The label arrow illustrate
coarse adjustment
Fine adjustment
The Correct Answer is A
Coarse adjustment: The arrow points to the coarse adjustment knob, a large focusing knob on the microscope used to move the stage up or down quickly to bring the specimen into general focus. It is typically used with low-power objective lenses to locate the specimen and obtain an initial image. Using it with high-power lenses can risk damaging the slide or lens because it moves the stage in large increments.
Fine adjustment: A smaller focusing knob that moves the stage very slightly to sharpen the image after the specimen has been brought into general focus. It is mainly used with high-power or oil immersion objectives to achieve precise, clear visualization of cellular details without risking damage to the specimen.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. A thick peptidoglycan layer: Gram-positive bacteria have a thick peptidoglycan layer, which retains the crystal violet-iodine complex during Gram staining. Gram-negative bacteria have a much thinner peptidoglycan layer, which does not retain the stain after decolorization.
B. No cell wall: Gram-negative bacteria do have a cell wall; it is just structurally different from Gram-positive bacteria. Their wall consists of a thin peptidoglycan layer sandwiched between the inner cytoplasmic membrane and an outer membrane containing lipopolysaccharides.
C. An outer membrane containing lipopolysaccharide (LPS): Gram-negative bacteria possess an outer membrane external to the peptidoglycan layer. This outer membrane contains LPS, which contributes to the structural integrity of the cell, acts as an endotoxin, and protects against certain antibiotics and host defenses. The presence of LPS is a key distinguishing feature.
D. Teichoic acids in their cell wall: Teichoic acids are found only in the cell walls of Gram-positive bacteria. They provide structural support, contribute to cell wall maintenance, and help with adherence, but are absent in Gram-negative bacteria.
Correct Answer is A
Explanation
A Petri dish is a shallow, cylindrical, lidded container commonly used in laboratories for culturing microorganisms such as bacteria, fungi, and cells. It is typically made of clear glass or disposable sterile plastic, which allows easy observation of microbial growth. The dish consists of two parts: a flat bottom portion that holds the growth medium and a slightly larger lid that covers it to protect the culture from contamination while still allowing gas exchange. In microbiology, the bottom of the dish is usually filled with a nutrient medium such as agar that supports microbial growth. Samples are inoculated onto the agar surface and incubated under controlled temperature conditions. As microorganisms multiply
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