Lecture #9 Flashcards
November 3, 2020
absorption
-major routes are gut, skin, and lungs/gills (exposed to environment) -must cross a membrane to be absorbed
phospholipids
-major constituent of membranes -contain cholesterol -polar, hydrophilic head and nonpolar hydrophobic tails (fatty acid chain) -4 major kinds, one has net negative charge -only small, neutral hydrophobic molecules can penetrate
plasma membrane is a mosaic of ______
-proteins and lipids -much of absorption is governed by proteins (membranes are selective barriers)
six major functions of membrane proteins
- transport 2. enzymatic activity 3. signal transduction 4. cell-cell recognition 5. intercellular joining 6. attachment to the cytoskeleton and extracellular matrix
intercellular joining
-cells at barrier tissues are organized into epithelia (sheets) -different types of epithelia, all are polarized (one side faces environment and one side faces blood) and rest on a basal lamina, this leads to specialization of membranes
typical junctions between cells in epithelia
usually have tight junction which greatly limit the movement of molecules between cells, seals cells together
adherens junction
connects actin bundles between cells
desomosome
joins intermediate filaments
gap junction
allows passage of small molecules between cells
simple epithelia

stratified epithelia

columnar epithelia

cuboidal epithelia

squamous epithelia

apical
faces the environment
basolateral
faces the blood
~ 25% of the genome codes for…
membrane proteins (more than half of all drugs target membrane proteins)
multidrug (ABC) transporters
-the cell’s bouncers -one transporter can expel many different kinds of chemicals -always being adapted to the environment, adding more of the kinds that are needed and taking away ones that are used less
distribution
-once absorbed, a compound (toxicant/drug/nutrient) has to move from the site of absorption to the site of action -a property of both organisms and cells
continuous capillary

fenestrated capillary

discontinuous capillary
leaks compounds from the blood into the liver so they can be detoxified

intracellular sequestration
can store chemicals after they’ve entered the cell to prevent them from causing harm plant cells –> vacuole animal cells –> lysosome
if Hg reacts with cysteine, mercury will accumulate in…
muscle/proteins


