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Microbiology > Bacterial Cell Structure > Flashcards

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
Q

Outer membrane structure in Gram negative bacteria

A

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
Q

Functions of cell wall

A
  • 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
Q

Cytoplasmic membrane structure

A

It is a semi-permeable thin membrane formed of a phospholipid bilayer

28
Q

Functions of cell membrane

A
  • Active transport of molecules into the cell by permease enzymes
  • Energy generation by oxidative phosphorylation
  • Synthesis of precursors of the cell wall
29
Q

Mesosome structure

A

It is an invagination of the cytoplasmic membrane

30
Q

Mesosome functions

A

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
Q

Ribosomes functions

A

They are sites of protein synthesis

32
Q

Ribosomes size and structure

A

They are sperical particles in the cytoplasm

Bacterial ribosomes are 70s in size formed of 2 subunits 30s and 50s

33
Q

How antibiotics work on ribosomes

A

Due to their 70s ribosomes while humans have 80s ribosomes so several antibiotics inhibit bacterial protein synthesis but not human protein synthesis.

34
Q

Intracytoplasmic inclusions description

A

The cytoplasm may contain granules which represent accumilation of food or energy reserve

35
Q

Intracytoplasmic inclusions example

A

The volutin granules rish in metaphosphate found in genus Corynebacterium

36
Q

Plasmids types

A
  • Transmissible plasmids

- Non-transmissible plasmids

37
Q

What are Plasmids?

A

Plasmids are extrachromosomal, double-stranded, circular DNA molecules that are capable of replicating independently of the bacterial chromosome

38
Q

Trasmissible plasmids

A
  • 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
Q

Non-transmissible plasmids

A
  • Does not contain transfer genes
  • Are small in molecular weight
  • many (10-60) cpoies per cell
40
Q

Capsule description

A

It is agelatinous layer covering the entrie of some bacteria
It is mostly composed of polysaccharides
It is present in vivo

41
Q

Capsule composition examples

A

Most bacterial capsules are made of polysaccharides except:

  • Streptococcus pyogenes is made of hyaluronic acid
  • Bacillus anthracis is made of polypeptide capsule
42
Q

Function of capsule

A
  • 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
Q

Flagella description

A

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
Q

Flagella are formed of protein subunits called ……. which is ……

A

FLAGELLIN

ANTIGENIC

Microbiology (3 decks)

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