Class notes
Class notes Biology 2290 (Bio2290)
- Course
- Institution
Class notes Biology 2290 (Bio2290)
[Show more]
Seller
Follow
xunthonguynlu
Content preview
Accuracy vs. Precision- These help us understand our measement
- Accuracy: How close a measurement or attempt is to the actual or target value
- Precision: How consistent our result are regardless of proximity to the actual or
target
- Comparison:
+ Accuracy is measuring near true value
+ Precision is getting consistent results
- It’s important that measuring devices are accurate and precise, if not result can be
misleading and fatal
Direct vs. Indirect Meserments
- Both types of measurements are routinely used in science
- Direct measuments: this is measuring the thing you are actually measuring
+ Example: FInding the thickness of a leaf with calipers
+ Counting the number of cells in a culture with a haemocytometer
- Indirect measurment: this is measuring something by measuring something else.
+ Example: Determing the number of cells in a solution by counting the number
of colonies in a dibute overnight culture
+ Determing the concentration of a solution by measuring the
absorbance of its metabolite
Pipetting
- Gilson Micropipette usage:
+ Use with plastic tip to transfer 0.2 microliters to 1000 microliters or 1 mililiter
+ Different pipette have a label on top indicates the maximum volume transfer
- P2: 0.2 - 2 microliters
- P20: 2- 20
- P200: 20- 200
- P1000: 200-1000
+ Setting volume:
- P2: (for ex: 152 means 1.52 micrliters)
- P20: ( for ex: 152 means 15.2 )
- P200: ( 152 means 152)
- P1000 ( 052 means 520) the 100= 1000 microliters which is the
maximum of the setting volume
- Setting volume:
+ Pipette tip:
- P20 and P200 use the same yellow tips
- P1000 use the larger white tips
+ Pipette volume:
- P20 set at 2 microliters require less push than the P20 set at 20
+ Common tip to avoid:
- Never use the pipette without the tip as the liquid should never enter the body
of pipette
, - Do not use the pipette that pass the volume maximum
- if the tip is falling down use the new one
- Eppendorf pipetting: has 3 stops
Principles of Spectrophotometry:
Absorbance
- Absorption Spectroscopy: using light to probe matter. Look for how a sample
absorbs light of a particular wavelength which related to concentration
+ In experiment, we look for a wavelength that is absorbed by a specific
sample. The light has an incoming power (P in). High power light or high
intensity light will have a lot of photons coming in. We also have a solution
with high concentration that can absorb the light, therefore, the P out is small.
+ A lot of photons get absorbed through the sample-> absorption spectroscopy
+ The ratio bwt the input power and output power related to sample
concentration
- Percent transmittance (%T): percentage of light that gets transmitted through our
sample = P out/ P in
- The spectrometry that can measure the output and input light intensity.
- Absorbance (A): linear related to the concentration. Does not have a unit. A= 2-
log(%T)= log(1/T)
- The transmittance and absorbance is inverslly related. 100% absorbance we will get
0% transmittance.
- Do different experiments by absorbance spectrum to know which suitable
wavelength. We scan through a lot of wavelengths. If a solution is blue, the red is
absorbed. FInd the lambda max.
Principles of Spectrophotometry: How
does a Spectronic 20 work?
- Energy source-> monochromator (prism to separate the different colour of light) to
select the wavelength -> get absorbed through the sample -> hit the detector.
- Turn the knob in the nanometer for the visible light to control the wavelength of light
the sample is exposed to
- The phototube in the detector is coated with photoemisive that can measure the light
intensity
- How to operate Spec 20 to generate an ansorption spectra of a dye called DCPIP:
+ A basic spectrophotometer with analog dials and manual setting of 0%
transmittance and blanking
+ The Specs 20s accept glass test tubes in the sample chamber (requires a
high volume of sample) about 3mL volume. Can ửok for one sample at a time
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller xunthonguynlu. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $15.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
50843 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now