Cell Bio Lecture 14: Membrane Proteins
potassium pump process
1) 3 NA+ go in from the inside 2) ATP phosphorylates alpha subunits 3) because of the change, the 3 NA+ get released to the outside 4) Pump is still open to the outside 5)Two K+ head inside the opening 6) Dephosphorylation triggers change again 7) 2 K+ go inside 8) Pump is open to the inside, and it restarts
Ion Channels transport _____ ions per second.
10^3
Size exclusion across lipid bilayers begins at about ______ (e.g., glucose).
180Da
Lipid bilayers are relatively impermeable to ions up to the amount of energy required ( _____ kcal/mol) required to move ions from an aqueous environment into a ______ environment.
40 kcal/mol, nonpolar
Uniport
A membrane transport process that carries a single substance.
antiport
A membrane transport process that carries one substance in one direction and another in the opposite direction.
symport
A membrane transport process that carries two substances in the same direction across the membrane.
Channel proteins may __________ which are specialized porins for water.
Aquaporins
________ _______ bind one or more solute molecules on one side of the membrane which initiates a conformational change in the protein that transfers the solute to the other side of the membrane (i.e., transporters, permeases).
Carrier Proteins
______ _______ form hydrophilic channels through the membrane that allow solutes to pass with little to no change in the conformation (i.e., porins, ion channels).
Channel Proteins
ligand gated channels extracellular vs intracellular
Extracellular ligand requires outside neurotransmitters to attach, while the site to attach for intracellular is on the inside
True or False? In facilitated diffusion solutes diffuse up concentration gradient.
False
True or False? Most large and polar substances cross membranes at appreciable rates
False
True or False? Passive transport is unidirectional.
False
What goes in and what comes out: Chloroplast
In: CO2, 3-phosphoglycerate Out: Triose phosphates, O2, glycodate
What goes in and what comes out: Glyoxomes
In: Fatty acids Out: Succinate
What goes in and what comes out: Peroxisome
In: Glycodate, Serine Out: Glycine, 3-phosphoglycerate
What goes in and what comes out: Nucleus
In: dATP, dCTP, dGTP, dTTP, UTP, CTP, GTP, ATP, proteins Out: mRNA, proteins
Channel proteins may form _______ _______ which allow passage of select ions.
Ion Channels
Channel proteins may _________ which allow passage of select molecules.
Porins
True or False? Active Transport allows for the removal of substances from inside the cell (or from within an organelle) where the concentration of the substance may be lower than the concentration of the same substance into the region into which it is being transferred.
True
True or False? Active Transport allows for the uptake of nutrients from the environment where they are at low concentrations (i.e., up the concentration gradient).
True
True or False? In facilitated diffusion no input energy is required.
True
True or False? Ion Channels are ion specific but some allow more than one ion to pass.
True
True or False? Most large and polar substances must move through transport proteins.
True
True or False? Passive transport usually involves the movement of one or two solutes.
True
True or False? Porins are typically less specific than ion channels (especially in bacteria).
True
sodium-potassium pump
a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell, ACTIVE TRANSPORT
Direct Active Transport
accumulation of solute or ions on one side of the membrane is directly coupled to an exergonic reaction (i.e., hydrolysis of ATP) which leads to transport across the membrane
Active Transport (always / sometimes / never) requires an input of energy.
always
Ion Channels (are / aren't) typically gated.
are
Transporters (are / are not) subject to competitive inhibition.
are
Volt gated channels
are activated by changes in the electrical membrane potential near the channel
Active Transport moves solutes ______ from thermodynamic equilibrium.
away
Indirect Active Transport
depends on the cotransport of two solutes with the movement of one solute down a concentration gradient driving movement of a second solute against a concentration gradient (may be symport or antiport)
Active Transport has __________ (only transports in one direction).
directionality
Rate of diffusion is ______ proportional to the concentration gradient.
directly
Passive transport (does, does not) require the input of additional energy.
does not
Diffusion is an _______ process (requires no input of metabolic energy).
exergonic
Channel proteins may be _______.
gated
Channel Proteins form __________ channels through the membrane bilayer thus facilitating diffusion of molecules across the membrane.
hydrophilic
The more ________ (i.e., nonpolar) a substance the more readily it can cross a membrane barrier.
hydrophobic
Active Transport allows the cell to maintain constant, non-equilibrium intracellular concentrations of ________ ions (i.e., K+, Na+, Ca2+, Cl- , H+.)
inorganic
Net flux will be in the direction of _________ free energy.
minimum
Lipid bilayers are relatively permeable to _______ molecules.
nonpolar
mechanically gated channels
open and close in response to physical deformation of receptors
Carrier proteins show ________ kinetics just like enzymes.
saturation
Simple diffusion is limited to _______, ________ molecules.
small, nonpolar (-ish)
F-type ATPase
stands for "factor"; pumps H+ using ATP hydrolysis against the gradient; found in bacteria, mitochondria, and chloroplasts; is reversible with ATP synthase that makes ATP when H+ falls with the gradient (1) pump ions (i.e., H+) to generate ATP (2) found in bacteria, mitochondria, and chloroplasts (3) part of photosynthetic and cellular respiration machinery in the cell
ABC ATPase
stands for ATP binding cassette, helps nutrient uptake, protein export, and removal of hydrophobic materials from cell. works with a variety of solutes and antitumor drugs (1) large family of transporters related by aa sequence and mechanism (2) specifically transport a variety of solutes (e.g., antibiotic pumps) (3) involved in drug resistance (e.g., MDR) and disease (e.g., CFTR)
Transporters and permeases have a high degree of specificity for solutes, some transporters are also ________ (e.g., will transport D-glucose only.)
stereospecific
For the movement of multiple solutes through one carrier protein (i.e., cotransport) the transfer may be either ______ or _______.
symport, antiport
Glycolysis
the breakdown of glucose by enzymes, releasing energy and pyruvic acid.
anion exchange
transport of one negatively charged ion for another in opposite directions across the cell membrane, FACILITATED DIFFUSION, Carrier protein
V-type ATPase
type of transport ATPase that pumps protons (h+) into such organelles as vesicles, vacuoles, lysosomes, endosomes, and the Golgi complex (1) pump protons (H+ ions) into organelles (e.g., vacuoles, lysosomes) (2) pump solutes into vesicles (i.e., neurotransmitters)
P-type ATPases
undergo phosphorylation as they transport cations such as Na+, K+, and Ca2+ across the membrane (1) reversibly phosphorylated by ATP at an aspartic acid (Asp) residue (2) found commonly at the plasma membrane and maintain [ion]
aquaporin
water channel protein in a cell, FACILITATED DIFFUSION, Channel protein
What type of protein: Permeases
carrier protein
What type of protein: Porins
channel protein
ligand-gated channels
channel that opens when a neurotransmitter attaches
Antitumor drugs ABD works with
colchicine, taxo, vinblastine, actinomycin D and puromycin