Cell Structure and Function: Cell Signalling Flashcards

1
Q

What is local signalling?

A

Signals that act on nearby targets

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2
Q

What is paracrine signalling

A

Is when a cell produces a signal to induce change in nearby cells

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3
Q

What is an example of paracrine signalling?

A

Growth factors such as fibroblasts growth factor (FGF1)

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4
Q

What is synaptic signalling?

A

similar to paracrine signalling but have junctions (synapses) between the cell produces the signal ( neurotransmitters) and the cell receiving the signal

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5
Q

What is an example of synaptic signalling?

A

Acetylcholine

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6
Q

What is long distance signalling?

A

are signals that act from a distance. Hormones produced by specialised cells travel via circulatory system to act on specific cells (produced from endocrine system)

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7
Q

What are some examples of long distance signalling?

A

insulin from pancreatic beta cells bind to insulin receptors (tyrosine kinase type) initiating a cascade which results in glucose uptake

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8
Q

What are the two types of local signalling?

A

Paracrine and Synaptic

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9
Q

What are the two types of secreted signals?

A

Local and long distance

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10
Q

What are the three steps of cell signalling?

A

Reception, transduction, response

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11
Q

What is the first step of cell signalling?

A

Reception

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12
Q

What is reception?

A

Allows or causes the activation of a protein

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13
Q

What are the two types of receptors?

A

Intracellular and membrane bound/cell surface receptors

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14
Q

What are intracellular receptors?

A

Receptors inside our cells

They are the least common type of receptor

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15
Q

Where are intracellular receptors located?

A

Cytoplasm or cytosol of the cell

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16
Q

Examples of ligands that bind to intracellular receptors

A

Testosterone, estrogen, progesterone, thyroid hormones bind to receptors in the cytoplasm (they are hydrophobic so they can pass through plasma membrane) and move to nucleus as a complex)

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17
Q

What is a ligand/primary messenger/signalling molecule?

A

a signalling molecule that binds to another (usually larger) specific protein

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18
Q

How can some ligands cross the plasma membrane to reach intracellular receptors?

A

They are hydrophobic and/or small

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19
Q

What are membrane bound/cell surface receptors?

A

Receptors embedded in the plasma membrane of the cell/membrane of organelles

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20
Q

Function of membrane bound receptors?

A

To allow primary messengers that are hydrophilic and/or large to cross the plasma membrane

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21
Q

Examples of membrane bound receptors

A

G Protein Coupled Receptor, Receptor Tyrosine Kinase, ligand-gated ion channel

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22
Q

What are G-protein coupled receptors (GPCRs)?

A

A membrane bound receptor that is also a transmembrane protein that crosses the plasma membrane 7 times

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23
Q

What are transmembrane domains?

A

The loops on a GPCR that are in the hydrophilic regions inside and outside a cell so they can interact with molecules

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24
Q

What are G proteins

A

the proteins that GPCR’s are coupled with. They are molecular switches that are either on or off depending on whether GDP or GTP is bound

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25
What is GTP
An energy source, similar to ATP
26
What is the process of GPCRs?
At rest, the receptor is unbound and G protein is bound to GDP (inactive). The enzyme is in an inactive state Ligand binds to the receptor and binds the G protein and causes a conformational shape change of GPCR. GTP displaces GDP causing G protein to become activated. The enzyme is still inactive Activated G protein dissociates from the receptor. Enzyme is activated and has a conformational shape change. It can elicit a cellular response G protein has GTPase activity (release of GTP) promoting its release from enzyme reverting it back to resting state
27
What are ligand gated ion channel/receptors?
A membrane bound receptor that contains a gate, which is closed until a ligand (e.g. a neurotransmitter) binds to it causing the gate to change shape and open
28
What is a receptor?
a molecule/protein which responds to a specific ligand
29
What is an ion channel?
membrane protein through which specific ions can travel
30
What is an ion channel receptor?
membrane protein through which specific ions can | travel, in response to ligand binding (also known as ionotropic receptors)
31
What is the process of ligand gated ion channels/receptors?
At rest ligand is unbound and the gate is closed Upon ligand binding, the ligand gated ion channel receptor undergoes a shape change and the gate is opened and specific ions can flow into the cell (down concentration gradient) Following ligand dissociation, the gate closes and goes back to resting
32
What system relies heavily on ligand fated ion channels?
The nervous system. Released neurotransmitters binds, as ligands, to ion channels on target cells to propagate action potentials
33
What is the second step of cell signalling?
Signal Transduction
34
What is signal transduction?
Signals are relayed from receptors to target molecules within the cell via a ‘cascade’ of molecular interactions
35
What is protein kinases
are enzymes that transfer a phosphate group from ATP to another protein. Typically, this activates the protein
36
What are phosphatases?
are enzymes that dephosphorylate (remove the phosphate) rendering the protein inactive, but recyclable
37
What does the last active protein kinases do?
activates an inactive protein which then carries out a cellular response
38
What are the amino acids that are typically phosphorylated?
serine or threonine
39
What is a secondary messenger?
A molecule that is generated when a specific substance attaches to a receptor on the outside of a cell membrane, which produces a change in cellular function.
40
What is cAMP (cyclic AMP)?
A secondary messenger that is created when activated enzyme adenylyl cyclase converts ATP to cAMP. cAMP acts as a second messenger and activates downstream protein (which could be the start of a phosphorylation cascade)
41
What disrupts the ATP to cAMP process
Cholera toxin
42
What is calcium?
A secondary messenger released from the endoplasmic reticulum
43
What is IP3?
A secondary messenger that diffuses through the cytoplasm and binds to a gated channel in the ER to release calcium ions
44
Where is there a low [Ca2+] ?
Inside the cell
45
Where is there a high [Ca2+]?
Outside the cell
46
Where is Ca2+ pumped to maintain low calcium levels inside the cell?
Extracellular space, ER, Mitochondria
47
What is PIP2
a specific phospholipid in calcium signalling
48
What is Phospholipase C?
An enzyme that catalyses the splitting of PIP2 to IP3 and DAG.
49
What is the process of IP3 and calcium acting as secondary messengers?
Here, the activated protein is phospholipase C which then cleaves PIP2 (a phospholipid) into DAG and IP3 IP3 (the secondary messenger) diffuses through cytosol and binds to a gated channel in the ER (as the ligand) Calcium ions flow out of ER down concentration gradient (high to low) and activate other proteins towards a cellular response
50
An example of a cellular response of calcium?
Muscles use Ca2+ to contract
51
Why are there multiple steps on cell signalling between reception and cell response?
Amplifies the response Provides multiple control points Allows for specificity of response (temporal and spatial) despite molecules in common Allows for coordination with other signalling pathways
52
What does the transduction of a signal lead to?
The regulation of one or more cellular activities like gene expression
53
Why is it important for cell signalling to be temporary/last a short period of time?
So that a cell can return to homeostatic equilibrium and be ready to respond again to another signal if required
54
What is phosphodiesterase?
An enzyme that converts cAMP to AMP
55
What blocks the action of phosphodiesterase?
Caffeine
56
What does viagra inhibit?
The specific cGMP which degrades phosphodiesterase
57
What is epinephrine?
Adrenalin
58
What is the function of active glycogen phosphorylase?
Converting glycogen to glucose 1-phosphate
59
How many glucose 1-phosphate molecules result from 1 adrenalin molecule?
108
60
What is glycogen?
is a long term energy store in the liver and skeletal muscle
61
What is glycogen breakdown?
Converting glycogen into glucose 1-phosphate
62
What is glucose 1-phosphate converted into?
Glucose g-phosphate which can be used in glycolysis to generate ATP