2019年5月IB生物SL真题下载-Paper3
1. Membrane structure can be investigated using a technique known as freeze fracture.Cells are frozen and then split. Fracturing often occurs between the two phospholipid layers of membranes in the cell. An electron micrograph of such a fractured membrane is shown.
(a) Using the scale bar, calculate the magnification of the image.
(b) Explain how electron micrographs such as this helped to falsify the Davson–Danielli model of membrane structure.
(c) Explain how the amphipathic nature of phospholipids allows them to form bilayers.
2. When feed for animals is stored, moisture levels need to be kept low to prevent the growth of fungi. Feed was exposed to 15 % moisture and placed into a respirometer. O2 consumption was monitored using the respirometer over a period of six days.
(a) (i) Outline how O2 consumption is measured using a respirometer.
(ii) Suggest one conclusion that can be drawn from the results shown in the graph.
(iii) Other than humidity, suggest a variable that would need to be controlled in this experiment.
(b) Outline the role of fungi in nutrient cycling.
3. In 1628, the physician William Harvey described details of the circulation of blood for the first time. In one experiment, he tied a tight bandage around the upper arm of a volunteer to display the blood vessels in the lower arm more clearly. He pressed his finger on the blood vessel at H. At the same time, he pushed the blood in the vessel from H to O with a second finger, removing the blood as shown in the diagram. When the finger at H was released, the blood vessel refilled with blood.
(a) Identify the type of blood vessels shown in the diagram.
(b) Deduce what the experiment demonstrated about the circulation of blood.
2019年5月IB生物SL真题余下省略！
你可能还关注