Describe a biochemical test to show that raffinose solution contains a non-reducing sugar. - Correct
Answer First heat the sample with an acid in a water bath and neutralise, then heat with Benedict
solution in a water bath for five minutes. A positive test should produce a red precipitate.
Explain the arrangement of phospholipids in a cell-surface membrane. - Correct Answer Phospholipids
are arranged in a phospholipid bilayer. The hydrophobic fatty acid tails point away from the water and
the hydrophilic heads attract the water.
Describe how an ester bond is formed in a phospholipid molecule. - Correct Answer An ester bond is
formed between a glycerol and a fatty acid, producing a water molecule in a condensation reaction.
State and explain the property of water that helps to prevent temperature increase in a cell. - Correct
Answer Water has a high specific heat capacity. This buffers changes in temperature, so lots of energy is
required to change the temperature.
Describe how a phagocyte destroys a pathogen present in the blood. - Correct Answer The phagocyte is
attracted to the pathogen by chemoattractants. The phagocyte binds to the pathogen. The pathogen is
engulfed and lysosomes migrate to the phagosome. The lysosomes then release lytic enzymes which
break down the pathogen. The breakdown products are then absorbed by the phagocyte.
Give two types of cell, other than pathogens, that can stimulate an immune response. - Correct Answer
Cancer cells and virus infected cells.
What is the role of a disulphide bridge in forming the quaternary structure of an antibody. - Correct
Answer It joins two polypeptide chains
Outline the role of organelles in the production, transport and release of proteins from Eukaryotic cells.
Do not include details of transcription or translation in your answer. - Correct Answer DNA in the
nucleus codes for the amino acids which make up proteins. Ribosomes on the RER then synthesise these
proteins. Mitochondria produce ATP for use in protein synthesis. The Golgi apparatus then packages and
modifies proteins which are transported to the cell surface membrane in vesicles where they fuse.
, Give one advantage of viewing a biological specimen using a transmission electron microscope
compared with using a scanning electron microscope. - Correct Answer There is a higher resolution /
view internal structures
Describe and explain the mechanism that causes lungs to fill with air. - Correct Answer The diaphragm
muscle contracts and external intercostal muscles contract. This causes an increase in volume and
decrease in pressure. This causes air to move down the pressure gradient and into the lungs.
Two solutions often used to stain tissues are haematoxylin solution and iodine solution.
-black colour.
The scientist used haematoxylin solution and not iodine solution to stain the lung tissue.
Suggest why. - Correct Answer The tissue doesn't contain starch and it makes the nucleus, which
contains DNA, visible.
Describe how mRNA is produced from an exposed template strand of DNA. Do not include DNA helices
or splicing in your answer. - Correct Answer Free RNA nucleotides form complementary base pairs. RNA
polymerase then forms phosphodiester bonds.
Define the term exon. - Correct Answer A triplet base sequence which codes for a sequence of amino
acids.
Describe binary fission in bacteria. - Correct Answer Circular DNA and plasmids are replicated, tenth
cytoplasm divides producing two daughter cells.
Suggest and explain how two environmental variables could be changed to increase the growth rate of
cells. - Correct Answer Increase the concentration of glucose and oxygen to increase the rate of
respiration, so growth rate increases.
Increasing the temperature increases enzyme activity.
Suggest and explain one advantage and one disadvantage of increased stomatal density on the growth
of tobacco plant leaves. - Correct Answer There is more carbon dioxide uptake therefore the rate of
photosynthesis increases resulting in more growth.
There is also more water loss via transpiration through the stomata, decreasing photosynthesis, slowing
growth.
Answer First heat the sample with an acid in a water bath and neutralise, then heat with Benedict
solution in a water bath for five minutes. A positive test should produce a red precipitate.
Explain the arrangement of phospholipids in a cell-surface membrane. - Correct Answer Phospholipids
are arranged in a phospholipid bilayer. The hydrophobic fatty acid tails point away from the water and
the hydrophilic heads attract the water.
Describe how an ester bond is formed in a phospholipid molecule. - Correct Answer An ester bond is
formed between a glycerol and a fatty acid, producing a water molecule in a condensation reaction.
State and explain the property of water that helps to prevent temperature increase in a cell. - Correct
Answer Water has a high specific heat capacity. This buffers changes in temperature, so lots of energy is
required to change the temperature.
Describe how a phagocyte destroys a pathogen present in the blood. - Correct Answer The phagocyte is
attracted to the pathogen by chemoattractants. The phagocyte binds to the pathogen. The pathogen is
engulfed and lysosomes migrate to the phagosome. The lysosomes then release lytic enzymes which
break down the pathogen. The breakdown products are then absorbed by the phagocyte.
Give two types of cell, other than pathogens, that can stimulate an immune response. - Correct Answer
Cancer cells and virus infected cells.
What is the role of a disulphide bridge in forming the quaternary structure of an antibody. - Correct
Answer It joins two polypeptide chains
Outline the role of organelles in the production, transport and release of proteins from Eukaryotic cells.
Do not include details of transcription or translation in your answer. - Correct Answer DNA in the
nucleus codes for the amino acids which make up proteins. Ribosomes on the RER then synthesise these
proteins. Mitochondria produce ATP for use in protein synthesis. The Golgi apparatus then packages and
modifies proteins which are transported to the cell surface membrane in vesicles where they fuse.
, Give one advantage of viewing a biological specimen using a transmission electron microscope
compared with using a scanning electron microscope. - Correct Answer There is a higher resolution /
view internal structures
Describe and explain the mechanism that causes lungs to fill with air. - Correct Answer The diaphragm
muscle contracts and external intercostal muscles contract. This causes an increase in volume and
decrease in pressure. This causes air to move down the pressure gradient and into the lungs.
Two solutions often used to stain tissues are haematoxylin solution and iodine solution.
-black colour.
The scientist used haematoxylin solution and not iodine solution to stain the lung tissue.
Suggest why. - Correct Answer The tissue doesn't contain starch and it makes the nucleus, which
contains DNA, visible.
Describe how mRNA is produced from an exposed template strand of DNA. Do not include DNA helices
or splicing in your answer. - Correct Answer Free RNA nucleotides form complementary base pairs. RNA
polymerase then forms phosphodiester bonds.
Define the term exon. - Correct Answer A triplet base sequence which codes for a sequence of amino
acids.
Describe binary fission in bacteria. - Correct Answer Circular DNA and plasmids are replicated, tenth
cytoplasm divides producing two daughter cells.
Suggest and explain how two environmental variables could be changed to increase the growth rate of
cells. - Correct Answer Increase the concentration of glucose and oxygen to increase the rate of
respiration, so growth rate increases.
Increasing the temperature increases enzyme activity.
Suggest and explain one advantage and one disadvantage of increased stomatal density on the growth
of tobacco plant leaves. - Correct Answer There is more carbon dioxide uptake therefore the rate of
photosynthesis increases resulting in more growth.
There is also more water loss via transpiration through the stomata, decreasing photosynthesis, slowing
growth.
