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