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Microbio > Lecture 2/3 > Flashcards

Lecture 2/3 Flashcards

1
Q

What are the primary features of prokaryotes?

A

-Smaller in size than eukaryotes
-Have 1 chromosome
-No nucleus
-No membrane-bound organelles
-Reproduce by binary fission

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2
Q

What were the first prokaryotic bacteria seen by the naked eye?

A

Thiomargarita Namibiensis (0.75mm) and was discovered in 1999

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3
Q

What prokaryotic cell was discovered in June of 2022?

A

Thiamargarita Magnific

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4
Q

__ is where the DNA of bacteria is packaged without being surrounded by a membrane

A

The nucleoid

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5
Q

The DNA is stabilized in the nucleoid by:

A

-The neutralization of the negative charge of the DNA by small polyamines and Mg 2+ ions
-Histone-like proteins

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6
Q

Prokaryotic cells are surrounded by complex envelope layers, which function as:

A

-Protection (from hostile environments such as osmolarity and harsh chemicals and antibiotics)
-Pathogenicity (contributes to the invasiveness of pathogenic bacteria)

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7
Q

What are the 3 layers of the prokaryotic cell envelope?

A
  1. The cell membrane- plasma or cytoplasmic membrane
    2.The cell wall - Gram + and Gram -
  2. The capsule - encapsulated and encapsulated bacteria
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8
Q

The cell membrane is based on the ___________ and is composed of ____ and ____

A

fluid mosaic model, phospholipids bilayer, proteins

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9
Q

____ are lipid molecules that play a role in the fluidity of the membrane

A

Hopanoids

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10
Q

What are the 5 functions of the cell membrane?

A
  1. Permeability and transport
  2. Electron transport and oxidative phosphorylation
  3. Excretion of hydrolytic exoenzymes and pathogenicity proteins
  4. Biosynthetic functions
  5. Chemotactic systems
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11
Q

What are the 4 types of permeability and transport?

A

GAPS
1. Group translocation = need energy to phosphorylate the molecule during the transport process and then use it in the metabolism. Used to uptake sugars
2. Active transport = need energy and transport proteins (from low to high concentration of solutes)
3. Passive transport = relies on diffusion. Simple diffusion (no energy, no protein) and facilitated diffusion (need channel proteins) ex. transport of O2, CO2, H2O
4. Special transport processes = using specialized molecules such as siderophores to transport ions which is locked up in nature as Fe(OH)3 and insoluble and unavailable for transport

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12
Q

How does electron transport and oxidative phosphorylation in the cell membrane occur?

A

Analog function to the mitochondria function in eukaryotes.
The cytochrome and other enzymes and components of the respiratory chain, are located in the cell membrane.

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13
Q

How does excretion of hydrolytic exoenzymes and pathogenicity proteins occur in the cell membrane?

A

6 pathways of protein secretion have been described in bacteria, the type I-VI secretion systems.
Used to secrete hydrolytic enzymes and pathogenicity toxins and other proteins

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14
Q

How do biosynthetic functions work in the cell membrane?

A

The cell membrane is the site of the enzymes and phospholipid and cell wall biosynthesis.

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15
Q

How does the chemotactic system work in the cell membrane?

A

The cell membrane has specific receptors that can bind to different kinds of attractants and repellents

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16
Q

Why is the cell wall important?

A

-Gives the cell shape
- Protects the cell from osmotic lysis
- have components that contribute to the bacteria pathogenicity
-It is the site of action of several antibiotics

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17
Q

What two groups can a bacteria species be divided into based on their cell wall?

A

Gram-positive and gram-negative

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18
Q

What layer of the cell wall is primarily responsible for the strength of the cell wall

A

Peptidoglycan layer (murein)

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19
Q

The peptidoglycan layer (murein) is composed of 3 parts:

A
  1. A backbone, composed of alternating sugar derivatives NAG and NAM
  2. A set of identical tetrapeptide side chains attached to NAM. Most have L-alanine, D-glutamate (DAP or L-lysine), and D-alanine
  3. Peptide cross-links or interbridges
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20
Q

What are the special components of Gram-positive cell walls:

A
  1. Teichoic acids - Wall teichoic acids (WTA) and Lipoteichoic acid (LTA)
  2. Polysaccharides
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21
Q

Teichoic acids:

A

Teichoic acids are partially responsible for the negative charge of the cell.
The peptidoglycan and teichoic acids together participate in the elasticity, porosity, and tensile strength of the envelope.

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22
Q

Polysaccharides in the cell wall:

A

in some species, sugars, such as mannose, arabinose, and glucuronic acid exist as subunits of polysaccharide in the cell wall

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23
Q

What are the special components of gram-negative cell walls:

A
  1. Outer membrane
  2. Lipopolysaccharide
  3. Porin channels
  4. Lipoprotein
  5. The periplasmic space
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24
Q

The outer layer of the gram-negative cell wall:

A

Is a bilayer structure, the outer leaflet contains LPS
It has channel proteins (porins)

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25
Q

Lipopolysaccharide in gram-negative cell wall:

A

Consists of glycolipids (lipid A) and polysaccharides and it prevents the diffusion of hydrophobic materials (toxic compounds) through the outer membrane.
Polysaccharide part consists of the core + side antigen (O antigen)
O antigen is highly variable (ex in salmonella)
In some bacteria lipid A acts as endotoxin

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26
Q

Porin channels in gram-negative cell wall:

A

Permit the passive diffusion of low molecular weight hydrophilic compounds, such as sugars, amino acids, and certain ions
Large antibiotic molecules (such as Beta lactams) have very low permeability -> Gram-negative bacteria have resistance to some antibiotics

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27
Q

Lipoprotein in the cell wall:

A

crosslink the outer membrane and peptidoglycan layers
-to stabilize and anchor the outer membrane layer
-it is the most abundant protein of Gram-negative cells

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28
Q

The periplasmic space in the cell wall:

A

is the space between the inner and outer membranes and peptidoglycan layers.
- the periplasmic space is approximately 20-40% of the cell volume
-it contains the peptidoglycan layer and a gel-like solution of proteins (binding proteins, hydrolytic enzymes, and detoxifying enzymes)

29
Q

Some bacteria such as Mycobacteria Tuberculosis have cell walls that contain large amounts of waxes, called :

A

mycolic acids

30
Q

Can the acid-fast bacteria cell wall be stained with gram stains?

A

No

31
Q

What is the acid-fast bacteria cell wall stained with?

A

acid-fast stain protocol

32
Q

Is the permeability of the acid-fast bacteria cell wall higher or lower than for E.Coli

A

Lower

33
Q

The low permeability of the acid-fast bacteria cell wall render these bacteria resistant to:

A

antibiotics, and many harsh chemicals, including detergents, and strong acids

34
Q

The Mycoplasmas are:

A

cell wall-lacking bacteria containing no peptidoglycans

35
Q

Mycoplasmas are resistant to:

A

cell walls-inhibiting antibiotics (ex penicillins and cephalosporins)

36
Q

What are 3 enzymes that attack cell walls?

A

Lysozymes
Autolysis hydrolytic enzymes
Hydrolytic enzymes of higher organisms

37
Q

-Found in human secretions (tears, saliva, and nasal)
-Break down the peptidoglycan backbone
-The outer membrane of the Gram-negative cell wall prevents access to ___

A

Lysozymes

38
Q

-Secreted by the bacteria itself to catalyze the degradation and turnover of peptidoglycan, to participate in cell wall growth and cell separation
-Responsible for dissolution of dead cells

A

Autolysins hydrolytic enzymes

39
Q

Such as protozoa and the phagocytic cells of animals that degrade bacterial cell walls and digest whole bacteria

A

Hydrolytic enzymes of higher organisms

40
Q

Is an extracellular layer lying outside the cell, composed mainly of polymer of polysaccharides

A

Capsule

41
Q

The capsule contributes to the invasiveness of pathogenic bacteria by:

A

-encapsulated bacteria are protected from phagocytosis
-the glycocalyx plays a role in the adherence of bacteria to the host cells

42
Q

_______ mutans adhere tightly to the tooth surface by _____

A

Streptococcus, glycocalyx

43
Q

What are the 5 cytoplasmic structures in prokaryotic cells?

A
  1. Intracytoplasmic membrane systems
  2. Carboxysomes
  3. Gas Vesicles
  4. Inclusion bodies (storage granules)
  5. Cytoskeleton-like proteins
44
Q

What cytoplasmic structure in the prokaryotic cell has photosynthetic pigments to preform photosynthesis in phototroph bacteria? Ex: thylakoids, lamellae, or chlorosomes

A

Intracytoplasmic membrane system

45
Q

What cytoplasmic structure in prokaryotic cells are protein-covered bodies packed with the enzyme ribulose-bisphosphate carboxylase (Rubisco) for CO2 fixation in autotrophic bacteria?

A

Carboxysomes

46
Q

What cytoplasmic structure in the prokaryotic cell is found in aquatic and marine bacteria and used to provide buoyancy and keep the cell high in the water column?

A

Gas vesicles

47
Q

What are inclusion bodies used for in the prokaryotic cell?

A

they are used to store reserve materials in the form of insoluble granules:
-Poly-B-hydroxybutyric acid (PHB) granules-> used to store PHB which is a lipid like compound
-Glycogen granules -> store glycogen
-Volutin granules or metachromatic granules -> used to store inorganic phosphate
-Magnetosomes -> used to store magnetic mineral magnetite (Fe3O4) in certain species of bacteria

48
Q

What are cytoskeleton-like proteins used for in prokaryotic cells?

A

They resemble both actin and non-actin cytoskeletal proteins of eukaryotes.
They:
-determine cell shape
-segregation of chromosomes
-regulation of cell division

49
Q

What are flagella?

A

Are threadlike appendages composed entirely of proteins and are responsible for bacterial movement.
They are made up of protein subunits called flagellin

50
Q

What are the 4 different types of flagella?

A

Monotrichous - single polar flagellum
Amphitrichous - one flagellum at each pole
Lopotrichous- multiple polar flagellum
Peritrichous - flagella distributed over the entire cell

51
Q

Flagella are highly ___ and some of the immune responses are directed against these proteins

A

antigenic (H antigens)

52
Q

____ are small rigid surface appendages on a cell. They inhibit the phagocytic ability of leukocytes and play a role in bacteria motility.

A

Pili (fimbriae)

53
Q

Pili are composed of structural protein subunits called ____ and at the tips of pili are __ ____ for attachment properties

A

pilins, adhesions proteins

54
Q

What do ordinary pili do?

A

They play a role in the adherence of the bacteria to the host cells and have antigenic function

55
Q

Sex pili are responsible for

A

DNA transfer between the donor cell and the recipient cell during the conjugation process

56
Q

What are endospores?

A

Heat-resistant spores that can remain viable for thousands of years.

57
Q

The process of sporulation is triggered in:

A

hard conditions such as lack of nutrients and heat

58
Q

The endospore consists of:

A

the bacterium’s DNA, ribosomes, and large amounts of calcium dipocolinate which help the endospores maintain dormancy

59
Q

What are endospores resistant to?

A

Starvation, high temperature, extreme freezing, UV radiation, desiccation, and chemical disinfectants

60
Q

What are the two most common spore-forming bacteria?

A

Gram-positive aerobic genus Bacillus and the anaerobic genus Clostridium

61
Q

Do eukaryotic cells have a nucleus?

A

Yes

62
Q

The nucleus is surrounded by _______

A

nuclear envelope

63
Q

The nuclear envelope is composed of:

A

double lipid-bilayer membranes and has pores and exhibits selective permeability

64
Q

Eukaryotic cells contain linear ____, which appear as thread-like structures called ____

A

DNA macromolecules, chromatin

65
Q

How many subunits do ribosomes have?

A

2

66
Q

How are ribosomal subunits synthesized?

A

By combining rRNA with ribosomal proteins

67
Q

What type of ribosomes do eukaryotes have?

A

80S (60S and 40S subunits)

68
Q

What type of ribosomes do prokaryotes have?

A

70 (50S and 30 S subunits)

69
Q

What is important about 16S RNA?

A

The gene coding of 16S RNA is highly conserved between different species of bacteria and is being used in the bacterial classification and phylogenetic studies)

Microbio (7 decks)

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