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
What are some changes created by signaling pathways?
Alteration of cytoskeleton, activation of Ser/Thr kinase cofactors that change preexisting transcription factors, or activation of preexisting translation factors
What is a time frame for a signaling pathway on proteins?
Can be immediate if proteins are already there or it can be delayed if it is needing to generate new transcription factors that effect further proteins downstream
How are tyrosine kinase receptors able to emit signals to different proteins?
Tyrosine residues are phosphorylated with different neighboring amino acids that give different specific sequences on the receptor to give binding to different coregulatory proteins
What are modular units of protein structure?
Domains that can create different combinations to give different specificity
Are signaling pathways independent of interactive?
Interactive - cross talk with eachother
Do signaling pathways have negative or positive feedback?
Both - need to be able to shut off upstream effects to block signaling event depending on signaling concentration and time, etc.
What is the defense mechanism in our bodies?
the immune system that defends against infectious disease
What is the point of the immune system?
To defend us against pathogens and infectious disease and to determine state of general health
What is the innate immune response?
Not specific to a particular pathogen, immune response depends on intrinsic systems to recognize a danger - it is the first line of response
What is the adaptive immune response?
It is specific to a particular pathogen
What are the progenitors of immune cells?
Myeloid and lymphoid progenitors from stem cells
What do myeloid progenitors create?
Megakaryocyte, erythrocytes, mast cells and myeloblasts
What are megakaryocytes?
Large cells that spit out platelettes
What are myeloblasts?
Basophils, neutrophils, eosinophils, monocytes like macrophages or DCs
What do lymphoid progenitors produce?
Small lymphocytes like T and B and natural killer cells
What are granulocytes?
A type of leukocyte that secrets granules into cytoplasm - basophils (promote inflammation), eosinophils (moderate allergic reaction), neutrophils (phagocytes)
What is the most abundant innate immune cell?
Neutrophils (granulocytes from myeloid progenitors) - 6 billion in 1 L human blood
What do phagocytes consist of?
neutrophils, macrophages, monocytes, mast cells, DCs
What are phagocytes crucial for?
Maintaining healthy tissues by removing dead and dying cells through apoptosis - does not elicit inflammatory response - occurs in orderly manner
What are monocytes?
Develop into macrophages or DCs - derived from Myeloid progenitors
What are some functions of monocytes?
Ingest and degrade bacteria by phagocytosis - coordinate immune response by notifying other cells of problem - housekeeping function of recycling dead cells and clearing away debris without activating inflammatory response
Where are dendritic cells found?
present in the tissues in contact with external environment like the skin, nose lining, lungs, stomach and intestines - but migrate to lymphoid tissues when matured to interact with T and B cells to initiate adaptive immune response
What are mast cells important for?
Defense against parasites, and allergic reaction by releasing histamine, responsible for classic inflammation signs like redness and swelling
What is mastocytosis?
a rare disorder where there are too many mast cells that can lead to related disorders that cause chronic inflammatory pain
What are natural killer cells?
Cells that come from lymphoid progenitors do not require activation to kill other cells - they are a type of cytotoxic lymphocyte that have small granules in their cytoplasm that contain proteases known as granzymes that cause apoptosis or cell lysis
Which cells are critical to innate immunity?
NK cells - but also important for adaptive immunity
What are T cells?
Are a type of lymphocyte from lymphoid progeniotrs that express a TCR on their surface and they mature in the thymus - play a role in cellular immunity and antibody mediated immunity
What are B cells?
A type of lympocyte from lymphoid progenitors that play a role in antibody mediate immune system, they express b cell receptors and initiate an antibody response and secret antibodies by binding antigens and getting chemical signals from helper t cells that differentiate into a plasma cell that secrets large amounts of antibody
How fast is innate and adaptive immune responses?
innate = hours/days, adaptive = dweeks
Which immune system creates memory and works on specific responses?
adaptive immune system
What cells work as messengers between the innate and adaptive immune systems?
DCs
