Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
20 Cards in this Set
- Front
- Back
|
What are the four steps of thr Gram- stain procedure?
|
1. Pour on crystal violet stain(blue dye) and wait 60 seconds.
2. Wash off with water and flood with iodine solution; wait 60 sec. 3. Wash off with water and then decolorize with 95% alcohol. 4 Finally counterstain with safranin(red dye) wait 30 sec and wash off with water. |
|
|
How do bacteria absorb these stains?
|
The different stains are the result of differences in the cell walls of gram+ and gram- bacteria. Both organisms have more than 1 layer protecting their cytoplasm and nucleus, unlike animal cells, which have only a single cytoplasmic membrane composed of a phospholipid bilayer. the layer just outside the bacterial cytoplasmic membrane is the peptidoglcan layer or cell wall.
|
|
|
What is the peptidoglycan layer?
|
it is also called a cell wall, and is composed of repeating disaccharides with 4 amino acids in a side chain extending from each disaccharide.
|
|
|
What makes up the cross linked structure of the peptidoglycan layer?
|
The AA chains of the peptidoglycan covalently bind to other AA from neighboring chains.
|
|
|
What is the enzyme that catalyzes the formation of this linkage?
|
Transpeptidase, and it is located in the inner cytoplasmic membrane. Penicillin binds to and inhibits this enzyme. This enzyme is also called penicillin binding protein.
|
|
|
What is the difference between the G+ and G- wall?
|
The G+ cell wall is very thick and has extensive cross-linking of the AA side chains. The G- wall is relatively thin.
|
|
|
What makes up the G+ cell wall?
|
The G+ cell envelope has an outer cell wall composed of complex cross linked peptidoglycan, teichoic acid and polysaccharides as well as other proteins. The bacterial cytoplasmic membrane has no cholesterol or other sterols, unlike that of animal cells.
|
|
|
What are the four steps of thr Gram- stain procedure?
|
1. Pour on crystal violet stain(blue dye) and wait 60 seconds.
2. Wash off with water and flood with iodine solution; wait 60 sec. 3. Wash off with water and then decolorize with 95% alcohol. 4 Finally counterstain with safranin(red dye) wait 30 sec and wash off with water. |
|
|
What makes up the G- cell envelope?
|
It has 3 layers not including the periplasmic space. Like G+ bacteria, it has 1. cytoplasmic membrane surrounded by, 2. a peptidoglycan layer, 3. unique outer cell membrane. Gram neg bacteria have a periplasmic space between the cytoplasmic membrane and an extremely thin peptidoglycan layer.The thin peptidoglycan layer does not contain teichoic acid, though it does have a small helical lipoprotein called murein lipoprotein. This last membrane is similar to other cell membrane in that it is composed of two layers of phospholipid(bilayer) with hydrophobic tails. What makes it unique is that the outermost portion of the bilayer contains lipopolysaccharide(LPS).
|
|
|
How do bacteria absorb these stains?
|
The different stains are the result of differences in the cell walls of gram+ and gram- bacteria. Both organisms have more than 1 layer protecting their cytoplasm and nucleus, unlike animal cells, which have only a single cytoplasmic membrane composed of a phospholipid bilayer. the layer just outside the bacterial cytoplasmic membrane is the peptidoglcan layer or cell wall.
|
|
|
LPS is composed of three covalently linked components. What are they?
|
O antigen/ core polysaccharide/Lipid A.
|
|
|
What is the peptidoglycan layer?
|
it is also called a cell wall, and is composed of repeating disaccharides with 4 amino acids in a side chain extending from each disaccharide.
|
|
|
What is Lipid A?
|
Interior to the core polysaccharide is Lipid A, which is a disaccharide with multiple fatty acid tails. Lipid a is toxic to humans, and is the G- endotoxin.
|
|
|
What makes up the cross linked structure of the peptidoglycan layer?
|
The AA chains of the peptidoglcan covalently bind to other AA from neighboring chains.
|
|
|
What is the enzyme that catalyzes the formation of this linkage?
|
Transpeptidase, and it is located in the inner cytoplasmic membrane. penicillin binds to and inhibits this enzyme. This enzyme is also called penicillin binding protein.
|
|
|
What is the difference between the G+ and G- wall?
|
The G+ cell wall is very thick and has extensive cross-linking of the AA side chains. The G- wall is relatively thin.
|
|
|
What makes up the G+ cell wall?
|
The G+ cell envelope has an outer cell wall composed of complex cross linked peptidoglycan, teichoic acid and polysaccharides as well as other proteins. The bacterial cytoplasmic membrane has no cholesterol or other sterols, unlike that of animal cells.
|
|
|
What makes up the G- cell envelope?
|
It has 3 layers not including the periplasmic space. Like G+ bacteria, it has 1. cytoplasmic membrane surrounded by, 2. a peptidoglycan layer, 3. unique outer cell membrane. Gram neg bacteria have a periplasmic space between the cytoplasmic membrane and an extremely thin peptidoglycan layer.The thin peptidoglycan layer does not contain teichoic acid, though it does have a small helical lipoprotein called murein lipoprotein. This last membrane is similar to other cell membrane in that it is composed of two layers of phospholipid(bilayer) with hydrophobic tails. What makes it unique is that the outermost portion of the bilayer contains lipopolysaccharide(LPS).
|
|
|
LPS is composed of three covalently linked components. What are they?
|
O antigen/ Core polysaccharide/Lipid A.
|
|
|
What is Lipid A?
|
Interior to the core polysaccharide is Lipid A, which is a disaccharide with multiple fatty acid tails. Lipid A is toxic to humans, and is the G- endotoxin.
|
