M19 Biology Paper 3

Using a scale bar, calculate the magnification of the image (2 marks)

Measure the scale bar image in mm
Convert (multiply by 1000)
Magnification \= scale bar image length / image (written in drawing)

x660

Explain how electron micrographs such as this helped falsify the Davson-Danielli model of membrane structure (2 marks)

The Davson-Danielli model proposed two layers of protein on either side of a lipid bilayer
Micrographs illustrate proteins are transmembrane proteins

Explain how the amphiphatic nature of phospholipids allows them to form bilayers (2 marks)

The outside hydrophilic parts are exposed to water
Hydrophobic parts are away from water inside

Outline how O2 consumption is measured using a respirometer (2 marks)

A CO2 absorber is added
A starting water level is measured
Rate of movement of the bubbles is a measure of O2 consumption

Suggest one conclusion that can be drawn from the results shown in the graph (1 mark)

As fungus grows, the rate of oxygen consumption increases

Other than humidity, suggest a variable that would need to be controlled in this experiment (1 mark)

Temperature

Outline the role of fungi in nutrient cycling (2 marks)

Act as decomposers
Feed on organic matter

Identify the type of blood vessels shown in the diagram (1 mark)

Veins

Deduce what the experiment demonstrated about the circulation of blood (2 marks)

Blood flows towards the heart
Valves prevent backflow

Question 1 a

Davson-Danielli

Question 1 b i

Protein (V)

Question 1 b ii

Phospholipid (head)

Question 1 c i

Phospholipids on the outside

Question 1 c ii

PH values away from optimum pH

substrate does not fit in active site

1 d

Scanning electronmicrography

2 a

0.45 mm

2 b

Thymine
Because thymine is not in RNA

3 a

Age and height

3 b

Both ventilation rates exercising is significantly more than at rest

Ventilation rate at 4000 m slightly higher than at sea level

3 c

Chest belt
Tidal volume recorded for a given period of time