Lab Midterm

Different types of microscopes

• Compound light microscope

• Dissecting (stereo) microscope

• Transmission Electron Microscope (TEM)

• Scanning Electron Microscope (SEM)

Methylene blue

tains animal cells, especially the nucleus.

Lugol's iodine (iodine stain)

Stains plant cells and starch, making cell structures easier to see.

Crystal violet

Primary stain used in Gram staining of bacteria.

Safranin

Counterstain used in Gram staining; also stains some plant tissues.

How do you calculate the total magnification of a microscope?

Total Magnification = Eyepiece × Objective

Ex:10× eyepiece × 4× objective = 40× total magnification

Cell wall

plant cell: present

animal cell: absent

Chloroplasts

Plant cell: present

Animal cell: absent

Vacuole

Plant cell: One large central vacuole

Animal cell: Small vacuoles (or several small vacuoles)

Shape:

Plant cell: Rectangular or box-like

Animal cell: Round or irregular

How is membrane permeability determined?

By measuring how much material (such as pigment) leaks out of the cell. More leakage means greater membrane permeability.

Which reagent damaged the cell membrane the most in our membrane permeability lab?

Alcohol (ethanol).

Which salt was used to precipitate proteins from milk?

Ammonium sulfate.

How is protein concentration determined?

Using the Biuret assay and a BSA standard curve.

What is serial dilution?

Repeatedly diluting a solution to make a series of lower concentrations.

How does SDS-PAGE work?

Separates proteins by size.

What is the function of SDS?

Denatures proteins and gives them a uniform negative charge

What determines the rate of migration?

Protein size (molecular weight). Smaller proteins migrate faster.