TECHNIQUES U4 Flashcards
Interpret investigations using chromatography to separate photosynthetic pigments
Using chromatography, it is easy to separate the main photosynthetic pigments within the plant.
Interpret investigations using gel electrophoresis
This technique is used to separate macromolecules (very large molecules) by size. This is done by passing an electric current through an agar gel to give a banding pattern showing the size of molecules/fragments that are contained within the sample.
Interpret investigations that measure enzyme activity/reaction rate
There are many investigations that involve enzymes and the factors that affect enzyme activity and reaction rate. Some might include:
Investigating the effect of substrate concentration on the rate of reaction.
Investigating the effects of competitive/non-competitive inhibitor concentrations on reaction rates.
Making sure you are familiar with these techniques
Interpret investigations for respiration using a respirometer
Respirometers are used to investigate respiration or the factors that can affect respiration. These involve living organisms such as invertebrates but can include yeast or germinating plants.
They require a control group, consisting of a dead organism or innate object. The same mass of glass beads, clay, dead invertebrates or boiled yeast.
Interpret investigations that measure metabolic rates using various different probes
The three different types of probes used are:
oxygen probe
carbon dioxide probe
temperature probe
Using your knowledge of respiration, you need to be able to interpret the different readings from probes over a period of time.
For example, if an organism with a higher metabolic rate will give out higher carbon dioxide readings than an organism with a lower metabolic rate.
Interpret results from photosynthesis experiments using a spectroscope
Spectroscopes allow for the filtration of light of different wavelengths. The rate of photosynthesis can be compared from visible light or filtered light.
You should be able to discuss the results for the rate of photosynthesis when in blue, red, green or visible light conditions.
Process information using averages, percentages and ratios
Percentages
Very often we use percentages to represent the number of bases in a DNA molecule – for example if a DNA molecule 1000 bases long has 30% of the bases are adenine.
You could be asked to work out the exact number of adenine bases.
You could be asked to work out the percentage number of guanine bases or the actual number of guanine bases on this strand of DNA.
Percentage increase or decrease
(The actual increase or decrease ÷ initial or starting value) × 100
Calculate the number of cycles it takes to produce a number of DNA molecules
This is a simple calculation to do – all you have to remember is that the number of DNA double every cycle.
The table represents how many DNA molecules are produced a different number of cycles of PCR.
It shows the number of DNA molecules doubling - if it takes 20 minutes to complete 1 cycle ow long would it take to get over 1000 DNA molecules.
Describe a relationship between variables/data
You have to describe the impact of the independent variable on the dependent variable. Look for patterns in graphs and you must describe all the relationships i.e. an increase and then a decrease. It is always good practise to give values when describing a relationship.
Example
As the temperature increase from 10°C to 40°C, enzyme activity increase from 1 to 10. As the temperature increased from 40°C to 60°C, enzyme activity decreased from 10 to 3
Make predictions based on evidence/information/knowledge
Predictions are educated guesses/hypotheses based on scientific evidence or knowledge about what could happen during certain investigations under controlled conditions.
Draw valid conclusions based on evidence or results
Use results/evidence from an investigation to come to a scientific conclusion. Use must always include the aim.
Example
Aim - To find out the effects of a competitive inhibitor on catalase activity.
Conclusion - A suitable conclusion would be:
The effects of a competitive inhibitor on catalase activity are…………
You could also be asked to look at results and give a valid explanation of what the results show.
Describe the independent and dependent variable
The independent variable is the variable that was changed during an investigation.
The dependent variable will be the results that have been collected throughout the investigation.
Suggest improvements to experiments
Most experiments can be improved. This can make the results more reliable; it can be because limitations in equipment or further experiments could be needed to validate a conclusion.
When looking at an experiment in an exam, you may or may not have seen anything like it before. Ask yourself these questions:
Are there any obvious errors?
How have they collected the results?
Are the results accurate?
Look at the equipment, could this be improved?
This approach will help give you an answer to the question.
Describe a suitable control for an investigation and the purpose of controls
All conditions/equipment when setting up an investigation must be the same - apart from the variable being investigated.
Example:
The effects of an inhibitor on catalase activity.
The control would be without the inhibitor to show enzyme activity alone.
Controls are present in an experiment to ensure that the results found are because of the variable being investigated.
Suggest how to increase the reliability of an investigation
To increase reliability of results this can be done in a variety of ways:
Repeating the investigation and calculating an average.
Increase the number of samples taken.
Increase the number of subjects used (living animals).
