CELS191 overview

This is the overview of the notes that I have come up with. All of these notes will be made available in the CELS191 blogspot webpage (currently being revised).


I have decided to summarise information which follows strictly to the objectives.

Module 1

Describe the different techniques used to study cells

Key technique: microscope

2 types of microscope

à the light microscope (often involve staining cells and letting light pass through the specimen)

à electron microscope (uses a beam of electron that is deflected and focused by electromagnetic field)

The electron microscope has higher power and have two basic designs: the SEM (scanning) and TEM (transmission). Same in working principle however the only difference is that TEM forms image from electrons transmitted through specimen while SEM scans surface of specimen and forms image by detecting electros that are deflected by surface of specimen.

Other microscopy is not relevant for CELS191 course.

Describe the cell theory.

1. All organisms consist of one or more cells
2. The cell is the basic unit of structure for all organism
3. All cells arise only from preexisting cells

Define the major hierarchies of body structure

Organism: composed of many interdependent organ systems

Organ systems: Association of organs to carry out a major bodily function

Organs: Aggregations of several tissues with a variety of related functions

Tissues: Associations of similar cells with a common purpose

Cells: A collection of organelles surrounded by a plasma membrane (minimum self replicating unit of life à can be prokaryote or eurkayote)

Organelles: microscopic organs composed mainly of membranes eg. Mitochondria, nuclei, golgi

Molecular: arrangements of atoms into simple or very often, complex structures

Atomic: the building blocks of life – CHON (carbon, hydrogen, oxygen, nitrogen)

Describe a possible pathway for the origin of life.

2 theories: Panspermia theory and chemical evolution

Panspermia theory

- Panspermia theory states that molecules of life come from extraterrestrial sources

- Speculated due to the finding of meteorite ALH84001 from Mars which contain water, magnetite and other available resources found on earth

- Terrestrial contamination which result of production of simple cells may go through four steps: abiotic synthesis of amino acids and nucleotides, joining to form nucleic acid and protein, enclosing these molecules with membrane, origin of self replicating molecules which enable inheritance

- A primordial soup hypothesis was tested by miller and urey through experiment and they found that it is possible for the production of numerous complex molecules like amino acid, purines and pyrimidines during early formation of the earth. However this remain questionable since earth’s atmosphere is required to be ‘reducing’ for these complex molecules to be form. No prove can be stated to support that earth’s atmosphere was ‘reducing’.

- Protobionts are aggregates of abiotically produced molecules surrounded by a membrane which clearly supports the production of simple cells as cited above.

- RNA is believed to provide a template for DNA as a self replicating molecule.

Chemical evolution

Chemical evolution theory states that life is the result of chemical evolution.

Discuss the endosymbiont theory and evolution of the mitochondria.

Endosymbiont theory:

Mitochondria and chloroplast are believed to derive from an ancient prokaryote that established mutualistic symbiotic relationship with primitive nucleated cells (a protoeukaryote) long time ago.

Why is mitochondria thought to be derived from somewhere else?

Mitochondria is a semiautonomous organelle which can synthesize their own proteins, contain their own DNA, mRNA, tRNA and ribosomes, divide on their own similar to binary fission. Mitochondria not only behave lik a bacterial cell, it also looks like one too.

Mitochondria is speculated to be from the aerobic purple bacteria and chloroplast from cyanobacteria.

Mitochondria evolved by having a protoeukaryote ingesting or phagocyting an ancient purple bacteria. Both develop a symbiotic relationship and became inseparable.

Tips: Remember the similarity in origin of the Mitochondria and chloroplast.



Module 2

Outline how the tetranucleotide hypothesis could be used as an argument against DNA being genetic material.

Tetranucleotide hypothesis: genetic material only has 4 bases (A, C, G and T)

Many refuse to believe the tetranucleotide hypothesis they think that genetic material cannot be so simple as to have only 4 bases. Hence many perceived protein as genetic material for the many variation in amino acid.

However, Griffith experiment proved that the tetranucleotide hypothesis was correct after all. Even tough there are 4 bases only, there are long chains of nucleotides forming genetic codes in DNA.

Outline the Griffith’s experiment and explain the conclusion that can be drawn from the results.

Griffith used mice for the experiment. In mouse A, he injected live S bacteria; mouse B with live R bacteria; mouse C with heat killed S and mouse D with heat killed S and live R bacteria. His conclusions are as follow:

Mouse A; live S died.

Mouse B; live R lived.

Mouse C; heat killed S lived.

Mouse D; heat killed S + live R died.

This is known as the ‘transformation’ experiment of Griffith.

Tips for exam:
Know the tetranucleotide hypothesis and the Griffith's experiment. Understand that researchers of the past had always thought that it is impossible for heredity units to be molecules with only 4 repeating units. The significance of the Griffith's experiment shed light to the world that the DNA was the heredity unit instead of protein.

Module 3

Understand the ‘germ theory’ for the origin of microorganisms.

Germ theory of disease suggested that microorganisms are causes of many diseases. This created a theory that there are microorganisms, minute size organisms unable to be seen by the naked eye. With the advent of the microscope, this theory proved that microorganisms exist.

Describe the scientific method used for discovery of microorganisms.

Using the microscope, magnifying to a size where it is possible to see. Antoni Von Leeuwenhock made the first discovery of the bacterial world through his invention of the microscope.

Pasteur used swan necked flasks to prove that when pure water is contaminated by microorganisms in the air, microbes appear in the infusion of pure water.

Discuss the role of yeast cells in fermentation.

Fermentation is the process of deriving energy from oxidation of organic compounds, such as fermenting alcohol from sugar or formation of lactic acid.

Discuss the principles of pasteurization.

Pasteurization is a process of heating liquids to kill viruses or harmful organisms. The normal way to pasteurize something is to heat certain liquid in high temperature and then leaving it to cool down. The high temperature kills most if not all organisms in the liquid.

etc.


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