A tárgy természete...

• A biológiai tudományok egysége• Molekuláris, organizmikus és populációs

megközelítés • Érdekes de NEHÉZ• Aki nem akar figyelni, az menjen ki!• Vizsga: írásban. Utóvizsga: szóban• Vizsganyag: az előadások (órai jegyzet és

diasorozat, cikkgyűjtenény)

Az élet kettős természete

Eörs Szathmáry

Eötvös University Collegium Budapest

Miért kettős?

• Homeosztázis—disszipatív—anyagcsere• Egyirányú vezérlés és öröklődés• A láng és az öröklődő tulajdonságokkal

rendelkező sejt különbözősége

Great thinkers on the nature of life

Gottfried Leibniz

Freeman Dyson

John Maynard Smith

Erwin Schrödinger

Leibniz

• Az „isteni gépek végtelenül oszthatónak tűnnek

• A gépszerű működés a „molekuláris” dimenzióban is érvényesül

Schrödinger

• A gén mint aperiodikus kristály

• Az entrópia alacsony szintjének fenntartása állandó munkavégzést igényel

Maynard Smith

• Anyagcsere és homeosztázis

• Genetikai szabályozás • Az evolvabilitást az

utóbbi adja

Freeman Dyson

• Az élet kettős eredete• Először az anyagcsere

és a homeosztázis, nukleinsvak nélkül

• A gének mint a rendszer parazitái jelenhettek meg

An irreversible system

• A B

A reversible reaction

• A B• Le Chatelier-Braun principle

A reversible, closed reaction system

Reaction systems

• A closed, reversible cycle

• An open, almost reversible system

Closed and open systems

Alul: a stacionárius állapot (steady state)

The skeleton of sugar decomposition

Chemical cycles are metabolic engines

• The cycle as a whole is a catalyst

• The Noble prize of Szent-Györgyi was awarded for catalysis by fumaric acid

• Krebs has recognized the whole cycle

• Enzymes are superimposed on the metabolic cycle

A simple chemical cycle

• It is formally a unit composed of a closed and an open part

• Acts as a catalys

Engines operate in cycles, and are hence are dynamically stable

Tibor Gánti• Born in 1933• Chemical engineer• Patents in industrial

biochemistry (artificial metabolism)

• Syntheses using the controlled operation of enzymatic reaction networks

• First book on molecular biology in Hungary (1966)

The first edition of the Principles• A serious book in a

popular science disguise (1971)

• There was no other way to publish

• Proposal included the term “chemoton”

• ‘reductionist’ and ‘vitalist’ at the same time!

The investigation of life criteria: absolute criteria

1. Inherent unity2. Metabolism3. Inherent stability 4. Information carrying subsystem5. Processes regulated and controlled by a

programmeVERBAL AND PHENOMENOLOGICAL

Quest for a biological minimal system

• Chemical supersystem• Should be conceptually as simple as

possible• Must not necessarily be realizable in its

simplest form• Comparison with other elementary units

(such as the elementary cell in crystallography)

• FORMAL AND EXACT

The latest edition: OUP 2003

• After several editions in Hungarian

• Two previous books (the Principles and Contra Crick) plus one essay

• Essays appreciating the biological and philosophical importance

Enzymes and cycle stoichiometry

Very important: the cyclic process sign with the number of turns

Structures built of amphipathic molecules

A two-dimensional fluid

A self-reproducing vesicle (1978)

• Metabolism and reproduction• No genetic subsystem

Pathways of supersystem evolution

boundary

template

metabolism M B

B T

M T M B T

INFRABIOLOGICAL SYSTEMS

Organisation of chemical systems into a supersystem (1974)

• CHEMOTON: a particular supersystem which is also a biological minimal system

Gánti’s chemoton model

ALL THREE SUBSYSTEMS ARE AUTOCATALYTIC

template copying

metabolism

membrane growth

The assembly of RNA structures

• Combinatorial assembly of RNA structures

• Submitted to selection for function between chemotons

• 1979

The channelled assembly of ribozymes (1983)

• The presence of substrates gives guidance to ribozyme assembly

• Good enzymes and bad enzymes will affect the fitness of the chemotons

Venter: professional but trivial (synthetic biology)

The monograph (Kluwer 2003)

The chemoton symbol

Evolution towards a Borromean arrangement?

Chemoton symbol Borromean rings