Tuesday 11 January 2011 Flashcards
What structures that are in an epithelial cell aren’t in a cholera bacterium? 2 Marks
- Nucleus
- Mitochondria
Give one advantage of using a TEM than a SEM. 1 mark
- Higher-resolution so a higher level of detail
- Allows structures within the cell to be seen
Give one advantage of using a SEM rather than a TEM. 1 mark
- Thin sections do not need to be prepared.
- Can have 3D images
Describe the induced fit model of enzyme action. 2 marks
- Active site not complementary
- Active site changes shape
- Change in enzyme allows the substrate to fit and E-S complexes are produced
Describe one way that the lock and key model is different from the induced fit model. 1 mark
- Active site is complementary before binding.
The diagram shows the structure of a molecule of PABA. It also shows the structure of a molecule of a drug called sulfanilamide, which can be used to treat bacterial infections. Sulfanilamide prevents bacteria producing folic acid. Use the diagram and your knowledge of enzymes to explain how sulfanilamide prevents bacteria producing folic acid. 3 marks
- Similar structure
- It is a competitive inhibitor
- Less PABA bind so less E-S complexes are produced
Explain, in terms of pressure, why the semilunar valves open. 1 mark
- Pressure is greater below valve/ in ventricle than artery
When a wave of electrical activity reaches the AVN, there is a short delay before a new wave leaves the AVN. Explain the importance of this short delay. 2 marks
- Allows atria to empty + ventricles fill
- Before ventricles contract
Use information from the table to explain how training has caused the resting heart rate of this athlete to be lower. 2 marks
- Increase in size or volume of heart
- Cardiac output is the same before and after training
- More blood leaves the heart in each beat
Omega-3 fatty acids are unsaturated. What is an unsaturated fatty acid? 2 marks
- Double bonds
- Between carbon
A triglyceride does not contain sucrose or glycosidic bonds.
Give one other way in which the structure of a triglyceride is different to olestra. 1 mark
- Contains glycerol
- Three fatty acids
- Forms 3 ester bonds
Before reweighing, the student blotted dry the outside of each cylinder. Explain why. 2 marks
- Only want to measure water taken up or lost;
- Ensures the same amount of water on outside
The student calculated the percentage change in mass rather than the change in mass.
Explain the advantage of this. 2 marks
- Allow comparison
- Idea that cylinders have different starting masses / weights
The student carried out several repeats at each concentration of sodium chloride solution. Explain why the repeats were important. 2 marks
- Allows anomalies to be found
- Produce a mean
HPV vaccine is offered to girls aged 12 to 13 (line 5). Suggest why it is offered to this age group. 1 mark
- Girls aren’t sexually active
- Not likely to carry HPV
The vaccine is made from HPV types 16 and 18 (line 5). Explain why this vaccine may not protect against other types of this virus. 2 marks
- Other HPV types have different antigens
- Memory cells not activated
- Antibodies aren’t complementary
Three injections of the vaccine are given (lines 5 to 6). Use your knowledge of immunity to suggest why. 2 marks
- More antigens
- More memory cells
- So more antibodies produced at a faster rate
t will be many years before it can be shown that this vaccination programme has reduced cases of cervical cancer (lines 7 to 9). Suggest two reasons why. 2 marks
- Cancer takes years to develop
- Females must be sexually active to obtain data
- Only teenagers vaccinated - small
Smear tests will continue to be offered to women, even if they have been vaccinated (lines 9 to 10). Suggest why women who have been vaccinated still need to be offered smear tests. 1 mark
- As a precaution in case, the vaccine doesn’t work
- (Some) women may have been infected (with HPV) before receiving the vaccine;
Suggest one reason why vaccinating a large number of people would reduce significantly the spread of HPV through the population (lines 14 to 16). 2 marks
- Virus cannot replicate
- Non-vaccinated people more likely to contact vaccinated people;
Pulmonary tuberculosis is a disease of the lungs.
Describe the transmission and course of infection of pulmonary tuberculosis. 5 marks
- Bacteria transmitted in droplets
- Ingested by phagocytes
- Bacteria encases in wall
- Bacteria not active
- If immunosuppressed, bacteria activate
- Bacteria destroy alveoli
- (Leads to) fibrosis/scar tissue
- (Damage) leads to less diffusion
- damage allows bacteria) to enter the blood
Emphysema is another disease of the lungs. People with emphysema may feel weak and tired. Explain why. 5 marks
- Alveoli break down
- Less surface area so less diffusion
- Loss of elastic tissue
- Reduced elasticity in the lungs
- Reduced diffusion gradient
- Less oxygen enters blood
- Less respiration
