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26 Cards in this Set
- Front
- Back
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define: Periplasmic space
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region between the plasma membrane and the cell wall. This area is loaded with enzymes. Enzymes are present for catabolizing growth media into smaller sub-units. In addition, there are enzymes called restriction exonucleases (these enzymes will destroy foreign DNA), another enzyme penicillinase may be found. (Penicillinase hydrolyzes and inactivates the antibiotic penicillin
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What is the responsibility of restriction exonucleases?
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an enzyme that will destroy foreign DNA
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What is the responsibility of penicillinase?
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hydrolyzes and inactivates the antibiotic penicillin
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define: Plasma membrane
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(cell membrane) phospholipid bilayer with non-stationary proteins. Described as the fluid mosaic model. The membrane serves as a site for selective permeability.
The plasma membrane serves as a site for chemical reactions. In prokaryotes, ATP production sites are located on the plasma membrane. In eukaryotes, ATP production occurs in the mitochondria. Electron micrographs depicted membranous intrusions of the bacterial plasma membrane (called mesosomes). Original theories considered these mesosomes to be structures associated with cell division or concentration of metabolic activity. Now they are considered to be artifacts of electron microscopy preparation |
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Selective permeability of molecules moving through the plasma membrane is a function of the following:
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a. size and molecular weight
b. electric charge or polarity c. lipid solubility d. presences or lack of presence of enzymes called permeases |
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define: mesosomes
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electron micrographs depicted membranous intrusions of the bacterial plasma membrane.
Original theories considered these mesosomes to be structures associated with cell division or concentration of metabolic activity. Now they are considered to be artifacts of electron microscope preparation. |
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Cytoplasmic contents
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a. nucleoid region
b. plasmids c. ribosomes d. RNA e. Inclusions f. endospores |
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What the the nucleoid region?
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a. The nucleoid region contains a single, looped, circular (no free ends) chromosome. This areas comprises approx. 10% of the cell volume. It is free within the cell as it is not membrane bound. The DNA on the chromosome is organized into 2000 to 3000 genes
(a cytoplasmic content) |
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What are plasmids?
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extrachomosomal loops of DNA that replicate independently of the chromosome
(a cytoplasmic content) |
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What are ribosomes?
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sites for protein synthesis. Thousands are present in a bacterial cell. They are made up of rRNA (ribosomal RNA) and protein
(a cytoplasmic content) |
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What is RNA?
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bacterial cells that have the full complement of RNA. This includes mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA)
(a cytoplasmic content) |
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What are inclusions?
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there are several kinds of inclusions or reserve deposits in prokaryote cells.
Such as: 1. volutin granules 2. polysaccharide granules 3. lipid inclusions 4. sulfer granules |
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What are volutin granules?
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(metachromatic granules) - concentrations of polymetaphosphates. These are reserves of excess inorganic phosphates often times seen in older cells
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What are polysaccharide granules?
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consists of glycogen and starch
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What are lipid inclusions?
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PHB (polyhydroxybutarate) is a common lipid storage material
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What is an endospore?
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resistant, dormant, non-metabolizing forms called spores.
- Spores are for protection and not reproduction, these structures are formed internally as endospores - resist staining and display refractility - contain low amounts of water and high amounts of calcium - contain high amounts of dipicolinic acid (DPA) |
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What is sporogenesis?
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members of the genera Bacillus and Clostridium can form resistant dormant, non-metabolizing forms of these cells called spores, during adverse conditions
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What is germination?
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favorable conditions will restore these cells to the vegetative form
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When observing an endospore in Clostridium tetani, where is the endospore located?
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terminally located and swollen
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What is sporulation?
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one of the biological models to study the process of differentiation
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What is cell wall synthesis?
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When gram positive cells divide, the new cell wall material is laid down at the septum, or area of cross wall formation/ When gram negative cells divide, the new cell wall growth is spread out in what is described as an intercalated pattern.
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What are the four phases of growth of bacterial populations in liquid media?
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a. Lag Phase
b. Log Phase c. Stationary Phase d. Death (Decline) Phase |
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What is the Lag Phase?
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1. This is the time of cellular adaptation. The bacterial cell is in its "physiologic youth"
2. Cells are not dividing, yet they are extremely active. We observe the induction of enzymes and the synthesis of precursor units 3. Increases in the cell metabolism and mass occur without cell division. Cell size increases |
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What is the Log Phase?
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1. Observed is exponential or geometric growth
2. Division occurs at a constant and maximal rate 3. These young cells are smaller in size and give the most consistent gram stain. The best time to gram stain is therefore in the Log Phase 4. The division is not synchronous. The population however, is dividing so often, the cells are uniformly small in size 5. Nutrients are still in excess and the cells are maximizing the utilization of the nutrients 6. Natality is greater than mortaility |
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What is the Stationary Phase?
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1. Natality is now equal to mortality
2. The medium is not supporting the maximum concentration of cells 3. Nutrient become limiting and are no longer in excess 4. We see the appearance of granules, the accumulation of toxic wastes and the initiation of sporogenesis during this phase 5. Cell walls may start to weaken. Old gram positive cells may now revert to gram negative 6. Carbon dioxide levels may increase, and pH will decrease. Oxygen levels decline |
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What is the Death or Decline Phase?
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1. Mortality rates now exceed natality rates
2. Death occurs at a constant and maximal rate. This geometric or exponential decline is the reverse of the Log Phase 3. We see the maximal activity of autolytic enzymes, if present. |
