The Nature & Origin of Life€¦ · carrier Phosphorous 15 3 component of nucleic acids, important in energy transfer Sulfur 16 1 component of most proteins Sodium 11 1 main positive

The Nature & Origin of Life

OCN 201 Biology SectionLecture 1

Grieg StewardDepartment of [email protected]

What is Life?

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‣ Self-replication (Growth, Division)

‣ Maintenance of order Requires controlled collection and transformation of matter and energy for replication and repair

‣ Evolution

General Defining Features Of Life:

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What is Life?

Life is marvelous...

but not miraculous!

Despite the astonishing diversity of life there is considerable underlying unity

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Features of Life as We Know it

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Life adheres to

- The principles of organic chemistry

- The laws of thermodynamics

Features of Life as We Know it

Life on earth today: • Based on cells as the fundamental unit

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• Carbon-based • Water-dependent • Building blocks: Carbohydrates, DNA, RNA, Protein, Lipid

Bruno C. Vellutini

Cell Building Blocks

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Carbohydrates

Lipids

Proteins

Nucleic Acids (DNA and RNA)

http://www.uic.edu/classes/bios/bios100/lectures/prok02.jpg

Information

Structure,energy storage

Sturcture, Catalysis

cell membranes

Major Building Blocks of Life

C

HH S

Lipids

Amino Acids

Nucleotides

Sugars ElementsHCNOPS

ydrogenarbonitrogenxygenhosphorusulfur

• carbohydrates (sugars)

• nucleic acids

• amino acids

• lipids

H, C, O

H, C, O, N, P

H, C, O, N, S

H, C, O, N, P, S

The Major Structural Elements of Life

Molecule Molecule

Cell juices (Cytoplasm)

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Carbohydrates

Lipids

Proteins

Nucleic Acids (DNA and RNA)

http://www.uic.edu/classes/bios/bios100/lectures/prok02.jpg

Water Salts sodium potassium calcium magnesium

Metals )(

The Chemistry of Life is Conserved

Chopra et al. 2010, Australian Space Science Conference Series

A

B

C

X

Y

Z

X

Y

Z

A

B

C

The Chemistry of Life is Conserved

Chopra et al. 2010, Australian Space Science Conference Series

Trace Elementspresent in small amounts,

but critical for cell chemistry!

SaltsStabilize structures.Create ion gradients

Major Structural ElementsBuilding blocks of the

factory and the machinery

KEY POINTS

• The chemistry of life is very similar across all types of organisms

• Carbon is the central element of life because of its versatility in bonding

• Just six elements make up most of living mass, but other elements (like salts and metals) are critical for cell chemistry

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Element Atomic number Percentage Role

Carbon 6 50 basis of organic molecules

Oxygen 8 20 cellular respiration, component of water

Nitrogen 7 14 component of all proteins and nucleic acids

Hydrogen 1 8 component of water & most organic molecules, electron carrier

Phosphorous 15 3 component of nucleic acids, important in energy transfer

Sulfur 16 1 component of most proteins

Sodium 11 1 main positive ion inside cells

Potassium 19 1 main positive ion outside cells

Magnesium 12 0.5 essential component of many energy-transferring enzymes

Chlorine 17 0.5 main negative ion outside cells

Calcium 20 0.5 cell structure, motility, and intracellular signalling

Iron 26 0.2 Redox reactions enzyme co-factor

other trace 0.3

Relative Mass of Elements in a Bacterium

Life is made from the most abundant elements

!15http://www.daviddarling.info/encyclopedia/E/elbio.html

Where do they all come from?Stellar nucleosynthesis!

And supernovae!

https://digital.wwnorton.com/

https://people.highline.edu/iglozman/classes/astronotes/media/he2c_fusion.jpg

Larger atoms built from smaller atoms

!17All elements heavier than iron are formed by supernovae

Origin of Life on Earth

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Divine Creation

Chemical Evolution(abiogenesis)

Panspermia

Origin of Life on Earth

Difficult task! Must combine knowledge of:

• Chemical nature of life• History of conditions on early earth

to make logical inferences about what happened in the very (very) distant past

Step 1: macromolecules; the building blocks of life

Can life’s building blocks be built from simple elements by pre-biotic chemistry?

HCH

H

HC

C

C

O

N

H

H

H

O

H

HH

H

The Miller-Urey Experiment

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SPARK

COOL

Water(Ocean)

Gas(Atmosphere)

H2OMethaneAmmoniaHydrogen

HEAT

Amino Acids& other organic

Compounds

Started with:

Ended with:

Murchison Meteorite

≥ 90 amino acids and other organic compunds

Samples from Comet Wild 2

contained organic compounds!

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Lesson Learned: Many building blocks of life are easy to make

• Many variations on Miller-Urey experiment have had similar results

• Meteorites and comets found to contain organic compounds similar to those produced in the Miller experiment

Wild 2

• Large gap to overcome from organic molecules to self-replicating entities

• Life forms today are complicated machines

Molecules to Life

Copyright M.W. Davidson and Florida State University Research Foundation

• In modern Cells all components are Interdependent

Chicken and Egg Problem

DNA

RNAPROTEIN

RNA

Lipid

DNA

RNAPROTEIN

RNA

Lipid

RNA

autocatalysis

The Central Dogma

“RNA World” hypothesis

RNA may have been the first self-replicating precursor to cellular life.

• information content

• structural functions

• catalytic activity

http://rna.berkeley.edu/Research/Movies/hdv-rbz-model-rotation.qt

Origin of Cells• Chemistry must be

contained to make a cell

• Lipids can form abiotically

• Lipids arrange spontaneously into cell-like structures

Protocells• Experiments show that protocells can grow and divide

• Recent work suggests how protocells could make the leap from random chemistry to simple cells with heritable traits that directly compete

Cold

Hot

• RNA probably came before DNA

• Protocell hypothesis an important step forward

• Life probably began in the sea:

• water is essential• hydrothermal vents may have provided

chemicals and energy for replication cycles

Origin Theories

KEY POINTS

• Organic building blocks of life (like amino acids) are very common in the universe

• Discovery of catalytic RNAs shows one way around the chicken-and-egg problem.

• Recent lab studies have shown how primitive “protocells" could acquire key characteristics of life (growth, division, evolution)

Origin Theories

Regardless of how the first self-replicating life forms came into existence - they would be

immediately subjected to the process of

NATURAL SELECTION