60 Questions
What role does the basal lamina play in the development of the nervous system?
Guiding migrating neurons along ECM pathways
In which tissues does the basal lamina surround each cell?
Muscle and fat
What is the main function of the basal lamina in tissues?
Providing a foundation for assembly of cells into tissue
How does the basal lamina contribute to the formation of a tight barrier in the kidney?
Serving as a selectively permeable blood filter
Which component of the ECM is a major secreted proteoglycan in Basal Laminae?
Perlecan
What condition is associated with mutations that alter the C-terminal globular domain of certain IV alpha chains?
Alport’s syndrome
What autoimmune disease involves antibodies binding to the a3 chains of type IV collagen in the glomerular basement membrane and lungs?
Goodpasture’s syndrome
What is the result of increased ECM breakdown by hyperactivation of ECM-destruction proteinases, such as MMPs and ADAMs?
Fibrosis
What is a crucial role of stromal cells within the tumor microenvironment in promoting tumorigenesis?
Regulating immune and cancer cell migration
What does ECM stiffening, caused by overexpression of ECM component genes, promote in tumor cells?
Cell proliferation
In tumors from breast cancer patients, what does increased expression of protease inhibitors correlate with?
Good prognosis
What is a crucial mechanism by which cancer cell ECM promotes tumor progression?
Regulating immune and cancer cell migration
What is a useful therapeutic target for improving drug delivery and efficacy, considering its ability to regulate drug transport and delivery?
Hyaluronic acid
What is an attractive therapeutic strategy for various diseases, including cancer, atherosclerosis, autoimmune, and inflammatory diseases?
Targeting disease-associated ECM molecules
What is a result of severe fibrosis caused by overproduction and excessive deposition of ECM?
Organ failure
What does balanced ECM contribute to, which regulates cell proliferation and apoptosis and restrains malignant tumor progression?
Upholding tissue architecture and cell polarity
Which protein forms a two-dimensional network in the extracellular matrix?
Laminins
What kind of proteins are laminins?
Cross-shaped proteins
Which protein is a large multidomain proteoglycan that binds to and cross-links many ECM components and cell-surface molecules?
Perlecan
What is the function of nidogen (entactin) in the extracellular matrix?
Cross-linking type IV collagen
How many chains does laminin consist of?
Three
How many laminin isoforms with distinct tissue- and developmental stage–specific expression patterns are there in vertebrates?
16
Which human diseases are associated with mutations in collagen and laminin genes?
Alport syndrome and dystrophic EB
What is the function of the basement membrane in relation to endothelial cells?
Inhibiting cell proliferation and migration
Which collagen is a major structural component of basal laminae?
Type IV collagen
How many polypeptides are type IV collagens made from?
Three
How does type IV collagen form its structure in the basal lamina?
Two-dimensional fibrous network
What distinguishes type IV collagen's properties?
Number and lengths of collagenous triple-helical segments
What is the approximate composition of ribosomes in terms of ribosomal RNA (rRNA) and protein?
60% ribosomal RNA (rRNA) and 40% protein
In which year were ribosomes first observed using an electron microscope?
1950s
Who was awarded the Nobel Prize in Medicine in 1974 for the discovery of ribosomes?
George Palade
Where are 70S ribosomes found?
Prokaryotic organisms and eukaryotic cell’s organelles (mitochondria and chloroplast)
Where does ribosome biogenesis take place in eukaryotic cells?
Nucleolus
What is the function of the Svedberg (S) unit of measurement in centrifugation?
Measuring the rate of sedimentation
Where are ribosomal RNA (rRNA) genes transcribed in eukaryotic cells?
Nucleus
What is the primary function of the aminoacyl-site (A site) on the ribosome?
Holding the incoming t-RNA charged with an amino acid
Where are free ribosomes mainly found?
Prokaryotes
What is the function of attached ribosomes to the membranes of the endoplasmic reticulum (ER)?
Making proteins for export or inclusion in cell membranes
What is the role of polysomes in the cell cytoplasm?
Connecting ribosomes during translation
What is the primary function of the peptidyl-site (P site) on the ribosome?
Holding the t-RNA molecule linked to the growing end of the polypeptide chain
What is the function of the exit site (E site) on the ribosome?
Releasing deacylated t-RNA
Where are ribosomal proteins primarily synthesized?
Cytoplasm
What is the function of the nucleolus in eukaryotic cells?
Synthesizing ribosomal RNA
What is the primary function of the 5S rRNA in ribosome biogenesis?
Incorporating into large subunits with ribosomal proteins
Who was awarded the Nobel Prize in Chemistry in 2009 for studies of the structure and function of the ribosome?
V Ramakrishnan
What are the approximate composition of ribosomes in terms of ribosomal RNA (rRNA) and protein?
60% ribosomal RNA, 40% protein
Where are 70S ribosomes found?
Prokaryotic organisms and eukaryotic cell's organelles
What did George Palade receive the Nobel Prize in Medicine for in 1974?
Discovery of the ribosomes
Where does ribosome biogenesis take place in eukaryotic cells?
Nucleolus
What is the function of the Svedberg (S) unit of measurement in centrifugation?
Measure the rate of sedimentation in centrifugation
Where are free ribosomes mainly found?
Cytosol
What is the primary function of the nucleolus in eukaryotic cells?
Synthesize ribosomal RNA (rRNA)
What is the approximate composition of ribosomes in terms of ribosomal RNA (rRNA) and protein?
40% rRNA and 60% protein
What is the primary function of the aminoacyl-site (A site) on the ribosome?
Hold the incoming t-RNA charged with an amino acid
What is the role of polysomes in the cell cytoplasm?
Translate m-RNA into proteins
What is the function of the exit site (E site) on the ribosome?
Release deacylated t-RNA
Where are 70S ribosomes found?
Prokaryotic cells
What is the function of attached ribosomes to the membranes of the endoplasmic reticulum (ER)?
Make proteins for export or inclusion in the cell's membranes
What is the function of the 5S rRNA in ribosome biogenesis?
Incorporate into large subunits with ribosomal proteins
Where are ribosomal RNA (rRNA) genes transcribed in eukaryotic cells?
Nucleolus
Study Notes
Extracellular Matrix Components and Basement Membrane Structure
- Type IV collagen and laminins are ubiquitous protein components of the extracellular matrix, forming a two-dimensional network.
- Laminins are multi-adhesive, cross-shaped proteins that bind to integrins and other adhesion receptors, and help cross-link components of the basal lamina.
- Perlecan is a large multidomain proteoglycan that binds to and cross-links many ECM components and cell-surface molecules.
- Nidogen (entactin) is a rodlike molecule that cross-links type IV collagen, perlecan, and laminin, incorporating other components into the ECM.
- Laminin is a key component of basal laminae and is a heterotrimeric protein consisting of α, ß, and γ chains.
- At least 16 laminin isoforms in vertebrates have distinct tissue- and developmental stage–specific expression patterns.
- Basement membranes are targets of human diseases, such as Alport syndrome and dystrophic EB, due to mutations in collagen and laminin genes.
- The basement membrane inhibits endothelial cell proliferation and migration, preventing angiogenesis, which is promoted by tumor cells and growth factors.
- Type IV collagen is a major structural component of basal laminae and can bind to adhesion receptors, including integrins.
- All collagens are trimeric proteins made from three polypeptides encoded by at least 43 genes in humans.
- Type IV collagen has unique properties due to differences in the number and lengths of collagenous triple-helical segments and covalent modifications of the alpha chains.
- Type IV collagen forms a 400-nm-long triple helix that assembles into a branching, irregular two-dimensional fibrous network, contributing to the basal lamina structure, such as the glomerular basement membrane in the kidney.
Test your knowledge of extracellular matrix components and basement membrane structure with this quiz. Explore the roles of type IV collagen, laminins, perlecan, and nidogen in forming the basal lamina and their relevance to human diseases.
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