Flashcards in Week 9 Deck (74)
What is a signal transduction pathway?
A series of steps by which a signal on a cell's surface is converted into a specific cellular response.
What are the types of chemical signal?
What is an autocrine signal?
The signalling mechanism acts on the same cell it has been secreted by.
What is a paracrine signal?
Acts on locally neighbouring cells and moves by diffusion.
What are neuroendocrine signals?
Released from neurones but act on distant cells.
What are pheromones ?
Released into the environment and act on a different individual.
What type of signalling molecules are used in endocrine signalling?
Give an example of a type go signalling molecule used in paracrine signalling.
What methods do animals use for local signalling?
By cellular direct contact or by using local messenger molecules which only travel short distances.
What methods do animals use for long distance signalling?
Hormones - endocrine system
How do steroid hormones reach receptors in the cytoplasm or nucleus?
Diffuse across the plasma membrane
Where are the receptors found that steroid hormones bind to?
Cytoplasm or nucleus
What are all steroid hormones synthesised from?
What are the 2 categories of steroid hormones?
What are corticosteroids?
Steroids produced in the adrenal Cortex
Where are sex steroids produced?
Give examples of sex steroids
Oestrogen, progesterone, testosterone
Give examples of cortiocosteroids
Glucocorticoids and mineralcorticoids
Which steroid hormones have a different structure and function to most steroids?
Vitamin D3, Retionic Acid and Thyroid hormone
Although thyroid hormone has a different structure and function to most steroids, what is its similarity to most steroids?
The mechanisms it uses
How do steroids acts as signalling molecules?
Steroids are soluble in plasma membrane so can readily enter the cell cytosol by diffusion and bind to mobile receptors.
The hormone-receptor complex formed then enters the nucleus of the cell by diffusion and binds to specific genes, acting as a transcription factor.
mRNA is transcribed and leaves the nucleus to be translated into specific proteins by ribosomes.
The specific proteins produced then carry out functions or produce structures in target cells
What is the overall purpose of steroid hormones?
Describe the solubility of steroid hormones in plasma membrane
Describe the time it takes steroid hormones to produce a response
Describe how long the effects of steroid hormones last
A long Tim
How do nitric oxide and carbon monoxide reach receptors when acting as target molecules.
Use simple diffusion to cross membranes.
How do nitric oxide and carbon monoxide affect cells when act as signalling molecules?
They alter the activity of intracellular target enzymes.
How wide spread are the effects of nitric oxide and carbon monoxide when they act as signalling molecules?
What is of the main bodily effects that NO and CO have when act as signalling molecules?
What are the stages of cell signalling?
Who discovered the steps of cell signalling?
Earl W. Sutherland
What happens in step 1 (reception) of cell signalling?
A signal molecule binds to a receptor protein, causing a conformational change. The signalling ligand molecule and the receptor then form a complex.
where are intracellular receptors found?
Cell cytosol or nucleus of target cells
What are the hydrophobic signalling molecules used by animals?
Steroid and thyroid hormones
What type of molecules mainly bind to receptor molecules on the plasma membrane?
Water soluble signalling molecules
What are the 3 main types of receptors in the plasma membrane?
G-protein linked receptors
Receptor Thyrosine Kinase
How does the G protein receptor affect activity of GDP?
If a G-protein is bound to GDP, it is inactive.
What type of molecules do receptor throne kinases bind to ?
Phosphates and Thyrosines
What is step 2 of cell signalling?
What are the possible methods of transduction in cell signalling?
Second messenger methods
Cytoplasmic and nuclear responses
What are the benefits of a multiple step transduction cell signalling pathway?
Amplify cellular signals and create a large cellular response.
What are the most common type of signalling molecules?
Outline the use of a phosphorylation cascade in the transduction process of cell signalling.
Phosphatase enzymes are used to remove phosphate groups and kinases are used to add phosphate groups.
Protein kinases each activate the next in a series by phosphorylating the inactive precursor.
What type of molecules are second messengers?
Small, non-protein, water-soluble molecules or ions
What is the 'first messenger' in a second messenger model?
The single molecule that binds to the membrane
How do second messengers spread through a cell?
Name a widely used second messenger
What enzyme in the plasma membrane converts ATP to cAMP?
What is the purpose of the enzyme Adenyl Cyclase?
coverts ATP to cAMP
What does cAMP activate?
Why are calcium ions important as second messengers?
They can regulate their own concentration.
What second messengers are used when Ca2+ is used as the first messenger?
Inositol triphosphate and diaculglycerol
What is usually the final outcome of cellular signalling transduction via a cytoplasmic or nuclear pathway ?
To synthesise enzymes or proteins by selectively transcribing genes and using signalling molecules as transcription factors.
What do signalling molecules often act as to regulate protein synthesis ?
What fine tuning methods are used in the response of cell signalling methods?
Making the response specific
Enhancing response efficiency
Terminating the signal
How are cell signalling responses amplified?
Enzyme cascades amplify the signal. The number of activated products at each step is greater than at the previous step.
By what method are cell signal often coordinated?
"Cross-talk" between branching pathways
What type of proteins are often used to enhance the responses of cell signalling?
How are cell signalling mechanisms terminated?
When signalling molecules leave the receptor and cause it to become inactive.
What causes target organ specificity ?
Specific receptor molecules for hormones either on the plasma membrane surface or in the cytoplasm of cell of the target organ.
What is a Kinase?
An enzyme that transfers phosphate groups from high-energy donor molecules such as ATP, to a specific substrate via phosphorylation.
In terms of local signalling, how do animal cells interact?
By direct contact or by local regulators which are messenger molecules that only travel a short distance.
What is used for long distance signalling in plants and animals ?
How do steroid hormones travel across the plasma membrane?
Where do steroid hormones bind to receptors in cells?
In the cytoplasm or in the nucleus.
What are steroid hormones synthesised from?
What are the 2 categories of steroids used for cellular communication?
Sex steroids and Corticosteroids
Name some steroids which have a different structure to the rest but perform the same function.
What are the purpose of the steroid receptor superfamily and what feature allows them to do this?
They have transcription factors that function as activators or repressors of transcription.
Can calcium be produced by cells on demand?
Where is calcium stored?
In the endoplasmic reticulum and sarcoplasmic reticulum.
Where is calcium bound in the sarcoplasmic reticulum?
Bound to specialised proteins.
What happens in terms of calcium when the sperm penetrates the egg ?
Calcium which is previously sequestered in the organelles is spread across the surface f the egg from the point of sperm entry.