L1: Structure of Bacterial Cell And Targets of Antibiotics Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What is microbiology?

A

Microbiology is the study of living organisms (‘microorganisms’ or ‘microbes’); simple in structure and usually small in size (cannot be seen with the naked eye).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does the study of microbiology include?

A

They include bacteria, fungi, protozoa, and viruses.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the importance of microbiology?

A

Microorganisms cause many diseases and some microorganisms have been used in the manufacture of antibiotics and foodstuffs.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are creatures classified into?

A
  1. Animalia (Eukaryotic): helminths
  2. Plantae (Eukaryotic)
  3. Protista (Eukaryotic): Protozoa
  4. Fungi (Eukaryotic)
  5. Monera (Prokaryotic): cellulars like bacteria and acellular like a virus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is another term for prokaryotic?

A

Pre-mature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the difference between cellular prokaryotic and eukaryotic?

A
Nuclear membrane: absent - present
Chromosomal number: haploid - diploid
Histones: absent - present
Ribosome: 70s - 80s
Peptidoglycan: present - absent
Mitochondria: absent - present
Mitosis: absent - present
Cell wall sterols: absent - present 
Membrane-bounded organelles: absent - present
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the size of bacterial cells?

A

Measured by micron (micron= 1/ 1000 mm).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the shape of bacterial cells?

A
  1. Cocci or spherical: e.g. Staphylococci.
  2. Bacilli or cylindrical: e.g. Diphtheria bacilli.
  3. Spiral:
     One curve: e.g. Vibrio.
     More than one: e.g. Spirochetes, Spirillum.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the habitat of bacterial cells?

A

a. Parasitic (need host): bacterial flora (commensally) and pathogenic bacteria.
b. Saprophytic: free-living in soil, air, and water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the structure of bacterial cells?

A
  1. Surface Structures (bacterial envelope):
    ● Cell wall.
    ● Cytoplasmic membrane.
    ● Capsule or slime layer.
  2. Internal structures:
    - Nuclear body
    - Flagellae
    - Inclusion bodies
    - Ribosomes
    - Fimbria
    - Mesosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the characters of the cell wall?

A

It is the rigid layer outside the cytoplasmic membrane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the chemical structure of the cell wall?

A

Composed of peptidoglycan.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the Differences between Gram-positive and Gram-negative cell walls?

A

Peptydoglycan:

 Thick (~ 40 sheets)
 Comprising up to 50% of the cell wall.

 Thin (One or two sheets)
 Comprising only 5–10% of the cell wall.

Special Components:

 Teichoicacid:ribitol or glycerol.
 Polysaccharides.

  • Outer membrane (thick).
     Lipoprotein.
 Lipopolysaccharide:
o Lipid A (the endotoxin).
o Polysaccharide (somatic antigen).

2- Periplasmic space
 Between cytoplasmic membrane and outer
membrane and contains hydrolytic enzymes and penicillinase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the function of the cell wall?

A

SPA GTG

  1. Preservation of the shape of the cell.
  2. Protectiveagainst high internal osmotic pressure.
  3. Antigenic character:
     In Gram-positive: Teichoic acid.
     In Gram-negative: somatic “O” antigen(Polysaccharide).
  4. Toxicity: The lipid A endotoxin of Gram-negative cell wall.
  5. Cell wall is responsible for Gram staining reaction (Gram-positive bacteria stain violet while Gram-negative bacteria stain pink)
  6. Cell wall is the target for the action of some antibiotics: penicillin and cephalosporins and vancomycin.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the enzymes that attack the cell wall?

A

The peptidoglycan is hydrolyzed by lysozyme found in tears, saliva, and nasal secretions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the characters of the cell membrane?

A

It is a very thin elastic membrane that lies immediately under the cell wall.

17
Q

What is the chemical structure of the cell membrane?

A
  • composed of biphospholipids and proteins.

- prokaryotes have no sterols in the cytoplasmic membrane except for Mycoplasma.

18
Q

What is the function of the cell membrane?

A
  1. Permeability and transport: transport nutrients into and waste products out of the cell.
  2. Electron transport and oxidative phosphorylation: for energy production (ATP).
  3. Excretion of hydrolytic enzymes.
  4. Biosynthetic function: carries enzymes and molecules for the biosynthesis of the cell wall, DNA, and membrane lipids.
  5. Chemotactic function: contain receptors of binding and repellents.
19
Q

What are the characters of the capsule?

A

-Some bacteria can produce a gelatinous layer surrounding the cell outside the cell wall.

Capsule: condensed well-fined layer closely surrounds the cell.

Glycocalyx: polysaccharide-containing material lying outside the cell.

Slim layer: if glycocalyx is loosely surrounding the cell.

20
Q

What is the chemical structure of the capsule?

A

Consists of polysaccharides, except in bacillus anthracis(protein polymers).

21
Q

What is the function of the capsule?

A
  1. Virulence factor as it protects the bacterial cell from phagocytosis.
  2. Protects the cell wall against attack by bacteriophages, complement, and lysozymes.
  3. Antigenic (K-antigen): used in serodiagnosis or vaccine preparation.
22
Q

What is the definition of flagella?

A

Long thread-like, helical filaments.

23
Q

What are the types of flagellate?

A
  1. Monotrichous (single polar flagellum).
  2. Lophotrichous (multiple polar flagellae).
  3. Amphitrichous (One flagellum in each pole of the
    cell) .
  4. Peritrichous (flagella distributed over the entire
    cell) e.g. E.coli.
24
Q

What is the structure of flagella?

A

made up of a contractile protein called flagellin.

25
Q

What are the functions of flagella?

A
  1. It is the organ of Motility:

> Movement toward the optimal nutrients.
Movement toward optimal oxygen concentration in aerobic bacteria.
Choosing the locality suitable for colonization.
Assist pathogenic bacteria in penetration through a viscid mucous secretion.

  1. Highly Antigenic (H-antigens).
26
Q

What is the color of gram stain in gram-positive and in gram-negative?

A

Positive: violet
Negative: red

27
Q

What are the smallest bacteria?

A

Serratla marcescens

28
Q

What are nuclear bodies?

A
  • No true nuclei but nucleoid
  • No nuclear membrane “prokaryotes”
  • They are made of DNA.

” There is a single chromosome that can be seen by E/M very long thin thread folded on itself

29
Q

What are pili (fimbrae)?

A

It is a short and rigid appendage formed in gram-negative bacteria

30
Q

What are pili classified into?

A

Ordinary and sex pili

31
Q

What kind of microscope is used to see pili?

A

EM

32
Q

How do pili differ from flagella?

A

-Differs from flagella in the following points:

Occur in motile as well as non-motile strains
> More numerous “100-500” per cell.
> Much shorter and thinner.
more or less straight, flagella are spiral.
> Not originated from the cytoplasm.

33
Q

What is the function of pili?

A
  1. Ordinary pili: adhesion to host cells, and to each other
    2 Sex pili: attachment of donor and recipient cells in bacterial conjugation
  2. Antigenic.
  3. Like capsule, inhibit phagocytosis.
  4. Ordinary pili are responsible for virulence (colonization Ag, surface virulent-factor