Signalling Between Cells 2 Flashcards Preview

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Flashcards in Signalling Between Cells 2 Deck (18)
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1
Q

What are ligands?

A

a molecule that binds to another (usually larger) molecule. Think of receptors

2
Q

How do ionotropic receptors work?

A

Ligand binds to the receptor protein Change in conformation of channel protein  opening of a pore Pore allows ions to move in or out of cell according to their respective concentration gradients

3
Q

Name an example of ionotropic receptors ?

A

Nicotonic Acetylcholine

GABA reeptor A

4
Q

Name the ligand, locatiob and physiological effect associated with Nicotinic Acetylcholine?

A

Ligand: Acetylcholine Location:Skeletal Muscle Physiological effect: Muscle contraction

5
Q

Name the ligand, locatiob and physiological effect associated with GABA receptor A?

A

Ligand: (GABA) gamma amino butyric acid Location: Neuronal Physiological effect: neuronal excitability

6
Q

How do G-proteins work?

A

7-TM receptor & heterotrimeric G-protein are inactive Ligand binding causes a change in conformation of receptor Unassociated G-Protein binds to the receptor causing GDP to be exchanged for GTP G-protein dissocaites into two active components -Alpha-subunit -Beta gamma subunit Causing the alpha subunit to bind to its target protein Internal GTPase activity on alpha-subunit dephosphorylates GTP to GDP Alpha subunit dissociates from target protein - inactive again because it binds to the Beta gamma subunit again Receptor remains active as long as ligand is bound and can activate further heterotrimeric G-proteins

7
Q

Give examples of G protien linked receptors?

A

Examplesbeta1 receptor - Gs stimulate AC & increase cAMP & PKA M2 receptor - Gi inhibit AC & decrease cAMP & PKA AT-1 receptor - Gq activate PLC- hydrolyses PIP2 into IP3 & DAG.

8
Q

What happens when an Gs protein linked receptor has binded with its ligand? Give an example of this type of receptor? State its effect ?

A

Stimulates adenylyl cyclase Converts adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP) cAMP activates protein kinase A (PKA) Example: Beta1-adrenergic receptor Effect: increase heart rate

9
Q

What happens when an Gi protein linked receptor has binded with its ligand? Give an example of this type of receptor? State its effect ?

A

Inhibits adenylyl cyclase Reduces levels of PKA Example: M2-muscarinic receptor Effect: Decrease heart rate

10
Q

What happens when an Gg protein linked receptor has binded with its ligand? Give an example of this type of receptor? State its effect ?

A

Stimulates phospholipase C (PLC) Converts PIP2 to IP3 and DAG IP3 stimulates Ca2+ release DAG activates PKC Example: AT-1 angiotensin receptor Effect: vasoconstriction

11
Q

What are G-proteins receptors?

A

G protein–linked receptors (GPLR), constitute a large protein family of receptors that detect molecules outside the cell and activate internal signal transduction pathways and, ultimately, cellular responses.

12
Q

Describe the process for enzyme-linked signal transduction?

A

Ligand binding  receptors clustering Receptor clustering activates enzyme activity within cytoplasmic domain Enzymes phosphorylate receptor Phosphorylation  binding of signalling proteins to cytoplasmic domain These signalling proteins  recruit other signalling proteins  signal is generated within cell  equals an arrow

13
Q

What is an enzyme linked receptor?

A

An enzyme-linked receptor, also known as a catalytic receptor, is a transmembrane receptor, where the binding of an extracellular ligand causes enzymatic activity on the intracellular side. Hence a catalytic receptor is an integral membrane protein possessing both enzymatic catalytic and receptor functions

14
Q

Give an example of enzyme linked receptors and their physiological effects?

A

Insulin receptor (CD220 antigen) Ligand: Insulin Physiological effect: Glucose uptake ErbB receptors Ligand: Epidermal Growth Factor, Transforming Growth Factor Beta Physiological effect: Cell growth, proliferation

15
Q

Name the two types of intracellular signal transduction?

A

Type1- Cytoplasmic Type 2-Nuclear

16
Q

Describe the steps for cytoplasmic intracellular signal transduction?

A

Located within the cytosolic compartment Associated with chaperone molecules (heat shock proteins, hsp) Hormone binds to receptor  hsp dissociates 2 hormone bound receptors form a homodimer. The homodimer translocates to the nucleus  binds to DNA  = arrow

17
Q

Describe the steps for Nuclear intracellular signal transduction?

A

Located within the nucleus Binding of hormone ligand  transcriptional regulation  = arrow

18
Q

Give an example of intracellular receptors?

A

Type 1 - Glucocorticoid receptor Ligands: Cortisol, corticosterone Physiological effect: decrease immune response, increase Gluconeogenesis Type 2 - Thyroid hormone receptor Ligand: Thyroxine (T4), triiodothyronine (T3) Physiological effect: Growth & development