CSU - BC 103 - Life 103-week 2 - Class Notes

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Schools > Colorado State University > Biology > BC 103 > CSU - BC 103 - Life 103-week 2 - Class Notes

School: Colorado State University

Department: Biology

Course: Biology of Organisms-Animals and Plants

Professor: Jennifer Dewey

Term: Fall 2016

Tags: Biology

Name: Life 103-week 2

Description: Second week of notes

Uploaded: 01/29/2016

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Week 2 Prokaryotes: Bacteria and Arachaea Eukaryotic cells of domain Eukarya , contains kingdoms protists, fungi, animals, and plants Prokaryotic cells of domains Bacteria and Archaea (the focus of this chapter) *Eukarya and Archaea more closely related than Bacteria Prokaryotes are remarkable in their ability to live in a pH of less than 1 or greater than 12 and
temperatures above boiling or freezing. They can photosynthesize, convert N 2 from the air into NH 4 (making it available to plants), degrade many organic compounds, and utilize iron oxide for respiration, making oxygen unnecessary. Archaea are known as extremophiles because they prefer to live in extreme environments. Extreme halophiles live in super salty
environments, and extreme thermophiles live in super hot environments. The most common prokaryotic cell shapes are spheres (“cocci”), rods (“bacilli”), and spirals. Most prokaryotic cells are .55µm, much smaller than eukaryotic cells of 10100µm. Because of
their tiny size, we know little about prokaryotes compared to larger organisms. The best way to research them is to grow them in a lab by culturing, but less than 1% of prokaryotes grow
artificially. Scientists have recently been studying them by analyzing their DNA. Bacteria make up the majority of prokaryotes that are known about. Physical characteristics of prokaryotes: ▪ Capsule sticky outer layer of sugar of protein which allows cell to adhere to environment, and it protects against immune response ▪ Cell wall for shape, protection, and strength to not explode in hypotonic environment o Bacterial cell walls are made of peptidoglycan chain of sugars interwoven with proteins
o Archaea cell walls contain chains of sugars and proteins, but different and not peptidoglycan *Antibiotics target cell walls by keeping the enzyme in bacteria that makes peptidoglycan from producing, resulting in a weakened cell wall
that lets membrane break, action called lysis. ▪ Fimbriae similar in appearance to cilia like little hairs off of capsule, allow for better adherence to other surfaces ▪ Nucleoid region where DNA resides
▪ Prokaryotic genome consists of a circular chromosome, and some also contain plasmids which are smaller rings of DNA which can be used for horizontal gene transfer through a sex pilus ▪ Bacterial endospores when cells encounter harsh environments or their nutrients become deficient, they condense their genetic material into endospores which can survive centuries
because they remain metabolically inactive (do not require anything). These spores are the hardiest form of life as they remain dormant yet viable (able to reproduce). They ‘wake up’ when
in the presence of water and a germination agent, continuing the lineage of that species. ▪ Flagella for motility can react to stimuli and direct their movement Reproduction:

Because of the small size of single celled prokaryotes, these organisms can reproduce very quickly, some with a generation time of 20 minutes. They split by way of binary fission, which is an asexual process in which the original cell copies its chromosome and enlarges so that
it can split its contents into two separate cells. As they have cell walls, the cells split by a protein band which forms between the divided chromosomes and other cell contents. Genetic Recombination: When DNA from two sources come together in one organism to create a new species. The movement of the DNA is called horizontal gene transfer. Prokaryotes do not give away their entire chromosome, but have plasmids, which replicate separately from the main chromosome,
and can easily be released in three methods: ● Transformation when bare DNA fragments are released and taken up by different bacteria (what we did in lab last semester) ● Transduction when DNA is transferred through a bacteriophage (virus) ● Conjugation when one bacteria extends a sex pilus, pulls another bacteria closer and moves plasmid through the tube into the recipient
*in order to make a pilus, the cell must have the F factor DNA, which is transferred as part of the plasmid through the pilus so that the recipient can then make a pilus also and continue spreading
the gene Nutrition and Metabolism: I: For energy ● phototrophs use sunlight as energy source through photosynthesis ● chemotrophs consume (in various ways) organic molecules and chemical compounds from which they extract energy II: For Carbon ● autotrophs take CO 2 (inorganic) from air ● heterotrophs must consume an organic nutrient/carbon from other living things *There can be any combination of these methods of obtaining energy and carbon. Oxygen ● Obligate aerobes are ‘obligated’/must use oxygen in respiration ● Obligate anaerobes absolutely cannot have oxygen, in fact would be poisoned by oxygen, and instead use fermentation as anaerobic respiration ● Facultative anaerobes can use oxygen, but are not dependant on it as they can also complete anaerobic respiration Examples: Methanogens archaea anaerobes, therefore cannot live with oxygen but live in swamps and marshes. They produce methane as a waste product, so we can attribute the past warming of the
earth so that it could be inhabitable to them. Pathogens bacteria some cause disease while others have positive effects in humans.

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