2010 Unit 2 Jan Flashcards
Give one feature of starch and explain how this feature enables it to act as a storage
substance.
• Helical /spiral/coiled; Compact Insoluble • Does not affect water potential Large molecule • Does not leave cell;
The structure of cellulose is related to its role in plant cell walls. Explain how
- Long/straight/unbranched chains (of glucose)
- (Joined by) hydrogen bonds;
- Form (micro)fibrils
- Provide rigidity/strength/support;
Explain the importance of elastic fibres in the wall of the aorta
- Stretches/’expands’ under high pressure
- Recoils/’springs back’ under low pressure
- Smooths blood flow / maintains blood pressure
Explain the importance of muscle fibres in the wall of an arteriole.
- (Muscle) contracts;
* (Arteriole) constricts /regulates blood flow (to capillaries);
The rate of blood flow decreases from the aorta to the capillaries. Use information
from the graph to explain why
• Large/increase in (total) cross sectional area
Efficient exchange of substances in the capillaries is linked to the rate of blood flow.
Explain how
• (More) time for exchange of substances
Whether mutation 1 affects the amino acid sequence
- Has no effect / same amino acid (sequence) / same primary structure;
- Glycine named as same amino acid;
How mutation 2 could lead to the formation of a non-functional enzyme
• Change in primary structure; • Change in hydrogen/ionic bonds; • Alters tertiary structure/active site; • Nlonger complementary / no enzyme-substrate complexes form;
During which part of the cell cycle are gene mutations most likely to occur?
• Interphase
Suggest why gene mutations are most likely to happen during interphase
• DNA/gene replication/synthesis occurs / longest stage;
Give one environmental factor that the student should have kept constant during this
investigation. She used a potometer to measure the rate of water uptake by the shoot
• Light (intensity) / temperature / air movement / humidity
The student cut the shoot and put it into the potometer under water. Explain why
• Prevent air entering / continuous water column;
The student wanted to calculate the rate of water uptake by the shoot in
cm3 per minute. What measurements did she need to make?
- Distance and time;
* Radius/diameter/area (of capillary tube);
The student assumed that water uptake was equivalent to the rate of transpiration.
Give two reasons why this might not be a valid assumption.
- (Used to provide) turgidity/support/
- (Used in) photosynthesis / (produced in) respiration;
- Apparatus not sealed/’leaks’;
Suggest how the reservoir allows repeat measurements to be made
• Returns bubble (to start)
Suggest why she made repeat measurements.
• Increases reliability (of results) / anomalous result can be identified;
What is an allele?
• (Different) form/type/version of a gene
Explain how the gametes with the combinations of alleles Ef and eF have been
produced.
- Crossing over;
- Exchange (of alleles) between chromatids/chromosomes;
•
Use Figure 6 to describe how haemoglobin loads and unloads oxygen in the body
• Loading of oxygen at high p.O2;
• In lungs (haemoglobin) is (almost) fully saturated / in lungs
haemoglobin has a high affinity for oxygen;
• Unloads/releases/dissociates oxygen at low p.O2;
• Unloading linked to higher carbon dioxide concentration
•
Heat from respiration helps mammals to maintain a constant body temperature.
Use this information to explain the relationship between the surface area to volume
ratio of mammals and the oxygen dissociation curves of their haemoglobins
• Smaller mammal has greater surface area to volume ratio;
• Larger SA:Vol ratio more heat lost
• Smaller mammal/larger SA:Vol ratio has greater rate of
respiration/metabolism;
• Oxygen required for respiration
•
Suggest two ways to reduce the transmission of MRSA in hospitals
- Isolation
- Sterilisation of wards/equipment
- Testing (of patients
When antibiotics are prescribed for treating patients, higher doses than the MIC are
recommended. Suggest two reasons why.
- May not all be absorbed;
- May be broken down /metabolised/excreted quickly;
- To kill the microorganisms/bacteria;
Suggest two ways in which a double-blind trial improves reliability
- Prevents bias;
* Prevents ‘placebo’ (in volunteers);
Use your knowledge of resistance to explain the results obtained with Norfloxacin and
drug X.
- No/little resistance shown to drug X
- Mutation present
- Gene/allele for (antibiotic) resistance;
- Bacteria with (antibiotic) resistance survive
- Vertical gene transmission;
- Frequency of gene/allele (for resistance) increases;
Explain why an isotonic salt solution is
used to dilute the blood sample.
- Has same water potential
- No (net) water movement / osmosis;
- Cells will not swell/burst/change size;
Describe the processes that lead to a reduction in the
genetic diversity of populations of organisms
• Reduced variety/number of
different alleles/DNA / reduced gene pool
• Founder effect
• A few individuals from a population become isolated
• (Genetic) bottlenecks
• (Significant) fall in size of population
• Selective breeding
• Using organisms with particular alleles
Comparing the base sequence of a gene provides more information than comparing
the amino acid sequence for which the gene codes. Explain why
• Triplet code / more bases than amino acids • Introns/non-coding DNA • Same amino acid may be coded for / DNA code is degenerate
