Cell Surface Membrane and the Fluid Mosaic Model

Fig. 1.1 shows a diagram of the fluid mosaic model of the structure of the cell surface membrane. Name the structures labelled A, B and C in Fig. 1.1. (a)   (b)   (c)  

• glycoprotein
• glycolipid
• cholesterol
• phospholipid bilayer
• phospholipid
• intrinsic protein

Fig. 1.1 shows a diagram of the fluid mosaic model of the structure of the cell surface membrane. Draw an arrow on Fig. 1.1 to show the movement of a molecule across the membrane into the cell by facilitated diffusion.

Fig. 1.1 shows a diagram of the fluid mosaic model of the structure of the cell surface membrane. Explain how the fluidity of the membrane would change if the proportion of unsaturated fatty acids in the phospholipid bilayer increased.

The R-groups of amino acids give them different properties. Suggest how the properties of the R-groups of the amino acids at position 1 of P may differ from the R-groups of the amino acids at position 2.

Haemoglobin is a globular protein containing haem groups. Explain how the presence of haem groups allows the haemoglobin molecule to transport oxygen.

In certain situations, such as during intense exercise, a person may breathe very quickly and deeply. This is known as hyperventilation. This hyperventilation causes more carbon dioxide to be exhaled. As a result, there is a lower concentration of carbon dioxide in the blood that passes through the capillary network in respiring tissues. This increases the affinity of haemoglobin for oxygen so that there is a decrease in the release of oxygen from red blood cells. Explain why a decrease in the concentration of carbon dioxide in the blood passing through respiring tissues leads to a decrease in the release of oxygen from red blood cells.

Fig. 2.1 is a diagram of a section through the heart. Describe and explain how the tunica media (middle layer of the wall) of blood vessel X adapts the blood vessel for its function.

Fig. 2.1 is a diagram of a section through the heart. Describe the role of the atrioventricular node (AVN) and the Purkyne tissue in the cardiac cycle.

The lock-and-key hypothesis and the induced-fit hypothesis are used to describe the interaction of enzymes and their substrates. Describe one similarity and one difference between the lock-and-key hypothesis and the induced-fit hypothesis.

Phosphorylase enzymes can catalyse the synthesis of starch and the breakdown of starch in some plant tissues. A reaction catalysed by starch phosphorylase is shown in Fig. 3.1. A student carried out an experiment to study the synthesis of starch by phosphorylase found in potato tissue. The student was provided with a solution, E, extracted from potato tissue. The extract was filtered to remove all the starch grains. Extract E contained biological molecules from the potato tissue including phosphorylase but no starch. Iodine solution was used to confirm that starch was not present in extract E. State the colour observed when iodine solution was added to a sample of extract E.

(a)