Chapter 20

How are prokaryotes important in ecology?

Because prokaryotes are a part of daily life and are everywhere surrounding us at all times. They also make up antibiotics.

Describe the structure of a prokaryote.

Cell wall, containing peptidoglycan; nucleoid region, containing genetic material; plasmid, circle of DNA that is independent from the chromosome and can replicate independently; pili, hairlike structures; flagella, whiplike tail; fimbriae, hairlike structures that are shorter and more numerous than pili; endospore, resistant cell for harsh conditions.

What is the difference between an exotoxin and an endotoxin?

Exotoxins are bacterial proteins that can produce disease without a prokaryote present (cholera). Endotoxins are caused by components of gram negative bacteria membranes after the prokaryote dies (salmonella).

Difference between Gram + and Gram - bacteria?

Gram positive bacteria is purple in the gram stain, has a thick layer of peptidoglycan, and functions as penicillin. Gram negative bacteria is red or pink in a Gram stain, little layer of peptidoglycan, cell wall has layer of lipopolysaccharides, most pathogens and acts against antibiotics.

Describe the process of Gram staining.

Gram staining is a test used to distinguish between different types of bacteria. Put the purple stain on first, then rinse, then use the red stain.

Describe 5 differences between members of the Archae and Bacteria domains.

In bacteria, the peptidoglycan in the cell wall is present but is absent in archae. In bacteria, the membrane is made of unbranched hydrocarbons and the archae membrane is made of some branched hydrocarbons. There is one type of RNA polymerase in bacteria but several kinds in archae. Histones associated with DNA are absent in bacteria but present in archae. Bacteria are not able to grow in temperatures greater than 100 degrees but some species of archae can.

Explain the difference between mutualism, commensalism, and parasitism.

Mutualism is a relationship between two organisms that benefits both. Commensalism is when one organism benefits and the other organism is not affected at all. Parasitism is when one organism is benefited and one is harmed.

What are the differences between an obligate aerobe, facultative anaerobe, and an obligate anaerobe?

Obligate aerobes must have O2 for cellular respiration; Facultative anaerobes can use O2 for respiration but will undergo fermentation without it; Obligate anaerobes are poisoned by O2.

Explain the difference between a photoautotroph, chemoautotroph, photoheterotroph, and a chemoheterotroph.

Photoautotrophs are photosynthetic and use light to make their own food; Chemoautotrophs use the oxidation of inorganic substances for energy; Photoheterotrophs use light to generate ATP but get carbon in an organic form; Chemoheterotrophs consume organic molecules for both food and energy.

Give a brief description of the major groups of bacteria.

Proteobacteria- includes photoautrophs, chemoautotrophs, and heterotrophs and are sometimes anaerobic. Chlamydias- parasites that can survive only within animal cells and depend on their hosts for something as simple as making ATP. Spirochetes- helical shaped heterotrophs that move with flagellum-like filaments. Gram positive bacteria- have a very thick cell wall made of a protein called peptidoglycan. Cyanobacteria- bacteria that produce molecular oxygen and use water as an electron-donating substrate in photosynthesis — called also blue-green alga.

Explain how colonial bacteria can cooperate and share metabolic processes.

Some colonial bacteria fix nitrogen while others photosynthesize. They secrete signaling molecules to make the colony grow. They share nutrients and collectively discard of wastes.

Describe how viruses reproduce.

The lytic cycle is when viruses inject their nucleic acids into a living cell host, causing the cell to explode and release replications of the virus (this is a very quick process). The lysogenic cycle is when a virus may invade a host but stay hidden for years. Eventually, the virus will activate and reproduce inside the cell (this is a slower process).

Describe the 3 major types of Archae and tell where each can be found.

Thermophiles are bacterium that like hot temperatures such as deep sea vents, volcanic vents, and hot springs. Halophiles are bacterium that like salty environments and can be found in the Dead Sea and the Great Salt Lake. Methanogens are obligate anaerobes that produce methane and live in places such as swamps and intestinal tracts.

Describe how bacteria can have specialized membranes but still lack true organelles.

They have infolding membranes with specialized functions which allow them more surface area and allows them to pass through the Electron Transport Chain, but not actually have organelles.

How are viruses different from bacteria?

Viruses are smaller than bacteria and require a living host to survive.

What are the 3 major shapes of prokaryotes?

cocci, round and spherical; bacilli, rod shaped; helical, spiral shaped.

What is symbiosis?

interaction between two different organisms living in close physical association, typically to the advantage of both.