A) Cytosine-Cytosine dimer B) Cytosine-Thymine dimer C) Thymine-Thymine dimer D) All of the above 36. What is passive transport? A) Movement of molecules against the concentration gradient requiring energy. B) Movement of molecules along the concentration gradient, without energy input. C) Movement of molecules in vesicles using ATP. D) The active uptake of molecules into the cell. 37. Which of the following is an example of passive transport? A) Sodium-potassium pump B) Calcium pump C) Na gated channel D) Endocytosis 38. Which structure allows passive transport of water across the cell membrane? A) Aquaporins B) Ion pumps C) Vesicles D) Sodium channels 39. Which type of ion channel is critical for propagating action potentials in neurons? A) Potassium (K+) channels B) Sodium (Na+) channels C) Calcium (Ca2+) channels D) Proton pumps 40. What type of transporter is GLUT? A) Passive ion channel B) Voltage-gated channel C) Facilitated diffusion transporter for glucose D) Active transport pump 41. How do mechanically gated channels function? A) By responding to voltage changes in the membrane. B) By opening in response to binding of specific ligands. C) By opening in response to physical deformation such as stretch or pressure. D) By transporting protons actively. 42. What distinguishes GLUT transporters from ion channels? A) GLUT transporters use ATP, whereas ion channels do not. B) GLUT transporters are selective for ions, while ion channels transport glucose. C) GLUT transporters facilitate diffusion of glucose, while ion channels transport charged particles. D) GLUT transporters are mechanically gated, while ion channels are always open. 43. Which of the following is an example of a voltage-gated ion channel? A) GLUT transporter B) Sodium (Na+) channel C) Mechanically gated channel D) Proton pump 44. Proton pumps are most commonly associated with which organelle? A) Nucleus B) Mitochondria C) Lysosome D) Endoplasmic reticulum