55 Questions
What guides the intracellular formation of triple-stranded collagen during synthesis?
Additional propeptides
Which molecule stabilizes collagen fibrils by forming covalent cross-links between lysines of adjacent molecules?
Heparin
What is the role of prolines and lysines in collagen assembly?
Formation of hydrogen bonds
Where does fibril assembly occur in the context of collagen synthesis?
Cell surfaces
Which sequence in fibronectin is involved in cell binding and increases binding affinity?
Synergy sequence
What is the main organiser of the basal lamina in the ECM?
Laminin
Which protein links the laminin and type IV collagen networks in the ECM?
Perlecan
What is the composition of laminins in the basal lamina?
α, β, and γ subunits
Which molecule is involved in linking cells to the basal lamina during collagen synthesis?
Heparan sulfate
What is the primary function of the cytoskeleton in a cell's interior?
Transporting between organelles
What is the main function of proteoglycans in the extracellular matrix?
Resisting compression and allowing diffusion of nutrients
Which cell type secretes most of the extracellular matrix (ECM) macromolecules?
Fibroblasts
What distinguishes Heparin from other glycosaminoglycans (GAGs) like Keratan sulfate and Heparan sulfate?
It is highly negatively charged
Which process is regulated by the extracellular matrix (ECM) in cells?
Cell differentiation
What is the role of proteoglycans in the extracellular matrix (ECM)?
Bind secreted growth factors to control diffusion and modulate growth factor activity
How do Fibroblasts contribute to collagen synthesis in the extracellular matrix?
Secreting fibrous proteins directly into the matrix
Which component is a part of the composition of aggrecan, a key component of cartilage?
Chondroitin sulfate: Glucuronic acid - N-acetyl galactosamine
Which statement best describes the basic structural motif of collagen?
Three polypeptide α-chains wound in a triple helix with Gly-X-Y sequences
How do fibroblasts contribute to collagen assembly process?
Arrange collagen molecules into higher order polymers like collagen fibrils
What is the main function of collagen fibrils in the extracellular matrix (ECM)?
Resist tensile forces in connective tissues
What is the primary function of protein degradation in cells?
To prevent the build-up of abnormal proteins
During vesicle transport mechanisms, what is the role of GTPase?
Tethering & docking
Which molecule is involved in the scission (pinching) of clathrin-coated pits during endocytosis?
Dynamin
What is the main function of antibodies in protein analysis techniques?
To identify specific proteins
Which organelle is primarily responsible for the degradation of cellular components, including proteins?
Lysosomes
What is the primary function of lysosomes?
Degrading proteins
Which process involves lysosomes digesting extracellular proteins taken into the cell by engulfing them?
Phagocytosis
What is the critical active site residue involved in lysosomal degradation of proteins?
Cysteine protease
Which process involves degrading cytoplasmic proteins via autophagy?
Proteasome degradation
What is the characteristic feature of lysosomes that supports their function in degrading proteins?
Acidic environment
What is the function of PEST sequences in proteins?
Targeting proteins for degradation
Which amino acids are considered destabilizing for proteins in terms of degradation pathways?
Phenylalanine and Aspartate
What is the role of E3 ligases in protein degradation by the proteasome?
Forming isopeptide bond between ubiquitin and substrate
What is the composition of the 26S proteasome?
2x 19S Regulatory complex and 1x 20S Catalytic complex
How does ubiquitination contribute to protein degradation?
Marks proteins for degradation by proteasome
Explain the role of the mannose-6-P receptor in lysosomal protein transport.
The mannose-6-P receptor recognizes lysosome resident precursor proteins for transport to the lysosome.
Describe the process of clathrin-mediated endocytosis, mentioning the key steps involved.
Ligand binds to receptor, which recruits adapter protein, leading to clathrin recruitment and vesicle budding. The mature pit is pinched by dynamin, then uncoated for vesicle fusion.
What is the common function of GTPase in vesicle transport mechanisms?
GTPase is involved in sorting vesicles to their correct destinations.
Explain the significance of protein degradation in preventing abnormal protein build-up.
Protein degradation helps in removing abnormal, misfolded, damaged, or unwanted proteins to maintain cellular health.
What is the primary role of lysosomes in cellular function?
Lysosomes are primarily responsible for degrading cellular components, including proteins.
What are the main proteolytic processes that occur in the cytosol for protein degradation?
Proteasome and cytosolic proteases
Describe the process of receptor-mediated endocytosis and its role in protein degradation.
Receptor-mediated endocytosis involves the uptake of specific molecules by cells through receptor-ligand interactions, leading to lysosomal degradation.
What is the function of antibodies in protein analysis techniques?
Antibodies are used to detect specific proteins in samples, aiding in protein identification and analysis.
Explain how lysosomes contribute to protein degradation within the cell.
Lysosomes contain various enzymes in an acidic environment that help in the breakdown of proteins, contributing to intracellular protein degradation.
Why is ubiquitin important in protein degradation pathways?
Ubiquitin marks proteins for degradation by proteasomes, playing a crucial role in regulating protein turnover and maintaining cellular homeostasis.
What are the different pathways through which proteins can be targeted for degradation?
ubiquitination, metal-catalysed oxidation, PEST sequences, particular N-terminal amino acids, SUMOlylation
Explain the process of degradation by the proteasome involving E1, E2, and E3 enzymes.
E1 activates Ubiquitin, E2 catalyzes Ub transfer, E3 forms isopeptide bond between Ub and substrate
What is the composition of the 26S proteasome and how does it function in protein degradation?
2x 19S Regulatory complex, 1x 20S Catalytic complex; Degrades ubiquitinated proteins
Explain the role of the extracellular matrix in regulating cellular processes.
Provides structural support, mediates cell signaling, influences cell behavior
What are the key functions of lysosomes in the cell?
Intracellular digestion, recycling cellular components, programmed cell death
Explain the role of GTP binding and hydrolysis in the process of vesicle trafficking.
GTP binding to Sar1 recruits COPII coat proteins for vesicle formation, while GTP hydrolysis triggers uncoating of the vesicle.
Describe the function of SNARE proteins in vesicle fusion.
SNARE proteins mediate the fusion of vesicle membranes by forming a complex that pulls the membranes together.
How does the NSF (ATPase) contribute to vesicle trafficking?
NSF binds to the SNARE complex, hydrolyses ATP, and pulls the SNARE proteins apart to facilitate membrane fusion.
Explain the role of Rab GTPase in vesicle targeting within the cell.
Rab GTPase directs vesicles to specific spots on the target membrane by interacting with Rab effectors.
How do phosphoinositides regulate trafficking from the trans-Golgi?
Phosphoinositides, phosphorylated derivatives of phosphatidylinositol, play a key role in directing vesicle trafficking from the trans-Golgi.
Test your knowledge on the formation of collagen fibrils, aggregation into bundles, and the synthesis of collagen polypeptide chains. Learn about the orientation and migration of fibrils to create tendons and ligaments.
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