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Lecture 1

BIOA01H3 Lecture Notes - Lecture 1: Louis Pasteur, Central Dogma Of Molecular Biology, Cell Nucleus


Department
Biological Sciences
Course Code
BIOA01H3
Professor
Ivana Stehlik
Lecture
1

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Lecture 1: chap 1
Chapter 1:
Observation is the act of viewing the world around us. Experimentation is a disciplined and
controlled way of asking and answering questions about the world in an unbiased manner.
Observations allows us to draw tentative explanations called hypothesis
Darwin appreciated that selective breeding is successful only if specific features of the animals
can be passed from one generation to the next by inheritance. argued that life has evolved
over time by means of natural selection
A hypothesis makes predictions that can be tested by observation and experiments.
The scientific method is a deliberate and careful way of asking questions about the unknown.
General explanations of natural phenomena supported by many experiments and observations are
called theories.
a theory, a general explanation of the world supported by a large body of experiments and
observations
characteristics of living organisms: (1) complexity, with precise spatial organization on several
scales; (2) the ability to change in response to the environment; (3) the ability to reproduce;
and (4) the capacity to evolve.
The living and nonliving worlds follow the same chemical rules and obey the same physical
laws.
The first law of thermodynamics states that energy can neither be created nor destroyed; it can
only be transformed from one form into another. In other words, the total energy in the
universe is constant, but the form that energy takes can change
The energy that is used to do work plus the heat that is generated is the total amount of energy,
which is the same as the input energy (Fig. 1.6). In other words, the total amount of energy
remains constant before and after energy transformation.
The second law of thermodynamics states that the degree of disorder (or the number of possible
positions and motions of molecules) in the universe tends to increase.
Physicists quantify the amount of disorder (or the number of possible positions and motions of
molecules) in a system as the entropy of the system.
In the 1600s, the Italian physician and naturalist Francesco Redi hypothesized that maggots (and
hence flies) in rotting meat come only from other flies that laid their eggs in the meat.
Maggots exp. Redi demonstrated that living organisms come from other organisms, but some
straight vertical neck and the other with a curved swan neck. As in Redi’s experiments, there
Redi’s and Pasteur’s experiments demonstrated that living organisms come from other living
functional molecules that do the work of the cell. Virtually every aspect of the cell’s
the cell then “read” the RNA molecule to determine what building bloc
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Maggots exp. Redi demonstrated that living organisms come from other organisms, but some
argued that his conclusion might apply only to larger organismsmicroscopic life might be
another matter entirely. It was not until the nineteenth century that the French chemist and
biologist Louis Pasteur tested the hypothesis that microorganisms can arise by spontaneous
generation
Pasteur filled two glass flasks with broth that had first been sterilized over heatone with a
straight vertical neck and the other with a curved swan neck. As in Redi’s experiments, there
was only one variable, in this case the shape of the neck of the flask. The straight-neck flask
allowed airborne dust particles carrying microbes to fall into the sterile broth, while the
swan-neck flask prevented dust from getting inside. Over time, Pasteur observed that
microbes grew in the broth inside the straight-neck flask but not in the swan-neck flask.
From these observations, Pasteur rejected the hypothesis that microbes arise spontaneously
from sterile broth. Instead, exposure to microbes carried on airborne dust particles is
necessary for microbial growth.
Redi’s and Pasteur’s experiments demonstrated that living organisms come from other living
organisms and are not generated spontaneously from chemical components.
The cell is the simplest entity that can exist as an independent unit of life.
Nucleic acids store and transmit information needed for growth, function, and reproduction.
A molecule of DNA. DNA is a double helix made up of varying sequences of four different
subunits.
the information encoded in DNA directs the formation of proteins, the key structural and
functional molecules that do the work of the cell. Virtually every aspect of the cell’s
existenceits internal architecture, its shape, its ability to move, and its various chemical
reactionsdepends on proteins.
The synthesis of RNA from a DNA template is called transcription, a term that describes the
copying of information from one form into another. Specialized molecular structures within
the cell then “read” the RNA molecule to determine what building blocks to use to create a
protein. This process, called translation, converts information stored in the language of
nucleic acids to information in the language of proteins.
The pathway from DNA to RNA (specifically to a form of RNA called messenger RNA, or
mRNA) to protein is known as the central dogma of molecular biology
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