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BIO230 lecture 1 notes.docx

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University of Toronto St. George
Darrel Desveaux

BIO230 lecture 1 notes - Tree of Life: Living organisms can be organized into 3 main branches and 2 cell types.  The 3 main branches are eubacteria, archaebacteria, and eucaryotes.  Eubacteria are what we traditionally refer to as bacteria.  Archaebacteria look very similar to eubacteria. They live in extreme conditions. It is believed that they diverged from the eubacteria group along the same time as eucaryotes did. The way they handle their genome is more similar to eucaryotes than to eubacteria.  The 2 cell types are prokaryotes and eukaryotes.  Prokaryotes  Eubacteria and archaebacteria are included in this group.  Mostly single-celled organisms  They can form communities, and often these communities are held together by sticky polysaccharides and sugars, known as biofilms. This makes it hard to get rid of and break because biofilms are very protective.  Prokaryotes are surrounded by a sugar coat made out of protein-sugar complexes called a cell wall that is outside the plasma membrane. The plasma membrane encloses a single compartment that encloses the DNA, RNA, and proteins; the plasma membrane is selectively permeable to certain substances. Prokaryotic cells don’t have a nucleus or organelles.  On slide 27  This is the bacteria vibrium  The little dots in the cytosol are the ribosomes.  The DNA is not surrounded by a membrane but it tends to localize in a specific area of the cell called the nucleoid.  Many bacteria have appendages like flagella (shown in the slide) that help it move. Other bacteria have other types of appendages like needle like structures that can inject proteins or DNA directly into closed cells; the proteins injected are virulent in nature and are used by the bacteria for virulence processes.  Vibrium is notorious because it produces cholera toxin and can bring about severe diarrhea in humans.  Eukaryotes  Plants, fungi, animals, and humans are included in this group.  They can be either single-celled (like yeast) or multi-cellular.  There are membranes inside that enclose the DNA and specialized compartments.  Eukaryotic cells have nuclei and organelles that carry out critical functions for these cells.  Eukaryotic cells are bigger and more complex than prokaryotic cells.  The cytoskeleton plays a very important role in moving molecules from one part of the cell to the other as well as in maintaining cell shape and moving the whole eukaryotic cell.  Animal cells can move around because they have no cell wall around them; cell walls are so rigid that they don’t allow cells to deform and change shape.  The mitochondria is the power house of the cell and produces ATP.  In plant cells, there is chloroplast which is important for converting light energy into chemical energy. They also have cell walls that maintains a rigid structure. Plant cells also have very large vacuoles, which is important for maintaining pressure, expansion, and growth of the cell. - How did a eukaryotic cell develop from a prokaryotic cell? A hypothesis is that one cell engulfed another.  Examples of this kind of behaviour have been seen in a white blood cell known as a neutrophil. It finds bacteria and engulfs it, thereby protecting the body from danger.  Originally, the ancestor cells might have been merely engulfing and eating but eventually it
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