2011 Unit 2 Jan Flashcards
Hydrogen bonds are important in cellulose molecules. Explain why
- Forms cross links between chains/forms microfibrils;
- Providing strength/rigidity (to cellulose/cell wall);
- Hydrogen bonds strong in large numbers
A starch molecule has a spiral shape. Explain why this shape is important to its function in cells.
• Compact/occupies small space/tightly packed;
The total number of bases in the DNA of the α-polypeptide gene is more than 423.
Give two reasons why there are more than 423 bases.
• Stop/start sequences; • Non coding DNA (in the gene)/introns • Two chains/a non-coding strand/complementary base pairs; • Addition of base by mutation;
The haemoglobin in one organism may have a different chemical structure from the
haemoglobin in another organism. Describe how
• Different primary structure
Use the graph to explain why llamas are better adapted to live in high mountains than
horses
• Low partial pressure of oxygen; • In lungs; • (Llama) haemoglobin able to load more oxygen/ • Higher affinity for oxygen
Explain what is meant by a phylogenetic relationship.
• Shows evolutionary relationship;
They made samples of hybrid DNA using a gene that was found in all three species.
Explain why it was important that they made samples of hybrid DNA from the same
gene.
• Base sequence will be similar
• These bases will bind together/hydrogen
bonds/complementary pairs;
Explain what caused the DNA to separate at a higher temperature.
• Relationship is closer/more complementary
bases
• More hydrogen bonds
• More hydrogen bonds
What information is required to calculate an index of diversity for a particular community?
•Number of a/each (species)
Farmers clear tropical forest and grow crops instead. Explain how this causes the
diversity of insects in the area to decrease.
- Lower diversity of plants/ few species of plants/
- Few sources/types of food
- Few habitats
- Aspect of agriculture (killing insects)
The points on the graph have been joined with straight lines rather than with a smooth
curve. Explain why they have been joined with straight lines.
• Cannot predict/ do not know intermediate values
It would have been useful to have had a control ditch in this investigation. Explain why
• To see what would happen
The gene that codes for this enzyme may be passed from one species of bacteria to
another species. Describe how.
- Horizontal (gene) transmission
* (Gene passed by) conjugation
Use your knowledge of enzyme action to explain why the different sort of penicillin is effective in treating the infection
Shape
• Active site has specific shape/different penicillin has different shape/
Binding
• Not complementary
to active site/does not form E-S complex;
Consequence
• (Different) penicillin not broken down
Suggest how adding antibiotics to the food of the cattle increased profit for the farmers.
- Suggest how adding antibiotics to the food of the cattle increased profit for the farmers.
- Reduces spread of infection;
- Faster growth/more productive animals
Use your knowledge of selection to explain why adding antibiotics was banned.
- Resistant bacteria more likely to survive;
- Increase in numbers
- May infect humans
Suggest an explanation for the difference in transpiration rate between
conditions A and B.
A Still air 15oC 1.2 trans rate
B Moving air 15oC 1.7 trans rate
• Removes water vapour/moisture/saturated air
• Increases water potential gradient/more
diffusion/more evaporation;
Suggest an explanation for the difference in transpiration rate between conditions A and C
A Still air 15oC 1.2.trans rate
C Still air 25oC 2.3trans rate
- Increases kinetic energy;
- Water molecules move faster
- Increases diffusion/evaporation;
Describe the relationship between the rate of water movement through the xylem and
the light intensity
• Positive correlation/as light intensity increases so does
rate of water movement
Explain the change in the rate of water movement through the xylem between
06.00 and 12.00 hours.
• Stomata open;
• Photosynthesis increases/transpiration increases;
• More water pulled up;
• Cohesion between water molecules/by cohesion
tension;
Arteries and arterioles take blood away from the heart.
Explain how the structures of the walls of arteries and arterioles are related to their
functions
Elastic tissue • Elastic tissue stretches under pressure/when heart beats; • Recoils/springs back • Evens out pressure/flow; Muscle • Muscle contracts; • Reduces diameter of lumen/ • Changes flow/pressure; Epithelium • Epithelium smooth • Reduces friction
Explain how standard deviations of these
mean values would help you to interpret the data in Figure 2.
• Standard deviation gives a measure of
spread/variation
• More standard deviations overlap, the less likely it is
that differences are real
Describe how the biologists should carry out these breeding experiments.
• Cross shrimps from two sites/watch courtship
• Breed young together
•
•
The results of breeding experiments would help the biologists to decide whether the
shrimps were the same species. Explain how
• If same species the shrimps would breed,
producing fertile young/courtship species specific
