Each statement is true of proteins, except one. Which is the exception?

Correct Answer: B

Rationale: The correct answer is B. The classification of the 20 common amino acids is not based on the properties of their side chains, but rather on the structure of their amino and carboxyl groups. These groups are consistent among all amino acids, while the side chains, also known as R groups, are what vary and give each amino acid its unique properties. Choice A is correct because proteins are indeed composed of amino acids. Choice C is incorrect because while the side chains of amino acids can vary, the general structure of an amino acid - a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a side chain - is consistent. Choice D is correct because amino acids do polymerize to form long chains called polypeptides, which can then fold into complex shapes to form proteins.

Correct Answer: D

Rationale: Prevident is indicated for all the situations listed in the choices. It is recommended for patients with a high risk of caries to reduce the risk of tooth decay. It is also used in dental procedures like crown and bridge work to strengthen enamel and prevent cavities. Furthermore, it is utilized for orthodontic decalcification to aid in remineralizing the tooth structure and prevent further damage. Therefore, the correct answer is 'All of the above.' While choices A, B, and C are individually correct, selecting 'All of the above' is the most appropriate as it encompasses all the possible indications for Prevident.

Correct Answer: A

Rationale: The correct answer is 'A: Avoid giving the infant nighttime bottles' because prolonged exposure to sugars in milk during the night can lead to caries. Options 'B: Have the infant drink pasteurized skim milk' and 'D: Give the infant fruit juice to drink' are not recommended as they contain sugars that can cause cavities, especially in infants. Option 'C: Feed the infant iron-rich foods' is incorrect because while a balanced diet is important, iron-rich foods do not directly prevent caries development.

Correct Answer: A

Rationale: Both statements are indeed true. The loss of teeth or supporting periodontium frequently leads to poor food selection and limited chewing ability, as these conditions can make certain foods difficult to consume. Additionally, a patient's masticatory efficiency and biting force do decline with each tooth lost, as there are fewer teeth to distribute the force of the bite. Choices B, C, and D are incorrect because they suggest that one or both of these statements are false, which is not the case.

Correct Answer: D

Rationale: The correct answer is 'D'. Fast food is generally not deficient in protein since it often contains meat, a significant source of protein. On the other hand, fast food is known to lack essential nutrients like Vitamin A and certain minerals, as mentioned in choices 'A' and 'C'. Choice 'B' is also accurate as many fast food establishments have started offering healthier options such as salads due to customer demands. Therefore, all options are true except 'D', which makes it the exception.