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Chapter 2

Chapter 2 Summary Notes Entire chapter 2 summary, includes all major topics, definitions, and explanations. Cuts all the excess fluff in the textbook, straight to the point biology


Department
Biology
Course Code
BI110
Professor
Diane Williams
Chapter
2

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BI110
CHAPTER 2
2.1 What is Life?
the differences between abiotic and biotic is a blur. The types of atoms and molecules
found in living things are no different from those found in nonliving forms of matter
living cells obey the same fundamental laws of chemistry and physics as does the
abiotic world
2.1a Seven Characteristics that All Forms of Life Share
1. Display order - all forms of life are arranged in a highly ordered manner, with the
cell as the fundamental unit
2. Harness and Utilize Energy - all forms of life acquire energy from the environment
and use it to maintain their highly ordered state
3. Reproduce - all organisms have the ability to make more of their own kind
4. Respond to Stimuli - organisms can make adjustments to their structure, function,
and behaviour in response to change to the external environment.
5. Exhibit Homeostasis - organisms are able to regulate their internal environment
such that conditions remain relatively constant
6. Growth and Development - all organisms increase their size by increasing the size
and/or number of cells
7. Evolve - populations of living organisms
characteristics of life that a virus possesses are based on it’s ability to infect other
cells.
2.1b The Fundamental Unit of Life Is The Cell
Cell Theory
All organisms are composed of one or more cells
The cell is the smallest unit that has the properties of life - if a cell is broken open,
they are unable to grow. reproduce, respond to stimuli etc.
Cells arise only from the growth and division of preexisting cells
2.2 The Chemical Origins of Life
2.2b Conditions on Primordial Earth
Evidence using a range of dating methods has firmly established that Earth, the Sun,
and the other planets of the solar system all formed at about the same time
formed by the gravitational condensation of matter present in a molecular cloud
intense heat and pressure generated in the central region of the cloud formed the Sun,
whereas the remainder of the spiraling dust and gas condensed into the planets
Once Earth was formed, its early history was marked by bombardment of rock from
the sill-forming solar system and extensive volcanic and seismic activity.
earth radiated away from of its heat and surface layers cooled and solidified into the
rocks of the crust

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BI110
The atmosphere was derived partly from the original dust cloud and partly from gases
released from the planet’s interior as it cooled.
Took approx 500m years for Earth to cool to temperatures that could nurture the
development of life
atmosphere contained an abundance of water vapour from the evaporation of water at
the surface, as well as large quantities of hydrogen sulphide (H2S), carbon dioxide
(CO2), ammonia (NH3), and methane (CH4)
ALEKSANDER OPARIN ad JOHN HALDANE independently proposed that organic
molecules essential to the formation of life could have been made in the absence of life
(abiotic synthesis) given the conditions and simple molecules thought to be present on
primordial Earth
Oparin-Haldane Hypothesis - the early atmosphere was a reducing atmosphere
because of the presence of large concentrations of molecules such as hydrogen,
methane and ammonia.
Todays atmosphere is an oxidizing atmosphere. The presence of O2 prevents
complex, electron-rich molecules from being formed because oxygen is a strong
oxidizing molecule (it accepts electrons readily)
2.2c The Miller-Urey Experiment
there was no ozone on primordial Earth
O&H hypothesized that the UV light, along with abundant lightning provided the
energy that, combined with the reducing conditions present in the atmosphere, would
lead to the accumulation of the simple “building blocks” required for life
STANLEY MILLER a graduate student of Harold Urey at Uof Chicago, created a
laboratory simulation of the reducing atmosphere believed to have existed on early
Earth.
when formaldehyde and hydrogen cyanide were added to the experiment, all the
building blocks of complex biological molecules were produced - amino acids, fatty
acids, purines and prymidines and some sugars
highly reducing conditions required for this would have been found near volcanoes and
near hydrothermal vents found on the ocean floor
VERY important experiment, showed that molecules critical to life, such as amino
acids, as well as many other biologically important molecules, could be produced
abiotically, and that they could be produced relatively simply.
2.2d The Synthesis of Polymers from Monomers
after organic molecules were synthesized, they could have existed for much longer
that would be possible in todays oxygen-rich world (recall, oxygen readily accepts
electrons, in our oxidizing atmosphere)
50 monomers would have been sufficient length to impart a specific function
it is doubtful that polymerization could have occured in the aqueous environment of
primordial Earth, as macromolecules would’ve been quickly broken down.
Clays would have provided a unique environment for polymerization to occur.
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BI110
2.2e Protobionts: The First Cells
Protobiont is the term given to a group of abiotically produced organic molecules that
are surrounded by a membrane or membrane-like structure
this allowed for an internal environment to develop that was distinctly different from the
external environment: the concentration of key molecules could be higher, and
molecules could attain more order in a closed space.
2.3 The Origins of Information and Metabolism
the development of a system for the storage, replication, and translation of information
for protein synthesis and the development of metabolic pathways that would capture and
harness energy for metabolism
2.3a The Origin of the Information System
The flow of information from DNA to RNA is common to all forms of life
Enzymes are required to catalyze the replication of DNA, the transcription of DNA into
RNA and subsequently, the translation of RNA into protein
2.3b Ribozymes are Biological Catalysts that are not Proteins
Thomas Czech and co discovered a group of RNA molecules that could act at
catalysts
Ribozymes can catalyze reactions on the precursor RNA molecules that lead to their
own synthesis, as well as on unrelated RNA molecules
RNA are single-stranded molecules that can fold into very specific shapes. Ribozyme
function depends on how it’s folded, similar to protein function.
early life may have existed in an RNA world where a single type of molecule could
serve as both a carrier of information and a catalyst
2.3c The Evolution of Proteins and DNA
respective jobs of information storage (DNA) and catalysis (protein) better than RNA
does by itself. The evolution of these gave those organisms a distinct advantage
RNA molecules evolved that could catalyze the formation of very simple proteins,
independent of the ribosome
the modern ribosome is compose of about RNA and protein, and the RNA⅔ ⅓
catalyzes the addition of amino acids
Proteins are more versitile for two reasons: the power of an enzyme is greater than
that or a ribozyme, and proteins are far more diverse, also, amino acids can interact
chemically with other amino acids in bonding arrangements not possible between
nucleotides
DNA nucleotides may have been produced by random removal of an oxygen atom
from the ribose subunits of the RNA nucleotides
DNA nucleotides paired with the RNA informational molecules and were assembled
into complementary copies of the RNA sequences
DNA was genetically favoured because:
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