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Intro to Microbiology Biol 357 > Chapter 2 > Flashcards

Chapter 2 Flashcards

Microbial Cell Structure and Function

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1
Q

What is the ABC transport system?

A

ABC stands for ATP-binding cassette. This transport system is a membrane transport system consisting of three proteins, one of which hydrolyzes ATP; the system transports specific nutrients into the cell.

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2
Q

What is the basal body?

A

the “motor” portion of the bacterial flagellum, embedded in the cytoplasmic membrane and wall.

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3
Q

What is the calvin cycle?

A

It is a series of biosynthetic reactions by which the most photosynthetic organisms convert CO2 to organic compounds.

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4
Q

What is a capsule?

A

It is a polysaccharide or protein outermost layer, usually rather slimy, present on some bacteria.

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5
Q

What is a polysaccharide?

A

A long chain of monosaccharides (sugars) linked by glycosidic bonds.

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6
Q

What is chemotaxis?

A

It is the directed movement of an organism toward (positive) or away (negative) from a chemical gradient.

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7
Q

What is a chloroplast?

A

It is the photosynthetic organelle of phototrophic eukaryotes. It absorb sunlight and use it in conjunction with water and carbon dioxide gas to produce food for the plant.

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8
Q

What is a cristae?

A

It is the internal membrane of a mitochondrion.

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9
Q

What is the cytoplasmic membrane? Why is it important?

A

It is the permeable barrier of the cell, separating the cytoplasm from the environment. If it is compromised, the integrity of the cell is destroyed, the cytoplasm will leak into the environment, and the cell dies. It is weak in structure and is selectively permeable.

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10
Q

What is the cytoskeleton?

A

The cellular scaffolding typical of eukaryotic cells in which microtubules, microfilaments, and intermediate filaments define the cell’s shape.

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11
Q

What is dipicolinic acid?

A

A substance unique to endospores that confers heat resistance on these structures.

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12
Q

What is an endospore?

A

A highly heat-resistant, thick-walled, differentiated structure produced by certain gram-positive Bacteria.

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13
Q

What is a endosymbiotic hypothesis?

A

The idea that mitochondria and chloroplasts originated from Bacteria.

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14
Q

What is a flagellum?

A

A long, thin cellular appendage that rotates (in prokaryotic cells) and is responsible for swimming motility.

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15
Q

What are gas vesicles?

A

They are gas-filled cytoplasmic structures bounded by protein and conferring buoyancy on cells.

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16
Q

What does it mean to be Gram-negative?

A

A bacterial cell with a cell wall containing small amounts of peptidoglycan and an outer membrane containing lipopysaccharide, lipoprotein, and other complex macromolecules.

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17
Q

What is a macromolecule?

A

A large molecule (polymer) formed by the connection of a number of small molecules (monomers); proteins, nucleic acids, lipids, and polysaccharides in a cell.

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18
Q

What is a Gram stain?

A

The most common staining procedure often done to begin characterization of newly isolated bacterium. A differential staining procedure that stains cells either purple (positive) or pink (negative). These color differences arise because of differences in the cell wall structure of gram-positive and gram-negative cells.

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19
Q

What is group translocation?

A

An energy-dependent transport system in which the substance transported is chemically modified during the process of being transported by a series of proteins.

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20
Q

What are histones?

A

Highly basic proteins that compact and wind DNA in the nucleus of eukaryotic cells.

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21
Q

What is a hydrogenosome?

A

An organelle of endosymbiotic origin present in certain microbial eukaryotes that oxidizes pyruvate to H2, CO2, acetate, and couples this to ATP synthesis.

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22
Q

What is an intermediate filament?

A

A filamentous polymer of fibrous keratin proteins, supercoiled into thicker fibers, that functions in maintaining cell shape and positioning of certain organelles in the eukaryotic cell.

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23
Q

What is a lipopolysaccharide, or LPS?

A

A combination of lipid with polysaccharide and protein that forms the major portion of the outer membrane in gram-negative Bacteria.

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24
Q

What is a lysosome?

A

An organelle containing digestive enzymes for hydrolysis of proteins, fats, and polysaccharides.

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25
Q

What is a magnetosome?

A

A particle of magnetite?= (Fe3O4) enclosed by a nonunit membrane in the cytoplasm of magetotactice Bacteria.

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26
Q

What is meiosis?

A

The nuclear division that halves the diploid number of chromosomes to the haploid.

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27
Q

What is a microfilament?

A

A filamentous polymer of the protein actin that helps maintain the shape of a eukaryotic cell.

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28
Q

What is a microtubule?

A

A filamentous polymer of the proteins a-tubulin and B-tubulin that functions in eukaryotic cell shape and motility.

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29
Q

What are mitochondrion?

A

The respiratory organelle of eukaryotic organisms.

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30
Q

What is mitosis?

A

Nuclear division in eukaryotic cells in which chromosomes are replicated and partitioned into two daughter cells during cell division.

31
Q

What is morphology?

A

The shape of a cell - rod, coccus, spirillum, and so on.

32
Q

What is a nucleus?

A

The organelle that contains the eukaryotic cell’s chromosomes.

33
Q

What is the outer membrane?

A

It is a phospholipid - and polysaccharide - containing unit membrane that lies external to the peptidoglycan layer in cells of gram-negative Bacteria.

34
Q

What is peptidoglycan?

A

A polysaccharide composed of alternating repeats of N-acetylmuramic acid arranged in adjacent layers and cross-linked by short peptides.

35
Q

What is periplasm?

A

A gel-like region between the outer surface of the cytoplasmic membrane and the inner surface of the lipopolysaccharide layer of the gram-negative Bacteria

36
Q

What does it mean to have peritrichous flagellation?

A

That is has flagella located in many places around the surface of the cell.

37
Q

What is phototaxis?

A

Movement of an organism toward light.

38
Q

What are pili?

A

Thin, filamentous structures that extend from the surface of a cell and, depending on the type, facilitate cell attachment, genetic exchange, or twitching motility.

39
Q

What is polar flagellation?

A

Having flagella emanating from one or both poles of the cell.

40
Q

What is Poly-B-hydroxybutyric acid, or PHB?

A

A common storage material of prokaryotic cells consisting of a polymer of B-hydroxybutyrate or another B-alkanoic acid or mixtures of B-alkanoic acids.

41
Q

What is resolution in terms of a microscope?

A

The ability to distinguish two objects as distinct and separate when viewed under a microscope. It is a function of the wavelength of light used and a characteristic of the objective lens known as its numerical aperture.

42
Q

What is the S-layer?

A

An outermost cell surface layer composed of protein or glycoprotein present on some Bacteria and Archea.

43
Q

What is the simple transport system?

A

A transporter that consists of only a membrane-spanning protein and is typically driven by energy from the proton motive force.

44
Q

What is a stroma?

A

The lumen of the chloroplast, surrounded by the inner membrane.

45
Q

What is teichoic acid?

A

A phosphorylated polyalcohol found in the cell-wall of some gram-positive Bacteria.

46
Q

What is a thylakoid?

A

A membrane layer containing the photosynthetic pigments in chloroplasts.

47
Q

What is the difference between magnification and resolution? Can either increase without the other? Section 2.1

A

Magnification is practically limitless in terms of increasing our ability to see small objects. , However, it is the resolution that actually governs our capacity to see the very small because it is a function of the physical properties of light.

48
Q

What is the function of staining in light microscopy? What is the advantage of phase-contrast microscopy over bright-field microscopy? What is the advantage of DIC microscopy over brightfield microscopy? Section 2.2 and 2.3

A

Staining allows the contrast of cells to increase so the specific cellular materials are more visible under a microscope. The problem with staining is that it kills cells and can distort cell features. Phase-contrast microscopy does not do these things. Instead it uses optics, phase shifting the light so that the amplitude and phase change, enabling certain colors to be visible. This happens because cells have different refractive indexes. In DIC microscopy, these refractive indexes allow for internal cell structures to be visualized without staining. This would be nearly impossible in bright-field.

49
Q

What is the major advantage of electron microscopes over light microscopes? What type of electron microscope would be used to view the three dimensional features of a cell? Section 2.4

A

Electron microscopes allow for the structures of a cell to be visible at a molecular level because electrons have much shorter wavelengths than light. To view a cell three dimensionally, a scanning electron microscope (SEM) would be used.

50
Q

What are the major morphologies of prokaryotes? Describe each. Draw cells for each morphology you list. Section 2.5

A

Coccus (cocci)- a cell that is spherical or ovoid in morphology.

Rod/Bacillus- a cylindrically shaped cell

Spirilla- rods that form spiral shapes.

51
Q

What is the magnification of a compound light microscope based upon?

A

It is the product of the magnification of the objective and ocular lenses.

52
Q

What is the upper limit for light microscopes? What happens at magnifications above this limit?

A

2000X. The resolution will not improve above this limit.

53
Q

What is numerical aperture?

A

The measure of light-gathering ability.

54
Q

What is the correlation between numerical aperture and magnification?

A

Lenses with higher magnification typically have higher number apertures.

55
Q

What is the best color of light to use and why.

A

Blue light. Resolution is highest when blue light is used to illuminate a specimen (blue light has shorter wavelengths than white or red light) and the objective has a very high numerical aperture.

56
Q

When is oil-immersion used? What does it enable?

A

Oil-immersion lenses are used when the objective is 100X. It increases the light-gathering ability of a lens by allowing the light rays emerging from the specimen at angles (that would otherwise be lost by an objective lens to be collected and viewed.

57
Q

What are common positively charged, basic dyes? Why are they useful?

A

Methylene Blue
Crystal Violet
Safranin

These positive, basic dyes bind strongly to negatively charged cell components, such as nucleic acids and acidic polysaccharides. They also combine with high affinity to the surfaces of cells.

58
Q

What is a differential stain?

A

Stains that render different types of cells different colors.

59
Q

What is a confocal scanning laser microscope (CSLM)? Why is it unique? Can they be stained?

A

It is a computer-controlled microscope that couples a laser to a fluorescent microscope. The laser generates a bright three-dimensional image and allows the viewer to access several planes of focus in the specimen. The laser acts so that only one layer within a specimen is in perfect focus at a time. This eliminates stray light from other focal planes. Specimens observed with this microscope can be stained with fluorescent dyes or with false color so that different layers will have different colors.

60
Q

What is a confocal scanning laser microscope (CSLM)? Why is it unique? Can they be stained?

A

It is a computer-controlled microscope that couples a laser to a fluorescent microscope. The laser generates a bright three-dimensional image and allows the viewer to access several planes of focus in the specimen. The laser acts so that only one layer within a specimen is in perfect focus at a time. This eliminates stray light from other focal planes. Specimens observed with this microscope can be stained with fluorescent dyes or with false color so that different layers will have different colors.

61
Q

Why is CSLM widely used?

A

It is good for identifying specific populations of cells in a microbial habitat or for resolving the different components of a structured microbial mat. It is particularly useful anywhere thick specimens need to be examined for their microbial content with depth.

62
Q

Describe an electron microscope.

A

It uses electrons instead of visible light (photons) to image cells and cell structures. In this microscope, electromagnets function as lenses, and the whole system operates in a vacuum. They are also fitted with cameras to allow a photograph, called an electron micrograph.

63
Q

Why is the resolving power of TEM much greater than that of a light microscope?

A

The wavelength of electrons is much shorter than light. The smaller the wavelength, the greater the resolution , allowing one to observe cell structures at a molecular level with a TEM microscope.

64
Q

Why is the resolving power of TEM much greater than that of a light microscope? What is the problem with electron microscopy?

A

The wavelength of electrons is much shorter than light. The smaller the wavelength, the greater the resolution , allowing one to observe cell structures at a molecular level with a TEM microscope. Even so, electrons are poor at penetrating therefore in order to view the internal structure of a cell you would need very thin slices which would then be examined individually.

65
Q

Compare and contrast the two types of electron microscopy, transmission and scanning.

A

Transmission and scanning both produce images black and white in color.

66
Q

Why is the resolving power of TEM much greater than that of a light microscope? What is the problem with electron microscopy?

A

The wavelength of electrons is much shorter than light. The smaller the wavelength, the greater the resolution , allowing one to observe cell structures at a molecular level with a TEM microscope. Even so, electrons are poor at penetrating therefore in order to view the internal structure of a cell you would need very thin slices which would then be examined individually. These slices needed to be treated with stains to improve contrast.

67
Q

What improves contrast in TEM?

A

Treating an organism with negative stains such as osmic acid, or permanganate, uranium, lanthanum, or lead salts. These substances have atoms with a high atomic weight enabling the electrons to scatter, improving contrast.

68
Q

Compare and contrast the two types of electron microscopy, transmission and scanning.

A

Transmission and scanning both produce images black and white in color. The electron gun and lenses are similar to those of a transmission electron microscope. The most important differences between a transmission electron microscope and a scanning electron microscope are:

Rather than the broad static beam used in TEM, the SEM beam is focused to a fine point and scans line by line over the sample surface in a rectangular raster pattern.
The accelerating voltages are much lower than in TEM because it is no longer necessary to penetrate the specimen; in a SEM they range from 50 to 30,000 volts.
The specimen need not be thin, greatly simplifying specimen preparation.
The interactions between the beam electrons and sample atoms are similar to those described for a transmission electron microscope:

The specimen itself emits secondary electrons.
Some of the primary electrons are reflected backscattered electrons (BSE). These backscattered electrons can also cause the emission of secondary electrons as they travel through the sample and exit the sample surface.
If the sample is thin, the SEM may be operated in STEM mode with a detector located below the sample to collect transmitted electrons.

69
Q

What are some unusual bacterial groups?

A

Spirochetes - tightly coiled bacteria

Budding and Appendaged Bacteria- bacteria that possess extensions of their cells as long tubes (Hypha) or stalks.

Filamentous Bacteria- bacteria with long, thin cells or chains of cells.

70
Q

What is the problem with using cell morphology as a predictor for other properties of a cell?

A

The morphology can be similar, but can be of different phylogenetic domains such as rod-shaped Archaea and rod-shaped Bacteria.

71
Q

What is the largest known prokaryote?

A

Sulfer chemolithotroph Thiomargarita 750 micrometer In diameter

It is barely visible to the human eye.

72
Q

How large can a prokaryote be? How small? Why is it that we likely know the lower limit more accurately than the upper limit? What are the dimensions of the rod-shaped bacterium Escherichia coli? Section 2.6

A

Prokaryotes can be a variety of sizes from 0.2 um to >700um in diameter. The rod shaped bacterium E-coli is 1x2um. The lower limit is much more easily determined because the components of a free living cell have to have so much room to compensate for their size. Anything lower than 0.1um in diameter could not be a bacterium because of this.

73
Q

What does the upper limit of prokaryotic cells result from?

A

It results from the decreasing ability of larger and larger cells to transport nutrients (their surface-to-volume ratio is very small). Since the metabolic weight of a cell varies inversely with the square of its size, for very large cells, nutrient uptake would eventually limit metabolism to the point that the cell would no longer be competitive with smaller cells. Vary large cells are uncommon.

74
Q

Describe in a single sentence the structure of a unit membrane. Section 2.7

A

It is the formation of the phospholipid bilayer with integrated proteins throughout.

Intro to Microbiology Biol 357 (6 decks)

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