AS Biology Practical Tips and Skills

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42 Terms

1
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What are the two words you should avoid?

amount and how much

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What quantitive measurements should you use instead of amount and how much?

concentration, mass, number etc

3
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What is the goal of paper chromatography?

seperate and analyse a mixture, usually used for colour

4
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What is the stationary phase of paper chromatography?

filter paper

5
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What is the mobile phase / equant of paper chromatography?

solvent

6
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What the goal of electrophoresis?

seperate RNA, DNA or protein molecules based on their size and electrical charge

7
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How does electrophoresis work?

electrical current used to move molecules through a gel or other matrix

8
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What is electrophoresis often used for?

haemoglobin levels, diagnosing anaemia, sickle cell

9
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What is a control?

experiment set up without the independent variable to compare with other results

10
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What is a control variable?

factors to keep the same to improve validity

11
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What is a photometer?

measures brightness of light through electromagnetic radiation

12
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What is a colorimeter?

measures intensity of colour, used to identify colour differences

13
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What is a potometer?

used to measure rate of water uptake of a leafy shoot

14
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What are three ways to improve reliability of an experiment?

repeats of measurements to calculate mean and identify and ignore anomalies, large sample size

15
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What are two ways to improve validity of an experiment?

keep (named) control variables the same, standardise procedures (example)

16
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What are two ways to increase accuracy of an experiment?

smaller intervals and example, equipment with higher resolutions e.g ruler with smaller intervals

17
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What can food tests be used for?

detecting biological molecules present in a sample, but not how much

18
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What does Benedicts solution test for?

reducing sugars (monosaccharides)

19
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What is the formula for Benedicts reagent?

CuSO4

20
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Chemically, how does the Benedicts test work?

blue Cu2+ ions reduce to form a brick red Cu2O

21
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How can a non-reducing sugar be identified?

Must undergo acid hydrolysis to break them down into monosaccharides. Acid hydrolysis is adding dilute hydrochloric acid then neutralising with sodium hydrogen carbonate solution.

22
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What else does the Benedicts test require?

water bath

23
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What is the benedicts test colour change?

blue to brick red

24
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What test tests for lipids?

emulsion test

25
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How is an emulsion test carried out?

shake sample with ethanol until dissolved, add water, if lipids present colour change from clear to milky white emulsion

26
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Why does an emulsion test work?

lipids are insoluble in water

27
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What is the test for proteins?

biurets

28
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What is biuret made out of?

sodium hydroxide and copper sulfate

29
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What is a positive colour change for biuret test?

blue to purple

30
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What is the test for starch?

iodine

31
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What is the colour change for an iodine test?

orange to blue black

32
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What is the test for Vitamin C?

DCPIP

33
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What is the colour change for DCPIP

blue to colourless

34
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What is catalase?

an enzyme

35
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What does catalase do?

protects bacteria/organisms from hydrogen peroxide by converting it to water and oxygen

36
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What is the chemical formula for the catalase reaction with hydrogen peroxide?

2H2O2 → catalase → 2H2O and O2

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What will happen if catalase is very active due to an abundance of 2H2O2?

lots of oxygen produced, so bubbles

38
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What is the positive result of a test for catalase activity?

bubbles of oxygen

39
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Why can an experiment to find catalase action not be carried out with blood ?

blood has catalase action

40
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What does ethanol do to catalase?

ethanol disables the ability of catalase to react with hydrogen peroxide

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What does a higher ethanol concentration result in for catalase?

increases denaturation

42
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What is the conclusion for this experiment?

as ethanol concentration increases, the number of oxygen bubbles produced decreases, indicating a lower rate of catalase activity so a lower rate of hydrogen peroxide being broken down