1.4 Communication and Signalling Flashcards
Action Potential
A wave of electrical excitation along a neurons plasma membrane
Cones
Photoreceptor cells responsible for colour vision, they only function in bright light
Cyclic GMP (cGMP)
A second messenger for visual transduction. It is present in high concentrations in photoreceptor cells
Depolarisation
An electrical state in an excitable cell whereby the inside of the cell is made less negative than the outside than it is at the resting membrane potential
Diabetes Mellitus
An inability to regulate blood glucose levels, in type 1 there is a failure to produce insulin, in type 2 there is a loss of function of insulin receptors
Extracellular signalling molecule
Cues (growth factors, hormones, neurotransmitters) designed to transmit specific information to target cells
GLUT4 glucose transporter proteins
Insulin regulated glucose transporter, insulin triggers the movement of GLUT4 transporters to the membrane surface, increasing uptake of glucose to be converted to glycogen
G-Proteins
AKA Guanine nucleotide-binding proteins, a family of proteins that act as a molecular switch inside cells, which are involved in transmitting signals from a variety of stimuli outside a cell to its interior
Hormone Response Elements (HREs)
A short sequence of DNA within the promoter of a gene that binds to a specific hormone-receptor complex and regulate transcription
Hormone-receptor complex
Formed when steroid hormones bind to specific receptors in the cytosol or the nucleus, they bind to specific sites on DNA and affect gene expression
Hydrophilic
Strong affinity for water
Hydrophilic signalling molecule
Signalling molecules that are not able to pass through the membrane, the signal is transduced across the membrane by receptor molecules on the cell surface
Hydrophobic
Water fearing, non polar and exclude water molecules, responsible for cell membrane and vesicle formation
Hydrophobic signalling molecule
Signalling molecules that can diffuse through membranes, so their receptor molecules can be within the nuclues
Ion concentration gradient
Gradients created by ion pump enzymes that transport ionic solutes, such as K, Na, H ions and Ca across the membrane, energy is required to produce a gradient so the gradient is a form of stored energy
Opsin
A light-sensitive protein molecule found in the animal kingdom
Phosphodiesterase (PDE)
Enzyme that catalyses the hydrolysis of cyclic GMP (cGMP)
Phosphorylation
The addition of a phosphate group to a protein or other organic molecule
Phosphorylation cascades
A series of events in which one kinase activates the next one in a sequence, they can result in the phosphorylation of many proteins as a result of the original signalling event
Photon
The basic unit of light
Photoreceptor cells
Cells (rods and cones) found in the retina that are capable of visual phototransduction (converting light-visible electromagnetic radiation- into electrical signals)
Repolarisation
The restoration of a membrane potential following depolarisation (restoring a negative internal charge)
Resting membrane potential
The difference in ion concentration between the inside and outside of a cell
Retinal
A light sensitive molecule within the eye that binds with opsin to form photoreceptors in the eye
Rhodopsin
The retinal-opsin complex in rod cells
Rods
Photoreceptor cells in the retina which function in dim light and respond to low light intensities, they do not allow colour perception
Signal Transduction
Conversion of extracellular signals into an intracellular response
Threshold value
When the depolarisation value reaches about -55mV, a neuron while fire an action potential- this is the threshold, if the neuron does not reach critical threshold level, the AP will not fire
Transcription factor
A protein that binds to specific DNA sequences, thereby controlling the rate of transcription of genetic information from DNA to mRNA
Transducin
Protein naturally expressed in vertebrate retina rods and cones, it is very important in vertebrate phototransduction
