The following statements relate to signaling by Proteolysis-Based Signal Pathway

Question

The following statements relate to signaling by Proteolysis-Based Signal Pathways (Wnt/beta-catenin). Choose the single CORRECT response. Activation of gene transcription in the nucleus by beta-catenin, via activation of Lef1/Tcf transcription factors, can lead to activation of Myc, which increases cell cycle activity. The APC protein functions to phosphorylate beta-catenin directly and thus acts as a tumour suppressor. Binding of Wnt ligands to the Frizzled receptor results in phosphorylation of Frizzled, which then phosphorylates Dishevelled. Groucho can repress Wnt signals by binding to beta-catenin and preventing it from engaging with other transcription factors, such as Lef1/Tcf on Wnt target genes. Desmosomes: (select the CORRECT answer) Connect epithelial cells to the basal lamina. Link cadherins via an intracellular plaque to the ends of cytokeratin filaments. Connect the intermediate filaments from adjacent cells into a network. Connect to adjacent cells via integrins. Select the CORRECT statement about gap junctions. They form a seal that separates apical membrane from baso-lateral membrane. They are formed from connexons that each consists of eight subunits. They allow passage of proteins between adjacent cells. They couple cells metabolically and electrically. Which of the following statements about the ground substance is CORRECT? It includes glycosoaminoglycans (GAGs), which have a strong net positive charge. It contains the fibrillar protein, collagen, which consists of alpha chains arranged in a double helix. It is resistant to tension due to the space filling nature of many of the molecules. It contributes to resisting compression due to the osmotic pressure of water interacting with Na* ions around the GAGs. Which of the following statements about epithelia is CORRECT? A simple squamous epithelium will consist of multiple layers of cells all with the same flattened shape. A transitional epithelium is a stratified epithelium where the superficial cells can change their shape from cuboidal to squamous if the organ they line is stretched. A pseudostratified epithelium is really stratified, but appears as a single layer of cells. The epidermis is a pseudostratified squamous epithelium.

Explanation / Answer

11C phosphorylation of frizzled occurs upon binding to the entire receptor.

12 B links cadherins via intracellular spaces plaques to ends of cytokeratin filaments

13 C gap junctions are connected the adjacent cells ..With 6 Connexions.

14) A it contains glycosaminoglycans mostly hyaluronic acid, doesn't consists of fibrous proteins like collagen or elastin. Mostly water as composition, gel like clear substance , net positive charge seen.

15)A a simple squamous epithelium is flattened multilayer cells, mostly seen in skin, peritoneal, pleural , pericardial, capillaries linings.

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