Summary Edexcel A-Level Unit 3 Revision Notes (WBI13) [New spec]
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Course
Unit 3 - Practical Biology and Research Skills
Institution
PEARSON (PEARSON)
It includes all practicals for International AS Level specifications. Easy to read, understand and study. I used these notes for Unit 3 and got an overall A in my AS level Biology. And I got an A* for my AL predicted grade.
Summarise these notes by adding the common answers in the mark schemes!...
Benedict’s reagent for reducing sugar / biuret test
Dependent Colour change of Benedict’s reagent
Independent Concentration of reducing sugar
Control - Temperature (thermostatically control water bath)
- Volume of Benedict’s solution
- Time
- Volume of solution being tested
Risk - Liquid (spillage)
- Glassware: cuts from sharp objects
Colour change Biuret test: blue to purple
Benedict’s reagent
Procedure 1. 5 different protein/ glucose concentration + examples
2. Same volume of protein/ glucose solution
3. Same volume of the biuret / benedict solution
4. Swirl the mixture of the same time
5. Thermostatically controlled water bath → keep the
temperature the same
6. Standardize the cuvette
7. Colourimeter to absorbance
8. Draw a table and record the data
9. Plot the graph absorbance against protein concentration
, Structure of mammalian heart by dissection -daphnia (reference)
Dependent beats per minute’ for heart rate
Independent Pesticide used
- allow Daphnia to acclimatize / equilibrate in the pesticide
- pencil and dots for set time period (30s) , count heart beats for
stated time
- controlling temperature
- obtaining Daphnia from pesticide-free water
- use of a cavity slide/ immobilizing Daphnia with cotton wool
- same concentration of pesticides
- same size Daphnia
- take several readings and calculate a mean
Why pesticide - pesticides may be water soluble ;
enter Daphnia - so enter by diffusion / facilitated diffusion
and cause a - absorbed by heart muscle cells / alters nerve function / alters
change in (muscle) contraction
heartbeat
Error - Daphnia not be same size
- Not enough data
- Too high conc kill the pesticide
- Counting of the heart beat not accurate
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