general exam tips

Question 1

why do the standard deviations differ

Answer 1

different groups have different spreads of data around the mean

Question 2

what does it mean when the standard deviations overlap

Answer 2

-the data is not significant - so there is no significant difference in the values

Question 3

what does it mean when the standard deviations dont overlap

Answer 3

-the data is significant - there is a significant difference between the means

Question 4

estimate the value of the correlation coeffeicent of a postive correlation

Answer 4

-close to +1
-so between 0.5 and 0.99

Question 5

estimate the value of a negative correlation coefficient

Answer 5

-close to 0
-0 to 0.5

Question 6

sugegst some considerations that should have been taken into account to ensure that the study was reliable

Answer 6

-large sample size
-chose ppl randomly
-chose ppl with a range of ages
-equal number of males and females
-repeat readings/measurements

Question 7

why do the shapes/size in the image appear to be different comapred to each other and in real life

Answer 7

shape- tissue has been treated/killed/damaged
size-cut through different sections/planes

Question 8

patients recorded the intensity of pain, suggest two reasons why it was
important to use a statistically valid scale.

Answer 8

1. (Sensation of) pain is subjective
   OR
   Pain sensitivity/threshold/tolerance varies;
2. To ensure that differences (in pain detection)
   were (statistically) significant
   OR
   For (valid) comparison;

Question 9

Suggest what the scientist should do to ensure that he has removed all the water from
the sample.

Answer 9

1. Weigh and heat;
2. (Until) mass is constant;

Question 10

suggest one explanation for why the transmission reaction was less than 45 ms in trial 3

Answer 10

-student started to move her hand before the ruler was released
-ruler didnt fall vertically
-ruler stuck to skin
- student b held ruler to high

Question 11

in response to touch, nerve impulses can be transmitted at speeds of 76.2 m s-1
-suggest three reasons why, in this investigation, the estimated speed of student A’s impulse transmission was less than 76.2 ms-1

Answer 11

-synaptic transmission OR transmission at a neuromuscular junction
-time for muscle contraction
-time taken for (stretch-mediated) sodium ion channels to open
-student may have been distracted/concentrating
-time taken for coordination/comprehension (by the brain)

Question 12

if not asked for % of mitoitc index

Answer 12

do not times by 100
-just divide number of cells in mitosis by the total number of cells

Question 13

give reasons why bacteria/ other organisms are able to use human DNA to produce human proteins

Answer 13

-genetic code is universal
-mechanism of transcription is universal
-mechanism of translation is universal

Question 14

explain the importance of the marker gene

Answer 14

-shows that the gene has been taken up by the cells
-shows the transgenic/transformed cells
-allows detection of GM cells/organims

Question 15

the enhancer only stimulates the region M in a certain area
-suggests reasons for the importance of the enhancer being included in the DNA fragment transferred

Answer 15

-milk/protein is easy to extract from a goat
-extracting milk does not harm the goat
-if gene was in the blood could prevent/affect clotting
-could damage other cells

Question 16

how is agar sterilised

Answer 16

-heating or boiling it

Question 17

how does the crossing over event occur

Answer 17

1. Homologous pairs of chromosomes associate / form a bivalent;
2. Chiasma(ta) form;
3. (Equal) lengths of (non-sister) chromatids / alleles are exchanged;
4. Producing new combinations of alleles;

Question 18

what is the equation that represents the reaction catalysed by ATP sythase

Answer 18

ADP + Pi = ATP + H2O

Question 19

what is the purpose of the disulfide bridges in an antibody, in response to its quaternary structure

Answer 19

Joins two (different) polypeptides;

Question 20

plasma cells produce the antibody
b/plasma cells produce memory cells

Question 21

what is a monoclonal antibody

Answer 21

(Antibodies with the) same tertiary structure
OR
(Antibody produced from) identical/cloned plasma cells/B cells/B
lymphocytes;

Question 22

what is the effect of a small increase in pressure and in rate of blood flow in the aorta

Answer 22

1. Elastic recoil (of the aorta wall/tissue);
2. Smooths the blood flow
   OR
   Maintains rate of blood flow
   OR
   Maintains blood pressure;

Question 23

use knowlegde of mem structure to explain why more pigment is released when there is ethanol and acid

Answer 23

1. Higher absorbance indicates more anthocyanin
   OR
   Higher absorbance indicates more membrane
   damage/permeability
   OR
   (G not zero because) some anthocyanin
   released when blueberries are crushed
   OR
   (G not zero because) some membrane damage
   when blueberries are crushed;
2. More membrane damage/permeability results in
   more anthocyanin release
3. (E and F greater than water because)
   phospholipids dissolve in ethanol;
4. (E greater than F because) acid denatures
   membrane proteins;

Question 24

say Tumour suppressor genes are not
transcribed/expressed instead of genes switched off

Question 25

why is it important that the student ledt apparatus for 1 hour - yeast in glucose

Answer 25

so oxygen is used

Question 26

why would furosemide cause decrease in bp

Answer 26

-lower vol of blood

Question 27

inhibition of Na+ and Cl- cause increase in urine why

Answer 27

water potential of filtrate/tubule decreased; 2. Less water (reabsorbed) by osmosis (from filtrate/tubule); 3. Collecting duct (is where osmosis occurs);

Question 28

process for separating organelles

Answer 28

1. Break open cells/tissue and filter OR Grind/blend cells/tissue/leaves and filter; 2. In cold, same water potential/concentration, pH controlled solution(buffer); 3. Centrifuge/spin and remove nuclei/cell debris; 4. (Centrifuge/spin) at high(er) speed, chloroplasts settle out;

Question 29

if asked abt how molecules form in condenstation say how much water is produced

Question 30

decrease in pH - more acidic - causes a decrease in muscle contraction less Ca2+ released and less myosin bind to actin as less troponin/ tropomysoin sites exposed

Question 31

why can steriod hormones enter cell surface membrane

Answer 31

1. Lipid soluble; 2. (Diffuse through) phospholipid (bilayer);

Question 32

why can rod cells enable animals to hunt at night

Answer 32

1. High (visual) sensitivity; 2. Several rods connected to a single neurone; 3. Enough (neuro)transmitter to reach/overcome threshold

Question 33

myelination provides electrical insulation -non-myelinated have to depolarise across entire length of axon

Question 34

inhibit on neuron - why resting pt goes from -70 to + 0

Answer 34

1. No/less ATP produced; 2. No/less active transport OR Sodium/potassium pump inhibited; 3. Electrochemical gradient not maintained OR (Facilitated) diffusion of ions causes change to 0 mV OR (Results in) same concentration of (sodium and potassium) ions (either side of membrane) OR No net movement of (sodium and potassium) ions;

Question 35

IAA produced in tip

Question 36

if only two phenotypes in a table - no cross over has occured - dominant and ressive genes not produeced together - as genes are linked

Question 37

elongation in PCR involves DNA polymarase joing nucleotides producing new strand 72 degrees

Question 38

equation to show net production of consumers

Answer 38

N = I - (F + R)