lab practical review Flashcards
1
Q
gram stain procedure
A
- crystal violet penetrates cell wall and plasma membrane of both types of cells
- Gram’s iodine binds to crystal violet, forming an insoluble precipitate that locks purple color into cells
- ethyl alcohol dehydrates the peptidoglycan layer and dissolves lipid-containing layers
* *peptidoglycan layer shrinks and traps violet in Gram +
* *peptidoglycan layer too thin, dye washes out of Gram - - safranin turns Gram - pink, while violet in Gram + masks the dye and they stay violet
2
Q
gram + vs gram - cells and examples
A
gram +: thick peptidoglycan layer (M. luteus)
gram -: thin peptidoglycan layer, more complex cell wall with a lipopolysaccharide layer (E. coli)
3
Q
antibiotic types, how they work, and which bacteria they work on
A
penicillin
- beta lactam antibiotic
- works on Gram + (M. luteus)
- inhibits transpeptidase enzyme which links chains in the peptidoglycan layer (death by osmosis)
- not effective on Gram - because peptidoglycan layer is smaller part of cell wall
streptomyosin
- aminoglycoside antibiotic
- works on Gram - (E. coli)
- changes ribosome structure, causing mRNA to be read incorrectly (producing nonfunctional proteins)
- not effective on Gram + because it’s too large to get through the peptidoglycan layer
4
Q
running ANOVA
A
- “treatment” in 1st column, number them (1, 2, 3, etc)
- dependent variable “response” in 2nd column corresponding to treatment
- stat–anova–general linear model–fit general linear model
- dependent variable in “response” box, independent variable in “factors”
- gives F and P-value, do Tukey if p < 0.05
5
Q
running Tukey
A
- stat–anova–general linear model–comparisons
- ensure: pairwise comparison, “treatment” is checked for terms, Tukey checked
- options–should be 95% confidence level
- graphs–interval plot for differences should be unchecked
- results–uncheck grouping info, check tests and confidence intervals
run test!
6
Q
parts of a conclusion statement
A
- what did you expect to find (hypothesis)
- what did you find? (f-value, p-values, figure reference) - did it match expectations?
- can you accept hypothesis? (use words “support” or “fail to support”)
- if accepted–broader scientific applications; if not accepted–biological explanations for unexpected findings
7
Q
hemacytometer use
A
focusing hemacytometer (before sample added)
- raise stage as high as it will go, and move down to focus
- triple line border distinguishes large corner squares
use
- remove slide after focusing microscope and put cover slip on
- use special “cut” pipette tip to load mixture into hemacytometer by placing the tip at the edge of these coverslip (works by capillary action)
8
Q
calculating dilution factor and cell concentrations in hemacytometer
A
dilution factor
DF = v2 (total after) / v1 (volume of concentrated stock solution)
*area of the major corner squares is 0.0001 ml
cell concentration = (average # of cells)(DF)(1 x 10^4) cells/ml stock solution