulate or inhibit
initiation of transcription.
what are some examples of hydrophobic signalling molecules
The steroid hormones oestrogen and testosterone are examples of hydrophobic signalling molecules
Steroid hormones bind to specific receptors in where?
Steroid hormones bind to specific receptors
in the cytosol or the nucleus
The hormone-receptor complex moves to the
nucleus where it binds to what which does what?
The hormone-receptor complex moves to the
nucleus where it binds to specific sites on
DNA and affects gene expression
The hormone-receptor complex binds to complex DNA sequences called what. what does this influence
The hormone-receptor complex binds to complex DNA sequences called hormone response elements (HREs). Binding at these
sites influences the rate of transcription, with
each steroid hormone affecting the gene
expression of many different genes.
Binding of the peptide hormone insulin to its receptor results in an intracellular signalling cascade that triggers what?
Binding of the peptide hormone insulin to its receptor results in an intracellular signalling cascade that triggers recruitment of GLUT4 glucose transporter proteins to the cell membrane of fat and muscle cells
Diabetes mellitus can be caused by what?
Diabetes mellitus can be caused by failure to
produce insulin (type 1) or loss of receptor
function (type 2)
Exercise also triggers what, which can improve what
Exercise also triggers recruitment of GLUT4,
so can improve uptake of glucose to fat and muscle cells in subjects with type 2
Binding of insulin to its receptor causes a conformational change that triggers phosphorylation of the receptor. what does this start
Binding of insulin to its receptor causes a conformational change that triggers phosphorylation of the receptor. This starts a
phosphorylation cascade inside the cell, which eventually leads to GLUT4-containing vesicles being transported to the cell
membrane.
what is resting membrane potential
Resting membrane potential is a state where there is no net flow of ions across the membrane
The transmission of a nerve impulse requires what?
The transmission of a nerve impulse requires changes in the membrane potential of the neuron’s plasma membrane
What is an action potential
An action potential is a wave of electrical excitation along a neuron’s plasma membrane
how do neurotransmitters initiate a response
Neurotransmitters initiate a response by binding to their receptors at a synapse
what are Neurotransmitter receptors
Neurotransmitter receptors are ligand-gated ion channels.
what is depolarisation
Depolarisation is a change in the membrane potential to a less negative value inside.
Depolarisation of the plasma membrane as a result of the entry of positive ions triggers the what
Depolarisation of the plasma membrane as a result of the entry of positive ions triggers the opening of voltage-gated sodium channels, and further depolarisation occurs
Inactivation of the sodium channels and the opening of potassium does what
Inactivation of the sodium channels and the opening of potassium channels restores the resting membrane potential
Depolarisation of a patch of membrane causes neighbouring regions of membrane to do what
Depolarisation of a patch of membrane causes neighbouring regions of membrane to depolarise and go through the same cycle, as
adjacent voltage-gated sodium channels are
opened
When the action potential reaches the end of
the neuron, what does it cause
When the action potential reaches the end of
the neuron it causes vesicles containing
neurotransmitter to fuse with the membrane
— this releases neurotransmitter, which
stimulates a response in a connecting cell
Restoration of the resting membrane potential allows what
Restoration of the resting membrane potential allows the inactive voltage-gated sodium channels to return to a conformation that allows them to open again in response to depolarisation of the membrane Ion concentration gradients are reestablished by the sodium-potassium pump, which actively transports excess ions in and out of the cell
Following repolarisation the sodium and potassium ion concentration gradients are reduced. what happens afterwards
Following repolarisation the sodium and potassium ion concentration gradients are reduced. The sodium-potassium pump restores the sodium and potassium ions back to resting potential levels.
The retina is the area within the eye that detects light and contains two types of photoreceptor cells, which are what
The retina is the area within the eye that detects light and contains two types of photoreceptor cells: rods and cones
explain rods and cones
Rods function in dim light but do not allow colour perception. Cones are responsible for colour vision and only function in bright light.
In animals the light-sensitive molecule retinal is combined with a membrane protein, opsin, to form what?
In animals the light-sensitive molecule retinal is combined with a membrane protein, opsin, to form the photoreceptors of the eye
In rod cells the retinal-opsin complex is called what
In rod cells the retinal-opsin complex is called rhodopsin
Retinal absorbs a photon of light and…
Retinal absorbs a photon of light and rhodopsin changes conformation to photoexcited rhodopsin. A cascade of proteins amplifies the signal
Photoexcited rhodopsin activates what
Photoexcited rhodopsin activates a Gprotein, called transducin, which activates the enzyme phosphodiesterase (PDE)
A single photoexcited rhodopsin activates what
A single photoexcited rhodopsin activates hundreds of molecules of G-protein. Each activated G-protein activates one molecule of
PDE
Each active PDE molecule breaks down thousands of cGMP molecules per second. then what happens
Each active PDE molecule breaks down thousands of cGMP molecules per second. The reduction in cGMP concentration as a result of its hydrolysis affects the function of ion channels in the membrane of rod cells.
PDE catalyses the hydrolysis of a molecule called what. and what does this cause
PDE catalyses the hydrolysis of a molecule called cyclic GMP (cGMP)This results in the closure of ion channels in the membrane of the rod cells, which triggers nerve impulses in neurons in the retina
A very high degree of amplification results in what
A very high degree of amplification results in
rod cells being able to respond to low intensities of light
In cone cells, different forms of opsin combine with what
In cone cells, different forms of opsin combine with retinal to give different photoreceptor proteins, each with a maximal
sensitivity to specific wavelengths: red,
green, blue or UV
