Wrong PPQS

Question 1

q4

An investigation was carried out into the effect of changing light intensity on the growth of tomato plants. Plants were placed under different intensities of light, and their growth wasdetermined by measuring the length and dry mass of the plants.
Which row in the table describes features of this investigation?

A - discreate and multi-factorial
B- continuous and not multi-factorial
C - discreate and not multi-factorial
D - continuous and multi-factorial

Answer 1

B

Its continuous as the results will be a range of numbers rather than a ‘yes’ or ‘no’

Multifactorial is when there is more than one independant variable - the independant variables of these studies should be monitored

Question 2

q5

A researcher studying a protein with an isoelectric point of pH 8.2 wanted to separate it from a mixture of proteins and determine its molecular mass (size). A solution containing the mixture of proteins was adjusted to pH 8.2 then centrifuged.
The most appropriate next steps would be to

A - collect the protein from the pellet and carry out SDS‑polyacrylamide electrophoresis
(SDS‑PAGE)
B - collect the protein from the supernatant and carry out SDS‑polyacrylamide
electrophoresis (SDS-PAGE)
C - collect the protein from the pellet and carry out native gel electrophoresis
D - collect the protein from the supernatant and carry out native gel electrophoresis.

Answer 2

A

The protein will be within the pellet after centrifugion
SDS-PAGE seperates out proteins soley based on their size
Native PAGE seperates by shape, size and chage

Question 3

q6

Which row in the table shows the direction of shift in the oxygen dissociation curve as a
result of changes in pH and temperature?

A - Shfit left, decrease pH, increase temp
B - shift right, increase pH, increase temp
C- shift left, increase pH, decrease temp
D - shift rigt, decrease pH, decrease temp

Answer 3

C

Decreassing Ph decreases affinity for oxygen (shifts right)
increasing pH increases affinity for oxygen (shift left)
Decreasing temperature increases affinity for oxygen (shift left)
Increasing temperature decreases affinity for oxygen (shift right)

Question 4

Q8

The following events occur during the transmission of a nerve impulse from one neuron to
the next:
1. The neurotransmitter binds to its receptor.
2. Voltage‑gated sodium channels open and sodium ions diffuse into the cell causing local
depolarisation.
3. Vesicles containing the neurotransmitter fuse with the membrane.
4. Ligand‑gated ion channels open.
5. The neurotransmitter diffuses across the synaptic cleft

The correct order of events is:
A - 5 3 4 1 2
B - 3 5 1 4 2
C - 3 5 1 2 4
D - 5 3 1 4 2

Answer 4

B

1. vesciles containing neurotransmitter fuse with the membreane
2. the neurotransmitter diffuses across te synaptic cleft
3. neutrotransmitter binds to its receptor
4. ligand - gated ion canngels open
5. VG sodium channels open, sodium ions diffuse into cell, depolarisation occurs

Question 5

Q11

An elimination programme has been developed to reduce the size of the ship rat population
on the islands. Scientists estimated the population size of the rats throughout the
programme by using mark and recapture techniques.
Which of the following is not an assumption of the mark and recapture technique

A - te sip rat population will increase due to their rapid reproduction rate
B - the marked and released rats can mix fully with the total ship rat population
C - None of the ship rats have left the survey area.
D - Every ship rat in the population has an equal chance of being captured during the
sample.

Answer 5

A

CMR assumed that no individuals die, are born, immigrate, emigrate or dissappear

Question 6

q13

Which of the following is a correct statement about X chromosome inactivation?

A - It is the cause of the Y chromosome being genetically inactive
B - In females, it prevents the expression of harmful alleles present on the X chromosome
C - The X chromosome inherited from the mother is active in all female cells.
D - It ensures the amount of protein encoded by X chromosomes in females is
approximately equal to that of males.

Answer 6

D

X chromosome inactivation ensures the amount of protien encoded by X chromosomes in females is equal to males

Question 7

Q19

Which of the following is the same for a secondary immune response?

A - speed of antibody production
B - antibody concentration in blood
C - antigen triggering response
D - duration of response

Answer 7

C

Secondary immune response occurs upon the second time your immune system encounters an antigen

Therefore the antigen triggering response is the only option that will not be more efficient/faster the second time

Question 8

1a

What is meant by a model organism

Answer 8

A model organism is an organims tat is easy to study and can apply the investigated information to other, harder to study species

Question 9

2aii

Explain the benefit of aspectic technique when culturing yeast cells

Answer 9

Eliminate contaminate microbes

Question 10

2bii

Describe a method that can be used to estimate the number of viable cells in a liquid culture

Answer 10

Using a vital stain to distinguish between dead and living cells and then using a haemocytometer

Question 11

4a

give an advantage of a randomised experimental block design

Answer 11

eliinates bias and reduces te effect of confounding variables

a confounding variable affects both the independant and dependant variable and must be monitored closely

Question 12

4b

what is the difference between a positive and negetive control

Answer 12

A negetive control gets the treatment that isnt expected to produce results

A positive cotnrol involved giving a group a treatmetn with a known outcome

Question 12

7

discuss methods of sharing and the importance of both sharing and reviewing scientific findings

Answer 12

scientific findings are published so waork can be repeated and or built upon
it can be puglished in hournals, articles or papers
this allowes it to be peer reviewed by scientists in te relevent field to assess the quality of the submitted manuscript
findings can also be shared at talks, media and conferences
it helps to educate the public and stop the spread of scientific misinformation

Question 13

8ai

state the term for a checklist of animal behaviours

Answer 13

Ethogram

Question 14

8aii

suggest shy roducing a checklist of animal behaviours increased the validity of the study

Answer 14

it reduces the risk of misidentification and the variability of the interpretation of behaviours

Question 15

8b

why would these:
each individual in a pack was analysed separately
the same video footage was analysed separately by two scientists.
reduce error in results

Answer 15

minimises te risk of missing behaviours, confusing animals or missing individuals

results can be compared, one can spot errors in the others work, findings arent only one persons opinon

Question 16

11ai

explain what is meant by sexual selection

Answer 16

non-random selection of alles that increase the individuals chances of mating

Question 17

11aii

why can female choice result in sexual dimorphism

Answer 17

female choice acts as a selection pressure on males

this results in the male looking physicallt different because those characteristics are not selected for in the female

Question 18

11aiii

state the term used for traits that indicate the reproductive fitness of an individual

Answer 18

honest signal

Question 19

Q1

the protenome is

A. all the genes expressed as proteins
B. the entire set of proteins expressed by the genome
C. the number of proteins expressed due to alternative RNA splicing
D. The number of proteins expressed due to alternative RNA spliting and post translational modification

Answer 19

B

The protenome is larger than the genome due to Post-translational modification and RNA splicing

Question 20

Q2

Transmembrane proteins carry a signal sequence, which halts translation and directs the ribosome synthesising the protein to dock with the

A. Plasma membrane
B. Endoplasmic reticulum
C. transport vesicle
D. golgi apparatus

Answer 20

B

To finish protein sythesis, the ribosome docks with the endoplasmic reticulum, becoming the RER. After that the protein will either go to the lysome in a vesicle or will move to the golgi apparatus (again in a vesicle) and undergo post translational modification

Question 21

Q5

what evens describe signalling by the hormone insulin

A. instracellular and G protein activation
B. Intracellular and phosphorylation
C. extracellular and G protein activation
D. Extracellular and phosphorylation

Answer 21

D

the hormone insulin is a hydrophilic signalling molecule and cannot pass through the cell membrane. after binding, the receptor undergoes a conformational change which causes a phosphorylatin cascade to occur

Question 22

Q7

which of the following is an example of replacement?

3 R’s

A. Use of most appropriate anaesthetic regimes for pain relief during procedures.
B. Smaller mammals such as mice or rats instead of larger mammals
C. Substitution of in vivo studies with tissue culture to test the effect of a new drug
D. Less invasive techniques instead of surgical techniques

Answer 22

C

In vivo means that the testing is happening inside of the organism, this is invasive and potentally harmful. Therefore, using a tissue culture instead will fill the requirement of replacement

Question 23

Q12

what is the difference between sister and non-sister chromatid?

Answer 23

Sister chromatids are identical copies of a single chromosome whilst non-sister chromatids are chromatids from homologous chromosomes

chiasmata formation occurs between non-sister chromatids, Meiosis II occurs with sister chromatids

Question 24

# Q13 what formula calculates absolute fitness?

Answer 24

Frequency of particular genome after selection / Frequency of a particular genome before selection

Question 25

# Q17 A student was planning an investigation into the effect of temperature on the rate of respiration in yeast; this was measured using a carbon dioxide probe. As part of their pilot studies, they used the probe to take three readings from one sample. This would be most useful for checking ## Footnote A . precision B. accuracy C. reliability D. validity

Answer 25

A ## Footnote To increase percision in an experiment, you regularly calibrate and maintain equipment, take multiple readings and record significant figures correctly and increasing sample size To increase accuracy keep controlable variables similar between repeats, use control groups and minimise human error to increase reliabiltiy

Question 26

# Q19 what best describes natural killer cells? ## Footnote A. specific, induce apoptosis in parasite-infected cells B. Specific, use enzymes in lysosomes to digest parasites C. non-specific, induce apoptosis in parasite-infected cells D. Non-specific, use enzymes in lysomes to digest parasites

Answer 26

C ## Footnote Natural killer cells are a part of apoptosis, lysomes are related to antibodies and the immune response killer cells are non-specific

Question 27

# Q20 what is antigenic variation

Answer 27

It is when pathogens have the ability to change their surface antigens to evade the bodies antibodies as they will not have the new onces memories and cannot elicite a secondary response, by doing this they can evade the hosts immune system

Question 28

# Q2bii What happens during western blotting

Answer 28

1. the protein is transferred to a solid medium by blotting 2. proteins are labelled with antibodies that are specific to their target protein 3. exvess is washed away but some antibodys bind specifically to their targets 4. a second antibody with a reporter (chemiluminescent, fluorescent or radioactive) 5. membreane places against photographic film

Question 29

# Q4a What name is given to a scientific article that summarises current knowledge and recent findings in a particular field

Answer 29

Review article

Question 30

# Q4cii T/F, small sample size indicated poor reliability

Answer 30

True, in experiments, especially more important ones, there should be several repeats of the experiment. This demonstrates that the results are consistant and not coincidental errors

Question 31

# Q4cv The authors reported that the patients had been selected as they were family members of homeopathic therapists. Suggest how this selection bias might have affected the validity of this study.

Answer 31

Sample may not be representative of average population Patients may be more responsive to treatment as they might believe in homeopathic remedies May result in a greater placebo effect (since they believe in homeopathy) May lie about symptoms/improvments due to family ties

Question 32

# Q5 describe how facillitated diffusion takes place

Answer 32

facilitated diffusion is a type of passive transport it occurs down the molecules concentration gradient it requires specific proteins that undergo conformational change when binding occurs the molecule can go through pores in channels or channels/transporters

Question 33

# Q6ai Give an example of an external death signal

Answer 33

Death signal molecules from lymphocytes

Question 34

give an example of an internal death signal

Answer 34

DNA damage It sends a signal, activating p53

Question 35

# q6c state a process in which apoptosis is essential

Answer 35

metamorphesis removing damaged or diseased (eg cancer) cells

Question 36

# Q7 Describe the structure of viruses, and explain why they are classified as parasites

Answer 36

Viruses contian thir genetic material in the form of DNA or RNA, packaged in a protective protein coat The outer surface of a virus contrians antigens the host cell may or may not be able to detect as forgein. Some viruses are surrounded by a phospholipid membrane. Parasitism is a symbiotic interaction. The parasite gains energy and nutriton at the expense of the host (+/-) Viruses can only replicate in the host cell

Question 37

# q10aiii State another environmental factor that may be important in sex change in other animal species.

Answer 37

Size, parasitic infection, competition and temperature

Question 38

# 10b what are the costs of external reproduction

Answer 38

1. lower chance of successful fertilisation 2. high energy requirements to produce so many gamates 3. gamates can be predated or lost 4. little parental care 5. very few offspring survive

Question 39

# 11c why is parthenogensis more common in cooler climates

Answer 39

There is less parasite burden in cooler climates and therefore there is less necessity for genetic variation to combat parasitism

Question 40

# 7 The response to an increase in insulin concentration in the blood involves the following events. 1. Recruitment of GLUT 4 to the cell membrane. 2. A phosphorylation cascade inside the cell. 3. Insulin receptor changes conformation. 4. Phosphorylation of the insulin receptor. 5. Binding of insulin to its receptor. Determine the correct sequence of events ## Footnote A. 5 4 3 1 2 B. 2 4 3 5 1 C. 5 3 4 2 1 D. 5 3 1 2 4

Answer 40

C Binding of insulin to receptor insulin receptor changes conformation phosphorylation of receptor phosphorylation cascade recruitment of GLUT 4 to the cell membrane

Question 41

# 8. what does phosphodiatrase (PDE) break down in photoreception

Answer 41

cGMP

Question 42

# 8 What is the G-protein in photoreception called

Answer 42

Transducin

Question 43

# 16 what is a gametocyte

Answer 43

A gametocyte is the cell that undergoes meiosis to form gamates

Question 44

# 4 which of the following is an advantage of an in vitro experiment ## Footnote a. the environment is closely controlled b. the effect on whole organisms can be monitored c. the organism is in its natural surroundings d the envrionmeetn is affected by confounding variables

Answer 44

A. The environment is closely monitored as it is done in an experimental lab