BIOL306 Ex 4 Part B & C: Simple Stain and Microscopy Measurements

flashcards covering the key concepts and procedural steps from BIOL306 Ex 4 Part B and Part C, including simple staining, staining procedure, and measuring microbial dimensions with ocular micrometry.

What is a simple stain and which dyes are commonly used?

A simple stain uses a single positively charged dye to color the cells; common dyes include methylene blue, crystal violet, and safranin.

Why do bacterial cells stain with a simple stain?

Because bacterial cell walls are negatively charged, allowing the positively charged dye to attach to the cell membrane.

In Exercise 4 Part B, what organism is smeared on the slide and how is the smear prepared?

Yeast culture in broth; smear the suspension on the slide without adding water.

What is the heat fixation step and why is it performed?

Pass the slide through a Bunsen burner flame two or three times to fix the cells; excessive heat distorts cells.

After heat fixing, which dye is used for staining and for how long?

Methylene blue; stain for one minute.

What is the washing step after staining?

Wash with a gentle stream of water, drain, then blot the slide with a paper towel.

What should you do after staining the yeast to prepare for viewing?

Examine the slide using high dry or oil immersion; use the ocular micrometer to measure cells.

In Part C, what shapes are observed on prepared slides and what dimensions are measured?

Rods and cocci; measure diameter for cocci; measure width and length for rods.

Which objective should be used when measuring bacteria?

Oil immersion objective.

How do you measure width and length of rods with the ocular micrometer?

Align the ocular micrometer ruler to determine both the width and the length of the rod.

Where should the measured dimensions be recorded?

In the results section.

What should be done to prepared slides after measurement?

Wash the prepared slides with lens cleaner.

What is a common property of the dyes used in simple staining?

They are all positively charged.

Why are dyes attracted to bacterial cells during simple staining?

Because bacterial cell walls carry a negative charge.