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Membrane e trasporti transmembrana Appunti scolastici Premium

Appunti di Chimica del prof. Liguri sulle membrane e i trasporti transmembrana: i lipidi, Glycocalyx, Structural elements of membrane proteins, Principles of membrane transport, Passive and facilitated diffusion, Ion channels, ATPases, active transport.

Esame di Chimica docente Prof. G. Liguri

Anteprima

ESTRATTO DOCUMENTO

ATPases

Many proteins use the energy of ATP hydrolysis to

fuel transport.

(2) V-type ATPase

Multimeric transporters often work in the reverse

direction (ATP synthesis)

F Fo ATPase is the mitochondrial ATP synthase

1 +

H -ATPase of lysosomes acidify the organelle

ATPases

(3) ABC Transporters

Many proteins have an

“ATP-Binding Cassette”

and move large molecules

across membranes

ATPases

(3) ABC Transporters

-Multi-drug resistant protein can pump drugs out

of cells. Some cancers become resistant to

cancer therapy by increasing expression of MDR,

either by gene duplication or increased

transcription Na ,K -ATPase

+ +

• Enzyme Structure

α

– -Subunit of about 100 kDa

• ATPase activity

• Contains all known substrate and inhibitor binding sites

β

– -Subunit, a small glycopeptide of 30-40 kDa

• Necessary for activity but role unknown

• Necessary for proper membrane insertion during synthesis.

Na ,K -ATPase: Mechanism

+ +

+ +

• Na and K bind to separate sites.

+

• Inhibition of K binding by drugs is associated with relief of

congestive heart failure (dropsy).

Na ,K -ATPase: Mechanism

+ +

+

• 3 Na bind

• ATP

phosphorylates

active site

• Conformational

change releases

+

Na +

• 2 K bind 2+

Mg

2+

• Mg catalyzes

dephosphorylation

of enzyme

• Conformational +

change releases K

Na+,K+-ATPase: Mechanism

• Digitalis class cardiac glycosides competitively bind to

+

(extracellular) K site.

– Digitalis purpurea (foxglove)

F.E. Köhler (1883-1914) Köhler's

Medizinal-Pflanzen in naturgetreuen

Abbildungen mit kurz erläuterndem

Texte, publ. Gera-Untermhaus.

Ion channels

Ion channels are pores that permit the movement of

specific ions.

When open, the channels allow ions to move down

concentration gradients

Ion channels

Can “transport” 100,000,000 ions/ sec

A “selectivity filter” restricts movement to specific ions

Movement is controlled by regulating “openness” –

the proportion of time spent in the open

configuration

Ion channels can be regulated by specific conditions

to be open or closed

If opened for a prolonged period, the channels can

become desensitized

Ion channels

-

Anion channel (Cl )

K+ channel

K+ channel

K+ channel

K+ channel

Acetylcholine receptor

Acetylcholine receptor

+

Voltage-gated Na channel protein

+

Voltage-gated Na channel protein


PAGINE

79

PESO

8.64 MB

PUBBLICATO

+1 anno fa


DETTAGLI
Esame: Chimica
Corso di laurea: Corso di laurea magistrale in odontoiatria e protesi dentaria (a ciclo unico - 5 anni)
SSD:
Università: Firenze - Unifi
A.A.: 2013-2014

I contenuti di questa pagina costituiscono rielaborazioni personali del Publisher valeria0186 di informazioni apprese con la frequenza delle lezioni di Chimica e studio autonomo di eventuali libri di riferimento in preparazione dell'esame finale o della tesi. Non devono intendersi come materiale ufficiale dell'università Firenze - Unifi o del prof Liguri Gianfranco.

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