Module 3: Physical and Chemical Structure of Microbial Cells

Question 1

True or False

It was probably thought that bacteria were essentially “bags of enzymes”
with no inherent cellular architecture.

Answer 1

True

Question 2

True or False

Prokaryotes are cells with relatively simple structure when compared to eukaryotes. Eukaryotic cells reportedly have a preponderance of
organelles with separate cellular functions while prokaryotes carry out all cellular functions as individual units.

Answer 2

True

Question 3

It contains a well-developed cell structure that is responsible for some unique biological processes to happen in the cell.

Answer 3

Bacterium

Question 4

True or False

There are three (3) recognized structural regions of bacteria. These include (from without inward) appendages in the form of flagella and pili (or fimbriae); a cell envelope consisting of the capsule, cell wall and plasma membrane; and a cytoplasmic region that contains the cell chromosome (DNA) and ribosomes and various sorts of inclusions.

Answer 4

True

Question 5

It is also called “attachment pili” are protein tubes that extend out from the outer membrane bacteria. These are numerous, shorter, thinner and straighter hairy appendages which are scattered in the entire bacterial cell surface.

Answer 5

Fimbrae

Question 6

Similar to fimbriae in structure but are longer and present on the bacterial cells in low numbers. Pili are involved in the process of bacterial
conjugation where they are called conjugation pili or “sex pili”.

Answer 6

Pili

Question 7

Whip-like structures that protrude from the bacterial cell wall and are responsible for creating definite motility in bacteria as they move toward nutrients and other attractants (chemotaxis).

Answer 7

Flagella

Question 8

Refers to the presence of a single flagellum.

Answer 8

Monotrichous

Question 9

Refers to the presence of flagella at both poles.

Answer 9

Amphitrichous

Question 10

Refers to the presence of flagella around the cell at random (Salmonella typhi).

Answer 10

Peritrichous

Question 11

Refers to the presence of a tuft or group of flagella at one pole
(Pseudomonas fluorescens).

Answer 11

Lophotrichous

Question 12

It is a mucoid gelatinous layer that covers the entire bacterium
and lies external to the cell wall. It is composed of polysaccharides and polymers composed of repeating oligosaccharide units of two to four monosaccharides. The sugar components of polysaccharides vary within the species of bacteria which
determines their serologic types.

Answer 12

Capsule

Question 13

True or False

The functions of the bacterial capsule include:

a. Virulence factor acting as antiphagocytic.

b. Protects cell wall from antibacterial action of lysozymes and bacteriophages.

c. Bacterial capsule prevents the direct access of lysosome contents with the bacterial cell and prevents bacterial killing.

d. Prevents complement-mediated bacterial cell lysis.

e. Protects of anaerobes from oxygen toxicity.

f. Facilitates bacterial attachment with the aid of glycocalyx.

g. Reservoir of some nutrients.

h. Used in serotyping (Neufeld Quellung reaction, capsular types).

Answer 13

True

Question 14

This is a structure that lies beneath the capsule and is claimed to be
responsible in giving rigidity to the cell. Bacterial cell walls are made up of peptidoglycan. In Gram-positive bacteria, the peptidoglycan cell wall is thick with a high amount of teichoic acid. Gram-negative bacteria contain peptidoglycan cell wall with high amounts of lipids and lipopolysaccharides.

Answer 14

Cell wall

Question 15

This structure acts in maintaining cell permeability and functions well as
an osmotic barrier. The cytoplasmic membrane presents an invagination known as mesosome.

Answer 15

Cytoplasmic membrane

Question 16

This is a clear, thick, watery substance that provides a place for cell organelles, enzymes and other parts of the cell. It allows movement of materials between the organelles that help the cell to function. It is composed of water, salt and proteins. It is enclosed by the cytoplasmic membrane and has a granular appearance due to the abundance of RNA-protein bodies known as ribosomes.

Answer 16

Cytoplasm

Question 17

It is structurally and chemically more complex than the vegetative cell. It contains more layers than vegetative cells. It is made up of dipicolinic acid, a calcium ion chelator.

Answer 17

Spore

Question 18

The bacterial DNA is not enclosed inside a membrane-bound nucleus but instead resides inside the bacterial cytoplasm. It is fibrillar and consists of a
circular double-stranded chromosome.

Answer 18

Nucleus

Question 19

True or False

All viruses contain 3 components and these include: 1) a nucleic acid
genome (core); 2) the protein capsid that covers the genome. These 2 structures sometimes come together and this is referred to as the nucleocapsid. Many animal viruses contain the third structure called the (3) lipid envelope which is a membrane that surrounds some viral particles.

Answer 19

True

Question 20

A protective shell which is made up of many identical protein subunits (capsomeres) that are organized symmetrically. It is made up of repeating structural subunits of a single polypeptide that are arranged in one of two symmetrical structures, a helix or an icosahedron.

Answer 20

Capsid

Question 21

It is the living substance within the cell wall. This lacks chloroplasts and is different from the other usual cell parts (such as plasma or cell membrane, vacuolated cytoplasm, cell organelles and one or more nuclei).

Answer 21

Protoplast

Question 22

This is a delicate, extremely thin, living membrane which closely holds the protoplast. The cell membrane is pressed against the cell wall except for occasional invaginations in some regions. There can be invagination in the form of an in-folded convoluted pocket or a pouch enclosing granular or vesicular material. The cell membrane of fungi is the surface layer of the protoplast altered to perform special functions. It is differentially permeable and shows a typical tripartite structure under the electron microscope.

Answer 22

Cell membrane

Question 23

Composed of water, salt and proteins. In young hyphae and hyphal tips, the cytoplasm appears uniform and homogeneous. It provides a storage place for organelles, enzymes and other cell
parts. It gives the fungal cells their shape and allows easy movement of material between the organelles that help the cell to function.

Answer 23

Cytoplasm

Question 24

Consists of three flattened sacs surrounded by many bubble-like structures in fungi (Saccharomyces cells).

Answer 24

Golgi apparatus

Question 25

True or False

Among the cell organelles include the endoplasmic reticulum,
mitochondria, ribosomes, Golgi apparatus and vacuoles. Lomasomes which are membranous structures lying between the cell wall and plasma membrane are common.

Answer 25

True

Question 26

Composed of Chitin, glucan, and mannose.

Answer 26

Cell wall

Question 27

Contains proteins and lipids.

Answer 27

Plasma membrane

Question 28

True or False

Many pathogens which cause pneumonia and meningitis like Streptococcus
pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Klebsiella
pneumoniae, Escherichia coli and group B streptococci have polysaccharide
capsules on their surface. The capsule of Bacillus anthracis is composed of polymerized D-glutamic acid.

Answer 28

True

Question 29

True or False

The peptidoglycan (also known as murein) is made up of insoluble, porous crosslinking polymers of enormous strength and rigidity thus it is considered as the shape-determining component of bacteria. The peptidoglycan is composed of N-acetyl glucosamine, N-acetyl muramic acid, L-alanine, D-alanine, D-glutamate and diamino acid (meso-diaminopimelic acid, L-lysine, L-ornithine or L-diamoni
butyric acid.)

Answer 29

True