Biology Practicals Flashcards
(13 cards)
Practical 4-Investigating into the effect of a named variable on the permeability of cell surface membrane(using beetroot)
IV-Temp
DV-absorbance of light using a colorimeter
CV-Same vol of water,length/SA of Beetroot
Risk Assessment-cut carefully using a knife
1.Add the same vol of water into each Test tube
2.place each Test tube in a water bath at different temperatures,20,40,60,80
3.let it acclimatise for 5 mins
4.add same amount of Beetroot in TT,may need to cut using a Cork borer and a knife
5.Wait for 10 mins for betalain to leak out and place in a cuvette
6.Place cuvette in a colorimeter and record results
7.Repeat,remove anomalies and calculate a mean
Practical 4 question:Why are tubes placed in water baths for 5 mins
To let it acclimatise to new conditions and let it reach same temperature as water bath
Why were beetroot cylinders washed with distilled water?
To remove excess pigment from cells,and this reduces inaccuracy
Practical 4-Describe the effect of increasing temp on percentage absorption?
Increasing temp,increases rate of absorption but decreases percentage transmission
Practical 4-Why should fresh beetroot be used instead of cooked beetroot?
Cooked beetroot will increase temp so there will be more gaps in the Phospholipid bilayer
How does temp affect beetroot membrane?
As temp increases,Greater kinetic energy is obtained meaning Phospholipid bilayer moves around more and is more fluid,making it more permeable
Permeability may increase as higher temp causes proteins to denature which creates gaps in Phospholipid bilayer
At low temp,Phospholipid bilayer remain intact,so betalain is too large to pass
Investigate the effect of temperature on rate of enzyme activity catalysed by trypsin?
Method
Add 5cm³ of milk powder into 3 Test tubes
Add 2cm³ of trypsin and 2cm³ of ph 7 buffer solution in TT
Place in water bath at temp of 30(increase by 10s after)
Let it acclimatise for 10 mins
Add the trypsin from TT and start the timer
Record how long it takes for milk sample to hydrolyse and become colourless
Find the mean time taken and record reaction time using equation
ROR=1/mean time
What are some Risk assessments for Investingating temp on Enzyme activity Practical
Broken glass-cuts from sharp object-take care,keep away from desk-seek medical assistance
Water baths-burns as its hot-seek medical assistance-run under cold water
Explain all variables in Rate of enzyme activity influenced by temperature practical?
IV-Temp
DV-Rate of reaction
CV-pH,conc of substrate,conc of enzyme
What is a conclusion for this practical?
Milk contains a protein called casein, which, when broken down, causes the milk to be colourless.Trypsin hydrolyses casein
As temp increases from 10 to 40,kinetic energy increases, so more enzyme substrate complexes form
As temp increases beyond the optimum,bonds in the enzyme tertiary structure break,which changes the shape of the active site
This means they are no longer complementary
Explain the method for Practical 3-Investigating Water potential
Prepare a dilution series of 1M sucrose solution at concentrations of 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0M, diluting with distilled water.
Measure 5cm³ of each sucrose solution into separate boiling tubes.
Use a cork borer to cut six potato chips from a potato and trim them to identical sizes.
Dry each chip with paper towels to remove surface water but do not squeeze them.
Weigh each chip using a digital balance and record its initial mass.
Place one potato chip in each boiling tube containing sucrose solution.
Leave the tubes undisturbed for 20 minutes.
Remove the chips, gently dry them with paper towels, and weigh each chip again.
Calculate the percentage change in mass for each sucrose concentration using the formula:
Explain all the variables for the Water Potential Practical?
IV-molarity of sucrose solution
DV-change in mass of potato in percentages
CV-temperature,type of potato,
Give a conclusion and analyses of water potential practical?
In dilute sucrose solutions (lower concentration), the potato chips gain mass because water moves into the cells by osmosis, from an area of higher water potential to lower water potential.
In concentrated sucrose solutions, the potato chips lose mass as water moves out of the cells.
The point of no mass change is the isotonic point, where there is no net movement of water, as the water potential of the solution equals the water potential of the potato tissue
