Cellular communication MCQ Quiz - Objective Question with Answer for Cellular communication - Download Free PDF

The correct answer is A and D only

Explanation:

• The Wnt/β-catenin signaling pathway is a crucial signaling mechanism that regulates various biological processes during embryonic development, tissue homeostasis, and disease progression.
• β-catenin plays dual roles in cellular function: it participates in cell adhesion at the plasma membrane and acts as a transcriptional coactivator in the nucleus during Wnt signaling.
• Statement A: This is correct. In the absence of Wnt ligands, β-catenin is phosphorylated by a destruction complex comprising APC (Adenomatous Polyposis Coli), Axin, and GSK-3β (Glycogen Synthase Kinase-3β). Phosphorylation tags β-catenin for ubiquitination and subsequent degradation by the proteasome, preventing its accumulation and nuclear translocation. This ensures the pathway remains inactive when Wnt ligands are not present.
• Statement D: This is correct. β-catenin is involved in two distinct cellular functions:
  • Cell-to-cell adhesion: β-catenin interacts with cadherins (cell adhesion molecules) at the plasma membrane, playing a critical role in maintaining cell junctions and tissue architecture.
  • Transcriptional regulation: When Wnt signaling is activated, β-catenin accumulates in the cytoplasm and translocates to the nucleus, where it forms a complex with TCF/LEF (T-cell factor/lymphoid enhancer-binding factor) transcription factors to regulate the expression of Wnt target genes.

Incorrect Statements:

• Statement B: This is incorrect. The β-catenin/TCF complex does not act as a repressor of gene expression. Instead, upon activation of Wnt signaling, β-catenin binds to TCF/LEF transcription factors in the nucleus, converting them from repressors to activators of gene expression. This leads to the transcription of Wnt target genes that govern cell proliferation, differentiation, and other processes.
• Statement C: This is incorrect. The Wnt/β-catenin pathway is initiated by the binding of Wnt ligands to Frizzled receptors (FZD) and LRP5/6 co-receptors, not receptor tyrosine kinases (RTKs). This ligand-receptor interaction triggers a cascade of events that stabilizes β-catenin and activates downstream signaling pathways.

The correct answer is Enh - Pro - Goi - IRES - GFP - PA

Concept:

• Gene expression constructs are designed to express specific genes in cells using regulatory elements like promoters, enhancers, and polyadenylation signals.
• To express two proteins, such as a gene of interest (Goi) and green fluorescent protein (GFP), in mammalian cells, these proteins should be encoded in a single mRNA but translated independently.
• An internal ribosome entry site (IRES) allows translation of downstream open reading frames (ORFs) in a polycistronic mRNA, ensuring independent translation of multiple proteins.
• The enhancer boosts transcription efficiency, while the promoter initiates transcription. The polyadenylation (pA) signal ensures proper mRNA processing and stability.

Explanation:

Enh - Pro - Goi - IRES - GFP - PA:

• The enhancer (Enh) increases transcription levels by boosting the activity of the promoter (Pro).
• The promoter drives transcription of the gene of interest (Goi) and GFP into a single mRNA.
• The IRES element allows independent translation of GFP from the same mRNA, ensuring that both Goi and GFP are translated separately.
• The polyadenylation signal (PA) ensures efficient transcription termination and mRNA stability.

Other Options:

• Pro - Enh - Goi - IRES - GFP - PA: Incorrect because the enhancer is positioned after the promoter. Enhancers must precede the promoter to effectively boost transcription activity.
• Enh - Pro - Goi - GFP - IRES - PA: Incorrect because the GFP is placed before the IRES. Without the IRES preceding GFP, independent translation of GFP cannot occur.

The correct answer is Non-classical cadherins Fat and Flamingo regulate epithelial growth and cell polarity, respectively.

Concept:

• The cadherin superfamily is a large group of proteins that play key roles in cell-cell adhesion, tissue morphogenesis, and signaling during development and homeostasis.
• Cadherins are characterized by their extracellular cadherin repeats, calcium dependency, and their ability to mediate homophilic adhesion (binding to the same type of cadherin molecule).
• The cadherin family can be broadly classified into classical cadherins and non-classical cadherins, such as protocadherins, desmogleins, Fat, and Flamingo.
• Non-classical cadherins are involved in specialized functions beyond cell adhesion, such as regulating growth, polarity, and signaling pathways.

Explanation:

Fat and Flamingo:

• Fat is a non-classical cadherin that plays a critical role in regulating epithelial growth. It is involved in the Hippo signaling pathway, which controls organ size by balancing cell proliferation and apoptosis.
• Flamingo (also known as CELSR) is another non-classical cadherin that regulates planar cell polarity (PCP). PCP ensures that cells are oriented correctly within a tissue, which is crucial for proper tissue structure and function.
• The functions of Fat and Flamingo highlight their importance in maintaining epithelial integrity and overall tissue organization.

Other Options:

In an early mouse embryo, anti-N cadherin antibody prevents compaction.

• This statement is incorrect because compaction in the mouse embryo is primarily mediated by E-cadherin, not N-cadherin.
• E-cadherin is a classical cadherin essential for cell-cell adhesion during the early stages of embryonic development.

P-cadherins lack transmembrane domain and are anchored to the membrane by GPI anchors.

• This statement is incorrect because P-cadherins, like other classical cadherins, have a transmembrane domain. They are not anchored to the membrane via glycosylphosphatidylinositol (GPI) anchors.
• Classical cadherins, including P-cadherin, have extracellular cadherin domains, a transmembrane domain, and an intracellular domain that interacts with catenins to link the cadherins to the cytoskeleton.

Loss of the non-classical cadherin desmoglein causes skin blistering due to increased keratinocyte cell-to-cell adhesion.

• This statement is incorrect because the loss of desmoglein, a non-classical cadherin, leads to decreased keratinocyte cell-to-cell adhesion, not increased adhesion.
• Desmogleins are essential components of desmosomes, which are specialized cell junctions in epithelial tissues. Their loss can cause skin blistering diseases such as pemphigus vulgaris, due to weakened cell adhesion.

The correct answer is B and C only

Concept:

• The insulin receptor is a receptor tyrosine kinase that plays a critical role in glucose metabolism, cell growth, and survival. It engages signaling pathways like the PI3 kinase pathway to regulate FOXO transcription factors.
• FOXO transcription factors are involved in cellular processes such as apoptosis, cell cycle regulation, and oxidative stress response. Their activity is regulated by phosphorylation events mediated by kinases, such as AKT and PDK1.
• PTEN is a phosphatase that negatively regulates the PI3K/AKT pathway by dephosphorylating PIP3, thus indirectly influencing FOXO activity.
• When FOXO is phosphorylated, it creates binding sites for proteins like 14-3-3, leading to its cytoplasmic retention and reduced transcriptional activity.

Explanation:

Statement A: Treating the cells with a PTEN inhibitor increases GeneX expression.

• PTEN inhibits the PI3K/AKT pathway.
• A PTEN inhibitor would enhance PI3K/AKT signaling, leading to FOXO phosphorylation and decreased FOXO activity.
• Reduced FOXO activity results in decreased expression of its target genes like GeneX.
• This statement is incorrect because it conflicts with the expected outcome of FOXO phosphorylation reducing GeneX expression.

Statement B: A cell line with an AKT (S308A) mutation has increased GeneX expression.

• The AKT (S308A) mutation likely results in a loss of AKT phosphorylation at serine 308, impairing AKT activity. Reduced AKT activity prevents FOXO phosphorylation, thereby allowing FOXO to remain active and promote GeneX expression.
• This statement is correct as the mutation disrupts AKT function, leading to increased GeneX expression.

Statement C: Change in GeneX expression due to a ligand-binding defective insulin receptor is partly reversed by a PTEN inhibitor.

• A ligand-binding defective insulin receptor would impair PI3K/AKT signaling, reducing FOXO phosphorylation and increasing GeneX expression. Introducing a PTEN inhibitor would enhance PI3K/AKT signaling, partially restoring FOXO phosphorylation and reducing GeneX expression.
• This statement is correct because the PTEN inhibitor counteracts the effect of the defective receptor, partly reversing the GeneX expression changes.

Statement D: Phosphorylation of FOXO by PDK1 creates a phosphoserine binding site for 14-3-3 protein, reducing GeneX expression.

• PDK1 primarily activates AKT by phosphorylating it, rather than directly phosphorylating FOXO. AKT then phosphorylates FOXO, leading to the creation of 14-3-3 binding sites and cytoplasmic retention of FOXO, reducing GeneX expression.
• This statement is incorrect because it incorrectly attributes FOXO phosphorylation to PDK1 instead of AKT.

Fig:PI3-kinase/Akt and the insulin signalling cascade in Drosophila (Source)

The correct answer is Miniature endplate potential

Explanation:

• Acetylcholine (ACh) is a neurotransmitter released from motor nerve terminals at the neuromuscular junction, which plays a vital role in muscle contraction.
• In skeletal muscle cells, single quanta of acetylcholine released from motor nerve terminals cause localized depolarization of the postsynaptic membrane.
• This localized depolarization is termed as Miniature Endplate Potential (MEPP).
• MEPP occurs without an action potential and is due to the spontaneous release of a single vesicle of acetylcholine.
• While MEPP is very small in amplitude, it serves as evidence of neurotransmitter release and receptor activation at the neuromuscular junction.

Other Options:

Endplate Potential:

• This refers to the depolarization of the muscle cell membrane caused by the release of multiple quanta of acetylcholine during nerve stimulation.
• Unlike MEPP, endplate potential is triggered by an action potential and is large enough to initiate muscle contraction.
• Since the question specifies "single quanta," this option is incorrect.

Inhibitory Post-Synaptic Potential (IPSP):

• IPSP refers to a hyperpolarization of the postsynaptic membrane caused by inhibitory neurotransmitters such as GABA or glycine.
• It reduces the likelihood of an action potential firing in the postsynaptic neuron.
• Acetylcholine does not produce IPSPs in skeletal muscle cells, so this option is incorrect.

Inhibitory Junction Potential:

• Inhibitory junction potential refers to inhibitory signals at a synapse, typically observed in smooth muscle or other types of cells.
• It does not apply to the neuromuscular junction in skeletal muscle, making this option incorrect.

The correct answer is  Pseudopodia.

Key Points

• The change in shape in amoeba which facilitates movement is due to Pseudopodia.
• The pseudopodia extends from the two sides of the food molecule and surrounds it and finally engulfs the food.
• Pseudopodia is used in movement and as a tool to capture prey or obtain required nutrition.

Structure of Amoeba:

Additional Information 

The correct answer is Option 3 i.e.A ‐ III, B ‐ I, C ‐ IV, D ‐ II

Concept:

• Collagen, fibrin, fibronectin, gelatin, and another extracellular matrix (ECM) proteins are routinely used with biomaterials in tissue engineering to increase the ability of the latter to support cell attachment, proliferation, and differentiation.
• ECM support surrounding cells structurally and biochemically.

Explanation:

Nidogen:-

• Nidogens/entactins are a family of highly conserved, sulfated glycoproteins.
• Biochemical studies have implicated them as having a major structural role in the basement membrane.

Fibronectin:-

• The extracellular matrix contains a large and varied assortment of glycoproteins that typically have multiple domains, each with specific binding sites for other matrix macromolecules and for receptors on the surface of cells.
• The best-understood member of this class of matrix proteins is fibronectin, a large glycoprotein found in all vertebrates and important for many cell-matrix interactions.
• Mutant mice that are unable to make fibronectin die early in embryogenesis because their endothelial cells fail to form proper blood vessels.
• Fibronectin is a dimer composed of two very large subunits joined by disulfide bonds at their C-terminal ends.
• in the human genome, there is only one fibronectin gene, containing about 50 exons of similar size, but the transcripts can be spliced in different ways to produce multiple fibronectin isoforms.
• The 20 or so isoforms of fibronectin are generated by alternative splicing of the RNA transcript produced from a single gene.

Integrin:- 

• Family of membrane proteins, Co-dependent, heterotypic binding.
• Hetero dimer a and ẞ chains(non-covalent) Alpha subunit- ca+2 binding domain.
• The binding site on the extracellular end. 24 different integrins. A large majority binds to components of the extracellular matrix, but a few to cells.
• Link actin cytoskeleton to various external structures.
• The cytoplasmic portion of integrin has adaptor proteins (talin, alpha-actinin, vinculin), that interact with actin filament(cytoskeleton) inside the cell.
• The extracellular portion of integrin binds to molecules like fibronectin, fibrinogen, and collagen in ECM.

Vimentin:

• Vimentin, a major constituent of the intermediate filament (IF) family of proteins, is ubiquitously expressed in normal mesenchymal cells and is known to maintain cellular integrity and provide resistance against stress.
• Increased vimentin expression has been reported in various epithelial cancers, including prostate, gastrointestinal, CNS, breast, malignant melanoma, lung cancer, and other types of cancers.

Hence, the correct answer is option 3: A ‐ III, B ‐ I, C ‐ IV, D ‐ II.

The correct answer is Option 1 i.e. A and B

Concept:

• Cell junctions are contact sites that link cells in the tissue to one another and to the extracellular matrix. 
• Cell junction plays an important role in the development and function of complex organisms.

Occluding junction - 

• this type of junction seals the cells together in the epithelium so as to prevent any leakage from one side of the sheet to the other. 
• It is located at the very apical end of the epithelial cells.
• They also help to maintain the polarity.

1. Tight junction: These are cell-cell junctions that are mediated by two transmembrane proteins called claudins and occluding. It prevents the passage of molecules across the epithelium sheet. 
2. Septate junction: These are occluding junctions found in invertebrates. 

Anchoring junction - 

• This junction mechanically attached cells to their neighbour or to the extracellular matrix. 
• Its main function is to hold cells together in the tissue. 
• It consists of:

1. Adherens junction: It connects actin filaments bundle between cells and between the cell and extracellular matrix. 
2. Desmosome: It connects intermediate filaments between cells and between cell and extracellular matrix.
3. Hemidesmosome: It connects the basal surface of epithelium cells to the underlying basal lamina. 

Communicating junction - 

• This allows exchange of the chemical or electrical information between cells of the tissues. 

1. Gap junction: It acts as the direct connection between the cytoplasm of the adjacent cells. It allows the passage of inorganic ions and small water-soluble molecules between the cytoplasm of adjacent cells. 
2. Plasmodesmata: These are found in plants and are functionally equivalent to gap junctions. 

Explanation:

Statement A: INCORRECT

• Tight junction do not connect the intermediate filament in one cell with that in the adjacent cell.
• Desomosome are the cell-cell junction connecting intermediate filament in one cell with that in the adjacent cell.
• Hence, this is incorrect statement.

Statement B: INCORRECT

• Desmosomes are cell-cell junctions.
• It connects intermediate filament in one cell with another cell.
• Hence, this is incorrect statement.

Statement C: CORRECT

• Gap junction acts as the channel that allows passage of the certain compounds between the cells. 
• Hence, this statement is correct.

Statement D: CORRECT 

• Occulant junction are type of junction that seals the cells together in the epithelium, thereby preventing any leakage from one side of the sheet to the other. 
• Tight junction is one type of occupant junction.
• Hence, this statement is correct.

Statement E: CORRECT 

• Hemidesmosome are the cell-anchoring junction that connect the cells to the matrix. 
• It contain integrin protein and it connect intermediate filaments of cell and matrix. 
• Hence, this statement is corect.

Hence, the correct answer is option 1.

Concept:

• The response to specific signals in a cell and tissues is mediated by the receptors it possesses, by the signal transduction pathway that it activates and then by the intra-cellular processes it affects. 
• Generally, each receptor binds to a single signalling molecule or to a group of closely related molecules. 
• Also, we will observe that in certain cases, a single type of molecule binds to multiple types of receptor molecules and hence, exhibit different responses in the cells. 
• Hence, we can conclude that receptors are characterised by binding specificity to particular ligands. 
• Receptors - ligand complex exhibits effectors specificity. 
• Cell-cell communication during development is controlled by a development signalling pathway that uses the diverse architecture of receptor-ligand binding. Pathway architecture determines the communication codes. 
• As we know, the ligand-receptor complex activates respective effector molecules which in turn regulate the transcription of the target genes and their expression. 
• But apart from this, signalling also activates various feedback loops as well that further modulate the signal-modulating capacity of the ligand-receptor complex.
• At the cellular level, every cell can determine the molecule identify of ligands present on the surface of the cell along with its receptors, the relative concentration of these multiple ligands and then the temporal dynamics of the ligand concentration 
• At the tissue level, the distribution of the extracellular ligands and intracellular signal (effectors) is modulated by the respective signalling pathway that is activated. This spatial-temporal control is mediated by the specific ligand-receptor interaction, resultant modulators, and feedback loops. 

Explanation: 

Option 1: 

• Specificity of receptors determine effector dynamics.
• For example, takes Dll1 and Dll4 which activate the Notch1 receptor with pulsatile or sustained dynamics, respectively. 
• Here, pulsatile Notch activation is sufficient to induce the Hes1 gene, but sustained Notch activity is required for Hey1/HeyL upregulation.
• So, Dll1 and Dll4 had opposite effects on cell fate, where DII1 promotes and DII4  inhibits myogenesis, respectively, when expressed in neural crest cells of the developing chick embryos.
• Hence, we can conclude that the relatively ‘direct’ Notch pathway is able of discriminate among similar ligands, also to process ligand identity into effector dynamics, and finally to decipher those dynamics into distinct target programs.
• Hence, this is an incorrect option.

Option 2:

• Receptors and ligands are clusters in the cell interface. It is the concentration of the ligands and receptors that determine the strength of the signal. 
• For example,  Dll1 preferentially and coordinately is known to activate Notch receptors as clusters, which results in releasing of a ‘pulse’ of many NICDs (notch intracellular domain) of the receptors in a single event,
• On the contrary Dll4 activates Notch within smaller clusters or individual ligand-receptor complexes, that results in a steady ‘trickle’ of NICDs to the nucleus 
• Hence, clustering of ligands on the cell interface contributes to dynamic ligand discrimination.
• Hence, this option is incorrect. 

Option 3: 

• In some cases, different ligand (morphogens)  concentrations can trigger distinct cellular responses. 
• Intracellular effectors molecule concentration determine the 
• Ligand concentration can also be represented by the amplitude and duration of adaptive pulses of effector activity.
• For example, in neural tube development multiple morphogens together specify complex tissue patterns. say for example,  Sonic hedgehog (SHH), which forms a concentration gradient along the ventral side of the neural tube,thereby specifying several neural progenitor fate domains. Hence, SHH concentration controls the amplitude and duration of an adaptive pulse of intracellular SHH signaling activity.
• Hence, this option is correct.

Option 4: 

• Receptors process ligand identity into effector dynamics. 
• Effector dynamics of a particular ligand-receptors complex depend on how many different types of ligands influence a single pathway.
• Hence, this is an incorrect option. 

Hence, the correct answer is option 3. 

The correct answer is Option 1 i.e. Each calmodulin molecule binds six Ca2+ ions in a cooperative fashion.

Concept:

• Calmodulin (CaM) (an abbreviation for calcium-modulated protein).
• It is a calcium-binding protein.
• Calmodulin is a small, highly conserved calcium binding cytosolic acidic protein found in all eukaryotic cells.
• It is an intracellular receptor of the secondary messenger Ca²⁺, and the binding of Ca²⁺ is required for the activation of calmodulin.
• Once bound to Ca²⁺, calmodulin acts as part of a calcium signal transduction pathway by modifying its interactions with various target proteins such as kinases or phosphatases.
• Calmodulin consists of a highly conserved, single polypeptide chain with four high-affinity Ca²⁺ binding sites.
• Ca²⁺/calmodulin has no enzymatic activity itself but instead acts by binding to and activating other proteins.
• This complex may activate CaM-kinases (Ca²⁺/calmodulin-dependent kinases)
• CaM-kinases activate or inhibit the transcription of specific genes.

Explanation:

Option A:- Each calmodulin molecule binds six Ca2+ ions in a cooperative fashion

• Numerous Ca²⁺ regulated activities are controlled by the multifunctional intracellular Ca2+ receptor known as calmodulin.
• It comprises of a single polypeptide chain that is highly conserved and has four Ca²⁺ binding sites with great affinity, where each end of CaM can bind 2 Ca²⁺ ions i.e. total of 4.
• Calmodulin + four Ca²⁺ = Conformational change in calmodulin.
• Hence, option A is incorrect, and the rest all are correct.

 Option B:- Binding of Ca2+ causes calmodulin to undergo a conformational change leading to active calmodulin.

• CaM undergoes a conformational shift that enables it to attach to its target location on CaM-kinases once it is saturated with four Ca2+ ions.

Option C:- Since binding of Ca2+ is cooperative, a small change in the level of cytosolic Ca leads to a large change in the level of active calmodulin.

• Four calcium sites are present in this protein, and when three or four of these sites are occupied by calcium, the calmodulin changes form and starts a number of internal cell processes, such as the activation or inhibition of protein kinases.

Option D:- One of the many enzymes activated by Ca2+‐ calmodulin is cAMP phosphodiesterase, which degrades cAMP and links Ca and cAMP signaling.

• In order to relieve autoinhibition, calcium-saturated calmodulin (CaM) binds to a site in the C-terminal regulatory sequence of CaM-dependent protein kinase I (CaMKI) and directly activates the enzyme.

The correct answer is  Pseudopodia.

Key Points

• The change in shape in amoeba which facilitates movement is due to Pseudopodia.
• The pseudopodia extends from the two sides of the food molecule and surrounds it and finally engulfs the food.
• Pseudopodia is used in movement and as a tool to capture prey or obtain required nutrition.

Structure of Amoeba:

Additional Information 

The correct answer is:Cerebroside

Explanation: 

• Cerebrosides are a type of glycolipid, which are lipids with one or more carbohydrate groups attached. They are important components of cell membranes, especially in nerve tissue. Glycolipids play crucial roles in cell recognition, signaling, and stability.
• Phosphatidylcholine: A phospholipid that is a major component of cell membranes.
• Phosphatidylserine: Another phospholipid important for cell cycle signaling, especially in apoptosis.
• Cardiolipin: A phospholipid that is integral to the function of mitochondrial membranes.

Additional Information:

Schematic View of Membrane Structure:

The correct answer is Phospholipase C

Explanation:

• Phospholipase C is the enzyme responsible for cleaving PIP2 into IP3 and DAG during signal transduction processes in cells.
• This is a key reaction in the inositol phosphate signaling pathway, which plays a crucial role in the transduction of extracellular signals into cellular responses.
• IP3 then typically goes on to release calcium ions from intracellular stores, while DAG acts as a secondary messenger that can activate protein kinase C (PKC) among other functions.

The correct answer is Option 2 i.e.Tight junction, desmosome, and gap junction together form the junctional complex. 

Cell junctions can be categorized into three functional groups: occluding junctions"(tight), which seal epithelial cells to prevent molecular leakage; anchoring junctions, which mechanically attach cells and their cytoskeletons to neighboring cells or the extracellular matrix; and communicating junctions, which facilitate the passage of chemical or electrical signals between interacting cells. 

Explanation-

• Gap Junctions: These are small tunnels that connect cells, allowing the exchange of small molecules and ions between the cytoplasmic compartments of adjacent cells. They are composed of two connexons (one from each of the contacting cells) in vertebrates, and each connexon is made up of six protein units called connexins.
• Tight Junctions: These are a type of cell-cell junction that prevent the free passage of molecules and ions through the intercellular space between the plasma membranes of adjacent cells. They create a selectively permeable barrier that regulates the movement of substances around cells, rather than between cells. They are crucial in maintaining the polarity of cells.
• Desmosomes: Often compared to rivets or spot-welds, desmosomes are sturdy cell junctions that anchor intermediate filaments of the cytoskeleton directly to the plasma membrane at cell-cell interfaces. They are especially common in tissues that encounter physical stress, such as skin and heart muscle.
• Hemidesmosomes: Similar in structure to desmosomes, these junctions anchor intermediate filaments in a cell to the extracellular matrix, effectively attaching the cell to a substrate. Hemidesmosomes use different proteins (mainly integrins) than desmosomes to connect to the cytoskeleton.
• Adherens Junctions: These junctions connect the actin filament (a type of cytoskeletal element) of one cell with that of the neighboring cell. The proteins making up adherens junctions (such as cadherins and catenins) bind the cell membrane to actin. They are particularly important in holding cells together in epithelial and endothelial tissues.
• Focal adhesions are large, dynamic protein complexes through which the actin filament (cytoskeleton) of a cell connects to the extracellular matrix (ECM). They play crucial roles in cell signaling and communication and are crucial in many biological processes including cellular motility, proliferation, differentiation, and survival.

The correct answer is A - iii, B - i, C - iv, D - ii

Explanation-

The correct pairings are as follows:-

A. Anchoring junction - iii. Desmoglein

B. Occluding junction - i. Claudins

C. Channel-forming junction - iv. Connexin

D. Signal-relaying junction - ii. Delta-Notch

Additional InformationAnchoring junction: These junctions provide mechanical stability to tissues and help form strong sheets of cells. Desmoglein is a type of cadherin protein that is involved in the formation of desmosomes, a type of anchoring junction.

Occluding junction (also known as tight junctions): These occur where a seal is required between cells to prevent the leakage of molecules across a layer of cells instead of passing through them. Claudins are the key proteins that form the backbone of these tight junctions.

Channel-forming junction (also known as gap junctions): These allow the passage of ions and small molecules between cells, thus facilitating communication. Connexin proteins create a pore for these ions and small molecules to move directly from one cell to another.

Signal-relaying junction (also known as communicating junctions): Delta-Notch signaling is a primary example of this, where the Delta protein on one cell interacts with the Notch protein on a neighboring cell to relay signals. Notch signaling is critical for cell differentiation and development.

Fig- Types of cell junction.