P3 2 mark EQs

mainly from paper 3, some 1 markers

The secretion of osteocalcin (in an inactive form) by osteoblasts is controlled by positive feedback.

Use information from Figure 1 to explain why this is positive feedback.

The acidic pH conditions created by osteoclasts cause the inactive form of the protein osteocalcin to change into the active form of osteocalcin.

Suggest how

Binding of insulin leads to an increase in the rate of respiration in cells such as osteoblasts.

Explain how

Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.

Explain why

Suggest why the student soaked the root tips in hydrochloric acid in step 2

Pressing the coverslip downwards enabled the student to observe the stages of mitosis clearly.

Explain why

Other students in the class followed the same method, but calculated different mitotic indices.

Apart from student errors, suggest two explanations why

Complete the following definitions:

1. The genome is…

2. The proteome is…

Recombinant DNA technology can involve the transfer of fragments of human DNA into bacteria. The bacteria are then used to produce human proteins.

Give two reasons why bacteria are able to use human DNA to produce human proteins

Recombinant DNA technology can involve the transfer of fragments of human DNA into bacteria. The bacteria are then used to produce human proteins.

Suggest and explain one reason why bacteria might not be able to produce every human protein [1 mark]

Describe the role of saprobionts in the nitrogen cycle

Give two safety precautions that should be followed when dissecting a heart [1 mark]

Explain how valve A in Figure 2 maintains a unidirectional flow of blood

Give the correct biological term for each numbered space

1. carrying

2. niche

3. abiotic

4. community

Suggest two reasons for conserving rainforests

Farming cattle for humans to eat is less efficient than farming crops because of energy transfer.

Explain why

Scientists were investigating the effect of mycorrhizal species on the growth of tomato plants under different water conditions. The soil used in the investigation had the recommended concentration of fertiliser.

Suggest two reasons why the soil contained the recommended concentration of fertiliser

Scientists were investigating the effect of mycorrhizal species on the growth of tomato plants under different water conditions. The tomato seeds were planted in sterilised soil.

Suggest two reasons why the soil was sterilised

With some samples, the scientists decided they needed to carry out a series of dilutions of the sample before counting the bacteria/

Use evidence from Figure 3 to explain why the dilutions were necessary for some samples but not for others

The enzyme-catalysed reactions activated by ATR only occur if the substrates have been phosphorylated.

Use your knowledge of energy changes in enzyme catalysed reactions to suggest why [1 mark]

The rate of water movement through a shoot in a potometer may not be the same as the rate of water movement through the shoot of a whole plant.

Suggest one reason why [1 mark]

• the plant has roots

• xylem cells are very narrow

Explanation:

Advantage:

The action of endopeptidases and exopeptidases can increase the rate of protein digestion.

Describe how

Define the biological term population [2 marks]