Q: What can prevent the passage of molecules and ions between cells, such as in the blood-brain barrier? Read this paragraph and choose the correct option from the provided answers: In addition to holding cells together, tight junctions play a role in the transport of materials. Tight junctions prevent the passage of molecules and ions through the space between cells. So these molecules and ions must actually enter cells (either by diffusion or active transport) in order to proceed through a tissue. This allows tight junctions to indirectly play a role over what substances are allowed into a specific cell. Tight junctions play this role in maintaining the blood-brain barrier. Choices: - fatty junctions - solid junctions - special junctions - tight junctions A:
tight junctions

Q: In what process is atp created by glycolysis, without oxygen? Read this paragraph and choose the correct option from the provided answers: Two different pathways accomplish the regeneration of NAD + with rather famous products: lactic acid (C 3 H 6 O 3 ) and ethyl alcohol (C 2 H 6 O) ( Figure above ). Making ATP in the absence of oxygen by glycolysis alone is known as fermentation . Therefore, these two pathways are called lactic acid fermentation and alcoholic fermentation . If you lack interest in organisms, such as yeast and bacteria, which have "stuck with" the anaerobic tradition, the products of these chemical reactions may still intrigue you. Fermentation makes bread, yogurt, beer, wine, and some new biofuels. In addition, some of your body's cells are facultative anaerobes, retaining one of these ancient pathways for short-term, emergency use. Choices: - sedimentation - oxidation - condensation - fermentation A:
fermentation

Q: Which structure includes sugar-phosphate "backbones", composed of alternating phosphate groups and deoxyribose sugars, and nitrogenous bases? Read this paragraph and choose the correct option from the provided answers: The DNA double helix. The two sides are the sugar-phosphate backbones, composed of alternating phosphate groups and deoxyribose sugars. The nitrogenous bases face the center of the double helix. As the base-pairing rules tell us, A always pairs with T, and G always pairs with C. Choices: - molecule double helix - mulecular triplex - dna triple helix - dna double helix A:
dna double helix