Exam 1: Chapter 5: Transport Flashcards
transport
can be the movement of individual ions across a membrane or glucose crossing the intestinal epithelia to enter the blood stream
the second law of thermodynamics
isolated system can only change in certain ways
this applies to equilibrium
what is equilibrium?
internal stability without change; homeostasis
passive transport…
seeks equilibrium
fish in fresh water
water is hypotonic to the fish, concentration of ions in the fish is much larger
simple diffusion
passive transport, movement occurs with the concentration gradient
electric gradients (diffusion)
can have an effect on diffusion of charged solutes across membranes
influences on simple diffusion
attraction and repulsion
what can cross membranes via simple diffusion?
small, non-polar molecules
gated ion channels
take many forms; positive ions in, negative ions out
selectively permeable channels
movement is the result of both concentrations and electrical gradients
charges of cells in animals
positive charge on the outside, negative charge on the inside
Na+ movement
not at equilibrium, tends to move into the cells
K+ movement
not at equilibrium, leaks out of cell
concentration gradients can cause
electrical gradients that alter concentration gradients
donnan equilibrium
the membrane is permeable to more than one kind of ion; attraction and repulsion develops due to ion movement
facilitated diffusion
can work with polar organic solvents; proceeds in the direction of electrochemical equilibrium
facilitated diffusion movement occurs…
quickly
in facilitated diffusion, solvents must bind to…
transporter proteins
example of facilitated diffusion
glucose movement across the membrane; requires specific transporters in blood cells
active transport
uses energy for transport and can do transport against a concentration or electrochemical gradient
active transport is a type of
carrier mediated transport
a receptor protein may undergo
conformational change in the process of facilitating transport
what is the source of energy for active transport?
main soure is ATP; GTP can also be used
how much ATP is used in the kidney for transport?
40%
Na+/K+/ATP pump
3 Na+ out, 2 K+ in; creates a negative potential on the inside; against concentration gradient, requires ATP
primary vs secondary active transport
In primary active transport, the energy is derived directly from the breakdown of ATP.
In the secondary active transport, the energy is derived secondarily from energy that has been stored in the form of ionic concentration differences between the two sides of a membrane.
Na+-K+-ATPase
consists of a pump, an enzyme, and a transporter
hydrolyzes ATP, and is primary type, because it relies on being phosphorylated during its action
Na+-K+-ATPase steps
- ATP is bound, about to bind Na+
- ATP is hydrolyzed, phosphorylated, Na+ binds
- releases Na+, can bind K+
- de-phosphorylated and K+ attatches
example of secondary active transport
glucose into an epithelial cell of the vertebrate small intestine
role of cotransporter protein in glucose movement
links the movement of Na+ and glucose; for every 2 Na+ ions it moves across the membrane, it must carry a molecule of glucose across in the same direction
osmotic pressure
water transport; osmosis of water is colligative
colligative properties depend on:
the number of dissolved entities per unit volume, not the chemical nature
3 most important colligative properties
osmotic pressure, freezing point, and water vapor pressure
freezing temperature
highest temperature that causes freezing
water vapor pressure
measures the tendency of a solution to evaporate
colligative properties change with changes in…
concentration of the dissolved entities
higher concentration increases osmotic pressure but lowers freezing point and vapor pressure
osmolarity
how osmotic pressure is expressed
osmosis
diffusion of water from lower osmotic pressure to higher osmotic pressure; water moves from hypo to hyper
aquaporins
water pores; water in the form of H2O is allowed to pass through
where are aquaporins present?
RBCs, the brains, and kidney-tubule epithelia
what do aquaporins play a role in?
urine formation, tears and sweat, aqueous humor, and blood-brain barrier
aquaporin shape
tetramers
mammalina RBC are ________ to water
highly permeable
some aquaporins are controlled by
protein kinases and have sites for phosphorylation
vassopressin
antidiuretic hormone (ADH)
blood plasma has a high concentration of
proteins; help water to enter the blood stream in capillaries by osmosis
blood pressure forces water
out of the blood in the capillaries
