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18 Cards in this Set

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What are the three forms of transport across a membrane and endocytosis?
Simple Diffusion:
-material moves down their concentration gradient through the phospholipid bilayer

Ex. oxygen or water int a cell, and CO2 out

Facilitated diffiusion:
-passage aided by both concentration gradient and transport protein

ex. glucose or amino acids

Active transport:
-move through a transport protein, but now energy must be expended to move against concentration gradient

ex. Pumping sodium out and potassium in against high concentration gradients
What is endocytosis?
moves large molecules into cell

liposomes help move big stuff (example)

most common form of endocytosis is pinocytosis:
-takes up proteins and other large molecules
-liquid verson of taking material
What is receptor-mediated endocytosis?
receptor proteins make this a HIGHLY SPECIFIC form of transport

cholesterol is taken up this way
What are some of the transport mechanisms found on an erythrocyte?
simple diffusion: CO2 and O2 diffuse through membrane

glucose transporter (facilitated):
-glucose changes form as it enters promoting its entrance and maintaining the gradient

anion exchange proteins

aquaporin - water pore, polar, thus porin allows faster uptake, diffusion is too slow through membrane

receptor proteins --> enzyems, have Vmax, Km (change shape after binding)
What are true of the membrane potential and the electrochemical gradient?
membrane potential:
-inside of cell is negatively charged with respect to outside

electrochemical gradient:
-electrical component due to charge separation and a concentration componenet
What is the direction of oxygen, CO2, and bicarbonate transport in blood?
oxygen:
-lung --> cytoplasm
-in capillaries: released from Hb and diffuses from cytoplasm into blood plasma

CO2:
-transported as bicarbonate
-converted to bicarbonate in capillaries and released into blood plasma
-in lungs: bicarbonate imported into cytoplasm and converted to CO2
-CO2 created by mitochondria is product of cellular respiration
What are properties of simple diffusion?
limited to small, nonpolar molecules, oxygen, carbon dioxide, and ethanol

membranes are impermeable to ions, especially mitochondria

proceeds from higher energy to lower, equilibrium is lowest energy state

osmosis is diffusion of water across a differentially-permeable membrane

water will always move to highest solute concentration (3D structure of water is disrupted by solutes increasing entropy and decreasing free energy)
What are hyper, hypo, and isotonic?
hyper:
-solution with higher solute than inside cell
-shriveled (animal)
-plasmolyzed (plant)

iso:
-equal inside and out (solute conc)
-normal (animal)
-flaccid (plant)
hypotonic:
-lower solute conc. than inside cell
-swell and lyse (animal)
-turgid (plant)
What is the diffusion rate comparison between simple and facilitated?
facilitated:
-hyperbolic

simple:
-linear
What are properties of facilitated diffusion?
Protein-mediated movement down the gradient

two main classes: carriers and channels

channel proteins:
-form hydrophilic channels, often transport ions (ion channels, porins, aquaporins)

carrier proteins:
-bind one or more solute molecules on one side of membrane and go through conformational change to deliver solute to other side of membrane (has enzyme kinetics but not true enzyme)
What are properties of Carrier proteins?
also called permeases or transporters

analogous to enzymes in their specificity and kinetics:
-some carriers are extremely specific (can discriminate between stereoisomers)

transport either one or two solutes:
-uniport: single solute
-contransport: two solutes (couple)
-symport: both in same direction
-antiport: transported in opposite directions
What are the erythrocyte glucose transporter and the anion exchange protein?
glucose transporter:
-a uniport carrier
-glucose higher in blood than cells
-low cellular glucose is maintained by hexokinase which phosphorylates glucose to glucose-6-phosphate
2 GLUT permeases:
-GLUT1 = erythrocytes
-GLUT2 = Liver cells

anion exchange protein:
-antiport carrier
-chloride-bicarbonate exchanger
-solute binding site of anion exchange protein interacts with different ions on opposite side of membrane
-regulated by insulin and glucagon
What are properties of Channel proteins?
3 kinds

ion channels: allow rapid passage of specific ions
-ligand gated = chemical that binds to receptor (eg. neuronal AMPA receptor)
-voltage gated = voltage passes and causes channels to open(eg. neuronal Ca channels)
-mechanosensitive = touch, heat, pain

Porins:
-allow passage of various solutes
-water filled pore at its center

Aquaporins:
-allow rapid passage of water
-several billion water molecules per second
-found in proximal tubules of kidneys that reabsorb water as part of urine formation
What are properties of Active transport?
unlike simple and facilitated diffusion, active transport has directionality, usually unidirectional.

3 functions:
-uptake of essential nutrients
-removal of waste
-maintain NONequilibrium concentrations of ions

DIRECT active transport depends on ATPases

INDIRECT depends on ion gradients

2/3 of body's energy is consumed to maintain gradients of ions such as H, K, Na, Ca
What is direct versus indirect active transport?
direct:
-accumulation of solute molecules or ions on one side of membrane coupled DIRECTLy to an exergonic chemical reaction (ATP hydrolysis)
-ATP added directly to enzyme
-uses ATP to build concentration gradient
-Na+/K+ pump

indirect:
-depends on cotransport of two solutes, one down gradient, one up (Na or H+)
-animal cells depend on Na gradients
-plant, bacteria, and fungi depend of proton gradients
-using ATP at one spot
-indirect uses gradient made by direct transporter, ALWAYS needs a "direct"
Ex. symport uptake of organic molecules, export of ions (Ca or K), ETC - F type ATPase
-uses Na+ gradient produced by Na+/K+ pump
What are the four types of transport ATPases?
P-type ATPase (P = phosphorylation):
-responsible for maintaining ion gradient (DIRECT)
Ex. Na/K pump and proton pump in stomach

V-type ATPases (V = vesicle):
-pump protons into vesicles, vacuoles, lysosomes, etc. (organelle membranes) (INDIRECT)

F-type ATPases ( F = Factor):
-ATP synthases
-maintain electrochemical gradients, and such gradients are used as energy source to synthesize ATP
INDIRECT

ABC-type ATPases (ATP-binding cassette):
-handles a wide variety of solutes (ions, sugars, AA, peptides, and polysaccharides
Ex. CFTR, multidrug resistance transport protein
What is the P-alpha subunit?
provides energy for molecule to change shape, releasing sodium, builds up concentration inside

-two K accepted, P leaves --> pump returns to initial conformation
What is Bacteriorhodopsin?
proton pump uses light energy to transport protons

absorbs all wavelength of light but purple, bacteria follow a nutrient concentration gradient