Bio Lab 117 Practical

Labeling

S27-T5-NS-A

When do u use serological tips and pipet bulbs

ONLY when there is a measurement between 1-10 MILLILITERS!

how to use pipet bulb

1. squeeze "A"

2. squeeze large bulb with other hand (should stay collapsed)

3. put pipet tip in the bulb (cotton part in)

4. put tip in liquid and squeeze "S" (suction) valve

5. squeeze "E" to expel liquid into another tube

p-20

2-20 MICROLITERS

p-200

20-200 MICROLITERS

p-1000

100-1000 MICROLITERS

pipetmen reminders

1st press to first stop (ONlY!) before putting tip in liquid

2nd stop is only for expelling possible stuck liquid

p-1000 volume

top to bottom = thousands (in red) -> hundreds -> tens

SO....

930 = 093

460 = 046

570 = 057

p-200 volume

top to bottom = hundreds -> tens -> ones

SO...

137 = 137

285 = 285

39 = 039

178 = 178

p-20 volume

top to bottom = tens -> ones -> tenths

SO...

4.2 = 042

5.8 = 058

17.3 = 173

20 = 200

what is a buffer

aqueous solution containing specific mixture of salts, buffering agents, and sometimes reducing agents, detergent or cofactors, in which each of the components has a purpose and is included to optimize a reaction.

uses of a buffer

resist changes in hydrogen ion concentrations (change in pH)

stock solution

concentrated solutions that last over long periods of time

benefits of a stock solution

take up less space

last long

easily diluted for use when necessary

how to make a dilute solution from stock solution

C1V1=C2V2

C1

concentraiton of stock solution

V1

volume of stock solution needed to make dilute solution

C2

final concentration of dilute solution

V2

final volume of dilute solution

what is dilution factor

factor by which the concentration of the dilute solution is reduced compared to the concentration of the stock solution

how to find dilution factor

DF = C1/C2=V2/V1

calculating volume of water in a stock solution

Vwater = V2-V1

what is a serial dilution

a stepwise dilution where the stock solution for each dilution in the series is the dilute solution from the previous dilution

total dilution factor

the product of the dilution factors for each dilution step

how to calculate total DF

DFtotal = DF1 DF2 DF3 ...

determining the concentration of an unknown sample

Cs/Cu=As/Au

Cs

concentration of the standard (given usually)

Cu

concentration of the unknown (find this)

As

absorbance of the standard

Au

absorbance of the unknown

derived equation for concentration of unknown sample

Cu= Au/As * Cs

linear regression

statisitcal method for modeling relationship between two variables, x and y

linear trendline

a straight line best fit to the data points by minimizing deviation of the data point from the line

r^2 value

a measure of how well the linear trendline fits the data

r^2 close to 1

perfect data

r^2 = 0

bad data

calculating absorbance using spectrovis (blank)

1. go to meter screen (looks like speedometer)

2. go to sensors

3. calibrate

4. place blank cuvette in cuvette holder of spectrovis

5. press finish calibration

6. press ok

collecting absorbance data using spectrovis (blank)

7. go to sensors, select data collection

8. change mode from full spectrum to time based

9. press ok

changing wavelength using spectrovis (blank)

10. tap red box on screen, select change wavelength

11. enter value 550, press ok

cuvette change (absorbance)

12. remove blank cuvette

13. put in other cuvette

to determine absorbance over time

14. begin data collection by pressing arrow

15. collect data for atleast 10 seconds

16. press stop button

recording data collection

17. click analyze at top of screen, select statistics, select run, record avg absorbance

18. continue with other cuvettes

creating a scatter plot chart on excel

charts -> scatter -> scatter with only markers -> click blank box -> click select data -> "legend entries (series)" -> click add data -> highlight x values in corresponding box -> highlight y values in corresponding box

using excel to add a trend line (SCATTER PLOT)

design -> chart layouts -> add chart element -> trendline tab -> click trendily -> linear

using excel to add r^2 value

click on trendline -> format trendline -> "trendline options" box -> check "display equation on chart" -> "display r^2 value on chart"m

independent variable

variable changed by researcher

dependent variable

variable that responds to the changes in the independent variable, and is variable measured by researcher

controlled variable

other factors that can affect dependent variable, so they must be kept constant (these aren't relevant, not something that is being tested but may alter results if they are different in each experiment)

- should be the same in both groups

experimental group

group in which the independent variable is added and/or changed

control group

group in which the independent variable is either not included or is kept constant in its natural state

qualitative data

descriptive rather than a measure

quantitative data

numerical, often a measure like weight, height, distance, etc.

determining pH with pH probe

plug pH sensor into channel 1 -> remove pH sensor from storage bottle -> rinse tip and blot off water with kimwipe -> place tip of probe into buffer 3-4 cm -> wait 15 sec for pH probe to stabilize -> begin data collection for 10 seconds

-> stop -> click analyze -> statistics -> select your run -> record average for pH

determining temperature with temperature probe

plug temperature probe into channel 1 -> bring probe and vernier to various temperature locations -> place tip of probe into first environment about 6 cm -> begin data collection for 10 secs -> stop data collection -> analyze -> click statistics

2 branches of statistics

descriptive statistics

inferential statistics

descriptive statistics DS

describe and summarize data; reduces data to a manageable form; central tendency, measures of dispersion, distributions

DS

mean, median, mode, standard deviation

Standard Deviation

used to describe the dispersion of the sample with respect to the mean

- think of it as the approximate average distance of all the values from the mean

inferential statistics IS

used to make estimate, draw conclusions or inferences about populations based on sample

IS

t-test

t-test

used to determine if the difference between the means of 2 samples is significantly different. provides a p value.

p value

p = 0.05% = 5% chance that the difference between sample means has occurred by chance.

Thus smaller p value = more confident that difference between 2 values is real.

using excel to do a t-test

select cell away from data -> click formulas menu -> functions library -> more functions -> statistical -> t. test -> array 1 box -> highlight data -> array 2 -> highlight date -> tails box -> 2 -> type box -> 3 -> OK

using excel to make a column chart with statistics

highlight calculated means -> insert menu -> charts -> column -> 2d column -> clustered column -> click chart -> chart tools -> design menu -> chart layout -> add chart element -> error bars -> more error bar options -> format error bars box -> custom -> specify value -> custom error bars box -> click box next to positive error value -> enter values of standard deviation -> negative error box -> enter values of standard deviation -> OK

In text citation of lab manual

(BRL117, 2018).