BS1001/CY1001Introduction to Biology

L t 1

S h l f Bi l i l S i

Lecture 1

School of Biological SciencesNanyang Technological University

12 August 2013

Professor Alex Law

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Approach of the BSc degree in SBS@NTU:Approach of the BSc degree in SBS@NTU:Understanding biology at the molecular level

Confucius said:

"To learn without thinking, one will be lost. To think without learning, one will be imperilled."

NTU Blue Ribbons Commission cover page

Remember: this is your first University course, h i lf l i d thi ki

2emphasis on self-learning, and thinking

Knowledge Acquisition

Understanding through Thinking

g q

Learning through Curiosity and Enthusiasm

Understanding by putting the facts together there are more ththan one way

Research may be generalized to tackling of new problems where standard answers or solutions do not existstandard answers, or solutions, do not exist.

If we knew what it was we were doing, it would not be called research, would it? Albert Einstein

There is no distinct boundaries between the different disciplines in science.

All information should be qualified with a ?, some with a BIG one, some with a small one. The size of the ? should be modified according to new information available.

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modified according to new information available.

50% of what we learn in University is useless, unfortunately we do not know which 50%. William Brody (President of the Salk Institute) in a Public Lecture at NTUSalk Institute) in a Public Lecture at NTU.

What was right yesterday is wrong todayWhat was right yesterday is wrong today, what is right today will be wrong tomorrow. George Wald (1906-1997, Nobel Laureate 1968 Professor at Harvard) inLaureate 1968, Professor at Harvard) in response to a comment by a junior faculty member that he was giving the out-of-date information in a lecture to the first yearinformation in a lecture to the first year undergraduates.

Half the things a man knows at 20 are no longer true at 40, and half the things he knows at 40 hadnt been discovered when he was 20. Sir Arthur C Clarke (1917-2008, science and science

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( ,fiction writer).

Textbook: Biology 10th Edition: R J h M L d SiRevan, Johnson, Mason, Losos, and SingerMcGraw-Hill, International Edition

There are MANY others clones of each other!There are MANY others clones of each other!

Popular science books, e.g. The Double Helix by James Watson

How to study? Or How to do well in the course?

Read the assigned Chapters in Raven, or the equivalent subject g p , q jin other textbooks before you come to Lecture.

Lectures will be recorded, but they are not really the same. A lecture is much more of a dialogue than many of you probably realize. As you lecture, you keep watching the faces, and information keeps coming back to you all the time. (George Wald)

Work on your tutorial questions BEFORE you attend tutorials. It is NOT the same as looking at formal answers which will be posted. Some of the questions or their variation will appear on exams or quiz

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Some of the questions, or their variation, will appear on exams or quiz.

Mandarin Pinyin Table

b p m f d t n l g k h

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a /

(12)

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v \

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b p m f d t n l g k h

/

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6What do I do as a student?

Attend the Practicals:Attend the Practicals:

Please hand in your reports within one week.

It really should be two days. You have to do it anyway.You will remember more when you do it fresh.y

CA marks (30%)C a s (30%)

A mid-term quiz and two lab reports.

Feel free to send in questions. I will answer them but not to you individually. I will post the questions and answers in edveNTUre.

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Three recurrent themes:

Lif E thLife on Earth

WaterWaterThe chemistry of life may be viewed as the organization of water activityas the organization of water activity by carbon-based macromolecules

EvolutionNothing in biology makes sense

fexcept in the light of evolution. Theodosius Dobzhansky (1900-1975)

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EARTHSingaporeSingapore

View from 149687715 km above 95'S 6327'ELatitude: 1 3 N Equator = 0 latitude

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View from 149687715 km above 9 5 S 63 27 E Latitude: 1.3 N

Longitude: 103.9 E

Equator 0 latitude

Longitude = 0 through Greenwich (Royal Observatory), England

Galaxy Cluster

101011 galaxies in the observable universe

Sometimes I think were alone in the universe, and sometimes I think were not. In either case the idea is quite staggering. (Arthur C Clarke)

1968 film with Stanley KubrickNote that the astronaut is reading news on an iPAD

O ( f )

Sequels2010: Odyssey Two (book and film)2061: Odyssey Three (book only)

O ( )11

3001: The Final Odyssey (book only)

The Milky Way: our own galaxyThe Milky Way: our own galaxy

1012 solar masses200-400 billion stars

Sagittarius Arm

Orion Arm

Sun

M13

12Perseus Arm SUNM13

Our Solar SystemOu So a Syste

Our Sun is a STARMass = 1.989 x 1030 Kg

13Diameter = 1.38 million km

The eight planets in the solar system

Mercury Mars Uranus

Venus Jupiter Neptune

Earth Saturn Pluto24 August 2006dwarf planet

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Planets of our Solar System

Planets Distance from sunmillion Km AU

DiameterKm

MassKgmillion Km AU Km Kg

Mercury 57.9 0.38 4880 3.30 x 1023

V 108 2 0 72 12104 4 87 1024Venus

Earth

108.2

149.6

0.72

(1)

12104

12756

4.87 x 1024

5.97 x 1024

23Mars

Jupiter

384.4

778.3

1.52

5.20

6794

142984

6.42 x 1023

1.90 x 1027

Saturn

Uranus

1429

2871

9.54

19.2

120536

51118

5.68 x 1026

8.68 x 1025

Neptune 4505 30.1 49532 1.02 x 1026

AU = astronomical unit = average distance between the Earth and the Sun

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AU = astronomical unit = average distance between the Earth and the Sun

AU academic unit

Venus transit across the Sun16

Venus transit across the Sun5 June 2012

Bodies that orbit the planets are satellitesBodies that orbit the planets are satellites

The moon is the satellite of Earth

Galileo1564-1642

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Our Moon is a satelliteOur Moon is a satellite

ParentPlanet

OrbitKm

DiameterKm

MassKgSatellites g

Moon Earth 384 000 3 476 7.35 x 1022

Galilean moons

22Io

Europa

Jupiter 422 000

671 000

3 630

3 139

8.49 x 1022

4.80 x 1022Jupiter

Ganymede 1 070 000 5 262 1.48 x 1023Jupiter

Callisto 1 883 000 4 800 1.08 x 1023Jupiter

As of today, there are 64 confirmed moons (satellites) of Jupiter

18http://www.bbc.co.uk/news/science-environment-14391929A possible second moon BBC news on 4 August 2011

Are there life other than on Earth?

Life within the Solar System?

E C lli tEuropa6th of the Jupiter satellites and fourth largest

Callisto8th of the Jupiter satellites and second largestand fourth largest and second largest

NASA Galileo 1997 NASA Galileo 2001

19Evidence of water in/on these satellites, and therefore the possibility of finding life, that NASA has plans to explore them more thoroughly.

Are there life other than on Earth?

SETI:Scan the sky for meaningful signals - SETI@homeSearch of Extra-Terrestrial Intelligence

y g g @

Allen Telescope Array

20http://www.bbc.co.uk/news/science-environment-11041449

The Wow! signal

Ohio State University (OSU) program the Big Ear Telescope received a signal for 72 seconds on 15 August 1977.

Jerry Ehmany

Only this print-out survived hard disc (1 Mb storage capacity so it was immediately wiped clean for future recording!)

21But no more signals! Why didnt they send at least one more for confirmation?

We are here!

Pioneer Plaque

Pioneer 10 (1972)Pioneer 11 (1973)

In the hope that whichever intelligence out there, from the clues on this plaque can figure out who we are: including our place in the solar

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plaque, can figure out who we are: including our place in the solar system and the intelligent species on the planet. (Check Wikipedia)

Arecibo Broadcast (1974)(Puerto Rico)

Arecibo Radio TelescopeM13 Star Cluster

~300,000 stars, at least some will have planets20 trillion watt

Arecibo Radio Telescope

25 000 light years awayA message detectable by a SETI-like setup anywhere in our The message

~ 25,000 light years away

(No information can be transmitted faster than

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ygalaxy 1679 (23 x 73)

binary digitstransmitted faster than the speed of light.)

Message beamed out in 1679 binary digitsMessage beamed out in 1679 binary digits1679 = 23 X 73

0 0 00 0 00 1 1 1 1 0 0001x

0 00 01 1x

010x

0 00 00 1x

011x

100x

101x

110x

111x

0 01 00 1x

241 2 3 4 5 6 7 8 9 10

Are we intelligent?

Life Intelligence (in SETIs context)

History of Wireless Communication

Pre-1900: theory onlyMi h l F d d t ti f i d ti Michael Faraday: demonstration of induction

Radio broadcasting after 1900

Before that we were NOT intelligentBefore that, we were NOT intelligentOr, nobody out THERE can tell if we were intelligent

If someone sent us a signal which arrived 100 years ago we were notIf someone sent us a signal which arrived 100 years ago, we were not intelligent enough to detect it.

Technical limitations:

Signal strength: Areciba Broadcast our galaxy, SETI-like setupC th fi t th i th A ib ?

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Can they figure out the message in the Arecibo message?

Communication with Extraterrestrial Intelligence

Intelligent beings onlyWho can see us?

Planets in other star systemsWhere are they?

When the signals reach them

y

When can they see us?When the signals reach them

Can we communicate?Yes in principleYes, in principle.

Sun: ~1.5 x 108 km (8 min 19 sec away)Moon: ~4 x 105 km (1.3 sec away)

Nearest stars Centauri: ~ 4 light years awayM13 cluster: 25,000 light years awayGalactic Centre: 27 000 light years away

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Galactic Centre: 27,000 light years awayAndromeda: 2.5 million light years away

Curiosity landed on Mars 6 August 2012Curiosity landed on Mars 6 August 2012Can Mars support life, and was there water?

R di ti l l t hibiti f di t t t MThere appears to be a streambed.

Chemicals that support the hypothesis that there was once water on the planet.

Radiation level not prohibitive of sending astronauts to Mars.

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Chemicals that support the hypothesis that there was once water on the planet.

Man-made satellites

Estimate, a few thousand artificial satellites are in orbit.

282009, a US satellite and a Russian satellite collided in space!

The Elements

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Atomic structureO

Location Mass ChargeHydrogen Oxygen

Proton Nucleus 1 +1

Neutron Nucleus 1 0

Electron Orbitals ~1/2000 -1

Atomic Number

Number of protons

Atomic Mass

Number of protons

P = 1N = 0E 1

P = 8N = 8E 8Number of protons

orNumber of electrons

Number of protons+

Number of neutrons

E = 1AN = 1AM = 1

E = 8AN = 8

AM = 16

30Mass Weight

Dmitri Mendeleev(1834 1907)(1834-1907)

H

Li Be N O FB

Na Mg Si ClP SAl

C

CaK Fe Co Cu

Au

Ag I

Br

Rb

Cs Ba W

SeSc Ti V Cr Mn Ni Zn Ga Ge As

Sr Y Zr Nb Mo Ru Rh Pd Cd In Sn Sb Te

Ta Os Ir Pt Hg Tl Pb BiAuCs Ba W

Ce

Ta Os Ir Pt

La

Hg Tl Pb Bi

ErDy

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CeLa

UTh

ErDy

The Periodic TableThe Periodic TableH HeLi Be N O F

A

B Ne

N M Si ClP SAl

C

ArNa Mg

CaK

Si

Fe Co Cu

Ag

Cl

I

Br

Rb

P S

SeSc Ti V Cr Mn Ni

Al

Zn Ga Ge As Kr

Sr Y Zr Nb Mo Tc Ru Rh Pd Cd In Sn Sb Te Xe

Au

Ag IRb

Cs Ba W

Sr Y Zr Nb Mo Tc Ru Rh Pd Cd In Sn Sb Te Xe

Hf Ta Re Os Ir Pt Hg Tl Pb Bi Po At Rn

Fr Ra DbRf Sg Bh Hs Mt Ds Rg Cn Fl Lv Uuo

La

Ac Uut Uup Uus

CeLa

A

Pr Nd Pm Sm Eu Gd Tb Dy

P UTh

Ho Er Tm Yb Lu

N P A C Bk Cf E F Md N LAc Pa UTh Np Pu Am Cm Bk Cf Es Fm Md No Lr

Mendeleevs elements Natural elements Synthetic elements

La: insert Lacthanide series; Ac: insert Actinide series

Why are the elements arranged this way?

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y g y

http://www.dayah.com/periodic/

Order of shell fillinghttp://www.dayah.com/periodic/

The lowest energy level orbital filled first

s p d f

1 2 X X X

2 2 6 X XNote that the lowest energy orbital is not necessarily the

Chemistry of the elements

3 2 6 10 X

4 2 6 10 14

orbital is not necessarily the outermost orbital

Chemistry of the elements solely depends on the outer shell electrons 5 2 6 10 14

6 2 6 10 146 2 6 10 14

7 2 6 10 14Thus, while the d-orbital of shell 3 is filled, the s-orbital of shell 4 had already been filledshell 4 had already been filled.

While the 3d shell is being filled, all the 10 elements have similar properties because their outer shell (4s) has two electrons they are

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properties because their outer shell (4s) has two electrons, they are the first 10 transition metals including iron, copper and zinc.

Element Symbol Atomic Atomic % Wt % Wt% WtElement Symbol Number Weight Earth Crust Human Body

OxygenSilicon

OSi

Earth

814

1628

65.0trace

46.627 7

30.115 1Silicon

AluminiumIron

SiAlFe

141326 56

2827

tracetracetrace

27.76.55.0

15.11.4

32.1CalciumSodiumPotassium

CaNaK

201119

2340

39

1.50.20.4

3.62.82.6

1.5tracetrace

HydrogenMagnesium

Manganese

MgH

Mn

121

251

24

55

0.19.5

trace

2.10.140.1

13.9tracetrace

FluorinePhosphorusCarbon

Manganese MnFPC

259

156 12

551931

tracetrace

1.018 5

0.10.070.070 03

tracetracetracetraceCarbon

SulphurChlorine

CSCl

61617

123235.5

18.50.30.2

0.030.030.01

trace2.9

trace

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Nitrogen NNickel Ni

728

1453

3.3trace

tracetrace

trace1.8

Number of electrons in the outermost shell:1 4 5 6

H N OC1(1s) 2(1s)

2(2s)2(2p)

2(1s)2(2s)3(2p)

2(1s)2(2s)4(2p)

the outermost shell:

2(2p) 3(2p) 4(2p)

The Periodic TableHe

Li Be N O F

Ar

B Ne

Na Mg Si ClP SAl

C

H

ArNa Mg

CaK

Si

Fe Co Cu

Ag

Cl

I

Br

Rb

P S

SeSc Ti V Cr Mn Ni

Al

Zn Ga Ge As Kr

Sr Y Zr Nb Mo Tc Ru Rh Pd Cd In Sn Sb Te Xe

Au

g

Cs Ba WHf Ta Re Os Ir Pt Hg Tl Pb Bi Po At Rn

Fr Ra DbRf Sg Bh Hs Mt Ds Rg Cn Fl Uus Uuo

La

Ac Uut Uup Lv

synthetic elements

bulk biological elements

trace elementspossible trace essential elements ?

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trace elements

El t li t d t i th h b d d t th t thElements listed as trace in the human body does not mean that they are not important. Indeed, some are VERY important.

I b l t l f h l bi t bi d dIron: absolutely necessary for your haemoglobin to bind oxygen and carbon dioxide. Iron deficiency anaemia.

I di f d i th i h t d b th th id I diIodine: found in thyroxine, a hormone secreted by the thyroid. Iodine deficiency is rather common, leading to common swelling of the thyroid gland.

Zinc, found in many enzymes, particular in what is known as zinc fingers in DNA binding domains.

Ceruloplasmin, a major copper-carrying enzyme in your blood.

Of the major elements found on Earth, Aluminium and Silicon are found at trace level in the human body and apparently play no role in

36bodily functions.

Nonreactive Reactive

2 protons 7 protons2 protons2 neutrons2 electrons

7 protons7 neutrons7 electrons

KK

LL

2+ 7+

Helium Nitrogen

37With 3 more protons and 3 more electrons, the nitrogen will become the inert gas neon, with 8 electrons in its outer shell.

38

Ionic Bond

Na+Na+NaNaNaCl

Sodium atom Sodium ion (+)

Cl Cl

Chlorine atom

a.

Chloride ion ()

Cl ClNa+Na+More illustration of this type of

Cl Cl

ClNa+Na+ Na+Na+

Na+Na+

bond when we talk about protein structures.

39b. NaCl crystal

Covalent bondCovalent bond

No net charge

Filled outermost shell (in this case 1)

No free electrons

Hydrogen H HH2 H H Single

Oxygen O OO2 O O Double

Nitrogen N NN2 N N Triple

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Top right corner of the periodic table

HeH H

NeF FO ON NC C

Cl Cl ArS SP P

inertgas

singlebond

doublebond

triplebond

41multiple bonds cannot form in outer shells

3.5

3.0

2.52.5

2.1

Electronegativity describes the relative ability of an atom to attract electrons in a covalent bond: it is a dimensionless quantity.

Thus if the covalent bond is between two atoms of different electronegativitiesThus, if the covalent bond is between two atoms of different electronegativities, the one with higher electronegativity would pull the electrons in the covalent bond towards its nucleus, rendering the bond polar.

Large difference in electronegativities between O and H (3 5 vs 2 1) makes

Alternatively, if the electronegativities of the two elements are similar, they will exert similar pull to the bond electrons, making the bond non-polar.

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Large difference in electronegativities between O and H (3.5 vs 2.1) makes O-H bond polar, and small difference between C and H (2.5 vs 2.1) makes C-H bond non-polar.

Water and hydrogen bondy g

Hydrogen bond

Also note that there are two pairs of electrons on the oxygen as well as two hydrogen. This symmetry allow the water molecules to form an infinite matrix.

43Clearly, hydrogen bond can also be formed between H and N.

and many other possible arrangementsWh f it i tWhen frozen, it is not tell exactly which hydrogen belongs to which oxygenwhich oxygen

44

Consequences:

Ice is less dense than water ( 0 9 )

Water at its densest: 4C.

Thus, not only ice floats, but f f(~0.9 sp gr).

Change is not abrupt: therefore it becomes less dense as it

water freezes from the top.

Ice is also a good insulator, so water below can be kept

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t beco es ess de se as tapproaches freezing point.

so water below can be kept from the coldness above.

Other properties of water (all derivatives of being H O)Other properties of water (all derivatives of being H2O)and being able to form network of hydrogen bonds

Higher freezing/melting point: 0C

High condensation/boiling point: 100C

Large temperature range to remain in a liquid state (from 0C to 100C)

High specific heat: 1 cal/gm/C

Large temperature range to remain in a liquid state (from 0C to 100C)

Excellent general solvent

Cohesion: Hydrogen bonds hold water molecules together; also allow water to hold onto other molecules/surfaces

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Top right corner of the periodic tableCompounds with Hydrogen

Compounds

MeltingPoint

BoilingPoint

Range

Compounds C

H2 -259.1 -253.9

C

5.2

C

HeH2HeCH4NH

-272.2-18277 7

-268.9-161.6

33 3

3.320.444 4

HCl

Ne

Ar

HFH2O

H S

NH3

PH

CH4NH3H2OHF

0.0-83.6

-77.7

19.5

-33.3100.0

103.1

44.4100.0

HCl ArH2SPH3

H2O is the only liquid at RT

NePH3

-248.6-133.5

-246.1-85.0

1.548.5H2O is the only liquid at RT H2S

HClAr

-85.5-114.2-189 2

-85.1-60.7

-185 729.114.8

3 5

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Ar -189.2 -185.7 3.5

Melting/freezing point: -77.7C

Consider ammonia

Condensation/boiling point: -33.5C

NH HNumber of lone pair electrons: 1

HH

H107 Number of hydrogen: 3

The asymmetry of the lone pair electrons and hydrogen atoms does not allow the formation of a spaceous matrix as water. Solid ammonia sinks.

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Adhesion: capillary actionp y

Adhesion force of water to glass surface is stronger than gravity hence water is drawn upwards in the glass tube togravity, hence water is drawn upwards in the glass tube to a height when the two forces are balanced.

The narrower the tube the larger the surface area for aThe narrower the tube, the larger the surface area for a given volume of water, hence water rises higher.

Cranberry jelly: Water held to polymeric fibers in this case

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p ygelatin, as a semi-solid gel.

Cohesion: may be regarded as self-Cohesion: may be regarded as selfadhesion of water molecules. In this case referred to as surface tension

S f fSince surface tension of the water is greater than the force applied by the insects foot, the insect is thus

bl t lk table to walk on water.

In previous exam questions on properties of water, students of cited this l h h i lk Thi b i d f hexample such that insects can walk on water. This must be viewed from the

other side. Water has this property where insects like this one exists or not. It is the insect that has evolved to take advantage of this property of water.

Another consequence on the self-adhesion of water molecules by h d b d i th i l i f l l th t h d h bi hydrogen bonds is their exclusion of molecules that are hydrophobic. The hydrophobic molecules are forced to organize away from the water to come different structures: formation of membranes, protein folding, etc.

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Solubilizing NaClSolubilizing NaCl

Water interacting with the individual Na+ and Cl ions to keep them apart. g p pNaCl is said to be soluble. When the amount of Na+ and Cl increase to the point where there is insufficient number of water molecules to keep them apart, they aggregate to form crystal. The maximum amount of NaCl

51can be kept apart without crystallizing defines the solubility of NaCl.

These properties of water should not be memorized as individual properties. They should be regarded as one property manifested in different ways.

52

Carbon and multiple bondsCarbon and multiple bonds

A: one bond only A Ay

B: two bonds B B

B B B B B BA A

B B B B

B BB BB

BB A string

B BB BB

C: three bonds A surfaceC: three bonds A surface

D: four bonds A three dimensional structure

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D: four bonds t ee d e s o a st uctu e

The versatility of carbon

methane

ethane ethyleneacetylene

methane

HHHH HH

H C CC C C C

HHHH

H

HH

54benzenehexane

NanotubeOther carbon structures

Football

55BuckyballBuckminsterfullerene

The Jubalani Ball WC2010

The versatility of carbon (valence 4)

A dwarf star with a 3 000 k i f

Di dG hit

3,000 km size core of crystallized carbon, i.e. a diamond of 2 27 x 1024 tonnes orDiamondGraphite 2.27 x 1024 tonnes, or 1 x 1034 carats.

Many industrial uses including pencils and

56Golden Jubilee Diamond

546 carats, 109 gm

including pencils and solid phase lubricants.

H HeTop of the periodic table

Li Be B C N O F Ne

H He

Carbon dioxide(gas)

Na Mg Al Si P S Cl Ar

Valence +1 +2 +3 4 -3 -2 -1 0Valence

Carbon: 6 electrons 1s2 2s2 2p2

Silicon: 14 eletrons 1s2 2s2 2p6 3s2 3p2

Cannot form double bond

Larger atomic radius of silicon, pi electrons are too far Silicone dioxideLarger atomic radius of silicon, pi electrons are too far away to take on the necessary geometry for pi-bonding. (solid)

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The chemistry of life may be viewed as the organization of water activity by carbon-based macromolecules

The Origin of Life

Earliest evidence of life: ~3.5 billion years agoFossils embedded in rock dated to the timeFound in Australia and Africa.

Age of Earth (and the Solar System) ~ 4 5 billion years ago~ 4.5 billion years ago.

Age of the Universe (big bang) 11.5 20 billion years ago.y g

Within the first 1 billion years, microorganisms came about. R k bl i t f th ti th

George Gamow

Remarkable since most of the time the Solar System was too violent for any sufficiently stable condition for life to

l A thi th t d t t ld George Gamow(1904-1968)

Sir Fred Hoyle(1915-2001)

evolve. Anything that made a start could easily be destroyed.

Collision of Earth with a Mars-size object,

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(1915 2001) Collision of Earth with a Mars size object, leading to formation of a moon or two.

Our Universe ~ 1050 tonnes of matter(1 tonne = 1000 kg).

Big Bang: too hot for atoms.g gOnly elementary particles including protons, neutrons, electrons.

Cool down to form atoms (hydrogen) due to expansion.Cool down to form atoms (hydrogen) due to expansion.

Uniformity implies order; in the cosmic scale of things, there must be local conditions that favours stars formationmust be local conditions that favours stars formation.

Collapse of hydrogen by gravity leads to the formation of stars, h it ti l f th t t k ti ht th twhere gravitational energy forces the atoms to pack so tight that

other elements, by nuclear reactions, began to form (in the stars): first helium, later heavier elements. Release of energy, in the form of light allows us to identify them as starsof light, allows us to identify them as stars.

Fate of primary stars (population II) vary - mostly dependent on size, lti t l l i b hi d d b i ith h i l t

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ultimately leaving behind debris with heavier elements.

O S d thi d ti t ( l ti I) thOur Sun: second or third generation stars (population I), thus our planet has the heavier elements (including carbon) necessary for the kind of life we are.

98% of the matter collapsed into a single mass, which is the Sun (1.39 x 106 km in diameter, 1.99 x 1030 kg). Other found ways to materialize into the planetsinto the planets.

Closer to the Sun favours heat resistant silicates, farther out allows li ht l l t d i l di tlighter molecules to condense, including water.

Violent nature of the early solar system resulted in the ejection and capture f i t l t t i l th i i f th k t d tof interplanetary material, the origin of earths rocky crust and water are

likely to be of planetary and cometary origin.

L t i ifi t i t f t it 65 ti ti f diLast significant impact of a meteorite ~ 65 mya, extinction of dinosaurs. Worldwide deposition of a layer of the rare layer of iridium. Giant crater (Chicxulub) under Mexico 180 km across, impact of an object estimated to be about 20 km in diameter

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be about 20 km in diameter.

The Chicxulub Crater in Mexica

The impact asteroid: at least 10 km in diameterSize of the Chicxulub Crater: 180 km in diameter

Energ released 100 million megatonsEnergy released: 100 million megatonsMost powerful man-made explosive device: 50 megatons

Consequences:Mega TsunamisEarthquakesVolcanic EruptionsDusts cover ~10 years

61

Venus Earth Mars

O bit 103 k 149 600108 200 227 940Orbit x 103 km 149 600Diameter (km) 12 756

Mass (kg) 5 97 x 1024

108 20012 104

4 87 x 1024

227 9406 794

6 42 x 1023Mass (kg) 5.97 x 10244.87 x 1024 6.42 x 1023

Atmosphere 90 1 0.01C t f At CO CO (95%)N (77%)Component of Atm CO2

(mostly)CO2 (95%)N2 (2.7%)

N2 (77%)O2 (21%)

Surface 71% waterH2SO4 Ice/CO2 capsSurface 71% waterH2SO4 Ice/CO2 caps

Surface temp Ave ~ 15C Ave ~ 55C>450C

Satellite none Moon Phobos

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Satellite none Moon PhobosDeimos

The Origin of Life and the Primordial Soup

You expressed quite correctly my views where you said that I had intentionally left the question of the Origin of Life uncanvassed as being altogether ultra vires in the presentuncanvassed as being altogether ultra vires in the present state of our knowledge. Charles DarwinUltra vires : beyond the power

some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc, Darwin conjectured that life might form by a process of chemical

Darwin(1809-1882) conjectured that life might form by a process of chemical

complexification.

A.I. Oparin and J.B.S. Haldane (1920s), the little pond was taken to the Earths entire oceans as the setting, which reached the consistency of hot dilute soup later stuck as described as the primordial soup.

63Haldane(1892-1964)

Oparin(1894-1980)

Whatever the origin is, we can be certain that all living organisms today has the same origin.

Basic building raw materials proteins, nucleic acids, carboh drates lipidscarbohydrates, lipids.

We can cross-feed each other.

Same genetic code and material.

With this argument, did life start only once? Not necessarily, since the other forms simply went extinct and cannot be detected now.

64

The Miller-Urey Experiment (1953, University of Chicago)

Harold Urey Stanley Miller(1893-1981)

Nobel Prize 1934

(1930-2007)

65Deuterium

66

The Miller-Urey experiment: resultsy p

67

Problems of the Miller-Urey experiment:

Alth h 15% f th b i th t d tAlthough 15% of the carbon in methane was converted to more complex compounds, the experiment was performed in an enclosure.

The ingredients in the primordial soup would be too dilute to encourage reaction (assembly).

The mixture of nitrogen, ammonia, carbon dioxide, carbon monoxide, methane and hydrogen probably did not represent the composition of early earth. Geologists now believe that ammonia, methane, and hydrogen probably did not present in abundance. Current estimate, the early atmosphere was mostly carbon dioxide and nitrogen.

Life in the primordial soup was difficult to survive as Earth was constantly under bombardment until about 200 million years ago.

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Barringer Crater: 1.2 km across100 m deep, 30 000 years old

Extinction of dinosaursCrater 180 km acrossCrater 180 km across65 million years ago

Oldest fossil of eukaryoteseukaryotes

MulticellularOrganisms

Impactor: 500 km in diameterCrater: 1500 km across and 50 km deepOceans boiled dry: all lives obliterated1000 f lt k d l t i

End of serious bombardment at less than 10 million years intervals: 200

g

1000 yr of molten rock droplet rain2000 yr of normal rain.

million years ago.

Next 2 slides

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600 million years

Catastrophes Affecting Evolution

70

Catastrophe and Extinction

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Black smokers: hydrothermal vents that can reach temperaturevents that can reach temperature of 350C. Hydrogen sulphide and other minerals spew out of the cracks in the Earths crust, able to ,catalyze the conversion of nitrogen to ammonia and more complex molecules.

In line with the characterization of t hil bl t iextremophiles able to survive and reproduce at temperatures of over 100C

Deep sea vents in rock strata could also offer protection from heavenly bombardments

Earliest microbes likely to be thermophiles.

heavenly bombardments.

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thermophiles.

A prebiotic simulation of a black smoker with pieces of minimal rich lava with seawater. When superheated, minerals from lava with carbon dioxide move to a second chamber where the chemicals react to form simple organic molecules.

73

a second chamber where the chemicals react to form simple organic molecules.

Even if we assume that organic molecules can be generated, how they were organized into something the resembled life was left unansweredorganized into something the resembled life was left unanswered.

Life is not free reactions of molecules. Certain set of molecules have to be packaged into a unit that can reproduce.

As far as we know, the package is inside a membranous structure.

However, once it started, the rest should be quite easy.

A protocell-like vesicle that self-assembles from simple organic p gmolecules in a similar way doesnt need proteins to transport molecules across its membranes.

Dreamer DW. (2008) How leaky were primitive cells? Nature N&V: 454 37-38cells? Nature N&V: 454, 37-38.

Mansy SS et al (2008) Template-directed synthesis of a genetic polymer in a model

t ll N t 454 122 12574

protocell. Nature 454, 122-125

Geological Timescale (in MYA) and the Evolution of Life on Earth

4600 MYA Formation of Earth (and our Solar System)3500 MYA Oldest fossils of prokaryotes3500 MYA Oldest fossils of prokaryotes2200 MYA Cyanobacteria2000 MYA Oxygen in atmosphere1500 MYA F il f k t1500 MYA Fossils of eukaryotes

850 MYA Multicellular organisms600 MYA Animal and land plantsp490 MYA Cambrian explosion440 MYA Vascular plants410 MYA B fi h t t d i t410 MYA Bony fish, tetrapods, insects200 MYA Dinosaurs140 MYA Flowering plants, birds, marsupial mammals

20 MYA First primates65 MYA Extinction of dinosaurs

2 5 MYA Various Homo species75MYA = millions of years ago

2.5 MYA Various Homo species0.25 MYA Homo sapiens

Earliest Classification System

Plants Animals

Microorganisms

Current Classification System

Bacteria Archaea Eukarya

Protista Fungi Plantae Animalia

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Fig. 1.7

77Anything else