Key Pratices Flashcards
What is the aim of Practical 1 in microscopy?
Use a light microscope to observe, draw, and label cells.
List the skills required for microscopy.
- Prepare a slide using a specimen and a coverslip
- Use iodine to stain the specimen
- Focus the microscope correctly using coarse and fine adjustment knobs
- Calculate magnification
What common mistakes can occur when using a microscope?
- Not using the lowest magnification first
- Over-staining
- Air bubbles under the coverslip
What is the aim of Practical 3 in osmosis?
Investigate the effect of different sugar or salt concentrations on the mass of potato cylinders.
What is osmosis?
The movement of water from a dilute solution to a more concentrated one through a partially permeable membrane.
What skills are needed to investigate osmosis in potatoes?
- Accurately measure and cut equal-length potato pieces
- Place in solutions of varying concentration
- Measure mass before and after soaking
- Calculate percentage change in mass
What is the aim of Practical 4 involving enzymes?
Investigate how temperature or pH affects the activity of an enzyme.
What are key concepts regarding enzymes?
- Enzymes work best at their optimum temperature and pH
- High temperatures can denature the enzyme
Describe how to prepare a slide to observe onion cells.
- Peel a thin layer of onion skin
- Place it flat on a microscope slide
- Add a drop of iodine stain
- Lower a coverslip carefully
Why is it important to start with the lowest magnification when using a microscope?
- It gives a wider field of view
- Reduces risk of damaging the slide or lens
Calculate the magnification if a cell has an actual size of 0.02 mm and appears 1.2 mm.
60×
Explain why the mass of potato strips changes in different sugar solutions.
- In dilute solutions, water moves into the potato, increasing mass
- In concentrated solutions, water moves out, decreasing mass
What is the role of iodine in the enzyme practical?
- Iodine is used as an indicator for starch; it turns blue-black if starch is present.
How do high temperatures affect enzyme activity?
- High temperatures can denature the enzyme, changing its active site shape.
What does ‘denatured’ mean in the context of enzymes?
The enzyme’s active site changes shape, preventing the substrate from fitting.
Describe how to test the effect of pH on amylase activity in the lab.
- Mix amylase, starch solution, and buffer with known pH
- Test samples with iodine at intervals
- Record time when iodine no longer turns blue-black
What is the aim of Practical 5 in food tests?
Test foods for starch, sugar, protein, and lipids.
What indicates the presence of starch in food tests?
Iodine turns blue-black.
What indicates the presence of sugar (glucose) in food tests?
Benedict’s solution turns brick red when heated.
What indicates the presence of protein in food tests?
Biuret turns purple.
What indicates the presence of lipids in food tests?
Ethanol creates a cloudy layer.
What is the aim of Practical 6 in photosynthesis?
Investigate the effect of light intensity on the rate of photosynthesis using pondweed.
What is a key equation related to photosynthesis?
Light intensity vs rate of photosynthesis.
