qs 2023 june exam

Question 1

how affinities of maternal/fetal Hb enable transfer of O2?

Answer 1

at the same partial pressure O2, fetal Hb has higher affinity for O2. Low pO2 in placenta, so oxygen dissociates from maternal HB and diffuses to fetal blood

Question 2

Explain why petri dishes observing plant growth are placed vertically and in dark

Answer 2

vertically- roots grow down and shoots grow up
in dark- light does not affect growth/prevent phototropism

Question 3

gwenIAA conc 100ppm- outline procedure students could use to prepare 8 test solutions

Answer 3

serial dilution
1cm3 stock sol and 9cm3 distilled water
repeat with each previously diluted sol

Question 4

precautions to ensure solutions prepared are accurate

Answer 4

new/clean pipette each transfer
ensure mixing at each step

Question 5

logarithmic results?

Answer 5

range of values- each interval is factor/power of 10

Question 6

functions of cytoskeleton

Answer 6

cell movement
support
hold organelles in place
form mitotic spindle
movement of chromosomes
cytokinises/cleavage

Question 7

how mutation in cytoskeleton causes nervous disease

Answer 7

change in protein structure
less movement of vesicles
less synaptic transmission
diameter of axon change
affect speed of nervous impulse

Question 8

mass reduction by 1kg- what happened to it?

Answer 8

Body fat/glycogen used for respiration to produce CO2 and H20.
Waste products excreted

Question 9

endotherm

Answer 9

use heat to maintain body temp.

Question 10

increase in thermogenic set point- consequences?

Answer 10

fever
raised temp body
increase immune response- antibody production

Question 11

cell membrane function

Answer 11

cell signalling
controls exit/entry
cell communication

Question 12

transpiration stream

Answer 12

movement of water
from root to leaves

Question 13

sunflower plants watered with conc solution 1000x than normal- why the plants wilted?

Answer 13

fertiliser lowers water potential
water moves out of root into soil by osmosis
plant loses more water than gained so turgor is reduced

Question 14

would plant be wilted if plant was watered with a sol containing cyanide ions that inhibit atp synthesis?

Answer 14

yes- atp required for active transport of ions into root so no water potential gradient

no- CN- ions many not have entered root and plant may be tolerant to CN- ions.

Question 15

explain why plants in high light intensity require more water than those in shade, even when at same temp

Answer 15

high light intensity increases rate of LDR.
more stomata open for gas exchange
increased transpiration so more water loss

Question 16

explain why mitosis is used in plant, not meiosis

Answer 16

produces genetically identical cells
maintains chromosome / diploid number (between
generations)

Question 17

why bacteria are unable to reproduce by mitosis

Answer 17

mitosis is nuclear division
bacteria have no nucleus

Question 18

for and against artificial cloning

Answer 18

+rapid production of large numbers of
individuals
* propagation of individuals with desirable
traits
* numbers of rare species can be increased
* production of large numbers of selectively
bred or genetically-modified individuals

• lack of genetic variation
  *population at greater risk of environmental
  change

Question 19

for/against cloning in plants

Answer 19

+propagation of seedless plants
* propagation of plants that are difficult to
grow from seed
* quicker than growing from seed
* growth of pathogen-free individuals

• if source material is infected with
  microorganisms offspring will be
• complex aseptic procedures

Question 20

for/against cloning animals

Answer 20

key individuals, e.g. beloved pets, can be
cloned

• process (SCNT) is inefficient / expensive
• high incidence of health issues

Question 21

describe how 8 a.u solution can be produced from 20 a.u. solution

Answer 21

(mix with) distilled water ✓
ratio of 3 (water) : 2 (stock solution

Question 22

liver has higher conc catalase than potato- why was potato used instead to observe

Answer 22

easier to control surface area
less chance of ethical objection

Question 23

potato cylinders were cut to same length- suggest further precaution to ensure validity

Answer 23

ensure no skin on potato
same variety of potato

Question 24

explain why activity of immobilised enzymes may be lower than that of free enzymes in sol

Answer 24

covalent bonding/matrix / carrier ,might affect shape of active site ✓
active site might be (partly) hidden (when bonded to the carrier) ✓
substrate must move through a matrix

Question 25

why immobilised yeast may be more expensive than immobilised invertebrase

Answer 25

yeast needs resources to stay alive e.g. food etc

Question 26

why varieties of pathogenic bacteria are resistant to range of antibiotics

Answer 26

widespread use at unfinished course
natural selection
variation and resistance

Question 27

how synthetic biology can be used in provision of new medicines

Answer 27

genetic modification of (named) organisms ✓
to produce, (named) drug / (therapeutic) proteins / vaccine

Question 28

beavers live in water in colonies. suggest why pop of beavers is measured in colonies rather than individuals

Answer 28

living in water makes them hard to count
easier to count (big) mounds (of wood)

Question 29

why reintro of beavers in example of conservation

Answer 29

human intervention ✓
habitat / ecosystem / biodiversity , changed / restored

Question 30

use nitrogen cycle to explain why plants do not grow well in low oxygen soil

Answer 30

increased denitrification / decreased nitrification ✓
conditions favour (named) denitrifying bacteria ✓
(more) nitrate / NO3 converted to nitrogen / N2 gas

Question 31

outline role of co-enzymes

Answer 31

assist enzymes
without permanently bound to enzymes
e.g. reduces activation energy, involved with binding etc

Question 32

describe how bioinformatics and computational biology can be used to compare genomes of different varieties

Answer 32

sequence genomes
develop appropriate software
use stat tests
analyse differences/similarities in DNA sequences

Question 33

genetic bottleneck?

Answer 33

large decrease in pop size reduces gene pool

Question 34

ways in which percentage error can be reduced

Answer 34

use equip with higher resolution e.g. pipette or measuring cylinder with higher resolution
use volumetric flask instead of measuring cylinder to measure water
use graduated pipette
one dilution not two etc

Question 35

describe general roles of homeobox genes and roles with development of the brain

Answer 35

General roles
* determine overall body plan
* switch different genes on and off in different cells and tissues
* (and therefore) determine cell identity
* expressed in a set order during development
* regulate patterning and positioning of
(named) structures
* determine polarity
* regulate levels of apoptosis and mitosis

Roles in brain development
* determine the head and tail regions / anterior and posterior regions and therefore where the brain and spinal cord will develop
* expressed in a set order to determine
(named) regions of the brain
* and neural organisation in the brain
* switch genes on or off in the brain
* to form specialised, neurones / nerve cells
* regulate mitosis and apoptosis of neurones to adjust neural organisation

Question 36

evaluate cites success using data

Answer 36

Positives (indicators of success)
* The majority of species identified as
threatened are protected under CITES (4.1)
* Approximately 20% of threatened species cannot
be traded (4.1)
* The number of species being assessed by the
IUCN is increasing every year, which means more
species can be added to the protected list (4.2)
* The number of species being assessed is rising
faster than the number of species identified as
threatened (4.2)
Negatives (indicators of lack of success)
* A large number (more than a quarter) of species
identified as threatened are not protected under
CITES (4.1)
* A large number (more than three quarters) of the
species identified as threatened can still be traded
(4.1)
* trade is only one aspect of protecting threatened
species (4.1)
* The number of species assessed is a small
fraction of the total number of species that exist,
which means most threatened species have not
been assessed or protected (4.2)
* The number of threatened species has increased
more rapidly in recent years (from 2018)
(suggesting conservation has not been
successful) (4.2)
* No data on the number of species that have
become extinct (4.2)
* the IUCN and CITES alone cannot prevent
extinctions (4.1 /4.2)