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Bacterial Cell Wall and Envelopes
Study
1
Question
What are the essential components of the bacterial cell?
Answer
The essential components of the bacterial cell are the cell wall, cytoplasmic membrane, and the cytoplasm.
2
Question
What is the structure of the bacterial cell wall?
Answer
The cell wall is the outermost component in all bacteria, except mycoplasma, and is composed of a peptidoglycan layer.
3
Question
What is the function of the peptidoglycan in the cell wall?
Answer
1. It provides rigid support for the cell and is important in maintaining the characteristic shape of the cell. 2. It is a good target for antibacterial drugs such as penicillins, cephalosporins, and vancomycin because of its absence in human cells.
4
Question
What are the components of the cell wall in Gram-positive bacteria?
Answer
1. The peptidoglycan layer, which is thick and forms about 50 to 80% of the cell wall materials. 2. Fibers of teichoic acid that protrude outside the peptidoglycan and are highly immunogenic antigens.
5
Question
What are the components of the cell wall in Gram-negative bacteria?
Answer
1. The peptidoglycan layer, which is very thin and forms 5-10% of the cell wall materials, lying in the periplasmic space and maintained by lipoprotein molecules. 2. Outer membrane, which is a bilayered structure with an inner layer composed of phospholipids and an outer layer composed of lipopolysaccharides.
6
Question
What is the composition of Gram-positive bacteria cell wall?
Answer
1. The peptidoglycan layer (thick, forming about 50-80% of the cell wall materials) 2. Fibers of teichoic acid that protrude outside the peptidoglycan and are highly immunogenic antigens
7
Question
What is the composition of Gram-negative bacteria cell wall?
Answer
1. The peptidoglycan layer (very thin, forming 5-10% of the cell wall materials) 2. Outer membrane (bilayered structure with inner layer composed of phospholipid and outer layer composed of lipopolysaccharide (LPS) 3. Periplasmic space (filled with gel, lying between the outer membrane layer and the cytoplasmic membrane)
8
Question
What are the functions of the cell wall in addition to the function of peptidoglycan?
Answer
Additional functions of the cell wall include maintaining stability by lipoprotein molecules, providing structural components unique to Gram-negative outer membrane (e.g., LPS), and separating the cytoplasmic membrane from the external environment.
9
Question
What is the space lying between the outer membrane layer and the cytoplasmic membrane filled with gel?
Answer
Periplasm
10
Question
What are the functions of the cell wall in addition to the function of peptidoglycan?
Answer
1. It plays a role in cell division 2. It acts as a channel to allow the entry of essential substances, such as sugars, amino acids, vitamins, and metals, as well as many antimicrobial drugs. 3. It plays an important role in determining the reaction to Gram stain.
Bacterial Size, Shape, Arrangement, Staining Properties, and Motility
Study
1
Question
What are the two fundamentally different types of cells?
Answer
Eukaryotic and prokaryotic cells
2
Question
How can eukaryotic and prokaryotic cells be distinguished?
Answer
On the basis of their structure and complexity of organization
3
Question
What distinguishes fungi from bacteria in terms of cell type?
Answer
Fungi are eukaryotic, whereas bacteria are prokaryotic
4
Question
What are the characteristics of eukaryotic human cells and prokaryotic bacterial cells?
Answer
1. Eukaryotic human cells have a cell wall containing peptidoglycan, while prokaryotic bacterial cells have a cell wall with no peptidoglycan except Mycoplasma. 2. Eukaryotic human cells have sterol in the cytoplasmic membrane, while prokaryotic bacterial cells do not, except Mycoplasma. 3. Eukaryotic human cells have organelles such as mitochondria and lysosomes, while prokaryotic bacterial cells have no organelles. 4. Eukaryotic human cells have a nucleus, nuclear membrane, and more than one linear chromosome, while prokaryotic bacterial cells have no nucleus, nuclear membrane, and one circular chromosome. 5. Eukaryotic human cells have 80S ribosomes, while prokaryotic bacterial cells have 70S ribosomes.
5
Question
What is the nomenclature of bacteria?
Answer
The phylum of bacteria is family, genus, species, and type or strain.
6
Question
What are the morphological characters of bacteria?
Answer
The morphological characters of bacteria include size, shape, arrangement, staining properties, and motility.
7
Question
What is the size range of bacteria?
Answer
Bacteria range in size from about 0.125 to 5 micrometers.
8
Question
How are bacteria classified by shape?
Answer
Bacteria are classified by shape into three basic groups: cocci, bacilli, and spiral. Some bacteria are variable in shape (pleomorphic).
9
Question
Why is the arrangement of bacteria important?
Answer
The arrangement of bacteria is important for classification and identification.
10
Question
What is the size range of bacteria?
Answer
Bacteria range in size from about 0.125 to 5 micrometers (m).
11
Question
How are bacteria classified based on shape and arrangement?
Answer
Bacteria are classified into three basic groups: cocci, bacilli, and spiral. Some bacteria can also be pleomorphic, meaning they are variable in shape.
12
Question
What are the two groups of bacteria based on their staining properties?
Answer
According to Gram stain, bacteria are divided into two groups: Gram-positive bacteria and Gram-negative bacteria.
13
Question
What are negative bacteria?
Answer
Negative bacteria are a group of bacteria that have a cell wall composed of a thin layer of peptidoglycan surrounded by an outer membrane of lipopolysaccharides.
14
Question
Give an example of a negative bacteria.
Answer
Escherichia coli (E. coli) is an example of a negative bacteria.
15
Question
How do negative bacteria differ from positive bacteria?
Answer
Negative bacteria have a more complex cell wall structure with an outer membrane, while positive bacteria have a simpler cell wall structure without an outer membrane.
General Bacteriology
Study
1
Question
What is microbiology?
Answer
Microbiology is the science of minute organisms invisible to the naked eye, named microbes.
2
Question
What are the subdivisions of medical microbiology?
Answer
Bacteriology, Virology, and Mycology.
3
Question
What is bacteriology?
Answer
Bacteriology is the science of bacteria, the causative agents of a number of infectious diseases.
4
Question
What is virology?
Answer
Virology is the science of viruses, non-cellular living agents capable of causing infectious diseases in man.
5
Question
What is mycology?
Answer
Mycology is the study of fungi pathogenic for man.