WEEK 8 (Cell signalling) Flashcards
With respect to their surrounding membrane system, which is the odd one out?
a) Nucleus
b) Endoplasmic reticulum
c) Mitochondria
d) Chloroplasts
Endoplasmic Reticulum
Which of the following proteins is a transmembrane protein responsible for anchoring the extracellular matrix (ECM)?
a) Laminin
b) Fibronectin
c) Integrins
d) Collagen
Integrins
What is the key role of fibroblasts?
Producing extracellular matrix
Which type of endomembrane secretion occurs in nerve cells?
a) constitutive
b) regulatory
c) non-continuous
d) intermittent
Regulatory
Which of the following biomolecules are contained in the lysosomes?
a) nucleic acids
b) ribonucleic acids
c) proteins
d) polysaccharides
Proteins
What happens in anaphase 1?
Each homolog reaches the opposite pole
There exists attraction between the homologs in Metaphase 1? (TRUE/FALSE)
FALSE
EXPLANATION: The homolog’s centromeres repel each other which assist separation to opposite pole
What is the function of axonemal dynein?
Responsible for the beating of flagella and cilia
What can Ehlers-Danlos Syndrome affect?
The production or organisation of collagen which is a critical component of connective tissue
What applies to both eukaryotic cell walls and animal cell extracellular matrices?
- They are built to a common overall structure that can be described as ‘fibres in a matrix’
- Their protein components are synthesised by ribosomes of the rough endoplasmic reticulum
Bacterial and eukaryotic cell walls have the same general function (TRUE/FALSE)
TRUE
EXPLANATION: The cell walls of bacteria and eukaryotic cells have the same general function of preventing cell lysis in hypotonic environments
What applies to fibronectins?
- They are disulphide linked dimers with each polypeptide composed of a number of binding domains joined together by short flexible segments
- They have an essential role in linking the extracellular matrix to its underlying cells
Glycosaminoglycans contribute to two of the tissue properties: withstand mechanical pressures and favour the movement of cells and molecules through tissues (TRUE/FALSE)
TRUE
The Elasticity of bones is partially provided by collagen fibers (TRUE/FALSE)
TRUE
Chronic pain is usually localised to the hyper mobile joints is a symptom of which disease?
Ehlers Danlos Syndrome (EDS)
What does cell signalling allow?
Cells to perceive and respond to extracellular environment allowing development, growth and immunity
What are the three stages of cell signalling?
1) RECEPTION = signal molecule binds the receptor
2) SIGNAL TRANSDUCTION = chemical signal results in a series of enzyme activations
3) RESPONSE = resulting cellular responses
How do cells usually communicate with each other?
Through extracellular messenger molecules
How do cells usually communicate with each other?
Through extracellular messenger molecules
How do extracellular messengers travel?
- SHORT DISTANCE and stimulate cells that are in close proximity to the origin of the message
- LONG DISTANCE stimulating cells that are far away from the source
What are the four types of chemical signalling?
- Endocrine signalling
- Paracrine signalling
- Neuronal signalling
- Contact-dependent signalling
What happens in Endocrine/Hormonal/Long-distance signalling?
Specialised cells release hormone molecules which travel to target cells elsewhere in the organism
What happens in Paracrine/Short-distance signalling?
Rather than entering the bloodstream, the signal molecules diffuse locally through the extracellular fluid, remaining in the neighborhood of the cell that secretes them.
What happens in Autocrine signalling?
The cell that is producing the messenger expresses receptors on its surface that can respond to the messenger that it itself produces -> Cells releasing the message stimulate or inhibit themselves
What happens in neuronal signalling?
A message is delivered quickly and specifically to individual target cells -> A neuron is activated by signals from the environment or from other nerve cells -> A neuron sends electrical impulses along its axon -> Once reaching the exon terminal, the electrical signal are converted into a chemical form
What happens in neuronal signalling?
A message is delivered quickly and specifically to individual target cells -> A neuron is activated by signals from the environment or from other nerve cells -> A neuron sends electrical impulses along its axon -> Once reaching the exon terminal, the electrical signal are converted into a chemical form
What happens in Contact-dependent signalling?
A cell surface bound signal molecule binds to a receptor protein on an adjacent cell
What is contact dependent signalling important in?
- Development
- Immune responses
What happens in Lateral inhibition?
Each future neuron delivers an inhibitory signal to the cells next to it deterring them from specialising as neurons too
What are the different signalling components?
- Signalling molecules
- Receptors
- Signalling intermediates
- Effector proteins
What is the difference between First messengers and Second messengers?
- FIRST MESSENGERS = extracellular factors (often hormones/neurotransmitters)
- SECOND MESSENGERS = intracellular signalling molecules released by the cell in response to exposure to extracellular signalling molecules
What are signalling molecules?
Molecules that are responsible for transmitting information between cells in your body
What are receptors?
- Proteins associated with cell membrane or located within the cell
- Recognise signalling molecules by binding to them
- Binding of receptors by signalling molecules causes cell behaviour changes
Describe Myasthenia Gravis
Myasthenia gravis is a long-term neuromuscular disorder that’s usually caused by an autoimmune problem which leads to varying degrees of skeletal muscle weakness. Most commonly affected muscles are eyes, face and swallowing.
DEFICIENCY: acetylcholine
SYMPTOMS:
- difficulty breathing
- difficulty swallowing/chewing
- facial paralysis
- problems walking up stairs/lifting objects
-droopiing of eyelids
[severity of symptoms increases over time if left untreated]
How do signal molecules work to regulate the behaviour of the cell?
Every cell type displays a set of receptor proteins that enables it to respond to a specific set of extracellular signal molecules produced by other cells -> the signal molecules work I combinations to regulate the behaviour of the cell
What are the two classes of Extracellular signal molecules?
- Molecules that are TOO LARGE or TOO HYDROPHILIC to cross the plasma membrane
- Molecules that are SMALL ENOUGH or HYDROPHOBIC ENOUGH to pass through the plasma membrane
Some small hydrophobic hormones binds to intracellular receptors that act as ______________________________
Transcription regulators
Describe how Cortisol acts
1) Cortisol cross the plasma membrane and a conformational change activates the receptor protein
2) Activated receptor-cortisol complex moves into the nucleus
3) Activated receptor-cortisol complex binds to regulatory region of target gene and activates transcription
Describe how acetylcholine causes the blood vessel to dilate
Acetylcholine binds to receptors on the surface of endothelial cells which stimulates cells to make and release NO -> NO is synthesised from the amino acid arginine and diffuses readily from its site of synthesis into adjacent smooth muscle cells -> NO regulates the activity of specific proteins causing the muscle cells to relax
What does NO activate in smooth muscle cells
GUANYLYL CYCLASE
[catalyses the production of cyclic GMP from GTP]
What are the functions of intracellular signalling pathways?
- RELAY the signal onward and spread it through the cell
- AMPLIFY the signal received making it stronger
- can detect signals from more than one intracellular signalling pathway and INTEGRATE them before relaying a signal onward
- DISTRIBUTE the signal to more than one effector protein
What are the two classes that proteins that act as molecular switches fall into?
- Proteins that are activated or inactivated by phosphorylation
- GTP-binding proteins
What switches the GTP-binding protein on and off?
GUANINE NUCLEOTIDE EXCHANGE FACTORS (GEFs) promote the exchange of GDP or GTP switching the GTP-binding protein ON
GTPASE-ACTIVATING PROTEINS (GAPs) stimulate the hydrolysis of GTP to GDP switching the GTP-binding protein OFF
What are the three different classes of cell-surface receptors which differ in the transduction mechanism?
- Ion-channel-coupled receptors
- G-protein-coupled receptors
- Enzyme-coupled receptors
What is the function of all cell-surface receptor proteins?
They bind to an extracellular signal molecule and transduce its message into one or more intracellular signalling molecules that alter the cell’s behaviour
Describe Ion-channel-coupled receptors
They change the permeability of the plasma membranes to selected ions such as Na+, K+ or Ca2+ altering the membrane potential and producing an electrical current
What are transmitter-gated ion channels?
Ion-channel-coupled receptor that opens in response to binding an extracellular signal molecule
What happens when a G-protein-coupled receptor binds its extracellular signal molecule?
The activated receptor signals to a G protein on the opposite side of the plasma membrane which turns on or off an enzyme in the same membrane
