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Bacterial Cell Structure Flashcards

1
Q

Bacteriology

A

The science of bacteria

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2
Q

Virology

A

The science of viruses (non-living agents)

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3
Q

Mycology

A

The science of pathogenic fungi

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4
Q

Immunology

A

The science which is concerne with the mechanisms of body protection against pathogenic micro-organisms and foreign cells

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5
Q

Bacteria size

A

Bacteria are very small. They are measured using micron (micrometer). Most bacteia size range from 0.2 - 7 microns

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6
Q

Bacteria classifications by shape

A 
Cocci
Bacilli
Coccobacilli
Spiral 
Some bacteria are variable in shape called Pleomorphic
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7
Q

Bacterial arrangments depends on:

A

Plane of cell division

Generation time

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8
Q

Definition of generation time

A

The between 2 successive divisions

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9
Q

Arrangement of bacteria if only 1 plane of division is …..

A

chain

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10
Q

Arrangement of bacteria if multiple plane of division is …..

A

clusters

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11
Q

Certain cocci arranged in pairs are called

A

diplococci

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12
Q

According to Gram stain, bacteria are divided into 2 groups:

A

Gram positive bacteria

Gram negative bacteria

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13
Q

Essential components of the bacterial cell

A 
Cell wall
Cytoplasmic membrane 
Cytoplasm which contains 
      - Nuclear material
      - Ribosomes
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14
Q

Non-essential components of the bacterial cell

A

Flagella
Pilli
Capsule
Spore

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15
Q

Bacterial chromosome

Description and function

A

It is a nucleoid with no nuclear membrane. It is single, circular, supercoiled, double stranded DNA
Contains essential chromosomes carrying genetic information

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16
Q

All bacteria posses cell wall except …..

A

Mycoplasma

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17
Q

Mycoplasma has ….. in its cytoplasmic membrane

A

steroids

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18
Q

Site of bacterial cell wall

A

Multilayered structure located external to the cytoplasmic membrane

19
Q

Structure of bacterial cell wall

A

It is composed of peptidoglycan layer that surrounds the entire cell.
It is formed of alternating molecules of N-acetyl glucosamine and N-acetyl muramic acid cross-linked by peptide bonds (tetrapeptide side chain)

20
Q

Functions of peptidoglycan in the cell wall of bacteria

A
  • Provides rigid support for the cell

- Good target for antibacterial drugs like penicillins, cephalosporins and vancomycin

21
Q

Bacterial cell in L-form:

A

Presence of the bacteria without the cell wall in an isotonic solution so it doesn’t die but can’t grow either. Until the environment changes, it re-forms the cell wall and grows again.

22
Q

Cell wall of Gram positive bacteria

A

Composed of:

  • Thick peptidoglycan layer forming 50%-80% (40 sheets) of the cell wall materials
  • Fibres of teichoic acid that protrude outside the peptidoglycan and is highly immunogenic
23
Q

Teichoic acid site and structure

A

Found in cell wall and it is a polymer of glycerol or ribitol phosphate

24
Q

Cell wall of Gram negative bacteria

A

It is composed of

  • Innermost peptidoglygan layer (very thin)
  • Outer membrane. It is bilayered structure composed of inner phospholipid and outer lipopolysaccharide (LPS) molecules
  • Periplasmic space It is space lying between the outer membrane layer and the cytoplasmic membrane and is filled with gel
25
Outer membrane structure in Gram negative bacteria
It is bilayered structure. The inner layer is made of phospholipids while the outer layer is made of lipopolyscaccharide (LPS) molecules LPS is unique to Gram negative bacteria in LPS, the lipid fraction is called lipid A (it is an endotoxin) and the polysaccharide is called somatic (O) antigen
26
Functions of cell wall
- It plays a role in cell division - It acts as a channel to allow entry of substances - It plays an important role in determining the reaction to Gram stain - Carry antigenic substances - Have a role in cel division - Osmotically insensitive
27
Cytoplasmic membrane structure
It is a semi-permeable thin membrane formed of a phospholipid bilayer
28
Functions of cell membrane
- Active transport of molecules into the cell by permease enzymes - Energy generation by oxidative phosphorylation - Synthesis of precursors of the cell wall
29
Mesosome structure
It is an invagination of the cytoplasmic membrane
30
Mesosome functions
It is important during cell division as it acts as: - The origin of the transverse septum - The binding site of the DNA which will become the genetic material of each daughter cell
31
Ribosomes functions
They are sites of protein synthesis
32
Ribosomes size and structure
They are sperical particles in the cytoplasm | Bacterial ribosomes are 70s in size formed of 2 subunits 30s and 50s
33
How antibiotics work on ribosomes
Due to their 70s ribosomes while humans have 80s ribosomes so several antibiotics inhibit bacterial protein synthesis but not human protein synthesis.
34
Intracytoplasmic inclusions description
The cytoplasm may contain granules which represent accumilation of food or energy reserve
35
Intracytoplasmic inclusions example
The volutin granules rish in metaphosphate found in genus Corynebacterium
36
Plasmids types
- Transmissible plasmids | - Non-transmissible plasmids
37
What are Plasmids?
Plasmids are extrachromosomal, double-stranded, circular DNA molecules that are capable of replicating independently of the bacterial chromosome
38
Trasmissible plasmids
- Can transfer from cell to cell by conjucation - Are large in molecular weight (contain about a dozen genes responsible for synthesis of sex pilus) - A few copies (1-3) per cell
39
Non-transmissible plasmids
- Does not contain transfer genes - Are small in molecular weight - many (10-60) cpoies per cell
40
Capsule description
It is agelatinous layer covering the entrie of some bacteria It is mostly composed of polysaccharides It is present in vivo
41
Capsule composition examples
Most bacterial capsules are made of polysaccharides except: - Streptococcus pyogenes is made of hyaluronic acid - Bacillus anthracis is made of polypeptide capsule
42
Function of capsule
- It is determinant of virulence of many bacteria as it limits the ability of phagocytes to engulf bateria - Identification and typing of bacteria (by anti-serum) due to specific capsular antigens - Adherence of bacteria to tissue - Capsular polysaccharides are used as the antigens in certain vaccines
43
Flagella description
They are organs of motility They are long, whip-like structure arising from the cytplasmic membrane They move the bacteria towards nutriens in a process called chemotaxis
44
Flagella are formed of protein subunits called ....... which is ......
FLAGELLIN | ANTIGENIC

Microbiology (3 decks)

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