Past paper questions - paper 1

Question 1

Explain why the conditions in peat bogs prevent decomposition (3)

Answer 1

-Conditions are anaerobic
-Therefore less aerobic respiration by decomposers
-Acidic conditions inhibit/denature enzymes
-Therefore enzymes cannot digest/break down organic material

Question 2

Devise a procedure to measure the rate of recovery of the peat bog (4)

Answer 2

-Use quadrats for sampling
-Use a random number to determine coordinates for random sampling
-Record percentage cover of the plant in each quadrat
-Several quadrats/samples measured and mean is calculated
-Sample at regular time intervals
-Calculate the rate of change in plant cover

Question 3

Describe the primary structure of a protein (2)

Answer 3

-Sequence of amino acids
-Joined by peptide bonds

Question 4

The primary structure of this protein is then converted to tertiary structure and modified by organelles in the cell

Describe the role of the organelles involved in these processes (5)

Answer 4

-Folding of protein inside the rough endoplasmic reticulum
-Bonds formed between G groups
-rER forms/packages proteins into vesicles
-Vesicles transport the protein to the Golgi apparatus
-Proteins modified in the Golgi
-Carbohydrates/sugar molecules added

Question 5

Porphyria is a life threatening genetic disease. it is caused by a mutation in the gene coding for an enzyme involved in the production of haem.
In people with porphyria, haem cannot be produced.

Explain why this mutation may prevent the enzyme involved in the production of haem from functioning correctly (4)

Answer 5

-Mutation will lead to a change in the sequence of bases in the DNA
-Therefore a mutation may lead to a change in amino acid sequence
-Different R groups would change the tertiary structure of the enzyme
-Therefore the shape of the active site is changed
-Meaning substrate does not fit active site of the enzyme

Question 6

Explain why a fertilised egg cell will contain only maternal mitochondria (2)

Answer 6

-Only the nucleus of the sperm enters the ovum
-Therefore all the mitochondria come from the egg cell (mitochondria from sperm don’t enter egg cell)

Question 7

Devise an investigation to compare the rate of the light-dependent reaction in shade tolerant and shade intolerant plants grown at different light intensities (6)

Answer 7

-Use shade tolerant and shade intolerant plants
-Plants grown in the same conditions e.g. temperature, humidity
-Plants grown in either 5% or 25% light/range of intensities
-Take same masses of leaf
-Add to equal volume of isolation medium
-Blend/grind in pestle and mortar for the same length of time
-Filter suspensions of plant material
-Expose suspensions to 5% and 25% light intensity
-Keep temperature controlled
-Add DCPIP and record time to decolourise DCPIP
-Shade tolerant plants would decolourise more quickly at lower light intensity

Question 8

It is thought that burning wood chips is more beneficial to the environment because in the long term it does not add CO2 to the armosphere

Explain why burning wood chips does not increase carbon dioxide to the atmosphere in the long term (4)

Answer 8

-Carbon dioxide produced by burning wood replaces CO2 that is absorbed by trees
-Trees absorb carbon dioxide for photosynthesis
-New trees are grown to replace those that are cut down
-Therefore there is no net increase in carbon dioxide, therefore it is carbon neutral

Question 9

Fertilised cells divide by…

Answer 9

Mitosis to produce genetically identical cells

Question 10

Describe the roles that zoos play in animal conservation (3)

Answer 10

-Protection from poachers
-Repopulation via captive breeding programmes
-Education via conservation
-Researching animals to improve their health and develop a genetic database