General Biology I Lab Exam I

1,000µL to mL

1mL

1mL to µL

1000µL

Molarity

The number of moles of solute per liter of solution

Formula for grams

Grams = Moles x Liters x Molecular weight

C₁V₁ = C₂V₂

Plug in your numbers, solve for the missing variable. Add V1 of stock, then add water up to the final volume V2, so the water is V2 - V1

Procedure when using a microcentrifuge

Make sure microcentrifuge tubes are balanced, if you have an uneven number of tubes, grab a blank (a microcentrifuge tube with something like water in it with the same volume) and add it to your missing spot.

Control variable

All the variables that might influence the dependent variable (e.g. reaction time)

Dependent variable

The aspect of the system that is showing response to the independent variable

Independent variable

The factor that is being tested in the current experiment

Research hypothesis

The opposite statement, the only way it can be supported is if there is experimental evidence to reject the null hypothesis (i.e. it can be falsified). For example: “Students who are not distracted will have different reaction time from distracted students.”

Null hypothesis

A statement of no difference. For example “Distracted and non-distracted students will have the same reaction time.”

Research Hypothesis

A statement that has a difference. For example: “Students who are not distracted will have different reaction time from distracted students.”

Interpret a p-value

The p-value is the evidence against a null hypothesis. The smaller the p-value, the stronger the evidence that you should reject the null hypothesis.

If p < 0.05

Reject the null and call it a significant difference

If p > 0.05

Fail to reject the null and call it no significant difference

Identify a proper negative control for an experimental setup

Water

Test that identifies simple sugars

Benedict’s test

Test that identifies starch

Lugol’s Reagent

Test that identifies lipids

Brown Bag/Paper Towel, Sudan IV

Test that identifies proteins

Biuret Test

How does Benedict’s test work

Causes a color change based on the percentage of sugar. It needs heat and goes blue to green to yellow to orange to brick red as sugar increases (reducing sugars reduce Cu²⁺)

How does Lugol’s Reagent work

Causes a color change based on if starch is present or not (Brown/Yellow = Negative, Blue/Purple = Positive)

How does the Brown Bag/Paper Towel Test work

Shows a grease spot if lipids are present and no spot if lipids are absent

How does Sudan IV work

It’s a lipid-soluble dye and shows darker red areas where it has stained lipids, if any

How does the Biuret test work

Shows a deep purple if proteins are present and a blue color if proteins are absent. Cu²⁺ binding peptide bonds in alkaline solution.

How does size exclusion chromatography work?

Larger molecules pass through, or are “excluded”, from the beads. As the liquid flows through the column, small molecules enter the beads and pass through the column more slowly.

Order of elution from a size exclusion chromatography column

The larger molecules pass quickly through the column and are collected in the initial set of tubes, and the smaller molecules end up in the later tubes.

How do you use a standard curve to calculate the molecular weight of an unknown protein

Find the unknown’s elution volume on the curve and read off its size.

Magnification

The extent to which an image is enlarged

Resolution

The distance between two objects that can be perceived

Microscope parts from the side

Microscope parts closer up

Scanning Electron Microscopy (SEM)

Uses a beam of electrons as a source of illumination. Electrons interact with the surface of the object, producing an image with a 3-D effect. The wavelength of the electron beam creates a resolution of ~0.4nm.

Maximum magnification of Scanning Electron Microscopy

~500,000x

How are specimens prepared for scanning electron microscopy

Coated with metal and imaged by electrons bouncing off the surface.

Transmission Electron Microscopy (TEM)

Uses a beam of electrons as a source of illumination. Electrons interact with the interior of the object. The wavelength of the electron beam creates a resolution of ~0.05nm.

Maximum magnification of Transmission Electron Microscopy

~1.000.000x

How are specimens prepared for Transmission Electron Microscopy

Uses ultra thin sections with heavy-metal stain and electrons passing through

Light Microscopy

Illumination: Visible light spectrum. Resolution ~0.2 micrometers. The unaided eye can resolve objects at ~0.2mm or ~200 micrometers.

Maximum magnification for Light microscopy

~1,000x

Eosin stain

Stains positively charged components of a cell (proteins located in the cytoplasm)

Methylene blue

Stains the nucleus (DNA located in the cell nucleus)

1mm to μm

1,000μm

1,000μm to nm

1,000,000nm

How alcohol size related to membrane damage

Longer alcohol chains increase membrane permeability

Relate absorbance values to membrane damage

The higher the absorbance value, the greater the membrane damage. Higher alcohol concentration also means more damage, and damaged membranes leak the beet pigment, which is why absorbance rises.

Instrumentation used to measure membrane damage

Colorimeter: measures the amount of light absorbed by a solution.