General Biology RAT#2

6. The term "endosymbiosis" can be broken into two parts, namely "endo" and "symbiosis". What is the meaning the "symbiosis" and how is the term relevant to the origin of internal organelles?

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

1. Describe the characteristics that distinguish eukaryotic cells from prokaryotic cells? (see Concept 4.2, Comparing prokaryotic and eukaryotic cells, pg. 69)

A major differences between prokaryotic and eukaryotic cells is the location of their DNA. In a eukaryotic cell, most of the DNA is in an organelle called the nucleus, which is bounded by a double membrane. In a prokaryotic cell, the DNA is concentrated in the nucleoid, a region that is not bounded by a membrane.

21. Understand the role that genetic recombination can play in the emergence of virulent and/or antibiotic resistant strains of bacteria.

The medical consequences are also predictable: Resistant strains of pathogens are becoming more common, making the treatment of certain bacterial infections more difficult. The problem is compounded by the fact that many R plasmids, like F plasmids, have genes that encode pili and enable DNA transfer from one bacterial cell to another by conjugation. Making the problem still worse, some R plasmids carry as many as ten genes for resistant to that many antibiotics.

4. Explain the origin of the endomembrane system (i.e. endoplasmic reticulum, golgi apparatus, etc.) in eukaryotic cells?

These membranes divide the cell into functional and structural compartments, or organelles. In eukaryotes the organelles of the endomembrane system include: the nuclear membrane, the endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles, endosomes and the cell membrane.

23. Explain the role of transduction in the appearance of a highly virulent E. coli strain, E. coli O157:H7.

This suggests that at least some of the ,1387 genes were incorporated into the genome of O157:H7 through phage-mediated horizontal gene transfer(transduction).

7. What is the meaning of the term virulence factor? Explain what makes both the capsule and fimbriae a virulence factor.

Virulence factors are molecules expressed and secreted by pathogens (bacteria, viruses, fungi and protozoa) that enable them to achieve the following: colonization of a niche in the host (this includes attachment to cells)

10. Explain the meaning of binary fission (see Binary Fission in Bacteria, pg. 182 and 183, and Fig. 9.12).

asexual reproduction in unicellular organisms by division into two daughter cells

12. Complete the following sentence: Evolution cannot occur without ________________.

genetic variation pg.g466

24. Explain the meaning of the abbreviation MRSA, and describe the health threat posed by MRSA and other antibiotic resistant bacterial strains.

"Methicillin" represents the semisynthetic penicillin-related antibiotic once effective against staphylococci (staph).2 Staph bacteria have developed a resistance to penicillin-related antibiotics, including methicillin - these resistant bacteria are called methicillin-resistant staphylococcus aureus, or MRSA. S. aureus can cause skin infections including: Boils Pimples Impetigo Abscesses Wound infections. Staph bacteria can also enter the body, and invade the bloodstream through broken or damaged skin or during medical procedures, and can cause infections and resulting conditions that range from mild to severely life-threatening. These conditions may include: Septicemia (blood poisoning) Pneumonia (lung infection) Osteomyelitis (bone infection) Endocarditis (heart valve infection) Urinary tract infection (eg. bladder infection) Septic bursitis (small fluid-filled sacs under the skin).

18. Briefly describe the steps involved in conjugation, i.e. the transfer of a plasmid from a donor cell to a recipient cell.

1. A cell carrying an F plasmid (an F+ cell) forms a mating bridge with an F- cell. One strand of the plasmid's DNA breaks at the point marked by the arrowhead 2. Using unbroken strand as template, the cell synthesizes a new strand(light blue). Meanwhile, the broken strand peels off (red arrow), and one end enters the F-cell. There synthesis of its complementary strand begins. 3. DNA Replication continues in both donor and recipient cells, as the transferred plasmid strand moves father into the recipient cell. 4. Once DNA transfer and synthesis are completed, the plasmid in the recipient cell circularizes. The recipient cell is now recipient F+ cell.

2. Understand the process of phagocytosis, and know the role or function of each of the following: (see Fig. 5.18, pg. 107, and Fig. 35.3, pg 712) a. Pseudopodia b. Food vacuole c. lysosome

1. Pseydopodia surround pathogens 2. Pathogens are engulfed by endocytosis 3. Vacuole forms, enclosing pathogens. 4. Vacuole and lysosome fuse. 5. Toxic compounds and lysosomal enzymes destroy pathogens 6. Debris from pathogens is released by exocytosis.

3. Explain the role of the cytoskeleton in the capture of prey by single-celled eukaryotes (hint: think pseudopodia)?

1. The eukaryotic cell used its cytoskeletal elements to surround and engulf smaller prey. 2. Instead of fusing with a lysosome and being digested, an engulfed bacterium began to live inside a eukaryotic cell. 3. The engulfed cell survived by absorbing carbon molecules with high potential energy from the eukaryotic cell and oxidizing them, using oxygen as a final electron acceptor. microfilaments-help the cell move and capture prey by forming rapidly in the direction of movement. intermediate filaments- provide support and structure to the cell. microtubules- provide structure to cells and facilitate the movement of materials inside the cell by serving as transport "rails".

22. Distinguish between exotoxins and endotoxins.

1. endotoxin is LPS, exotoxins are proteins 2. endotoxin is part of cell structure, exotoxin is secreted 3. endotoxins vary in strength, exotoxins are powerful in microgram quantities 4. endotoxins are difficult to convert into vaccine antigens (toxoiding), exotoxins easy by adding aldehydes 5. endotoxins have low natural antigenicity, exotoxins have high natural antigenicity 6. endotoxins from all gram negative bacteria, exotoxins from some gram positive and some gram negative bacteria

15. Given that bacterial reproduction is estimated to produce 2 x 1010 new E. coli cells each day within our intestinal system, how many of these E. coli cells would be expect to have acquired a DNA mutation, on a per gene basis?

2,000 bacteria that would have a gene. Thus, the total number of mutations when all 4,300 E.coli genes are considered is about 4,300 x 2,000 = 9 million per day per human host.

10. In terms of the mitochondria, explain how each of the following provides evidence in support of the theory of the endosymbiotic origin of the mitochondria. a. The plasma membrane(s) of the mitochondria. b. The presence of mitochondrial DNA and expression of mitochondrial genes. c. The ability of mitochondria to replicate. d. The antibiotic sensitivity of mitochondrial ribosomes

Although all eukaryotes have mitochondria or remnants of these organelles, they do not all have plastids, Thus the serial endosymbiosis hypothesis supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events. 1. The inner membranes of both organelles have enymes and transport systems that are homologous to those found in the plasma membranes of living prokaryotes. 2. Mitochondria and plastids replicate by a splitting process that is similar to that of certain prokaryotes. Mitochondria and plastids both contain circular DNA molecules that, like the chromosomes of bacteria, are not associated with hisstones or large amounts of other proteins. 3. As might be expected of organelles decsended from free-living organisms, mitochondria and plastids also have the cellular machinery (including ribosomes) needed to transcribe and translate their DNA into proteins

Of the three domains of life, which domains are prokaryotes?

Archaea and Bacteria

9. Explain what is meant by the terms heterotroph, chemoheterotroph, photoautotroph, and chemoautotroph in regards to how bacteria acquire their carbon and energy?

Autotrophs require inorganic nutrients it uses inorganic CO2 as its carbon source. Heterotrophs require inorganic and organic nutrients and it must obtain carbon in an organic form. chemoautotrophs survive totally on inorganic substances such as minerals. They require neither light nor organic nutrients in any form. They remove electrons from inorganic substrates and combine them with carbon dioxide and hydrogen. This reaction gives off simple organic molecules and the amount of energy to drive the synthetic processes of the cell. Chemoheterotrophs derive both carbon and energy from organic compounds. Processing these organic molecules by respiration or fermintation releases energy that is stored as ATP. -photoautotrophs are photosynthetic. they capture the energy of light rays and transform it into chemical energy that can be used in cell metabolism. photosynthesis relies on special pigments to collect the light and uses the energy to convert CO2 into simple organic compounds. Oxygenic photosynthesis occurs in plants, algae, and cyanobacteria and uses chlorophyll as the primary pigment. Carbohydrates are formed from this reaction and can be used by the cell to synthesize other cell components. Anoxygenic photosynthesis uses bacteriochlorophyll as its pigment, it gives off elemental sulfur as one product. - chemoautotrophs survive on inorganic substances such as minerals. they dont require light or organic nutients. They

8. Know the meaning of the term chemotaxis, and the difference between negative chemotaxis and positive chemotaxis.

Chemotaxis (from chemo- + taxis) is the movement of an organism in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. Positive chemotaxis is movement of a cell in the direction of a favorable chemical stimulus (usually from a nutrient); negative chemotaxis is movement away from a repellent (potentially harmful) compound.

20. Distinguish between each of the following sources of genetic recombination: a. Conjugation b. Transformation c. Transduction

Conjugation = DNA is transferred between two prokaryotic cells(usually from the same species that are temporarily joined. In bacteria, the DNA transfer is always one-way: One cell donates the DNA, and the other receives it. Transformation = The genotype and possibly phenotype of a prokaryotic cell are altered by the uptake of foreign DNA from its surrounding. For example, a harmless strain of Streptococcus pneumoniae can be transformed into pneumonia-causing cells if the cells are exposed to DNA from pathogenic straing Transduction = carry prokaryotic genes from one host cell to another. In most cases, transduction results from accidents that occur during the phage replicative cycle. A virus that carries prokaryotic DNA may not be able to replicate because it lacks some or all of its own genetic material. However, the virus can attach to another prokaryotic cell (a recipient) and inject prokaryotic DNA acquired from the first cell(the donor)

Know the similarities and the differences between the gram-negative cell wall and the gram-positive cell wall? a. Which type of cell wall is composed entirely of peptidoglycan? b. Which type of cell wall has peptidoglycan and lipopolysaccharides?

Gram positive and gram negative refers to how a bacteria reacts to a gram stain. If it takes the initial stain, it will be purple and be considered gram positive. If it doesn't take the initial stain, it will be pink and gram negative. The difference is the outer casing of the bacteria. A gram positive bacteria will have a thick layer of peptidoglycan (a sugar-protein shell) that the stain can penetrate. A gram negative bacteria has an outer membrane covering a thin layer of peptidoglycan on the outside. The outer membrane prevents the initial stain from penetrating.

17. What is the role or function of an F plasmid and an R plasmid?

If I understand the nomenclature correctly, an R plasmid is just any plasmid containing an antibiotic (R)esistance gene (eg. Amp, Kan, Cm, etc.). It's a bit of an outdated name from when people didn't know how exactly the plasmids conferred such resistance. An F-plasmid is any plasmid that contains the genes necessary for (F)ertility, eg:horizontal gene transfer via the tra operon. The two do not have to appear together -- eg: Many F plamids will contain resistance genes (along with other random chunks from the genome), but resistance doesn't always have to be part of the payload. Likewise, it is common in labs to build pure resistance vectors that lack any horizontal transfer capability in order to select for particular clones.

13. Understand how each of the following contributes to genetic diversity in bacterial population. a. Short generation times. b. Large population size. c. Mutations

In population biology and demography, the generation time is a quantity that reflects the average time between two consecutive generations in the lineages of a population. However, there is no single definition of the generation time, and several quantities are each better suited for a particular use.

9. Understand the significance of secondary endosymbiosis in the evolution of eukaryotic cell diversity (Fig. 25.4, pg 486). Recognize that an ancestral eukaryotic cell could engulf and hold as an endosymbiont another eukaryotic cell that contained both mitochondria and chloroplast.

On several occasions during eukaryotic evolution, red algae and green algae underwent secondary endosymbiosis: They were ingested in the food vacuoles of heterotrophic eukaryotes and became endosymbionts themselves. Studies of plastid-bearing eukaryotes suggest that plastids evolved from a cyanobacterium that was engulfed by an ancestral heterotrophic eukaryote(primary endosymbiosis). That ancestor then diversified into red algae and green algae, some of which were subsequently engulfed by other eukaryotes (secondary endosymbiosis)

Know the general characteristics of a prokaryotic cell as described

Prokaryotes lack an organized nucleus and other membrane-bound organelles. Prokaryotic DNA is found in a central part of the cell called the nucleoid. The cell wall of a prokaryote acts as an extra layer of protection, helps maintain cell shape, and prevents dehydration. Prokaryotic cell size ranges from 0.1 to 5.0 μm in diameter. The small size of prokaryotes allows quick entry and diffusion of ions and molecules to other parts of the cell while also allowing fast removal of waste products out of the cell.

5. Briefly outline the steps leading to the formation of the endospore. Under its purpose or function, as well as the condition or circumstance that will trigger endospore formation.

Sporulation Process of endospore formation that consist of 6 stages [SP] First Stage -DNA IS REPLICATED -The spore septum begins to isolate the newly replicated DNA and a SMALL PORTION OF THE CYTOPLASM [SP] Second stage The PLASMA MEMBRANE starts to surround the replicated DNA and cytoplasm [SP] Third stage The spore septum surrounds the isolate portion forming a forespore [SP] Fourth Stage The peptidoglycan layer forms btwn the 2 membranes [SP] Fifth Stage -THiCK spore coat forms around the outside membrane, making endospores resistant to many harsh chemicals -The new spore loses its water and becomes highly dehydrated to the point that all that remains in the spore is: ~DNA ; SMALL AMNTS OF RNA ; RIBOSOMES; ENZYMES; FEW IMPORTANT MOLECULES [SP] Sixth Stage -THE ENDOSPORE IS RELEASED FROM THE CELL AND CAN REMAIN DORMANT FOR 1000 OF YEARS -Germination ( the process where the endospores return to a vegetative state) is triggered by PHYSICAL OR CHEMICAL damage to the endospores coat.

19. Understand the meaning of the term genetic recombination.

The combining of DNA from two sources. In Eukaryotes, the sexual processes of meiosis and fertilization combine DNA from two individuals in a single zygote. But meiosis and fertilization do not occur in prokaryotes. Genetic recombination is the production of offspring with combinations of traits that differ from those found in either parent. In eukaryotes, genetic recombination during meiosis can lead to a novel set of genetic information that can be passed on from the parents to the offspring.

14. According to the textbook, what is the probability that a DNA mutation will occur within the genome of E. coli gene each time the cell divides?

The probability of such a mutation occuring in a given E. coli gene is about one in 10 million (1 x 10^-7) per cell division.

5. Understand how serial endosymbiosis explains the origin of internal organelles, mitochondria and chloroplasts, in eukaryotic cells.

The serial endosymbiosis hypothesis supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events.

16. What is a plasmid and why is the plasmid important to the cell?

a genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium or protozoan. Plasmids are much used in the laboratory manipulation of genes. Scientists use plasmids in laboratory experiments as a vector, or vehicle, for DNA of interest, typically a gene. Plasmids are usually represented by a simple circle with the important features noted. To be an effective tool for scientists, a plasmid typically possesses three basic features: a multiple cloning site, an origin of replication, and a selectable marker.

What is the composition of a bacterial capsule, how is it formed, and what is its function?

cell wall of prokaryotes is surrounded by a sticky layer of polysaccharide or protein. Enable prokaryote to adhere to their substrate or other individuals colony

6. Describe the structure and function of the fimbriae. What are the similarities and differences between fimbriae and a capsule?

sticky, bristlelike projections to adhere to one another and to substances in the environment. Their function is to attach cells to their substrate or to neighboring cells