Quiz 2 Flashcards
plasma membrane structure and function
structure: lipid bilayer
function: physical barrier, gateway for exchange, communication, and site of attachment
transcellular
transport that goes THROUGH the membrane
paracellular
transport that goes PARALLEL to the membrane
passive transport
materials move down gradient, no energy is required
active transport
materials move against gradient, requires energy (ATP)
What are the four types of passive flux?
simple diffusion
osmosis
facilitated diffusion
bulk filtration
simple diffusion
passive and random motion of molecules in solution
moving from high to low concentration
rapid over short distances
directly related to temp
indirectly related to molecular size and fluid viscocity
osmosis
diffusion of water across a selectively permeable membrane
high solute conc.= low H2O conc.
cells with high solute conc. have high osmotic pressures
isotonic solution
conc. of solute outside cell=conc inside the cell
hypertonic solution
conc. of solute outside cell>conc. inside the cell
water flows out (cell shrinks)
hypotonic solution
conc. of solute outside cell<conc. inside the cell
water flows in (cell swells)
aquaporins
membrane-transport proteins providing a facilitated pathway for water flow through the membrane
facilitated diffusion
“easier diffusion”
movement from high to low conc. through a protein
bulk filtration
concentrated movement of large groups of molecules (often including water)
everything moves in the same direction
often occurs in response to pressure
Fick’s law (equation)
Jnet=-Ds(dCs/dx)
- jnet= flu
- Ds= diffusion coefficient
- dCs/dx= concentration gradient of solute
Fick’s Law says…
flux is PROPORTIONAL to temp, concentration gradient, area, and membrane permeability
flux is INVERSELY proportional to friction, molecule size, fluid viscosity, and membrane thickness
Types of Transporters
ion channel
carriers
pumps
Ion channels
membrane proteins that, when open, act as a passive conduit for ions through the membrane
cycle between open and closed conformations
Ion channels gated by…
leaky
ligand
mechanical “pull”
voltage
some are sensitive to temp-how we detect hot/cold
leaky gated
channel randomly opens/closes
ligand gated
chemical stimulus opens the channel
mechanically gated
mechanical stimulus opens the channel
voltage
change in membrane potential opens the channel
Carriers/transporters
transport of solutes across a cell membrane
can facilitate active/passive transport
mechanistic theme for carriers
conformational changes
alternating access model
carriers cycle between multiple conformations in which a solute binding site is accessible on one side of the membrane or the other
never an open channel all the way through membrane
occlusion state
state where the solute may not access either the inside or the outside
Pumps
movement of molecules against concentration gradient
Primary Active transport
directly requires ATP
movement of one (or more) solutes AGAINST their gradient using chemical energy (ATP)
Secondary Active transport
utilizes energy stored in pre-existing conc. gradients
movement of one or more solutes down their conc. gradients provides the energy for the movement of other solutes AGAINST their conc. gradients
uniport
movement of 1 thing in 1 direction
symport
movement of 2+ things in the same direction
antiport
movement of 2+ things in different directions
Epithelial tissue
appears on surfaces
involved in exchange, transport, movement/clearing, protection, secretion, and sensation
two types of secretion
duct (exocrine)- outside body
ductless (endocrine)- inside body
merocrine
secretory products secreted by vesicular exocytosis
most common form, often continuous
ex. sweat and saliva
apocrine
partial cellular breakdown (fragmentation)
cytoplasm and vesicular contents secreted
ex. milk and underarm sweat
holocrine
entire cell lost with secretion
stem cells divide to replace lost cells
ex. oil glads
types of intercellular junctions
tight junctions
adhering junctions
desmosomes
gap junctions
tight junctions
“gatekeeper”
prevent substances from moving between cells
encircle cells near apical surface
adhering junctions
actin-filament based systems
encircle cells immediately adjacent to all its neighbors
located deep to the tight junctions
desmosomes
tie cells together
allow bending and twisting
do not encircle cell
provide resistance to stress
gap junctions
protein channels that allow rapid communication between cells
Connective tissue forms
connective tissue proper (loose and dense)
supporting connective tissue
fluid connective tissue
connective tissue consists of…
specialized cells
protein fibers
ground substance
extracellular matrix is made up of…
protein fibers
ground substance
muscle tissue function
contract (shorten) when stimulated to create movement
three types of muscle tissue
skeletal- multinucleated + striated
cardiac- striations + intercalated discs
smooth- no striations
nervous tissue function
communication and control of the body
two types of nervous tissue
neuron- nerve cells capable of initiating/conducting electrical activity
neuroglia (glia)- cells that support neurons
