set a Flashcards
Sunflower oil is used to make biodiesel, which contains methyl esters. The fatty acids in the
triglyceride molecule are reacted with methanol in a process called transesterification. After the reaction, two liquid products form which naturally separate from each other. The methyl esters float on top of a more dense liquid. Name the part of the molecule seen in Fig. 22 that forms this more dense liquid.
- glycerol
Living organisms have many uses for triglycerides, one of which is the production of
phospholipids.Name three other functions of triglycerides in living organisms
- energy storage
- energy source for respiration
- thermal insulation
- electrical insulation
Phospholipid molecules also contain fatty acids.
Explain how the fatty acids in phospholipids allow the formation of membranes
- hydrophillic heads that face outwards and hydrophobic tails that face inwards this form the bilayer
Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical (light) microscope.
- Add drop of water to (glass) slide;
- Obtain thin section and place on
slide on drop of water; - Stain with iodine in potassium iodide;
- Lower cover slip using mounted needle;
what is the function of the chloroplast and the nucleus?
- chloroplast, photosynthesis
- nucleus, contains dna
State what assumption is made when using this apparatus to measure the rate of transpiration.
- water loss equals uptake
There must be no air in the apparatus in Fig. 4.1 for it to work correctly.
Describe and explain the precautions that need to be taken when setting up and using
the apparatus in Fig. 4.1 to ensure that no air is present.
- cut stem under water so no air can enter the apparatus
- insert stem under water as air could block the xylem
- do not allow the bubble to move too far so that it doesn’t enter the xylem
Suggest why it might be considered better to use a capillary tube rather than a calibrated
pipette to measure water uptake
- capillary tube measures smaller volumes
The student wanted to compare the rates of transpiration of the two leafy shoots shown in
Fig. 4.3. Describe how the student could ensure that a valid comparison could be made between the
two leafy shoots.
- find leaf area
- calculate transpiration rate per unit area
Give two safety precautions that should be followed when dissecting a heart.
- wash hands
- cover any cuts
- use a sharp scalpel
Explain how the atrioventricular valve maintains a unidirectional flow of blood.
- Pressure in (left) atrium is higher than in
ventricle causing valve to open - Pressure in (left) ventricle is higher than in
atrium causing valve to close
Caffeine affects the autonomic nervous system.
Suggest how caffeine could account for the results of Group I in Figure 3 at
60 minutes.
- More impulses along sympathetic nervous system pathway
- To SAN increasing the heart rate
The increase seen in Group I could be due to the combination of caffeine and sugar.
Suggest one drink to be given to an additional group that should be investigated to
find out if this is true.
Give a reason for your answer.
- A drink with sugar (and no caffeine)
- To show that sugar (alone) is not causing
the increases (in HR)
What is meant by ‘species richness’?
- the amount of different species in a ecosystem
Three of the bee species collected in the farmland areas were Peponapis pruinosa,
Andrena chlorogaster and Andrena piperi.
What do these names suggest about the evolutionary relationships between these
bee species?
- A. chlorogaster and A.piperi are more closely related (share common ancestor) than to P.prumosa
- because they are in the same genus
Botulinum toxin is produced by the anaerobic bacterium Clostridium botulinum.
What information does the word ‘anaerobic’ suggest about the bacterium?
- it only respires in the absence of oxygen
The toxin is initially produced as a large single polypeptide that has low potency. After the toxin has been acted upon by a protease, two chains are produced which remain
connected by a disulfide bond. In this form it is far more toxic. Describe the action of the protease when it acts on the toxin.
it hydrolyses a peptide bond between two amino acids
(residues) which are joined by a disulfide bond 9
A mouse assay, using 99 mice, was used to determine the median lethal dose of the toxin. Suggest what is meant by the term median lethal dose.
- amount that is required to kill the 50th mouse when they are arranged in order of lethal dose
The toxin acts primarily at the cholinergic nerve terminals of stimulatory motor neurones. Part of the molecule binds irreversibly to specific receptors on the presynaptic membrane. The toxin–receptor complex is then taken into the cytoplasm of the neurone where the disulfide bond is broken, releasing the section of the molecule which acts to block the release of the neurotransmitter. Explain why botulism can be fatal
- diaphragm muscles are paralysed
- ventillation and oxygenation of blood is reduced
- cells cannot obtain oxygen for respiration
There are a number of different strains of the Clostridium botulinum bacterium. Different strains
produce immunologically distinct forms of the toxin.
Explain why the toxins produced by the different strains are described as being ‘immunologically
distinct’ and how they will be dealt with by the immune system
- toxins produced by each strain will be different
- each toaxin will have difference amino acid sequence
- toxin acts as a antigen
- antigen presenting cells ingest antigen and display on the their surface
- t cells stimulate b cells
- b cells divide to form plasma cells
- plasma cells produce antibodies
- by protein synthesis the antibodies bind to and neutralise toxins
