BMSC 240

Question 1

Controlled Variables

Answer 1

Constant and unchanged throughout all experiments

• age of mice
• temperature
• same thickness of test tubes walls

Question 2

Independent Variable

Answer 2

What we are changing in the experiment

• what drug we are giving/not giving to the two groups
• just 1

Question 3

Dependent variable

Answer 3

What you are observing in the experiment; what changes in response to the independent variable

• can be more than 1: how does this drug change mouse’s heart rate, body temp, etc.

Question 4

Controls

Answer 4

Give internal verification of experiments - check if your system is working

if you’re checking effect of bee venom on scarring:

• positive control: a drug against scarring to compare effect of bee venom with
• negative control - absence; no bee venom but other treatment (stitching and stuff) the same

Question 5

Positive control

Answer 5

An experimental treatment which will give the desired result

• testing drug that increases HR, give caffeine as a control (known to inc. HR), if HR increases, you know things are right
• sample amount with specific amount of lead, if the reading shows that same amount, you good
• new battery should make smoke alarm work

Question 6

Negative control

Answer 6

An experimental treatment which will not give the desired result

• pure water showing as lead filled in the machine

Question 7

False negative

Answer 7

comes from a positive control

Question 8

False positive

Answer 8

comes from a negative control

Question 9

Sensitivity

Answer 9

minimum amount of something needed to produce a positive result

Question 10

Specificity

Answer 10

specificity to molecule of interest

• positive result only coming from a truly positive sample - doesn’t change with the quantity of something else
• only the dependent variable that you are measuring is responding to the independent variable that you are manipulating

Question 11

Random error

Answer 11

Introduced with each measurement

• happen ONCE
• if the pipette tip you use was shit in one try, but the rest are fine

Question 12

Accuracy

Answer 12

how close is an individual value to what it is supposed to be

Question 13

Systematic error

Answer 13

error that is consistently present

• meter stick isn’t a meter long

Question 14

Precision

Answer 14

how reliably you can measure a value (multiple)

• measure the same thing a 100 times, do you get the same value

Question 15

pH meter

Answer 15

• we can calibrate to reduce systematic error
• quantitative (improves precision and accuracy)
• glass probe permeable to H+, generates an electrical current
• rinsed and stored in KCl or acidic buffer between use
• systematic error: calibrated wrong
• random error: more H+ near probe (solution not heterogeneous)

Question 16

Scale

Answer 16

• systematic error: calibrated wrong; didn’t zero properly
• random error: stuff accidentally fell off after you measured

Question 17

Volumetric pipettes

Answer 17

measure just one volume (line at 5 mL)

Question 18

Graduated pipettes

Answer 18

lines along length to determine volume

Question 19

Serological pipettes

Answer 19

Calibrated to empty so they need to be empty when you’re done

• random error: leaving drop of liquid in pipette; liquid on the outside of pipette

Question 20

P10

Answer 20

0.5 to 10 uL

Question 21

systematic error in micropipettes

Answer 21

not going down to 2 stops to dispose

Question 22

pH

Answer 22

• log [H+]

Question 23

Buffer

Answer 23

combination of a weak acid and its conjugate base

Question 25

pKa

Answer 25

pH at which equal amounts of acid and conjugate base are present