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The Nature & Origin of Life
OCN 201 Biology SectionLecture 1
Grieg StewardDepartment of Oceanographygrieg@hawaii.edu
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