An important characteristic of amino acids is that they can:

Correct Answer: A

Rationale: The correct answer is A: act as buffers. Amino acids can act as buffers by helping to maintain the pH balance in the body. Choice B is incorrect because amino acids do not primarily facilitate glucose storage. Choice C is incorrect as amino acids do not regulate the heartbeat. Choice D is also incorrect because amino acids do not control the level of blood cholesterol.

Correct Answer: C

Rationale: The correct answer is C, albumin. Albumin is a plasma protein that plays a crucial role in maintaining fluid balance in the blood. Collagen (choice A) is a structural protein found in connective tissues, not a plasma protein. Myosin (choice B) is a protein involved in muscle contraction, not found in the blood plasma. Phospholipid (choice D) is a type of lipid molecule, not a protein present in plasma.

Correct Answer: C

Rationale: A complete protein is the term used to describe a protein that contains all the essential amino acids required by the body in the right proportions. This makes choice C the correct answer. Choice A, 'simple,' is incorrect as it does not reflect the concept of essential amino acids. Choice B, 'indispensable,' while related to importance, does not specifically address the presence of all essential amino acids. Choice D, 'complementary,' is also incorrect as it refers to combining proteins to achieve a complete amino acid profile, rather than describing a protein that already contains all essential amino acids.

Correct Answer: B

Rationale: The correct answer is B, a peanut butter sandwich. A peanut butter sandwich combines grains from the bread and proteins from the nuts in the peanut butter, providing complementary proteins. This combination offers all essential amino acids. Choices A, C, and D do not contain complementary proteins as they lack the combination of different protein sources necessary to provide a complete amino acid profile.

Correct Answer: A

Rationale: The correct answer is A: 'incomplete.' Proteins from plant sources like grains, nuts, and legumes are considered incomplete because they often lack one or more essential amino acids required by the body. Choice B, 'complete,' is incorrect because complete proteins contain all essential amino acids in adequate amounts. Choice C, 'indispensable,' is incorrect as it refers to essential amino acids rather than the classification of plant proteins. Choice D, 'dispensable,' is also incorrect as it implies that these proteins are not necessary, which is not the case.