Cell structure and organellesIB MYP Sciences: Subtopic test

1. 1
   A biology class in Nairobi compares cells from three sources under a microscope: cells from a cheek swab, cells from a leaf of pondweed, and bacteria from a sample of yoghurt.

   (a)

   Which part of the cheek cells contains the DNA that controls the cell's activities?

   [1 mark]

   • AMitochondrion
   • BNucleus
   • CCytoplasm
   • DCell membrane

   (b)

   Which structure is found in the pondweed cells but not in the cheek cells?

   [1 mark]

   • ANucleus
   • BMitochondrion
   • CChloroplast
   • DCytoplasm

   (c)

   Outline two ways in which the structure of a bacterial cell from the yoghurt differs from that of a cheek cell.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Researchers compare cells from a long-distance runner's thigh muscle with skin cells from her arm. The muscle cells need a large, continuous supply of energy for running, and under the microscope they contain many more mitochondria than the skin cells.

   (a)

   Which process takes place in the mitochondria of the muscle cells?

   [1 mark]

   • APhotosynthesis
   • BOsmosis
   • CDigestion of food
   • DAerobic respiration

   (b)

   In which types of cell are mitochondria found?

   [1 mark]

   • APlant cells and animal cells
   • BAnimal cells only
   • CPlant cells only
   • DBacterial cells only

   (c)

   Explain why the runner's muscle cells contain many more mitochondria than her skin cells.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A horticulturalist in the Netherlands grows lettuce. On a hot day the unwatered lettuce leaves wilt and droop, but after watering they become firm again. She examines a lettuce leaf cell and a cheek cell and notes the differences in their structures.

   (a)

   Describe the function of each of these structures in a lettuce leaf cell: the cell wall, the chloroplasts and the permanent vacuole.

   [3 marks]

   (b)

   Explain, with reference to cell structures, how the lettuce leaf cells help the leaf stay firm when the plant is well watered, and why a cheek cell cannot give an animal tissue the same rigid support.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A plant science institute in Nairobi studies maize plants. Researchers are examining how the cells in different parts of a maize plant are built. They are also considering a project to breed or genetically modify maize so that its leaf cells contain more chloroplasts, in the hope of growing more food on limited farmland.

   (a)

   Plan an investigation to test a hypothesis about whether cells from the leaf and the root of a maize plant differ in their structure. In your answer, state your hypothesis with a scientific reason, identify the variables, and describe a safe method that uses a light microscope.

   [6 marks]

   (b)

   Discuss and evaluate the project to breed or genetically modify maize with more chloroplasts in its leaf cells. Consider social, economic and environmental implications, and finish with a justified conclusion.

   [6 marks]

   Total for question 4: 12 marks

End of questions