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2 - Membranes > deck_615846 > Flashcards

deck_615846 Flashcards

1
Q

What are three ways in which cells can communicate?

A

ParacrineEndocrineSynaptic

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2
Q

What is paracrine communication?

A

Adjacent cells are effected within a tissue by local chemical mediators

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3
Q

What is endocrine communication?

A

Message released into bloodstream and affects a distant cell

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4
Q

What is synaptic communication?

A

Neurotransmitter crosses a synaptic cleft and binds to receptors on the post synaptic membrane of the target cell

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5
Q

What kind of molecule do cell surface receptors bind?

A

Hydrophillic, such as insulin and glucagon

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6
Q

What kind of molecule do intracellular receptors bind?

A

Small hydrophobic signalling molecules (bound to a carrier in blood) bind to intracellular recptors in nucleus or cytoplasm. (Thyroid and steroid hormones)

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7
Q

What is a ligand?

A

Any small molecule that binds to a receptor site.

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8
Q

What is a ligand called if it produces a response in a receptor?

A

An agonist

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9
Q

What is an antagonist?

A

A ligand which binds to a receptor without causing any activation.

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10
Q

What is an agonist which stimulates a receptor but are unable to elicit the maximum cell response called?

A

Partial agonists

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11
Q

What is the definition of a receptor?

A

A molecule which specifically recognises a ligand or family of ligands and which, in response to ligand binding brings about regulation of a cellular process. In the unbound state, a receptor is functionally silent.

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12
Q

What are the 8 roles of receptors?

A
  1. Signalling by hormones/ local chemical mediators2. Neurotransmission3. Cellular delivery4. Control of gene expression5. Cell adhesion6. Modulation of the immune response7. Sorting of intracellular proteins8. Release of intracellular calcium stores
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13
Q

What is an acceptor?

A

A molecule whos basic function can be carried out without the interaction of a ligand.

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14
Q

What are the two types of acetylcholine receptors?

A

Nicotinic and muscarinic

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15
Q

What are the three muscarinic receptors, and their antagonists?

A

M1 PirenzipineM2 GallamineM3 Hexahydrosiladiphenol

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16
Q

What is a ligand?

A

Definition: any molecule that binds specifically to a receptor site

17
Q

What are receptors classified according to?

A

Which specific physiological signalling molecule (agonist) recognised

18
Q

How are receptors subclassified?

A

By its affinity to a series of antagonists

19
Q

What are the similarities between receptor binding and active and regulatory sites of enzymes?

A
  • Specific binding- Specificity shape related- Specificity of binding confers specificity to the regulation of processes by ligand binding- Binding reversible- Ligand binding to a receptor and regulator binding to enzyme allosteric sites induce a conformational change in activity- No chemical modification of ligand in receptor binding sites or enzyme regulatory sites
20
Q

What are the differences between receptor binding and active and regulatory sites of enzymes?

A
  • The affinity of ligand binding > binding of substrate and regulators to enzyme sites * Ligand bound to a receptor site is not modified chemically whereas substrate is converted to product by an enzyme
21
Q

Explain how membrane bound receptors with intergral ion channels have an effect

A
  • Agonist binds to ligand-gated ion channels > conformational change > gated channel opens > permits flow of ions down an electrochemical gradient > signal transduced into an electrical event
22
Q

What is the subunit structure of a classical ligand gates ion channel family?

A
  • Similar pentameric subunit structures* E.g. nicotinic acetylcholine receptors (nAChR), GABA receptors, glycine receptors (GlyR)* Subunits have four transmembrane domains – M2 forms the lining to the channel pore
23
Q

Describe the activation of membrane bound receptors with intergral enzyme activity

A
  • Agonist binds to extracellular domain > conformational change > activation of intrinsic enzyme e.g. tyrosine kinase-linked receptors
24
Q

How are tyrosine kinase linked receptors operated?

A
  • Binding of hormone to extracellular domain > activation of protein kinase activity in the cytoplasmic domain of the receptor protein kinase activity
25
Q

What is the effect of tyrosine kinase linked receptor activation?

A

Autophosphorylates tyrosine residues on the cytoplasmic domain of the adjacent receptor

26
Q

What are phosphorylated tyrosine residues recognised by?

A

o Transducing proteinso Directly by enzymes containing phosphotyrosine recognition sites

27
Q

How is does phosphorylated tyrosine activate shizzle?

A
  • On association with receptor or transducing protein > effector enzymes become activated allosterically > transduce message into an intracellular event
28
Q

Describe structure of membrane-bound receptors which couple to effectors through transducing proteins

A
  • Seven transmembrane domains receptors (7TMDR) couple to effector molecules via G-proteins
29
Q

What are the effectors of membrane-bound receptors which couple to effectors through transducing proteins

A

o Adenyl cyclase (ATP > cyclic AMP)o Ion channels e.g. Ca2+ and K+ channels

30
Q

What are membrane-bound receptors which couple to effectors through transducing proteins used by? (4)

A

o Muscarinic receptorso Dopamine receptorso Peptide receptorso Purine receptors e.g. ATP

31
Q

Describe the four roles of intracellular receptors

A
  • Hydrophobic ligands e.g. steroid and thyroid hormones* Bind to monomeric receptors in the cytoplasm or nucleus* Receptors stabilised in resting state by association with heat shock or chaperone proteins* Activated receptors dissociates from the chaperone proteins and translocates to the nucleus > regulates gene expression
32
Q

Define amplification

A
  • Cascade event* Binding of a chemical signal molecule to a single receptor can cause the modification of hundreds or thousands of substrate molecules
33
Q

Define cellular activation and inhibition

A
  • Responses to receptor activations can lead to either cellular activation or inhibition
34
Q

Give an example of cellular inhibitionv

A

o E.g. noradrenaline binding to B1 adrenoreceptors in cardiac pacemaker cells > increased heart rate / ACh acting on M2 > decreased heart rate

2 - Membranes (24 decks)

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