Bio 101 Test 2

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Types of Prokaryotes

Back 1

Bacteria

Archaea

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Prokaryotes

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Thrive almost anywhere

Two domains

The typical genome is one circular chromosome that is not surrounded by a membrane and that is located in a nucleoid region.

Most common shapes: Cocci (spheres), bacilli (rods), spirals

Can reproduce by binary fission in as few as 6 minutes, and can evolve rapidly because of their short generation times.

Many form metabolically inactive endospores.

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Functions of cell wall

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Maintains cell shape

Provides physical protection

Prevents the cell from bursting in a hypotonic environment.

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Peptidoglycan

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Sugars and proteins

Found in bacterial cell walls.

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Gram-Positive

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indicates thick cell walls

purple in color

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Gram-negative

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indicates thin cell walls

appears pink in color

Tend to be more antibiotic resistant

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Bacteria

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Almost all are either Gram-positive or Gram-negative + an outer membrane that may be toxic.

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Capsule

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A plysaccharide or "slime" layer covers many prokaryotes.

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Fimbriae

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Found in some prokaryotes.

Also called attachment pili

Allows them to stick to their substrate or other individuals in a colony.

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Sex pili

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longer than fimbriae and allow prokaryotes to exchange DNA

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Nucleoid region

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Where a typical prokaryotic genome is found.

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Plasmids

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Smaller rings of DNA found in some species of bacteria.

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Genetic recombination

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The combining of DNA from two sources.

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Transformation

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The genotype and possibly phenotype of a prokaryotic cell are altered by the uptake of foreign DNA from its surroundings.

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Transduction

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Phages carry prokaryotic genes from one host cell to another.

In most cases, happens 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). If some of this DNA is then incorporated into the recipient cell's chromosome by DNA recombination, a recombinant cell is formed.

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Conjugation

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DNA is transferred between two prokaryotic cells, usually of the same species, that are temporarily joined. When the two cells are members of different species; results in horizontal gene transfer.

In ciliates, a sexual process in which two cells exchange haploid micronuclei but do not reproduce.

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Major Nutritional Modes

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Autotroph:

Photoautotroph

Chemoautotroph

Heterotroph:

Phtoheterotroph

Chemoheterotroph

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Autotroph

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Two types: Photoautotroph and chemoautotroph

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Heterotroph

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Two types: Phtoheterotroph and chemoheterotroph

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Photoautotroph

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Energy source: Light

Carbon source: CO2

Types of organisms: photosynthetic prokaryotes (ex. cyanobacteria); plants; certain protists (ex. algae)

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Chemoautotroph

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Energy source: inorganic chemicals

Carbon source: CO2

Types of organisms: Certain prokaryotes (ex. sulfolobus)

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Heterotroph

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two types:

Photoheterotroph

Chemoheterotroph

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Photoheterotroph

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Energy Source: Light

Carbon Source: organic compound

Types of organisms: Certain prokaryotes (ex. Rhodobacter, Chloroflexus)

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Chemoheterotroph

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Energy Source: organic compounds

Carbon source: organic compounds

Types of organisms: Many prokaryotes (ex. Clostridium) and protists; fungi; animals, some plants.

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Obligate aerobes

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require O2 for cellular respiration

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Obligate anaerobes

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are poisoned by O2 and use fermentation

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Facultative anaerobes

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can survive with or without O2

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Types of bacterial symbiosis

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nitrogen fixation

root nodules

biofilms

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Nitrogen fixation

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The conversion of atmospheric nitrogen (N2) to ammonia (NH3). Biological nitrogen fixation is carried out by certain prokaryotes, some of which may mutualistic relationships with plants.

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Root nodules

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occur on the roots of plants (primarily Fabaceae) that associate with symbiotic nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia.

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Biofilms

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A surface-coating colony of one or more species of prokaryotes that engage in metabolic cooperation.

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Three domains of life

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Bacteria, Archaea, Eukarya

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Domain Bacteria

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Characteristics:

Peptidoglycan in cell wall.

Membrane lipids: unbranched hydrocarbons.

RNA Polymerase: one kind.

Initiator amino acid for protein synthesis: Formylmethionine.

Introns in genes: very rare.

Response to the antibiotics streptomycin and chloramphenicol: Growth inhibited.

Cicular chromosome: Present.

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Domain Archaea

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Membrane lipids: some branched hydrocarbons.

RNA polymerase: Several kinds

Initiator amino acid for protein synthesis: Methionine.

Introns in genes: Present in some genes.

Response to the antibiotics streptomycin and chloramphenicol: Growth NOT inhibited.

Histones associated w/DNA: Present in some species.

Circular chromosome: present.

Growth at temperatures >100: some species

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Domain Eukarya

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Nuclear envelope: present.

Membrane-enclosed organelles: present.

Membrane lipids: unbranched hydrocarbons.

RNA polymerase: several kinds

Initiator amino acid for protein synthesis: Methionine.

Introns in genes: Present.

Response to the antibiotics streptomycin and chloramphenicol: Growth NOT inhibited.

Histones associated with DNA: Present.

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Mutualism

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Both symbiotic organisms benefit.

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Commensalism

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one organism benefits while neither harming nor helping the other in any significant way.

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Parasitism

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An organism called a parasite harms but does not kill its host.

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Pathogen

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Parasites that cause disease.

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Uses of bacteria

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bioremediation & product synthesis

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Bioremediation

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uses prokaryotes to remove pollutants from the environment.

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Product synthesis

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i.e. antibiotics, hormones, fuels, etc.

Recovery of metals from ores, etc.

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Microbial antagonism

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Under the influence of antagonists, microorga-nisms cease to grow and reproduce in some cases, their cells lyse or dissolve In other cases, or such biochemical processes within the cells as respiration and synthesis of amino acids become inhibited or cease in still other cases. Antagonism is most pronounced among actinomycetes, bacteria, and fungi. Pseudomonasaeruginosa actively suppresses the plague microorganism

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Hershey Chase

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Helped to show that the "instruction manual" of life is written in DNA NOT protein as was thought at the time.

The phage in this experiment consisted of a DNA molecule surrounded by a protein coat.

When phage infect a bacteria, they attach to the surface of the bacterium and inject the DNA into the cell. The protein remains on the outside. In the first part of the experiment, the phage were produced in a radioactive medium resulting in radioactive phage but not DNA. The phages were then allowed to infect the bacteria. The phage attached to the bacteria and injected the DNA, the radio active protein coat remained on the outside. The phage produced in these cells contained no radioactivity.

In the second part of the experiment the phage was produced in a P-32 deoxyribonucleotides solution, resulting in phage with a P-32 labeled DNA, but no radioactive label in the proteins. When the phage infected the bacteria the P-32 labeled DNA entered the cells and could be found in the phage subsequently produced in the infected bacteria. This demonstrated that the DNA, not the protein, carries the genetic information for a new generation of phage.

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Ames Test

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Purpose: tells if chemical are mutagens or not.

Determines change in the DNA.

The more mutation = the more likely to develop cancer.

Uses a mutated form of Salmonella bacteria which cannot produce their own histidine.

The plate is smeared with the mutated salmonella then the chemical agent is added. Since the salmonella cannot produce its own histidine, if it begins to produce histidine it means that the chemical has initiated a mutation. The more growth found on the plate, the more deadly the added chemical agent is.

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Protists

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Informal name of the kingdom of mostly unicellular eukaryotes.

(there are some colonial and mulitcellular species).

Constitute a paraphyletic group, and protsista no longer valid as a kingdom.

Exhibit more structural and functional diversity than any other group of eukaryotes.

Can reproduce asexually or sexually, or by the sexual processes of meiosis and syngamy.

Some are capable of conjugation.

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Secondary endosymbiosis in eukaryotic evolution

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A eukaryote cell engulfs another eukaryote cell that has undergone primary endosymbiosis.

The engulfed cell is dependent upon the host.

Ex. red & green algae were ingested by a heterotrophic eukaryote.

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Trichomonas vaginalis

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protist that causes yeast infections.

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Giardia intestinalis

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protist that causes intestinal pathogen (fecal-oral route)

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Trypanosoma

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Protist that causes African sleeping sickness, transmitted by fly bite.

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Dinoflagellate blooms

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Protist responsible for "red tides" caused by eutrophication.

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Diatoms

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Protist silicone tests used in industry and forensics.

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Phytophthora infestans e

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Protist

Irish potato famine

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Entamoeba histolytica

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Causes amebic dysentery (protist)

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Pfesteria

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(protist)

A dinoflagellate that causes million of "fish kills"

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Plasmodium

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infects red blood cells in mammals (including humans), birds, and reptiles, occurs worldwide, especially in tropical and temperate zones. The organism is transmitted by the bite of the female Anopheles mosquito.

Infect liver cells.

Depending on strain, life cycle is between 24-72 hours.

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Algae

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Protists NOT plants, they do not have protected embryos like true plants nor do thay have true roots, stems or leaves.

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Thallus

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An algal body which is plantlike but lacks true roots, stems and leaves.

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Holdfast

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anchors the stemlike stipe of an algae.

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Stipe

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stemlike structure of a seaweed

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Blades

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A leaflike structure of a seaweed that provides most of the surface area for photosynthesis.

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Alternation of generations

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alternation of muticellular haploid and diploid forms.

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Producers

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Obtain energy from the sun.

An organism that produces organic compounds from CO2 by harnessing light energy (in photosynthesis) or by oxidizing inorganic chemicals.

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Lichens

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Are symbiotic relationships between protists and fungi.

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Obligate intracellular parasites

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Viruses that can reproduce only within a host cell.

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Acellular

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containing of only one cell. Too small for light microscopy.

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Viruses

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very small infectious particles consisting of a nucleic acid (either DNA or RNA) enclosed in a protein coat and, sometimes, a membranous envelope.

Have glycoprotein spikes on their capsids that bind to receptors on host cells.

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Viral genomes can be:

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DNA or RNA

double or single stranded

postive or negative "sense" strands:

positive or negative

Some carry enzymes that make RNA from RNA or DNA from RNA; these enzymes are not found in cells.

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Positive "sense" strands

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codes for protein

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Negative "sense" strands

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A template to make the coding strand.

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Capsid

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The protein shell that encloses the viral genome. Built from protein subunits called capsomeres.

Three basic shapes: Polyhedral (equilateral triangles assembled into geodesic dome structures), helical (rod shaped), complex (polyhedral + helical)

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Capsomeres

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protein subunits that build capsids.

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Envelopes

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Derived from the host cell's membrane, contains a comination of viral and host cell molecules.

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Host range

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The limited number of species whose cells can be infected by a particular virus.

Determined by the spike shape of the glycoprotein spike on the capsid of a virus.

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Viral specificity

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determined by the spike shape of the glycoprotein spike on the capsid of a virus.

viruses are selective in who/what they infect. Indicates that the virus can "determine" whether it only infects certain species, etc

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Lytic Cycle

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A phage relicative cycle that culminates in the death of the host cell.

Produces new phages and lyses (breaks open) the host's cell wall, releasing the progeny viruses.

A phage that reproduces only by this cycle is called a virulent phage.

Steps:

1. Adsorption (attachment)

2. Penetration (entry to cell)

3. Biosynthesis (nucleic acid used to make protein)

4. Maturation (assembly)

5. Release (to infect new cells)

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Lysogenic Cycle

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Involves integration of viral DNA and does not kill the host cell. This integrated viral DNA is known as a prophage.

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FLU

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H5N1 - bird flu, closely related to Spanish Flu of 1918.

Most really nasty flu strains are chimeras

About every 40 yeas there is a pandemic flu.

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Vaccines

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harmless derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the actual pathogen.

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Can viral infections be treated with antibiotics

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NO

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Viroids

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Circular RNA molecules that infect plants and disrupt their growth.

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Prions

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Slow-acting, virtually indestructible infectious proteins that cause brain diseases in mammals.

Propagate by converting normal proteins into the prion version.

ex. Scrapie in sheep, mad cow disease, Creutzfeldt-Jakob disease and Kuru in humans.

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Metabolism

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the totality of an organism's chemical reactions.

Are subject to the laws of thermodynamics.

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Metabolic pathways

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begin with a specific molecule and ends with a product. Each step is catalyzed by a specific enzyme

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Substrates

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The reactant an enzyme acts on

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Enzymes

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a macromolecule that acts as a catalyst.

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products

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A material resulting from a chemical reaction.

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Catabolic pathways

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Release energy by breaking down complex molecules into simpler compounds. (gives off energy)

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Anabolic pathways

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Consume energy to build complex molecules from simpler ones. (requires energy)

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1st law of thermodynamics

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Energy can be transferred and transformed, but it cannot be created or destroyed.

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2nd law of thermodynamics

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Every energy transfer or transformation increases the entropy (disorder) of the universe.

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Entropy

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Chaos or disorder.

May decrease in an organism, but the universe's total entropy increases.

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Biological order and disorder

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Living cells unavoidably convert organized forms of energy to heat.

Cells create ordered structures from less ordered materials.

Spontaneous processes occur without energy input; they can happen quickly or slowly.

For a process to occur without energy input, it must increase the entropy of the universe.

Evergy flows into an ecosystem in the form of light and exits in the form of heat.

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Free energy (Delta G)

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The evolution of more complex organisms does not violate the second law of thermodynamics. Entropy may decrease in an organism, but the universe's total entropy increases.

Products - reactants - G

-G = spontaneous

+G = requires additional energy

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Free energy: spontaneous change

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The free energy of the system decreases.

The system becomes more stable.

The released free energy can be harnessed to do work.

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More free energy

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Less stable;

Greater work capacity.

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Less free energy

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More stable;

Less work capacity.

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Exergonic reaction

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Proceeds with a net release of free energy and is spontaneous.

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Endergonic reaction

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Absorbs free energy from its surroundings and is nospontaneous.