Hydrogen bonds are important in cellulose molecules. Explain why
. Holds chains/cellulose molecules together/forms
cross links between chains/cellulose molecules/forms
microfibrils;
2. Providing strength/rigidity (to cellulose/cell wall);
3. 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;
What is the evidence from the diagram that haemoglobin has a quaternary structure?
More that one polypeptide/chain;
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/multiple
repeats/junk DNA; - 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/amino acids/different number
of polypeptide chains;
Name the other three taxonomic groups to which fruit flies and
mosquitoes both belong.
Kingdom, phylum and class;;
Explain what is meant by a phylogenetic relationship.
Shows evolutionary relationship;
Explain why it was important that they made samples of hybrid DNA from the same
gene.
- Base sequence will be similar/some bases in
common; - 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 base pairs; - More hydrogen bonds;
- More heat energy needed (to separate bonds);
Variety B cannot produce fertile gametes. Use information in the table to explain why.
) 1. Odd number of chromosomes/33 chromosomes (in
leaf cell);
2. Chromosomes cannot pair/cannot undergo
meiosis/would result in half chromosomes/cannot
form haploid cells;
Use your knowledge of cell division to explain how growing variety B on a large scale
will affect the genetic diversity of bananas.
Low genetic diversity because they are produced by
mitosis;
Will all have the same DNA/genes/alleles/ will be
genetically identical/will be clones;
OR
Low genetic diversity because they are not produced by
meiosis;
No crossing over/independent segregation/will not be
genetically different;
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/less
variety of plants/few plant layers; - Few sources/types of food/feeding sites;
- Few habitats/ niches;
- Fewer (species of) herbivore so few (species of)
carnivores; - Aspect of agriculture (killing insects);
The gene that codes for this enzyme may be passed from one species of bacteria to
another species. Describe how.
- Horizontal (gene) transmission;
2. (Gene passed by) conjugation/through pilus;
Use your knowledge of enzyme action to explain why the different
sort of penicillin is effective in treating the infection.
Shape
1. Different penicillin has different shape/structure/
enzyme/active site has specific shape/structure;
Binding
2. No longer fits/binds to active site/not complementary
to active site/does not form E-S complex;
Consequence
3. (Different) penicillin not broken down;
- Kills pathogenic/harmful bacteria/pathogens;
- Disease less likely/improves health/animals
healthier/reduces spread of infection; - Faster growth/more productive animals/more food
converted to meat/greater survival/lower vet‟s
bills/increased yield/less energy (for „fighting
infection‟);
- Kills pathogenic/harmful bacteria/pathogens;
- Disease less likely/improves health/animals
healthier/reduces spread of infection; - Faster growth/more productive animals/more food
converted to meat/greater survival/lower vet‟s
bills/increased yield/less energy (for „fighting
infection‟);
Adding antibiotics to the food of cattle is now banned in many countries. Use your
knowledge of selection to explain why adding antibiotics was banned.
- (Adding antibiotics) selects in favour of antibiotic
resistance/resistant bacteria more likely to survive; - Increase in numbers/higher proportion of resistant
bacteria; - May infect humans/may spread resistance to other
species/ horizontal transfer;
Suggest an explanation for the difference in transpiration rate between
conditions A and B.
A)Still air 15degrees 1.2
B )Moving air 15degrees 1.7
- 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 15degrees 1.2
C )still air 25degrees 2.3
- Increases kinetic energy;
- Water molecules move faster;
- Increases diffusion/evaporation;
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 1) Elastic tissue stretches under pressure/when heart beats; 2) Recoils/springs back; 3) Evens out pressure/flow; Muscle 4) Muscle contracts; 5) Reduces diameter of lumen/vasoconstriction/constricts vessel; 6) Changes flow/pressure; Epithelium 7) Epithelium smooth; 8) Reduces friction/blood clots/less resistance
