Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ICPP > L6- Receptors > Flashcards

L6- Receptors Flashcards

1
Q

What is:
A) Paracrine signalling
B) Synaptic signalling
C) endocrine signalling

A

A) - cells communicate over short distances
- mediated by local chemicals

B)

  • type of paracrine signalling
  • nerve cells transmit signals
  • involves action potential and neurotransmitter release

C)

  • over long distances, uses circulatory system
  • signals produced, released in blood stream, carries to target cell
  • signals are hormones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define: receptor

A

A molecule that recognises specifically a second molecule (ligand) or family of molecules and which in response to ligand binding brings about regulation of a cellular process

  • silent in the unbound state
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

A) Define: ligand

B) What is the difference between an agonist and antagonist?

A

A) Any molecule that binds specifically to a receptor site

B)

Agonist: a ligand that will bind to a receptor site and produce activation of a receptor - leading to IC signal transduction events e.g. anti-asthma

Antagonist: a ligand will bind to a receptor site without causing activation (doesn’t switch off receptors it just opposes the actions of an agonist)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Examples of roles of receptors

A
  • signalling by hormones/local chemical mediators
  • neurotransmission
  • cell delivery
  • control of gene expression
  • cell adhesion
  • immune response
  • sorting of intracellular proteins
  • release of intracellular calcium stores
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Compare the affinity of a ligand with a receptor site and an enzyme with an active site

A

Affinity of ligand binding is much higher

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

A) What is signal transduction?

B) What are the 4 types of receptors that are involved in signal transduction?

A

A) converting an extracellular signal into an intracellular signal that triggers a response

B)

  1. Membrane- bound receptors with integral ion channels
  2. Membrane- bound receptors with integral enzyme activity
  3. Membrane- bound receptors which couple to effectors through transducing proteins
  4. Intracellular receptors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Difference between cell-surface/ plasma membrane receptors and intracellular/nuclear receptors?

A

Cell-surface receptors

  • membrane-anchors proteins
  • bind to ligand on the outside surface of the cell
  • ligand doesn’t need to cross the plasma membrane (often hydrophilic and large)
  • 3 domains: extracellular ligand-binding domain, a hydrophobic membrane spanning domain and intracellular domain
  • examples: ion channel-linked receptors, g-protein linked and enzyme-linked receptors

Intracellular receptors:

  • receptor proteins found on inside of cell: cytoplasm or nucleus
  • ligands are small hydrophobic molecules (can cross membrane) e.g. steroid hormones
  • cause changes directly, binding to the DNA and altering transcription
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Outline how intracellular receptors work

A
  • hormone enters a cell and binds to receptor
  • conformational change in receptor shape allowing receptor-hormone complex to enter nucleus and regulate gene activity
  • hormone binding exposes regions of receptor that have DNA-binding activity so they can attach to specific sequences of DNA
  • these sequences are found next to certain genes in the DNA of the cell and when receptor binds next to these genes it alters their level of transcription
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

A) What are some membrane-bound receptors with integral ions channels?
B) Structure

A

A) Ligand- gated ion channels

  • Nicotinic acetylcholine receptor (nAChR): ligand gated Na, K and Ca channel
  • GABA receptor: gated Cl channel
  • glycine receptor
  • glutamate receptors
  • Ryanodine receptor (Ca2+)

B)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the general structure of membrane-bound receptors with integral enzyme activity?

A
  • Extracellular binding domain
  • transmembrane domain
  • intracellular Catalytic domain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Examples of memb-bound receptors with integral enzyme activity?

Name the enzyme they are linked with

A

Growth factor receptors: insulin, epidermal growth factor (EGF) and platelet-derived growth factor (PDGF)
- linked to tyrosine kinase

ANP receptor: linked directly to guanylyl cyclase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Outline how Receptor- tyrosine kinases (RTKs) work

A
  • A kinase it an enzyme that transfers phosphate groups to a protein or other target
  • Receptor tyrosine kinase: transfers Po4 groups to the AA tyrosine
  • Signalling molecules bind to the EC domain of 2 receptor tyrosine kinases
  • the 2 neighbouring receptors dimerise (come together)
  • receptors then attach Po4s to tyrosines in each other’s IC domains (autophosphorylation)
  • the phosphorylated tyrosine can transmit the signal to other molecules in the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the membrane-bound receptors that signal through transducing proteins?

A
  • 7 transmembrane domain (7TMD) receptors —> coupling through GTP-binding regulatory proteins (g-proteins) to enzymes or channels

E.g.
- Adrenaline binding to B-adrenoreceptors activates the enzyme adenylyl cyclase (ATP cAMP) via a G-protein Gs

  • ACh binding to M2 muscarinic ACh receptors, stimulates k+ channel opening via G protein Gi
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Outline the structure of the G-protein coupled receptors

A

Ggfdgfgdf

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are receptor superfamilies?

A

Receptors that fall into structurally related types: based on common structural motifs

  • 7TDM Receptor: 7-transmembrane domain receptor
  • Tyrosine kinase-linked receptors: insulin receptor, epidermal growth factor (EGF) and platelet-derived growth factor (PDGF)
  • ion channel-linked receptors: Nicotinic acetylcholine receptor, GABAA and glycine receptors, the 5HT3 receptor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In the cardiac pacemaker cells:
A) What receptor does Noradrenaline act on and what does it cause?
B) What receptor does ACh act on what does it cause?

A

A) B1-adrenoreceptors increasing the heart rate

B) M2 Muscarinic receptors, slowing the Heart rate

17
Q

In hepatocytes:
A) What does insulin do?
B) What does glucagon do?

A

A) Stimulates glycogen synthesis from glucose

B) stimulates glycogen breakdown to glucose

18
Q

Outline the general structure of intracellular receptors?

A

Simple polypeptide chain that has 3 distinct domains:

  • C-terminal: ligand binding domain
  • DNA binding domain: AA in this region are responsible for binding of the receptor to specific sequences of DNA
  • N-terminal: Transcription activating domain
19
Q

Types of intracellular receptors in the intracellular receptor super family?

A
  • Cortisol receptor
  • Oestrogen receptor
  • Progesterone receptor
  • Vitamin D receptor
  • Thyroid hormone receptor
  • Retinoic acid receptor
20
Q

What are hydrophobic signalling molecules?

A

Hydrophobic signal molecules include steroid hormones such as cortisol, oestrogen (estradiol), progesterone and testosterone and thyroid hormones such as thyroxine.

Steroid hormones diffuse directly through the cell membrane and bind to an inactive intracellular receptor protein known as a gene regulatory protein located in the cytosol or in the nucleus. On binding the intracellular receptor becomes active allowing it to bind to the equivalent regulatory sequence in the DNA.

21
Q

What are hydrophilic signalling molecules?

A

Hormones, such as peptide hormones, are produced in endocrine glands, secreted into the bloodstream and carried throughout the body.
These signal molecules only produce a response in target molecules with the appropriate surface receptor.

  • A second group of hydrophilic signalling molecules are neurotransmitters.
  • An electrical signal is passed along a nerve and on reaching the terminal point stimulates the release of neurotransmitter signalling molecules
22
Q

What are the 3 superfamilies of cell-surface receptor?

A
  1. G Protein coupled (7TM) receptors e.g. muscarinic acetylcholine receptors
  2. Ligand-gated (receptor operated) ion channels e.g. nicotinic acetylcholine receptors
  3. Receptors with intrinsic enzymatic activity e.g. receptor tyrosine kinases e.g. insulin receptor
23
Q

What can different G-protein coupling receptors respond to?

A
  • Sense light e.g. rhodopsin
  • ions –> H+ and Ca2+
  • Neurotransmitters e.g. acH
  • peptide and non-peptide hormones
  • large glycoproteins
24
Q

Where does the ligand bind to the GPCR?

A

TWO OPTIONS:

  1. to 2-3 of the transmembrane domains
    or
  2. N-terminal region
25
Q

How do GPCRs cause a change in cellular activity?

A
  1. Ligand binds
  2. GPCR changes 3D shape (conformation)
  3. Signal transduction- cascade initiated- attracts G-Protein
26
Q

What is a G-protein and what is the structure?

A

Guanine-nucleotide binding protein

Structure: heterotrimeric
3 subunits : alpha, beta and gamma

27
Q

Outline the signal transduction process of GPCR from Activation of g-protein to termination

A

Activation of G-protein:
- GDP on protein replaced with GTP on alpha subunits (loses GDP and binds to GTP)

Signalling:
- The alpha-betagamma complex immediately dissociates into alpha-GTP and free Beta-gamma subunits and then each can interact with effector proteins (2nd messenger generating enzymes or ion channels)

Termination:

  • the alpha-GTP and/or BY interaction with effectors lasts until the alpha subunit GTPase activity hydrolyses GTP back to GDP.
  • alpha GDP and BY subunits then reform an inactive heterotrimeric complex
28
Q

How come GPCR is specific?

A
  • activated GPCRs preferentially interact with specific types of G protein
  • the G alpha subunit is a primary determinant
  • an extracellular signal working via a specific gpcr will activate a single or small sub population of G proteins and effectors in the cell to bring about a specific cellular response
29
Q

How do a) cholera toxin (CTx) and b) pertussis toxin (PTx) interfere with the G protein function?

A
  • toxin complex binds to the cell and an enzyme is injected into the cell
    a) Prevents termination of signalling by Gs- preffering GPCRs leading to long lasting activation of downstream pathways (GTPase activity does not work)
    b) Uncouples Gi preferring GPCRs from mediating signal transduction events (stops alpha GTP forming) hence cannot pass on signal

ICPP (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions