Cerrar
Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells.
(5 marks)
Describe the principles and limitations of using a transmission electron microscope to
investigate cell structure.
(5 marks)
Describe how you could use cell fractionation to isolate chloroplasts from leaf tissue.
(3 marks)
Name two structures in a eukaryotic cell that cannot be identified using an optical
microscope.
(2 marks)
Describe what happens during anaphase that results in the production of two
genetically identical cells.
(2 marks)
A sample of epithelial tissue was analysed. Some of the cells had 8.4 units of DNA, others had only 4.2 units. Use your knowledge of the cell cycle to explain why some cells had 8.4 units of DNA and others had only 4.2 units.
(2 marks)
Mitosis is important in the life of an organism. Give two reasons why.
(2 marks)
Name two structures present in an epithelial cell from the small intestine that are not present in a cholera bacterium.
(2 marks)
Give one advantage of using a TEM rather than a SEM.
(1 mark)
Give one advantage of using a SEM rather than a TEM.
(1 mark)
An optical microscope cannot be used to see a plasma membrane. Explain why.
(2 marks)
Give one property of molecules which can diffuse through a cell membrane.
(1 mark)
A group of scientists homogenised pancreatic tissue before carrying out cell fractionation to isolate an organelle.
Explain why scientists:
Homogenised the tissue.
(1 mark)
A group of scientists homogenised pancreatic tissue before carrying out cell fractionation to isolate an organelle.
Explain why scientists:
Filtered the resulting suspension.
(1 mark)
A group of scientists homogenised pancreatic tissue before carrying out cell fractionation to isolate an organelle.
Explain why scientists:
Kept the suspension ice cold during the process.
(1 mark)
A group of scientists homogenised pancreatic tissue before carrying out cell fractionation to isolate an organelle.
Explain why scientists:
Used isotonic solution during the process.
(2 marks)
Contrast the processes of facilitated diffusion and active transport.
(3 marks)
Explain why an antibody attaches only to a specific protein.
(2 marks)
If the DNA of the cell is damaged, a protein called p53 stops the cell cycle.
Mutation in the gene for p53 could cause cancer to develop. Explain how.
(3 marks)
Drugs are used to treat cancer. At what phase in the cell cycle would each of the following drugs act?
(i) A drug that prevents DNA replication
(ii) A drug that prevents spindle fibres shortening.
(2 marks)
A mutation of a tumour suppressor gene can result in the formation of a tumour.
Explain how.
(2 marks)
Some cancer cells have a receptor protein in their cell-surface membrane that binds to a hormone called growth factor. This stimulates the cancer cells to divide.
Scientists have produced a monoclonal antibody that stops this stimulation.
Use your knowledge of monoclonal antibodies to suggest how this antibody stops the growth of a tumour.
(3 marks)
Scientists use a specific antibody to detect an antigen on the bacterium that causes stomach ulcers. Explain why the antibody will only detect this antigen.
(3 marks)
People with AIDS die because they are unable to produce an immune response to
pathogens.
Explain why this leads to death.
(3 marks)
What is an antigen?
(2 marks)
Describe how B-lymphocytes respond when they are stimulated by antigens.
(4 marks)
Most of the water uptake in a root takes place in the region just behind the root tip. Explain why.
(2 marks)
Name the stage of mitosis that immediately follows anaphase.
(1 mark)
A clone of genetically identical animals can be obtained from one embryo. Explain how.
(2 marks)
Describe and explain 3 organelles you would see in large numbers in an exocrine cell in the pancreas.
(6 marks)
Describe and explain 3 organelles you would see in large numbers in an epithelial cell lining the small intestine.
(6 marks)
What is a pathogen?
(1 mark)
