Graphs/ maths/ practical skills .

Question 1

How would you join points on a graph when there is no pattern

Answer 1

Straight lines point to point as not possible to predict intermediate values

Question 2

Describe how mouse getting injected with antigen forms antibody (5)

Answer 2

• antigen binds to specific T cell -> activates T cell
• T cell activates specific B cell
• B cell divides by clonal selection
• forms plasma cells
• plasma cells produce antibodies

Question 3

Describe how sample of chloroplasts can be separated from leaves (4)

Answer 3

• homogenised and filter
• in cold, isotonic, buffered solution
• centrifuge and remove nuclei
• centrifuge again at higher speed: chloroplasts settle out

Question 4

outline the role of organelles in the production transport and release of proteins from a eukaryotic cell

Answer 4

• DNA in nucleus is code for protein
• rER produces protein
• mitochondria produces ATP for protein synthesis
• golgi apparatus package/ modify
• vesicles transport

Question 5

What are the advantages of using standard deviation instead of the range?

Answer 5

• SD shows the spread of data around the mean, whereas the range is only the difference between the highest on the lowest values
• SD reduces the effect of anomalies, whereas the range includes anomalies.
• SD can be used to indicate whether a difference between results is significant.

Question 6

Explain the results for increasing substrate concentration and no inhibitor. (2)

Answer 6

• (rate of reaction) increases because more enzyme-substrate complexes are formed
• levels off because enzyme concentration becomes limiting factor (no free active sites left)

Question 7

what would the students have used to monitor the temperature of water in each tube?

Answer 7

Take readings using a thermometer during experiment at regular intervals.
* correct the temperature if fluctuated

Question 8

What does OH- do to the bilayer?

Answer 8

dissolves the phos. bilayer

Question 9

When explaining graphs:

Answer 9

include eg:
* uptake initially slower because..
* uptake levels of because..
DESCRIBE the graph even if it is an ‘explain’ question

Question 10

Imatinib is taken up by blood cells by active transport.
Explain how the data for the two different temperatures support this statement.

Answer 10

• all concentrations show that uptake is higher at 37 degrees, rather than 25 degrees.
• Respiration/ ATP production is faster at higher temperatures.
• Therefore, active transport will be faster at higher temperatures, so uptake will increase at higher temperatures.

Question 11

5 ways to improve a scientific sketch:

Answer 11

1. Only use single lines/do not use sketching (lines)/ensure lines are continuous/connected;
2. Add labels/annotations/title;
3. Add magnification/scale (bar);
4. Draw all parts to same scale/relative size;
5. Do not use shading/hatching;

Question 12

instead of plataeu say:

Answer 12

levelled out

Question 13

Give two reasons why it was important that the student counted the number of stomata in several parts of each piece of leaf tissue.

Answer 13

1. So it is a representative sample;
2. To obtain a (reliable) mean;

Question 14

When there is many DV to compare and conclude:

Answer 14

• some support reasons
• some against
• correlation NOT causation
• other factors could have affected eg….

Question 15

Why is statistical testing in biology important?

Answer 15

Aim:
To find the probability that difference/correlation in results is due to chance

This allows acceptance or rejection of the null hypothesis

Question 16

P < 0.05 means:

Answer 16

Probability that results are due to chance less than 5%
* so we can reject the null hypothesis
* difference is statistically significant

else not significant difference, null hypothesis is accepted