Biology: Intracellular Signalling Pathways

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of the transduction stage in signal transduction?

Recognition of signaling molecules by receptors

Binding of ligands to receptors

Generation of secondary messengers (correct)

Regulation of cellular activities

What type of receptor recognizes signaling molecules in the cytosol?

GPCR (G protein-coupled receptor)

Ligand receptor

Intracellular receptor (correct)

Membrane receptor

What is the outcome of an agonist binding to a receptor?

Activation of intracellular signal transduction events (correct)

Binding of ligands to G proteins

Inhibition of intracellular signal transduction events

Regulation of cellular activities without signal transduction

What is the role of G proteins in G protein-coupled receptor signaling?

Activation of effector proteins Signup and view all the answers

What is the final stage of signal transduction?

Regulation of cellular activities Signup and view all the answers

What is the term for the binding of a signaling molecule to its receptor?

Ligand binding Signup and view all the answers

What is the primary function of parathyroid hormone in the body?

Regulating serum calcium concentration Signup and view all the answers

What is the significance of calcium in the body?

It is essential for skeletal mineralization and bone health Signup and view all the answers

What is the characteristic of hypocalcaemia?

Calcium levels are < 8.5 mg/dL Signup and view all the answers

Where is the largest concentration of calcium found in cells?

Endoplasmic reticulum Signup and view all the answers

What is the function of PMCA in cells?

To maintain low cytosolic calcium levels Signup and view all the answers

How do calcium sinks work in cells?

Calcium flows from the extracellular matrix to the cytosol and then to the smooth endoplasmic reticulum Signup and view all the answers

What is the significance of calcium in skeletal mineralization?

It is essential for bone growth and development Signup and view all the answers

What percentage of calcium in the body is found in the bones of the skeleton?

> 99% Signup and view all the answers

What is the function of an antagonist in a GPCR signalling pathway?

It binds to the receptor but does not activate it, blocking the effects of agonists Signup and view all the answers

What is the structure of the receptor part of GPCRs?

A membrane receptor with 7 transmembrane regions and extracellular and cytosolic regions Signup and view all the answers

What is the function of Gα in GPCR signalling pathways?

It carries the binding site for GDP and GTP Signup and view all the answers

What is the outcome of activation of a Gs active alpha subunit?

Activation of adenylyl cyclase and cAMP signalling pathway Signup and view all the answers

What is the function of adenyl cyclase in GPCR signalling pathways?

It converts ATP into cAMP Signup and view all the answers

What is the outcome of activation of a Gq active alpha subunit?

Activation of phospholipase C and IP3/DAG signalling pathway Signup and view all the answers

What is the function of signal amplification in GPCR signalling pathways?

It increases the signal received by the cell Signup and view all the answers

What is the outcome of activation of a Gi active alpha subunit?

Inhibition of adenylyl cyclase and cAMP signalling pathway Signup and view all the answers

What is the structure of G-proteins in GPCR signalling pathways?

Heterotrimeric proteins made up of alpha, beta, and gamma subunits Signup and view all the answers

What is the function of the beta-gamma subunit in GPCR signalling pathways?

It activates signal transduction pathways Signup and view all the answers

What is the primary function of NCX in the cell?

To maintain low cytosolic Ca2+ levels Signup and view all the answers

What is the energy requirement for SERCA to function?

ATP dependent Signup and view all the answers

Which of the following channels is opened by ligand binding?

Ligand-gated ion channels Signup and view all the answers

What is the number of binding sites for calcium in calmodulin?

4 Signup and view all the answers

What is the primary mechanism of action of calcium channel blockers?

Blocking calcium influx Signup and view all the answers

Which of the following is NOT a mechanism that increases intracellular Ca2+?

NCX Signup and view all the answers

What is the primary effect of calcium channel blockers on blood vessels?

Vasodilation Signup and view all the answers

What is the role of calmodulin in the cell?

To bind to calcium and activate other proteins Signup and view all the answers

Study Notes

Signal Transduction Pathways

The 4 sections of signal transduction are:
- Signals: ligand
- Receptors: recognise signalling molecules, cause a conformation change
- Transduction: signalling cascade with secondary messengers
- Response: regulation of cellular activities
Signalling molecules are recognised by:
- Membrane receptors (such as GPCRs)
- Intracellular receptors

G-Protein Coupled Receptors (GPCRs)

GPCRs are cell receptors linked to a G protein on the plasma membrane
GPCRs work in the plasma membrane by:
- Ligand binds to receptor on plasma membrane
- Activates G-protein
- G-protein activates effector
- Generates secondary messengers
Structure of GPCRs:
- Membrane receptors (except rhodopsin)
- Single α-helix polypeptide chain
- 7-Transmembrane regions (H)
- Extracellular (E) and cytosolic regions (C)

Agonists and Antagonists

Agonists: bind to the receptor and activate it, leading to intracellular signal transduction events
Antagonists: bind to the receptor, but do not activate it, blocking the effects of agonists at the receptor

G-Protein Structure

G-proteins: Guanine nucleotide (GTP) binding proteins
G-proteins are heterotrimeric, made up of 3 subunits: α, β, and γ
Gα: carries the binding site for the nucleotide (GDP, GTP)
Gβ: beta subunit
Gγ: gamma subunit

GPCR Function

GPCR function:
- Ligand binds to receptor at the 7-transmembrane region
- Nucleotide exchange at the α subunit, GDP → GTP
- Activation occurs, α subunit dissociates
- Subunits carry on signal transduction and amplification
- After binding to receptor is finished, signalling quantity decreases
- α unit is favoured back to its resting conformational state (GTP → GDP)

Active Alpha Subunit

The 4 names of the active alpha subunit are:
- (names not specified)
These names recognise the secondary messengers they cascade

Outcomes of Active Alpha Subunit

Activation of Gs or Gi active alpha subunit:
- Adenylyl cyclase/cAMP signalling activity
Activation of G12/13 active alpha subunit:
- Small GTPase families
Activation of Gq active alpha subunit:
- Activates phospholipase C/IP3/DAG Signalling pathway (target enzyme)

Beta-Gamma Subunit

The 3 names of the active beta-gamma subunit are:
- (names not specified)

Adenyl Cyclase

Adenyl cyclase is an enzyme that changes bonds in ATP molecule (linear → Cyclic structure)
Produces cAMP (secondary messenger) (can be activated/inhibited by different ligands)

Signal Amplification

Signal amplification: magnifies and enhances signals received by cells, particularly during various signalling pathways
This amplification is essential for cells to respond effectively to extracellular stimuli and orchestrate complex cellular responses

Calcium Regulation

Parathyroid hormone regulates Ca levels
Calcium is an essential element in the body:
- Important role in skeletal mineralisation
- >99% of calcium in the body is found in the bones of the skeleton
Hypocalcaemia: calcium levels are < 8.5 mg/dL
The largest concentration of calcium is found in the Endoplasmic Reticulum

Calcium Sinks

Calcium sinks work by:
- Cytoplasm/cytosol acts as a sink
- Calcium flows from the extracellular matrix
- Calcium flows through the cytoplasm
- Calcium is stored in the SR/ER (smooth endoplasmic reticulum)

Calcium Transport

PMCA (Ca2+ transport, ATPase):
- Transporter that requires ATP, releases calcium from cytosol to extracellular matrix
- Maintains low cytosolic Ca2+
NCX (Na+/Ca2+ exchanger):
- Transporter mechanism from cytosol to extracellular matrix
- No need for ATP
- Maintains low cytosolic Ca2+
SERCA:
- Transporter
- ATP-dependent
- Fills the smooth endoplasmic reticulum's Ca2+ storage from Cystolic Ca2+

Mechanisms of Increasing Intracellular Ca2+

The 4 mechanisms/channels that increase intracellular Ca2+ are:
- Ca2+ ion channels: selectively permeable for calcium ions
- Voltage-gated calcium channels: open in response to cell depolarization
- Ligand-gated ion channels: opened by ligand binding
- Store-operated channels

Calmodulin

Calmodulin is a protein that binds to calcium
Calmodulin has 4 binding sites for calcium
Calmodulin will move and activate other proteins

Clinical Use of Calcium Channel Blockers

Calcium channel blockers are medications used to lower blood pressure
They block calcium influx, allowing blood vessels to relax and open

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Understand the mechanisms of signal transduction, including the 4 sections: signals, receptors, transduction, and response. Learn how signals are transmitted and regulated within cells.