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Cellular Biology and Biochemistry > Communication between cells > Flashcards

Communication between cells Flashcards

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1
Q

What are the basic principles of cell signalling?

A

Conversion of a message (signal transduction)
Target cells have receptors for signalling molecules
Most cells both generate and receive signals

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2
Q

What are the different categories of signal?

A

Endocrine
Paracrine
Neuronal
Contact-dependent

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3
Q

How many responses can a signal trigger?

A

Many

Varying responses in different cell types

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4
Q

What determines the response triggered?

A

The target cells interpretation of the signal

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5
Q

What are the two types of receptor?

A

Cell surface

Intracellular

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6
Q

What is an intracellular signalling pathway?

A

Extracellular signal binds to transmembrane receptor

Triggers an intracellular signal molecule

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7
Q

What is relay?

A

Spreading the signal through the cell

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8
Q

What is amplification?

A

Making the signal stronger so that a few extracellular signals trigger a large intracellular response

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9
Q

What is integrating?

A

Receiving more than one signalling input and generating appropriate output

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10
Q

What is distributing?

A

Passing on the signal to more than one pathway

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11
Q

What role do kinases play in cell signalling?

A

Phosphorylate serine, threonine and tyrosine residues
Alter conformation and activity
Recruitment of effector proteins

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12
Q

What are the categories of cell surface receptors?

A

Ion-channel coupled receptors
G-protein coupled receptors
Enzyme-coupled receptors

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13
Q

How do ion channel coupled receptors work?

A

Open or close in response to a signalling molecule
Changes in membrane potential
Chemical signal becomes an electrical signal

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14
Q

How do G-proten coupled receptors work?

A

Activated by proteins, peptides, amino acid derivatives and fatty acids
Binding ligand induces conformation change activating a G-protein on intracellular side of the membrane
Activated G-proteins activate enzymes or ion channels

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15
Q

How do enzyme-coupled receptors work?

A

Tyrosine kinases

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16
Q

Describe the structure of a G-protein coupled receptor

A

Single polypetide

7 pass transmembrane protein

17
Q

Describe the structure of a G-protein

A

Alpha, beta and gamma subunit

18
Q

What happens when a signal molecule binds to a G-protein coupled receptor?

A

Conformational changes result in exchange of GDP for GTP
Alpha subunit dissociates
Activated subunits activate downstream signals
Switched off when GTP is hydrolysed to GDP

19
Q

What increases in response to GPCR activation?

A

cAMP

20
Q

What does cyclic AMP do?

A

Activates phospholipase C

21
Q

What does phospholipase do?

A

Generates diacylglycerol and inositol trisphosphate

22
Q

What does inositol trisphosphase do?

A

Increase intracellular calcium

23
Q

How is cyclic AMP generated?

A

Generated from ATP by the enzyme adenylyl cyclase

Activated by G alpha subunit

24
Q

What switches off cyclic AMP?

A

Cyclic AMP phosphodiesterase

25
Q

What does cAMP act through?

A

Protein kinase A

26
Q

What is protein kinase A responsible for?

A

Transcription factors and gene expression
Hormone synthesis
Protein production in long term memory

27
Q

What happens if cell growth is disregulated?

A

Cancer

28
Q

How are receptor tyrosine kinases activated?

A

By dimerisation

29
Q

What does the signal molecule trigger in tyrosine kinases?

A

Receptor dimerisation
Activation of intracellular kinase domains
Trans-phosphorylation of tyrosine residues
Recruitment of signalling proteins

30
Q

What does Grb2 trigger?

A

Recruits the Ras activating protein which exchanges GDP for GTP
Conformational changes in Ras activates downstream proteins

31
Q

Why is Ras a molecular switch?

A

GTPases cycle Ras between active GTP bound and inactive GDP bound form

32
Q

What is the most commonly mutated oncogene?

A

Ras

Prevention of GTP hydrolysis causes it to be permanently switched on

33
Q

Describe MAP kinase signalling

A

Activated Ras protein activates Raf
Raf activates Mek
Mek activates Erk
Erk targets transcription factors

34
Q

What drives cells into the G1 phase of the cell cycle?

A

Receptor tyrosine kinases

35
Q

What is the effect of inositol triphosphate activation?

A

Raises Ca2+ levels in the cell

Ca2+ interacts with Ca2+ responsive proteins

36
Q

What properties do transformed cells express?

A 
Immortalisation
Loss of contact inhibition
High saturation density
Altered morphology
Anchorage independent growth

Cellular Biology and Biochemistry (22 decks)

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