Lecture #9

Question 1

absorption

Answer 1

-major routes are gut, skin, and lungs/gills (exposed to environment) -must cross a membrane to be absorbed

Question 2

phospholipids

Answer 2

-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

Question 3

plasma membrane is a mosaic of ______

Answer 3

-proteins and lipids -much of absorption is governed by proteins (membranes are selective barriers)

Question 4

six major functions of membrane proteins

Answer 4

1. transport 2. enzymatic activity 3. signal transduction 4. cell-cell recognition 5. intercellular joining 6. attachment to the cytoskeleton and extracellular matrix

Question 5

intercellular joining

Answer 5

-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

Question 6

typical junctions between cells in epithelia

Answer 6

usually have tight junction which greatly limit the movement of molecules between cells, seals cells together

Question 7

adherens junction

Answer 7

connects actin bundles between cells

Question 8

desomosome

Answer 8

joins intermediate filaments

Question 9

gap junction

Answer 9

allows passage of small molecules between cells

Question 10

simple epithelia

Answer 10

Question 11

stratified epithelia

Answer 11

Question 12

columnar epithelia

Answer 12

Question 13

cuboidal epithelia

Answer 13

Question 14

squamous epithelia

Answer 14

Question 15

apical

Answer 15

faces the environment

Question 16

basolateral

Answer 16

faces the blood

Question 17

~ 25% of the genome codes for…

Answer 17

membrane proteins (more than half of all drugs target membrane proteins)

Question 18

multidrug (ABC) transporters

Answer 18

-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

Question 19

distribution

Answer 19

-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

Question 20

continuous capillary

Answer 20

Question 21

fenestrated capillary

Answer 21

Question 22

discontinuous capillary

Answer 22

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

Question 23

intracellular sequestration

Answer 23

can store chemicals after they’ve entered the cell to prevent them from causing harm plant cells –> vacuole animal cells –> lysosome

Question 24

if Hg reacts with cysteine, mercury will accumulate in…

Answer 24

muscle/proteins

Question 25

metabolism and excretion

Answer 25

-occurs in LIVER, kidneys, and lungs -happens on a cellular level

Question 26

Membranes can take things out of the cell or bring them in. This sometimes leads to…?

Answer 26

removing beneficial compounds or taking up harmful ones

Question 27

What compound is this?

Answer 27

alpha-amanitin, found in poisonous mushrooms

Question 28

What compound is this?

Answer 28

flunterazipam (roofies)

Question 29

the mechanisms by which chemicals cause harm

Answer 29

1. mutations 2. epigenetic mechanisms 3. interference with cellular signaling 4. interference with metabolism 5. membrane disruption

Question 30

To investigate the mechanisms by which chemicals cause harm, we …

Answer 30

run bioassay systems on other species

Question 31

ames assay

Answer 31

used to determine mutagenicity

Question 32

To determine if a compound causes harm, we can look at the following endpoints:

Answer 32

gene expression, morphological defects, protein modification, etc…

Question 33

two general mechanisms of intoxication

Answer 33

1. calcium signaling 2. oxidative phosphorylation

Question 34

calcium signaling

Answer 34

-low intracellular calcium concentrations, high extracellular concentrations -calcium is a signaling molecule -level increases in response to stimuli -toxicants cause the cell to release stored calcium, convinces the cell that things are very bad –> programmed cell death -calcium also signals development of sea urchin eggs after encountering sperm, an early signal would prevent the sea urchin from properly developing bc no male DNA

Question 35

oxidative phosphorylation

Answer 35

-uses energy in nutrients to produce ATP -occurs in mitochondria -toxicants/pesticides interfere with production of ATP