Membrane Proteins- Advanced topics 11 (L14)

ATP-Binding Cassette type (ABC-type)

(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)

Factor-type (F-type) ATPase

(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

Vesicle-type (V-type) ATPase

(1) pump protons (H+ ions) into organelles (e.g., vacuoles, lysosomes) (2) pump solutes into vesicles (i.e., neurotransmitters)

Phosphorylation-type (P-type) ATPase

(1) reversibly phosphorylated by ATP at an aspartic acid (Asp) residue (2) found commonly at the plasma membrane and maintain [ion]

Ion channels transport ____ ions per second.

-10^3

____ transport has _____.

-active -directionality

There are several families of ____.

-aquaporins

Channel proteins may have ____ which are specialized _____ for ____.

-aquaporins -porins -water

_____ are porins dedicated to ____ flux of ___ across membranes.

-aquaporins -rapid -water

Active transport moves solutes ___ from ____ _____.

-away -thermodynamic equilibrium

____ proteins bind ___ or more solute molecules on one side of the membrane which initiates a ____ change in the ____ that transfers the ___ to the other side of the membrane.

-carrier -one -conformational -protein -solute

_____ proteins show ____ _____ just like enzymes.

-carrier -saturation kinetics

_____ proteins are _____ proteins that alternate between two conformational states, such that the ____ binding site of the proteins is ___ or accessible first to one side of the membrane and after the ________ change, then ____ to the other side of the membrane.

-carrier -allosteric -solute -open -conformational -open

_____ proteins form _____ channels through the membrane bilayer thus facilitating ____ of molecules across the membrane.

-channel -hydrophilic -diffusion

_____ proteins form _____ channels through the membrane that allow ____ to pass through with little to no change in the conformation of the channel protein.

-channel -hydrophilic -solutes

Passive transport:

-channel proteins -carrier proteins

Transporters are subject to _____ inhibition.

-competitive

Rate of ____ is directly ____ to the concentration gradient.

-diffusion -proportional

____ active transport is the accumulation of _____ or ____ on one side of the membrane is directly coupled to an _____ reaction which leads to ____ across the membrane.

-direct -solutes -ions -exergonic -transport

Active transport always requires an input of _____.

-energy

Diffusion is a ____ process.

-exergonic

In ____ diffusion ___ input ____ is required.

-facilitated -no -energy

In _____ diffusion solutes diffuse ___ concentration gradient.

-facilitated -down

Channel proteins may be ____.

-gated

Ion channels are typically ____.

-gated

The more ______ a substance, the _____ readily it can ____ a membrane barrier.

-hydrophobic -more -cross

_____ active transport depends on the ____ of two ____ with the movement of one solute ____ a concentration gradient driving movement of a ____ solute ____ a concentration gradient. ( may be symport or antiport)

-indirect -cotransport -soultes -against -second -against

____ channels allow passage of ions ___ their electrochemical gradient.

-ion -down

Ion channels are ___ specific but some allow ___ than one ion to pass.

-ion -more

Channel proteins may form ____ channels which allows passage of ___ ions.

-ion -select

Most ____ and _____ substances must move through _____ proteins.

-large -polar -transport

Most ___ and ____ substances do ___ cross membranes at _____ rates.

-large -polar -not -appreciable

Photoactivated receptors respond to...

-light

_____ bilayers are relatively ____ to ____ to the amount of ____ required to move ____ from an aqueous environment into a ____ environment.

-lipid -impermeable -ions -energy -ions -nonpolar

_____ bilayers are relatively permeable to _____ molecules.

-lipid -nonpolar

Net flux will be in the direction of ______ free energy.

-minimun

For the movement of ____ solutes through one ____ protein the transfer may be either ____ or _____.

-multiple -carrier -symport -antiport

Active transport allows the cell to maintain constant, ___-______ intracellular concentration of _____ ions.

-non equilibrium -inorganic

____ transport usually involves the ____ of one or ___ solutes.

-passive -movement -two

___ transport does __ require the input of additional ____.

-passive -not -energy

____ are typically ___ specific than ___ channels.

-porins -less -ion

Channel proteins may have ____ which allow passage of ____ ions.

-porins -select

____ allow ___ passage of various solutes through the membrane "____".

-porins -rapid -pores

Active transport allows for the ____ of substances from ____ the cell where the concentration of the substance may be ____ than the concentration of the same substance into the region into which is being _____.

-removal -inside -lower -transferred

____ diffusion is limited to ____, ____ ish molecules.

-simple -small -nonpolar

_____ exclusion across ____ bilayer begins at about _____ Da.

-size -lipid -180

Membranes are more permeable to ____ molecules than _____ molecules.

-small -large

Some transporters are also _______

-stereospecific

_____ and ____ have a high degree of specificity for solutes.

-transporters -permeases

Passive transport is not _____.

-unidirectional

Active transport allows for the ____ of nutrients from environment where they are at ___ concentrations.

-uptake -low