Hard questions Flashcards
Describe why facilitated diffusion requires no metabolic energy
- Particles have their own kinetic energy
2. Move down the concentration gradient
Explain why glucose cannot pass through a cell membrane by simple diffusion
- Phospholipids act as a barrier
2. The molecules are too large
Suggest how the leaf of pondweed is supported
- Air spaces give buoyancy
2. Supported by surrounding water
Suggest why antibodies specific to nuclear proteins are not normally made
- Nuclear proteins normally hidden in the nucleus
Suggest how water is being lost from the cut stem when leaves have been treated with petroleum jelly in a potometer experiment
- Evaporation form upper leaf surfaces
Suggest two sources of error in a potometer experiment
- Not all lower leaf surfaces covered
- leaks in apparatus
- Shoot not cut under water
- Error in reading position of the meniscus
Explain why bone is described as a tissue and gills are described as organs
- Tissue has few types of cells and performs one function
- Bone has a few types of cells and performs one function
- Organs consist of several tissues
- Gills contain blood, bones, epithelial and connective tissue
How would the calculated rate differ form the true initial rate of reaction in an enzyme reaction
- Initial rate is likely to be greater
2. Because higher concentration of substrate at start, so more chance of substrate entering the active site
Give ways to refine an experiment so reproducible results would be obtained
- Specify volumes of reactants added
- Specify volume that should be removed for testing
- Stir before taking the sample
- Test with iodine- for starch, or other chemicals
- Carry them all out at the same temperature
Explain why vaccinations are examples of active immunity
- Antibodies are produced
- Activation of lymphocytes
- Memory cells remain
State 3 properties of fibrous proteins that are different to globular proteins
- Insoluble
- Strong
- Unreactive
How could haemoglobin be identified in urine
- Add biurets reagent
- Colour change from blue to purple
- Compare with control
Outline how the difference in lumen size between arteries and veins is related to their function
- In arteries small lumen maintains high pressure
- In veins large lumen- low resistance needed because of low pressure
- Same flow rate is achieved by having a larger volume
Why is movement of molecules from the plasma membrane towards the centre of living cells greater than in an experiment
- Involvement of vesicles/ cytoskeleton