1.4 Communication And Signalling Flashcards
Describe how hydrophobic signal molecules can enter cells
Pass directly through phospholipid bilayer
Describe how hydrophobic signal molecules can effect gene expression
Enter cell and bind with receptor in cytosol/ nucleus
Hormone-receptor complex binds to DNA in nucleus
At hormone response elements (HRE)
Affect transcription of genes
Describe how hydrophilic molecules act specifically
Signal molecule/hormone acts as ligand
Binds to complementary/specific receptor in cell membrane
Hormones are a type of what?
Signal molecule
Describe the process of signal transduction
When signal bound, receptor causes G-protein/kinase
Activates cellular response
Explain how insulin can cause a decrease in blood glucose concentration
Insulin binds to receptor
Phosphorylation cascade
GLU4 vesicles recruited into membrane
GLUT4s allow glucose into cell
Membrane polarity refers to what?
The degree of difference in charge on one side of the membrane compared to the other.
What does the restoration of the resting potential allow?
The system to be sensitive again and respond to new signals.
Describe how action potential is achieved in neurons
Neurotransmitter binds to receptor
Sodium channels open
Change in potential opens voltage-gated sodium channels
Further sodium entry takes membrane to threshold
Describe how the resting potential is restored following the passage of an action potential
Sodium channels close
Potassium channels open and potassium ions leave
Sodium-potassium pump is activated
Pump causes net loss of sodium ions
Describe the structure of rhodopsin
Opsin that is bound to retinal
Describe how a photon of light has its effect amplified in a rod cell to produce a nervous impulse
Photon affects conformation of rhodopsin to excited state
Cascade of hundreds of transducins
Activate PDE
PDE breaks down cyclic GMP/cGMP
Reduction in cGMP closes ion channels and impulse fires
Name the components of a rhodopsin molecule from a vertebrate eye
Retinal and opsin
When a photon of light strikes a rhodopsin molecule, transducin proteins are activated. Describe your effects of activated transducins.
They activate a cascade of phosphodieterase (PDE) molecules
Which breakdown cyclic GMP/cGMP molecules
Describe the effects of reduced levels of cyclic GMP on sodium ion channels in the rod cell
Sodium ion channels close
Rod cells amplify the effects of light.
State why this is an advantage to vertebrates.
It allows vision in dim light/allows nocturnal/crepuscular activities/hunting/foraging
State how the photoreceptor molecules of cone cells differ from those in rod cells.
Different opsins
What are is opsin?
A light sensitive protein molecule found in the animal kingdom.
Describe how voltage-gated channels are activated and their effects on the resting potential.
Increased positive change inside membrane opens voltage-gated channels,
Allows more sodium ions to enter.
Explain why it is important that the neuron is restored to resting potential following the transmission of a nervous impulse.
Allows the system/neuron to remain sensitive to further stimulation.
Give account of the role of insulin in the decrease in glucose concentration in blood.
Insulin binds with receptor
Triggers a cascade of phosphorylation
GLUT containing vesicles are recruited into membrane
Glucose enters through the GLUT from bloodstream
Give an account of hydrophobic cell signalling
Hydrophobic signal/steroid hormone
Enters cell through phospholipid layer
Combines with receptor in cytosol/nucleus
Hormone receptor binds with hormone response elements (HRE) on DNA
Gene expression affected