unit 5 Flashcards
What are tissues composed of?
Cells and the ECM
What is the cell wall (in plants) made of?
Cellulose and other polysacharrides
What do cellulose microfibrils do?
Confer tensil strentg
How do microtubules function in cell walls?
They help to direct and position cellulose in the cell wall
What mainly makes up connective tissues?
The extracellular matrix
What are all cell types differentiated from
fibroblasts
What are the two types of ECM
Basal lamina and connective tissue
What is the basal lamina and what types of tissues is it commonly found in?
An ECM type that forms a sheet of proteins; often in epithelial tissues
What is connective tissue and where is often found?
An ECM type that is a dense packing of ECM proteins. Found in dermis, bones, tendons, etc.
What are the 3 classes of ECM?
Proteoglycans, collagen, and multi-adhesive matrix proteins
What are some functions of the ECM?
Provide structure, important for tissue development, cell migration, sequestering growth factors
What is the function of proteoglycans? How are they composed?
Cell-ECM interactions and signaling; glycoproteins containing covalently linked polysaccharide chins
What is the function of collagen? What is its composition?
Tissue strength; cross linked fibers and sheets
What is the main difference in function between collagen and glycosaminoglycans
Collagen provides tensile strength, while glycosaminoglycans (which form proteoglycans) act as spacefillers and resist compression
How are collage fibrils organized?
Triple stranded collagen molecules forms collagen fibrils.
What path does collagen take during its synthesis?
Three singlular collagen polypeptide chains wind in the ER to create a procollagen molecule. They then enter the golgi apparatus and enter the extracellular space via exocytosis, where they are processed (terminal polypeptides removed), and the collegen molecules are assembled.
What are the two ways that cells can interact with the ECM?
Focal adhesions and hemidesmosomes
What are focal adhesions?
Cluster of integrins linked to actin
What are hesmidesmosomes?
Composed of integrin molecules. Inside the cell, they bind to intermediate filaments via linker molecules
What percent of cells are migatory in your body?
90%
What are the two major ways that of cell-cell interactions can happen?
Homophilic (same molecule interacts on both cells) vs r (different molecules interact on each cell).
What are some CAMs (cell adhesion molecules)?
Cadherins, integrins, selectins
What are the 4 types of cell-cell adhesions?
Adherens junctions, desmosomes, tight junctions, gap junctions
What do junctional adhesions help with?
Tissue integrity, cell recognition/sorting, gate/barrier functions
What do signaling adhesions help with?
Electrical coupling, developmental patterning, cell growth, cell survival, motility
What are adherens junctions?
Type of cell-cell adhesions. Composed of E-cadherins. In the cell, binds to actin via linker molecules.
What are desmosomes?
Type of cell-cell adhesions. Composed of desmosomal cadherin molecules. In the cell, binds to intermediate filaments via linker molecules.
What are tight junctions?
A linear arrange of molecules. They act as a fence to segregate apical (facing external environment) and basolateral (adjacent to internal facing) membrane components. Also acts as a gate to regulate passage of molecules between apical and basal compartments.
What are gap junctions?
Made of connexins. Form intercellular molecules to allow passage of water soluble molecules, ions, and second messengers.
Why does the molecular targeting of desmosomal cadherins lead to blistering?
ETA toxin cleaves desmosome (introduces PF IgG antibodies, which causes blistering skin disease).
What are the three lines of defense against pathogens?
1 (Skin, mucus, saliva stomach acid); 2 (innate immune system); 3 (adaptive immune system)?
What is involved in the innate immune system?
Complement (proteins that enhance pathogen clearance), and phagocytic cells (neutrophils and macrophages)
What is opsonization?
Particles targeted for destruction by an immunce cell such as a phagocyte. Complements on bacteria bind to phagocytic cell, phagocytosis.
How do complement proteins work?
They induce pores in bacteria, leading to lysis (hole in the membrane, fluids leak in/out)
What are neutrophils?
First cells that respond to an infection. Neutrophils engulf and destroy bacteria marked with antibodies
What are macrophages
Phagocytes that instruct other immune cells
What are the two types of adaptive immunity and what types of immune cells mediate it?
Humoral (B cell mediated - secretes antibodies) and cellular (T cell mediated - aids and kills cells)
How do B cells work?
Naive B cells make different antibodies and display it on the plasma membrane. Antigen binding + Th signaling stimulates B cell dividing, resulting in cell cloning
Track B cell development (starting from stem cells and ending at memory/plasma B cells)
Stem cells develop into pre-B cells (immature antibodies in cytoplasm) —> immature B cells (IgM on surface) —> Mature B cell (IgM and IgD on surface) —> Memory B cell (IgG, IgA, IgM on surface) or Plasma cell (IgG, IgA, IgM secretion)
How does antibody binding induce phagocytosis?
Antibodies on antigens (pathogen) bind to antibody receptors on macrophages
How do T cell receptors bind antigens on cell surfaces molecularly?
Antigen and MHC molecules bind at T cell receptors (a hydrophobic region anchors the chain in the plasma membrane)
Track the movement of an antigen to a Th cell?
1) antigen presenting cell takes up antigen by phagocytosis 2) cell breaks down antigen into fragments in phagosome 3) class II MHC protein binds antigen fragment 4) MHC presents antigen to Th cell
What types of cell activates a Th cell?
Interleukin-1 (a cytokine)
What are cytokines?
Proteins released by Th cells that activate other immune cells and cause inflammation.
What two types of t cells are activated by antigen presenting cells?
T helper cells and cytotoxic T cells
What do helper T cells do
No cytotoxic activity (CD4+ receptor), secrete cytokines
What do killer T cells do
Cytotoxic cells (CD8+), kill virally infected and tumor cells
