Unifying Concepts of Biology... CELL DOCTRINE, EVOLUTION, &
Modern Biology is often looked upon as... Biochemistry of the Cell next
Properties of Life...
Top Ten things that characterize a Cell as Living.
1. Cells obey Laws of Energetics - i.e., they transform energy
2. Cells are Highly Structured
with emergent properties
3. Cells have an Evolutionary Origin
(from a single primordial cell)NAS-1
4. Cells Metabolize
possess metabolic pathways, process nutrients,
to environment via metabolic regulation
5. Cells Self-Replicate (divide)
6. Cells Osmoregulate
7. Cells Communicate
8. Cells show Animation (cyclosis)
9. Cells Grow, Divide, & Differentiate
10. Cells Die
Top 10 Properties of Life...
basic unit of life is the CELL...
"inanimate mix of biomolecules
- selected for their fitness
to perform certain (cell) biochemical functions
characteristic of life".
1. Life & Cells
LAWS of Universe
all living things are parts of larger systems of matter & energy, and
matter continually recycles through systems as energy flows thru the systems
unique laws defining the Living State separate different from natural/physical laws.
transform energy via: 1. capturing light energy, 2.
redox rxs, & 3. e-flow
a) extract energy
(light) & heterotrophs (food)
b) transform energy
--> to do 'work': osmotic, mechanical, electrical
constantly expend energy to maintain a non-equilibrium ordered state
2. Cells are Highly Structured
all living things maintain a high degree of order & complexity
Diverse, yet similar... (all have membranes, nuclei,
structural organization brought about by
interaction of elemental
molecules selected for by living systems next
- elements of body*mix
All cells are derived from a single
PRIMORDIAL cell* NAS-1
all living things are descended from a common ancestor
a Fundamental Question of Human Inquiry has been...
Where did we come from
µ What chemical conditions
may have lead to origins of life?
How did the first cells
What were the first living
living cells elsewhere in the Universe?
There are 3 major
hypotheses of ORIGIN of LIFE...
1. Special Creation... benevolent supreme being suspends
laws of physics & chemistry to create life. [not
treatable by scientific method]
2. Extraterrestrial... life was formed or evolved
elsewhere in Universe
seeded on the newly formed planet Earth,
includes such concepts as..."Panspermia". next
Chemical Evolution Origin ideas
which are based upon...
evolution is... simple chemical rx's that form complex molecular systems favoring life
1) today's known
molecules of "living cells" are made from small number
functional groups [ OH,
NH3, C=O, COOH, etc. ]
chemical functional groups easily form into simple monomers...
such as - amino acids, fatty acids, nucleotides, sugars.
easily make polymers or
which favored the energy transforming & self-replicating
so called - emergent properties that help define today's living cells...
* the concept of chemical evolution
life conforms to scientific method,
for it is
1st experiments by geochemists - Miller
& Urey* (U
Chicago 1953) -->
[ including HCN and
--precursors to --> amino acids & sugars ]
today, cryochemists (NASA) study
such molecular activity @ absolute 00 next
Ultimate Goal may be
"creation of an artificial cell, as a model of a life system"
experimental approaches are active in today's origins research
...mostly searchs for sources of early precursor
organic molecules of Life ???
I) classical chemical
evolution approach... [life
began when chemistry begat biology]
i.e., life formed from a chemically reactive soup... in
oceans of Earth
early Earth had a
one rich in gases as
NH3, CH4, H2, & H2O
- Miller & Urey ---> make organics in
> abiotic origin of organic molecules from simple inorganics
> H2O, NH3, CH4,
& H2 from a reducing atmosphere
> produce HCN and formaldehyde which leads to... next
as amino acids and sugars.
CRITICISM of research:
it was not
really a reducing atmosphere,
so chemically unlikely
but, experiments recently redone by J.L. Bada
& S.L. Miller using a weakly reducing
atmosphere (irradiated with protons)... have obtained bioorganic compounds
in amounts comparable to those of original Miller/Urey type
2007 ACS Annual Meeting Bada Presentation*
II) Deep dwelling (ocean)
discovered in 1979 by researchers @ Oregon
State U. - hot vents on Pacific seafloor
with minerals spewing up from pressurized, hot springs; source of chemical evolution?...
areas (660oF) are full of organically rich molecules --->
(tube worms @ vents)
& bacteria living in hydrothermal vents.
speculation is that life's
molecules may have originated in
the hydrothermal vents
A role for the
hydrothermal vents in
Wachterschauser (German biochemist) has
speculated that origins of
bioorganic chemical reactivity may have
originated near hydrothermal vents
before genetics - a cycle of chemical reactions that produce energy. > earliest primordial biochemical
cycles may have functioned there... > metabolic cycles likely predate cells...
took place on mineral surfaces
as catalysts & surfaces for early reactions √ key reaction may have been a
reductive reaction like citric acid cycle...
Researchers including M.J. Russell, M.M. Hanczyc, D. Deamer, C. Huber, and G. Cody
have synthesized amino acids and assembled/disassembled polypeptides
under vent like conditions,
all crucial metabolic processes that might have arisen at hydrothermal vents
so maybe the bioorganic molecules evolved at hydrothermal vents.
What is source of
bioorganic molecules ?
(chemical evolutionary precursors to life)
a) Miller &
Urey - abiotic synthesis in tidal pools of Earth's
hydrothermal vents (spewed up from "middle
early bombardment with dust, meteorites, asteroids, & comets
deposited organics on newly forming planet Earth.
bumper stickers now have more
meaning in terms of chemical evolution.
may have originated when the mix of different molecules in the primordial
passed a certain level of complexity and self-organized into living entities;
(if so, then life is not a highly improbable chance event, but almost
ICE may have been the cradle of Life... all ice contains some water... Max Berstein
(NASA - 1999)
reactions in the lab,
to look at molecular events within
he has observed...
...chemical reactions can occur even in very low temps [25K
...UV light can break
- forming ketones, esters, alcohols, and quinones
(for e- transport).
...some molecules formed
spherical, capsule-like droplets when
- exposed to water, with properties akin to cell membranes. some experiments have shown that units
of RNA can spontaneously string themselves in ice. → so
besides abiotic or hydrothermal origins a new speculation ??? maybe
aa's built 1st proteins
wait, there's still a possible Role for Minerals* in
Earth's chemical evolution...
3rd experimental approach of Origins of Life research
III) study of the Origins of
Self-Replicating Chemical Systems...
i.e., Evolution of an RNA
(which came 1st DNA or RNA) ►a key characteristic of life is self-replication...
Can molecules self-replicate???
in 1989 Sidney Altman and
Thomas Cech - received
for demonstrating that RNA molecules may
i.e., these RNA's catalyze hydrolysis & condensation rxs
of phosphodiester bonds.
catalyze polymerization of like molecules maybe it
can be a template also,
to DNA -->
figure* i.e., replicate itself, then RNA
molecules may have been the
1st SELF-REPLICATING living entity.
RNA molecules exists naturally today, but lab experimentation may
establish that it was feasible, and that
RNA molecules can be selected for via
Darwinian evolutionary mechanisms (natural selection). next
a metabolism first - thermodynamic alternative
experimental approach of Origins of Life research
IV) Knock-out Cells...
Release - new funding
modifying a simple microbe, scientists hope to create a
new form of single cell life.
J. Craig Venter, a principle investigator (P.I.) of
the Human Genome Project is attempting
to make a new type of bacterium using DNA manufactured in the lab;
> using the sequenced the genes of a
Mycoplasmagenitalium, a gram-positive
parasitic bacterium, whose primary infection site may be the human urogenital
(it probably causes
and it is also one of the simplest
known microbes with only one chromosome and
> researchers began
removing genes to determine how many genes
are essential for life. In 1999, they published a paper that narrowed the needs
of M. genitalium to between 265 and
350 genes using
> a genomic goal will be to learn on
a molecular level the minimum genes a cell needs
and reproduce and how to artificially make those and other genes. > Venter plans to construct a synthetic chromosome
that is 381 genes (580,000 bp) long using lab-made chemicals,
& transplant it into bacterial cell = new synthetic life form. next
self-assembly has lead to complex self-replicating systems"
5 Steps in Chemical Evolution of Life-
"It was a Dark and Stormy Night"
in Chemical Evolution of Eukaryotes... it's a long way from a protobiont to a typical eukaryotic
cell of today the evolution of the
eukarya was single most
important step in evolution
of multi-cellular life forms & was a key step that
lead to plant & animal life. 1. cell membrane encapsulates
genetic DNA... development of nucleus
invention - it internalized the genome
2. loss of a rigid cell wall... cells developed ability of phagocytosis - allowed engulfing of foods
also allowed cells to clump
together --> multi-cellularity --> tissues
3. evolve a selectively permeable membrane... protects cell, allows uptake gases & nutrients & exchange with environment
4. evolve a cytoskeleton... provides framework- allowed cell to grow
larger, move, & permitted
metabolism; eukarya are 10x larger that bacteria
5. evolve aerobic respiration...
more efficient energy transformation
6. develop various organelles
endosymbiosis)... a sub-cell part that catalyzes a specific
7. development of sexual cell cycles
(transposons - moveable genes)... a
method to shuffle genes along chromosomes favored cellular evolution end
a possibleScript for Life*read?
Top 10 Characteristics of life... cont'
4. All cells METABOLIZE all life depends on
chemical reactions that take place within cells
is chemical processes &
reactivity in living cells, where molecules are broken
down to yield energy for
vital processes & other molecules are made.
When classifying organisms, biology often looks at the mode of Nutrition,
i.e., how cells obtain
carbon from their environment [metabolism]
µ AUTOTROPHS - capable of synthesizing all
their organic molecules
using CO2 as sole
1) photosynthetic autotrophs... use solar light energy
...capture light by
transfer e- from hydrogen donor
2 to reduce it to CH
reductant H2S, now...H2O)
2) chemotrophic = use simple inorganic
molecules as their energy source
µ HETEROTROPHS - obtain energy from chemical fuels (as sugars)
unable to synthesize all needed molecules -
i.e., obtain nutrients by dietary means
Cells possess Metabolic
Pathways (linked sequences of individual chemical
ANABOLIC - synthetic reactions... making larger from smaller molecules
2 + H
20 <----> C
CATABOLIC - degradatory reactions.. breakdown of larger into smaller
------> B ------> C ------> D
e1 e2 e3 e4
economy & efficiency...
dynamic steady state... equal
rates of intermediates
rate of synthesis = rate of degradation
living things regulate use of energy and respond to their environment
is... by ENZYMES...
i.e., they are Self-Regulating...
negative feedback (feedback inhibition*) -->
can lead to
Concept Activities -
Chapter 1.2 -
Positive-Negative Feedback* integration... work in a coordinated fashion...
everything at the right time
One definition of Life
carefully orchestrated chemical reactions.
Self-replication (reproduction is
single most definitive property of life) all living things share same
genetic code, which is passed from parent to offspring
genetic info is
asexual* cell division = MITOSIS &
- sexual* cell divsion = MEIOSIS
inanimate counterparts (or model systems)
growth of crystals in chemistry
computer simulation models of evolution...
is a computer simulations of evolution
by Thomas Ray @ U. Delaware - TIERRA
small computer programs of assembly code with directions on how to copy self...
like a computer virus, competes for cpu time & memory space,
is designed to be able to mutate & evolve
a simple computer program with
instructions allowing code changes
(mutation & evolution)
Primordial program had some 80 instructions and....
[some anthropomorphic analogies]
it was stored in cpu (lived),
it consumed cpu cycles (metabolized),
copied itself (reproduced),
up in que (animation), &
it was removed (died)
(code changed) emerged (mutated & evolved)...
first variant had 79 instructions,
variant had 22 instructions, but replicated 6x faster,
variants had only 45 lines,
but lost the ability to replicate
however, it borrowed instructions from others = acted like a parasite
some programs became defensive,
itself against parasites
SKIP this Material
"Life is too improbable to be due to
chance" - Creationists & Intelligent Design Theorists just as watch needs a
watchmaker, an eye, a biochemical pathways is too improbable
to be due to chance... it must be due to
Richard Dawkins - "the
Natural selection, is the unconscious, automatic, blind, yet essentially non-random process that
Darwin discovered, and has no purpose in mind. If it can be said to play the role of
watchmaker in nature, it is the blind watchmaker. The only watchmaker
in nature is the blind forces of physics, albeit deployed in a very special way.
A true watchmaker has foresight: he designs his cogs and springs, and plans
their interconnections, with a future purpose in his mind's eye. Natural
selection is a blind, automatic process, which scientists now know is the best explanation for the existence and
apparently purposeful form of all life, has no purpose in mind. It has no mind
and no mind's eye. It does not plan for the future. It has no vision, no
foresight, no sight at all.
By gradual, step- by-step
transformations from simple
beginnings, and with each successive change in the gradual evolutionary process,
relative to its predecessor, leads a whole sequence of cumulative steps
leads to complexity of a final end-product relative to the original starting
point. The cumulative process is directed by nonrandom survival.
selection is a fundamentally nonrandom process and evolution has no
long-term goal. There is no long-distance target, no final perfection to serve
as a criterion for selection.
Is it Experimentally Testable ?
Weasel Applet -
a computer "breeding"
program = possible solutions to match a supplied phrase; exhaustive search --
systematically trying all possible guesses -- that would virtually never
complete, but artificial selection via random chance can lead to a solution and
seeming great complexity. Biomorph Applet
- plausibly lifelike forms -
a variety of tree-like shapes... coded by 8 genes,
with change allowed. Result: wide variety of forms from a limited
genome - total of 1,071,794,405 different biomorphs! The accumulation of changes
turns one form into quite different forms. next
all life requires liquid water
(water's properties will be
regulate exchange material across cell membrane
with the environment - solvents & solutes in/out
helps maintain differences between in/out
intra (within) & inter (between) individual cells
8. show Animation (cells
especially @ molecular level:
vesicles moving along
flagella, and molecules across membranes;
also cyclosis or
all living organisms change form & function at different statges of their life
(increase in mass), Divide...
(increase in cell number),
become structurally, functionally &
from a fertilized egg ---> to adult cells
10. Die... absence of properties of
Life, Cells, & Living Systems
Life is manifest in the structure we call the
all cells are presumed to derive from a single primordial cell
born some 4 billion years ago,
√ it out reproduced its contemporary competitors,
√ and had a family resemblance to today's cells...
same basic molecules ...all have
similar properties &
...all use same metabolic pathways that define properties of life
...all are very
has a number
of unique intra-cellular parts common among all cells,
properties of all cells* next
animal cell 7.7* [animal cell]
plant cell 7.8*
is a .....
isothermal mix of biomolecules,
held in a specific 3-D conformation by weak non-covalent forces,
which can extract raw materials (precursors)
& free energy from its surroundings,
and can catalyze reactions with specific
biocatalysts (enzymes), that it makes,
which shows great efficiency & economy of
and maintains a dynamic steady state far from
that can self-replicate, using the linear information molecule DNA.