A level biology practical questions

Practical 7- Chromatography- Give 2 factors that affect the rate of mobility?
Affinity- Those with lower affinitites will travel further up. Solubility- Pigments that are more soluble will travel faster up.
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If a pigment has a hgih Rf value what does this mean?
The pigment will travel further up the paper
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Practical 8- Dehydrogenase activity- What role does dehyrdrogenase enzymes play in photosystem 1 of photosynthesis?
Dehydrogenase enzymes catalyse the reaction that produces NADPH.
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Explain how a redox indicator dye is able to indicate dehydrogenase activity in photosystem 1?
Redox indicator dye takes the place of NADP as an electron acceptor. This means the dehydrogenase activity redcues the dye instead of NADP. The reduction is coupled with a colour change.
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To make this practical more reliable what sould be done?
This experiment should be done in a​ darkened room​​ to make results more reliable. The sample should not be put too close to the lamp as ​temperature​​ may affect results.
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What colour does DCPIP change from when it is reduced?
It turns from blue to colourless
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Practical 9- Respiration in single celled organisms- Why stick liquid paraffin down the inside of the test tubes?
To stop oxygen getting into the solution, which forces the yeast to respire anaerobically.
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Why would measuring the rate of carbon dioxide production help to find out how quickly ethanol was being produced?
Both ethanol and carbon dioxide are products of anaerobic respiration. Measuring how fast carbon dioxide was being produced would indicate how fast ethanol is being produced.
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Give 2 variables that should be controlled in this experiment and describe how each of these variables should have been controlled?
Temperature- By putting the test tubes in a water bath at a set temperature/ The mass of yeast- by weighing out a set amount of yeast to use in each test tube./ The volume of glucose concentration- Measuirn out known volume of glucose
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What negative control should have been used in this experiment and why?
A control tube should be set up for each pH being investigated, which contains glucose but no yeast. No cO2 should be produced. This will allow the student to check that any CO2 being released is by yeast.
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practical 11- Colorimetry to determine conc of a glucose solution- Describe the differences in urine colour?
The blood is filtered in the ​glomerulus​​. A high concentration of glucose in the blood leads to a high concentration of glucose in the glomerular filtrate. Consequently, some is ​not able to be reabsorbed​​ in the proximal convoluted tubule thus ur
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What is an independent variable? What is a dependent variable?
The variable that you change. The variable that you measure
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Tje 3 things to think about when evaluating methods and results?
1. Repeatability 2. Reproducibility 3. Validity
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What are the 2 ways of measuring the rate of an enzyme controlled reaction?
1. You can measure how fast the product of the reaction is made. 2. You can measure how fast the substrate is broken down.
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Other cards in this set

Card 2

Front

If a pigment has a hgih Rf value what does this mean?

Back

The pigment will travel further up the paper

Card 3

Front

Practical 8- Dehydrogenase activity- What role does dehyrdrogenase enzymes play in photosystem 1 of photosynthesis?

Back

Preview of the front of card 3

Card 4

Front

Explain how a redox indicator dye is able to indicate dehydrogenase activity in photosystem 1?

Back

Preview of the front of card 4

Card 5

Front

To make this practical more reliable what sould be done?

Back

Preview of the front of card 5
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