Wednesday 18th January 2012 Flashcards
Describe the function of a chloroplast. 2 marks
- Absorbs sunlight
- For photosynthesis
- Produces carbs/ sugars/ lipids/ proteins
Describe what happens during anaphase that results in the production of two genetically identical cells. 2 marks
- Sister chromatids
- To opposite poles
Use your knowledge of the cell cycle to explain why some cells had 8.4 units of DNA and other had only 4.2 units. 2 marks
- 8.4 - cells with twice DNA content as the DNA had replicated.
- 4.2 = DNA not replicated
How many units of DNA would you expect to be present in a gamete formed in this animal as a result of meiosis?
2.1
A scientist carried out breeding experiments with catfish from different populations. Describe how the results could show that the catfish belong to the same species. 1 mark
Fertile offspring produced
The variety of colours displayed by catfish is important in courtship. Give 2 ways in which courtship increases the probability of successful mating. 2 marks
- Recognise opposite sex
- Recognise same species
- Synchronises mating
Explain how this mutation leads to the formation of non-functioning PAH. 3 marks
- Change in amino acids
- Change in hydrogen bonds
- Alters active site of enzyme
- Substates can’t bind as they are no longer complementary so no E-S complexes can form.
One mutation causing phenylketonuria was originally only found in one population in Central Asia. It is now found in many different populations across Asia. Suggest how the spread this mutation may have occurred. 1 mark
Interbreeding - reproduction between individuals from different populations
Vancomycin acts on the cell wall - explain why vancomycin does not affect human cells. 1 mark
Human cells don’t have cell walls
Tetracycline acts on ribosomes - how does tetracycline prevent bacterial growth. 1 mark
Affects protein synthesis
Frequent treatment with vancomycin can result in resistant strains of bacteria. Explain how. 3 marks
- Mutation occurs
- Resistant allele
- Resistant bacteria survive and reproduce
- Vertical gene transmission
Use your knowledge of gene transmission to explain how the gene was passed from one species of bacterium to another. 3 marks
- Horizontal gene transmission
- Via conjugation
- Plasmid copied
- Plasmid transferred to s.aureus
Scientists can use protein structure to investigate the evolutionary relationships between different species. explain why. 2 marks
- Amino acid sequences
- Close the amino acid sequence the closer the relationship.
- Protein structure related to DNA base sequence.
Comparing the base sequence of genes provides more evolutionary information than comparing the structure of proteins. Explain why. 2 marks
- More bases than amino acids
- Introns
- More than once code for each amino acid.
Explain the importance of taking a large number of samples at each site. 1 mark
- Produces a more reliable mean
Explain the importance of taking samples at random. 1 mark
- Removes bias
Explain the effect of developing this golf course on the index of diversity of insects. 3 marks
- Increase in variety of plants
- More habitats
- Greater variety of food sources
Root pressure moves water through the xylem. Describe what causes root pressure. 3 marks
- Active transport by endodermis
- Ions into xylem
- Lowers water potential in xylem
- Water enters by osmosis
Explain how oxygen is loaded, transported and unloaded in the blood. 6 marks
- Haemoglobin carries oxygen
- In red blood cells
- At high potential of oxygen
- Unloads to respiring cells
- At low potential of oxygen
- Unloading linked to higher oxygen
The larvae in this investigation were kept at a temperature of 17 degrees, why was it important that the larvae of both species were kept at the same temperatures? 2 marks
- Allows comparison
- Different temperature affects enzymes
- Different temperature affects metabolism
- Different temperature affects amount of dissolved oxygen.
Apart from age, suggest two factors that the scientists should have considered when selecting volunteers for this trial. 2 marks
- Sex
- Health
- Ethnicity
In analysing the results of the investigation, the scientists took into account the age of the volunteers. Suggest why. 1 mark
Age affects risk of cancer
Tea and coffee contain caffeine. A newspaper reported the results of this investigation under the headline ‘ Caffeine helps cut cancer risk’. Explain why scientists could not support this view solely on the basis of this investigation. 4 marks
- Correlation does not mean causation
- Tea/coffee contains other substances
- Contain different amounts of caffeine
- No control group
- Only one type of cancer studied
- Further studies required.
Describe how the control group should have been treated. 2 marks
- Treated the same
- No caffeine
Volunteers who drank the same concentration of caffeine solution often had different concentrations of caffeine in their blood. Suggest one reason for the difference in concentration of caffeine in the blood of volunteers. 1 mark
- Absorb different amounts
- Broken down by enzymes
- Difference in metabolisms
The investigation showed that caffeine reduces the blood flow to certain parts of the brain. Suggest one way in which this could lead to a reduced risk of brain cancers. 1 mark
- Less oxygen to cancer cells
- Reduced spread of cancer cells
