Exam 2 Flashcards
What is the basis of the Baltimore system?
Since viruses have developed independently more than once we cannot classify them by evolutionary relatedness. The Baltimore system classifies viruses by the type of nucleic acid the virus contains and how the messenger RNA is synthesized.
Are all types of cells susceptible to viral infections?
Yes
Can a virus infect any cell in any host?
No, because viruses can only infect cells that have specific molecules for their attachment proteins to bind to.
What are the different shapes of the viruses?
They can be an icosahedron + 20 sides of triangles, this shape looks basically spherical. ex: adenovirus.
They can also be helical.
How does a virus carry out molecular self-assembly?
Progeny virus particles are formed according to molecular self-assembly. When the viral components are present proper amount and under the right conditions, they interact spontaneously to
Which two domains lack a membrane-bound nucleus
Archaea and Bacteria
Describe bacterial genome
Smaller then euk genome, lack non-coding DNA, do not undergo meiotic cell division. Replicate through horizontal gene transfer. In conjugation they transfer plasmids
What is a plasmid?
Another question for this answer: How does horizontal gene transfer provide genetic diversity?
Inside a bacterial cell there are plasmids, which are small circles of DNA that replicate independently of the cells circular chromosome. It is not essential for survival of the bacteria but rather, helpful for having genetic diversity. It can contain genes that have adaptive value.
Why are bacterial cells small?
Because they have to do diffusion. Diffusion only works over small areas. The cell being so small also means that it has more surface area relative to volume meaning that molecule do not have to travel far to reach all parts of the cell.
What are the similarities and differences between bacteria and archaea? What makes archaea different?
Similarities: No membrane bound organelles, DNA in circular form, ribosome size = 70S, can grow at temp greater than 80C, Operons present in DNA, introns are not present in most genes, Capable of nitrogen fixation, capable of chemoautotrophy.
Differences: Archaea specifically: membrane lipids are not ester-linked, does not do photosynthesis with chlorophyll, have histones present, capable of methanogenesis, not sensitive to antibiotics.
What are the environmental niches that the archaea inhabit?
Archaea are capable of inhabiting extreme environments. Some live in highly acidic environment. Some live in extreme hot or cold temperatures.
What is the difference between oxygenic and anoxygenic photosynthesis?
Anoxygenic does not produce oxygen because it does not use water as the electron donor while oxygenic photosynthesis does. Anoxygenic only uses one photosystem. Organisms who use anoxygenic have to live in an area without oxygen due to the compounds they use as electron donors oxidizing very quickly.
How does fermentation work?
Fermentation produces ATP in the absence of oxygen through glycolysis. During glycolysis, a glucose molecule is broken down into two pyruvate molecules, which produces a net gain of two ATP molecules.
Where do photoautotrophs and photoheterotrophs get their carbon?
Photoautotrophs get their carbon from CO2
Photoheterotrophs get their carbon from organic molecules.
How is chemoautotrophy unique to Bacteria and Archaea.
Gain carbon from reducing CO2 to carbohydrates. They do not get their energy from sunlight, but from chemical reactions. They oxidize molecules such as H2 or Fe2+ to generate ATP. Chemoautotrophs are normally found in the deep sea.
Describe nitrogen fixation in bacteria and archaea.
Only certain bacteria and archaea can reduce nitrogen gas (N2) to ammonia NH3. Ammonia is a form of nitrogen that can be incorporated into biomolecules.
Relate the role bacteria and archaea play in linking the nitrogen cycle to the carbon cycle.
As Bacteria and Archaea have already shown us, mechanisms of metabolism at work where oxygen is absent can also complete the carbon cycle, taking in and releasing CO2. They do so by coupling the cycling of carbon to the cycling of other elements, in this case, sulfur. Once again, we see complementary metabolic pathways. The expanded carbon cycle of Bacteria and Archaea promotes the cycling of sulfur, nitrogen, and other biologically important elements.
What are the three main categories traditionally used to define bacterial groups
Proteobacteria are the most diverse group and include many organisms that participate in the expanded carbon and other biogeochemical cycles,
Gram-positive bacteria include both pathogens and bacteria that produce antibiotics
Cyanobacteria are species of bacteria that include can carry out oxygenic photosynthesis.
How do we discover new bacteria?
By sequencing a small subunit of ribosomal RNA (rRNA). These sequences can be found out in the environment like from soil or water. Now, whole genomes can be sequenced from findings in the environment too.
Describe Proteobacteria
The most diverse group of bacteria. Grouped by their similar rRNA sequences. Some proteobacteria are helpful to eukaryotes by having mutually beneficial relationships with them for example soybeans and the bacteria on their root nodules that use the nitrogen cycle. Other proteobacteria are extremely harmful and cause some disease such a typhoid fever and cholera. For example Salmonella
What defines Gram-Positive bacteria?
Gram-positive bacteria are bacteria with thick cell walls made of peptidoglycan. When these bacteria are dyed they retain the dye while the bacteria with a thin wall don’t. The gram-positive will appear purple.
What are the three major groups of Archaeons?
Euryarchaeota, TACK and DPANN
What are the characteristics of each of the three groups of Archaea?
Euryarchaeota- include methanogens, which usually live in intestines. Also halobacteria that can survive in extremely salty environments. Also extreme thermophilic bacteria.
TACK- T: Thaumarchaeota, A: Aigarchaeota, C: Crenarchaeota, K: Korarchaeota
DPANN- Diapherotrites, Parvarchaeota, Aenigmarchaeota, Nanoarchaeota, and Nanohaloarchaeota.
