lab pt 1

What are the main objective lenses on a compound light microscope?

Scanning: 4×; low power: 10×; high dry: 40×; oil immersion: 100×.

What is the magnification of the ocular lens?

10×.

How is total magnification calculated?

Ocular magnification × objective magnification.

What are the total magnifications of the four objectives?

4× = 40×; 10× = 100×; 40× = 400×; 100× = 1000×.

What is the purpose of immersion oil?

It reduces light refraction, allowing more light into the objective and improving resolution.

Why is immersion oil used with the 100× objective?

The oil immersion objective is designed to use oil for improved image clarity and resolution.

What is resolution?

The ability to distinguish two closely spaced objects as separate.

What are the functions of the microscope's focusing and lighting controls?

Coarse adjustment: general focusing; fine adjustment: sharpens focus; condenser: focuses light; iris diaphragm: controls light quantity.

What is aseptic technique?

Procedures used to prevent contamination by unwanted microorganisms.

Why is aseptic technique important?

It prevents contamination of cultures, equipment, the environment, and the person performing experiments.

Why is an inoculating loop flamed before use?

To sterilize it and kill microorganisms already present.

Why must an inoculating loop cool before touching bacteria?

To prevent killing the bacteria with the hot loop.

Why is the opening of a culture tube briefly flamed?

To reduce contamination around the opening.

Why should culture tube caps not touch the laboratory bench?

They could become contaminated.

Why should culture tubes be held at an angle and opened briefly?

To reduce the chance of airborne contaminants entering.

Why are laboratory surfaces disinfected and hands washed?

To reduce microorganisms and prevent their spread.

What are the three basic bacterial shapes?

Cocci (spherical), bacilli (rod-shaped), and spiral-shaped bacteria.

What are spirilla, spirochetes, vibrios, and coccobacilli?

Spirilla: rigid spirals; spirochetes: flexible spirals; vibrios: curved comma-shaped; coccobacilli: short oval rods.

What are diplococci, streptococci, and staphylococci?

Diplococci: pairs; streptococci: chains; staphylococci: grape-like clusters.

What are tetrads and sarcinae?

Tetrads: groups of four cocci; sarcinae: cubical packets, typically groups of eight.

What is a prokaryotic cell?

A cell without a membrane-bound nucleus or membrane-bound organelles.

What is a eukaryotic cell?

A cell with a membrane-bound nucleus and membrane-bound organelles.

Which organisms are prokaryotic and which are eukaryotic?

Prokaryotic: Bacteria and Archaea. Eukaryotic: animals, plants, fungi, and protists.

How does DNA differ between prokaryotes and eukaryotes?

Prokaryotes generally have one circular chromosome in a nucleoid; eukaryotes have multiple linear chromosomes inside a nucleus.

How do prokaryotic and eukaryotic ribosomes differ?

Prokaryotes have 70S ribosomes; eukaryotic cytoplasm has 80S ribosomes.

Which type of cell is generally smaller?

Prokaryotic cells.

What is a bacterial smear and why is it prepared?

A thin layer of bacteria on a microscope slide, prepared for staining and microscopic examination.

How do you prepare a smear from a liquid culture?

Place a loopful on a clean slide, spread thinly, air-dry, and heat-fix.

How do you prepare a smear from a solid culture?

Place a drop of water on the slide, mix in a small amount of bacteria, spread thinly, air-dry, and heat-fix.

What constitutes a good bacterial smear?

A thin, even layer of bacteria that is not overly concentrated.