Lab Practical Tufts Bio 13
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- What is the test for small sugars? (mono/di sacherides)
- Bededict's reagent
- What are the limitations of Benedict's reagent?
- Can't determine type of sugar, doesn't work for sucrose
- What represents a positive Benedict's test?
- A colored (yellow, green, orange or red) percipitate forms
- What represents a negative Benedict's test?
- a clear substance
- In the Benedict's test what can be used as a control.
- water + benedicts
- What reagent is used to test for the resence of starch?
- Iodine reagent
- What constitutes a positive result for an iodine test?
- a dark blue/purple color
- What constitutes a negative result for an iodine test?
- an amber color
- What are the limitations to an iodine reagent?
- After a certain time and/or hydrolisis starchs helical structure breaks down and the iodine can no longer bind to it.
- What monosacherides will result from the hydrolisis of sucrose?
- glucose and fructose
- What monosacheride will result for the hydrolisis of starch?
- gluctose
- What is hydrolisis?
- the process by which polysacherides are broken down into their components
- What is used as a test for the presence of proteins?
- Biruets reagent
- What constitutes a positive Birutet test?
- A blue or lavender color
-
How did we perform a serial dilution?
For 5 test tubes?
What will be the concentration of each? -
Start with a stock sample of a substance (40mg/ml of BSA for example)
pipette 5ml of water into 4 tubes 1-4
Pipette 9.5 ml of water into tube 5
Using a 1ml pipette add .5 of the stock BSA into tube 5 and mix
Remove 5 ml (half) of this solution and put it into tube 4 repeat for all
The stock solution will have a concentation of 40,000μg/ml, tube 5 will have 2000μg/ml, tube 4 will have 1000μg/ml - How do you blank a Spec?
-
1. set wavelength
2. set 0%transmitance with NO blank in chamber
3. put in blank and set transmitance to 100%
4. Switch to absorbance - What is an assay?
- A means of detecting and measuring the activity of an enzyme
- How is enzyme activity expressed?
-
amount of substrate used per unit of time
or
amount of product produced per unit of time - What is a compound that is colorless but yeilds a colored product upon reaction called?
- a chromogenic substance
- What was the enzyme used in the Enzyme lab called?
- phosphatase
- What were the substrates for the enzyme lab I ?
- (chromogenic substance) p-nitrophenyl phosphate (PNPP)
- What was the product for the enzyme lab I?
- (colored product)p-nirtophenol (PNP)
- When does p-nirtophenol (PNP) turn yellow?
- Under high pH
- Why was NaOH added to the enzyme reaction
- stop reaction and raise pH
- Why do you establish a standard curve?
- In order to convert the value of absorbance into concentration of protein
- How do you establish a standard curve?
-
Make known concentrations of enzyme with varying concentrations of product, and controled concentrations of buffer, protein, NaOH
test absorbance and plot - What kind of a graph do you expect to get if you vary the amount of enzyme but keep the substrate the same?
- linear relationship
- How do you find the mass of a product?
- Conc. (u moles/liter) X Volume (L) = Mass PNP (u moles)
- How do you find the concntration of a product?
- net absorbace solved for standar curve
- How do you find the volume of product?
- C1V1 = C2V2
- how do you recognize a cell that is hypertonic?
- it is shrivaled inside the cell wall because water has exited the cell
- what does it mean to be hypertonic
- there is a higher concentrantion of solutes OUTSIDE of a cell
- what does it mean to be hypotonic
- there is a higher concentration of solutes inside the cell
- what does it mean to be isotonic
- same concentration of solutes inside and outside the cell.
- How do you recognize a hypotonic cell
- there is high turgor pressure: the cell is swollen
- In the alcohol fermentation lab what are you measuring?
- CO2 evolved
- In the alcohol fermentation lab what does amound of CO2 evolved indicate
- relative rate of fermentation
- In the cellular respiration lab why is the mitochondrial suspension kept on ice?
- to keep it from degrading
- In the cellular respiration lab why is sucrose added to the mitichondrial suspension?
- to maintain an osmotic balence
- What is DPIP and why is it used in the cellular respiration lab?
- DPIP is an electron acceptor that intercepts the hydrogen ions and electrons released from succinate, changing the DPIP to a reduced state changing its color form blue to clear. we can use this color change to measure the rate of respiration
- In the cellular respiration lab where does DPIP get hydrogen ions from?
- succinate (in the Krebs cycle)
- In the phososynthesis lab what was used as a supply of CO2?
- sodium bicarbonate
- in a chi square table for a dihybryd cross what constitutes a deviation explained by chance?
- greater than .05
- How do you calculate deviation in a chi square?
- deviation= (observed-expected)²/expected
- How do you calculate number expected in a chi square?
- (total #) x (mendelean prediction) = number expected
- How do you identify a drisophela male?
- a dark genital disk
- how do you identify a female drisophela
- a white pointed bottom
- What are wild type eyes in drisophela
- large red eyes