Lecture 1 - Quiz 1 Flashcards
What is a major difference between eukaryotes and prokaryotes?
The presence of physical compartments (organelles) that are membrane bound within the cell to allow for specialization of processes - eukaryotes
What are the components of cell theory?
All living things are made of cells
Cells are the most basic building unit of life and maintain their own existence
New cells created from old cells
What are some components of modern cell theory that were added?
Activity of an organism depends on the total activity of independent cells
Energy flow occurs within cells
Cells contain hereditary information passed from cell to cell
Cells are basically the same in chemical composition
What layers do signaling pathways consist of?
Input layer, signal processing layer and output layer
What makes up the input layer of signaling pathways?
Growth factors/ligands/signals and their receptors on the surface of the cell that bind to the ligands and span the membrane
What makes up the signal processing layer of a signaling pathway?
Adapters and enzyme, signaling cascades and the transcription factors that they act upon
What makes up the output layer of a signaling pathway?
The results of the signaling pathway like apoptosis, migration, growth, adhesion, differentiation
What is an example of cell signaling in the GI tract?
Stem cells in the crypts proliferate and move up the villus where apoptosis and sloughing off occurs - 4-5 cell types interacting to make sure new epithelial cells are continuously generated
What is a major post translational modification of proteins that causes signaling?
Phosphorylation
What does Akt pathway demonstrate?
Pleiotropic actions of a protein kinase that can activate or inhibit many downstream effectors simulatenously
What part of a receptor interacts with the ligand?
Extracellular domain
What part of a receptor transduces signal to the rest of the proteins in a signaling pathway?
Cytoplasmic domain
What is transphosphorylation and what is an example of it?
When receptors across from each other as part of a dimer phosphorylate eachother - non covalently linked to tyrosine kinases - jak1 and tyk2
How does the TGF beta receptor phosphorylate?
As a heterodimer - in the serine/threonine kinase domains - type II phosphorylates type I which activates downstream signals - SARA interacts with smad2 to recruit it to the receptor - phosphorylation induces dissociation of smad2 from SARA
What is juxtacrine signaling and what is an example?
When ligand receptor interactions require close physical association between the signal emitting and signal receiving cells - Notch receptor - ligand becomes endocytosed causing cleavage of receptor and fragment sent to nucleus - primitive form
What is the patched-smoothened signaling system?
Patched protein has many transmembrane domains that sequesters smoothened protein to interact with Gli the effector protein that induces transcription - without hedgehog as the ligand, smoothened is inhibited and Gli is cleaved
What is the Wnt pathway?
Wnt binds to frizzled which sequesters LRP co receptor to bind axin and dishevelled which prevents phosphorylation of beta catenin (if phosphorylated then tagged for degradation)
What receptors sense association between the cell and the extracellular matrix?
Integrin receptors that function as heterodimers in different forms to give specificity (alpha and beta subunits) - interact with cytoskeleton proteins to change shape such as vinculin, paxillin, talin, and actinin
Focal adhesions of cells are __? and this can be demonstrated how?
Dynamic and transient, demonstrated by induction of stress fibers and focal adhesions in media with serum that has growth factor ligands present to interact with signaling
What are two preconditions necessary for growth and division in normal cells?
Cells must sense the presence of adequate levels of growth factors and existence of adequate anchoring to specific ECM components