Page 03 3. The diagram below represents a transmembrane protein. Some of the amino acids in the protein have been identified. Membrane Intracellular Extracellular Arg Ala Ser Leu Leu Ser Which row in the table classifies the amino acids shown in this protein? Arginine (Arg) Alanine (Ala) Leucine (Leu) Serine (Ser) A polar hydrophobic hydrophobic polar B hydrophobic polar hydrophobic polar C polar hydrophobic polar hydrophobic D hydrophobic polar polar hydrophobic [Turn over Page 04 Questions 4 and 5 refer to the following information. During muscle contraction, the protein myosin moves along an actin protein filament by the head of the myosin detaching from the actin, swinging forward and rebinding, as shown in the diagram. myosin 36 nm actin [1 nm = 1 × 10–9 m] 4. This reversible conformational change can be brought about by binding of ATP to the myosin head followed by hydrolysis and release of phosphate and ADP. The myosin head is acting as A a kinase B an ATPase C a proteinase D a phosphatase. 5. When the myosin head detaches and swings forward it moves a distance of 36 nanometres (nm). Myosin has been observed to move at a speed of 18 × 103 nm s–1. How many times will the myosin head detach and swing forward in one second? A 50 B 200 C 500 D 2000 6. In animal rod cells rhodopsin absorbs a photon of light initiating the following cell events. 1 nerve impulse is generated 2 sufficient product formation is triggered 3 activation of hundreds of G-protein molecules 4 activation of hundreds of molecules of an enzyme The correct order of events is A 4, 2, 1, 3 B 3, 4, 2, 1 C 4, 3, 1, 2 D 3, 2, 4, 1.