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What role do the amino acids methionine, tyrosine, and tryptophan play?
- A. Forming neurotransmitters.
- B. Blocking excess protein breakdown.
- C. Increasing production of insulin and thyroxine.
- D. Decreasing energy expenditure.
Correct Answer: A
Rationale: The correct answer is A: Forming neurotransmitters. Methionine, tyrosine, and tryptophan are important amino acids involved in the production of neurotransmitters in the body. Neurotransmitters are chemical messengers that transmit signals across nerve cells, influencing various functions such as mood, memory, and muscle control. Choices B, C, and D are incorrect because these amino acids do not primarily play a role in blocking protein breakdown, increasing insulin and thyroxine production, or decreasing energy expenditure.
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Which lipoprotein increases the risk of cardiovascular disease?
- A. Low-density lipoprotein (LDL)
- B. High-density lipoprotein (HDL)
- C. Very low-density lipoprotein (VLDL)
- D. Chylomicrons
Correct Answer: A
Rationale: The correct answer is A: Low-density lipoprotein (LDL). LDL is often referred to as 'bad cholesterol' because it can lead to plaque buildup in arteries, increasing the risk of cardiovascular disease. High-density lipoprotein (HDL) is considered 'good cholesterol' as it helps remove LDL from the arteries, reducing the risk of cardiovascular issues. Very low-density lipoprotein (VLDL) and chylomicrons are also lipoproteins that transport fats in the bloodstream, but they are not as strongly associated with an increased risk of cardiovascular disease as LDL.
Which condition may benefit from branched chain amino acids (leucine, isoleucine, and valine)?
- A. cancer-related malnutrition
- B. marasmus
- C. cardiovascular disease
- D. severe depression
Correct Answer: A
Rationale: Branched chain amino acids, such as leucine, isoleucine, and valine, are essential in preventing muscle breakdown. Therefore, they may be particularly important for a patient with cancer-related malnutrition, where maintaining muscle mass is crucial. Marasmus is a severe form of malnutrition characterized by energy deficiency, not specifically related to cancer. Cardiovascular disease and severe depression do not have a direct correlation with the need for branched chain amino acids to prevent muscle breakdown.
Protein is constantly being exchanged between which two components?
- A. tissue and plasma.
- B. the liver and the small intestine.
- C. blood and lymph.
- D. the heart and lungs.
Correct Answer: A
Rationale: The correct answer is 'tissue and plasma.' Protein turnover involves the continuous exchange of proteins between body tissues and the bloodstream (plasma) as part of normal metabolic processes. This process ensures a balance in protein levels throughout the body. Choices B, C, and D are incorrect as they do not represent the primary sites for protein turnover in the body.
Which compound is necessary for emulsification of fat in the body?
- A. Bile salts
- B. Cholecystokinin
- C. Chyme
- D. Trypsin
Correct Answer: A
Rationale: Bile salts are essential for emulsifying fats in the body. They break down fats into smaller droplets, increasing the surface area for enzymes to work on during digestion. Cholecystokinin is a hormone that stimulates the release of bile and pancreatic enzymes, but it is not directly involved in emulsification. Chyme is the semi-fluid mass of partly digested food that moves from the stomach to the small intestine and does not play a role in emulsifying fats. Trypsin is an enzyme produced by the pancreas that acts on proteins, not fats.
Which of the following is an example of a protein?
- A. Saline.
- B. Hemoglobin.
- C. Cellulose.
- D. Prostaglandins.
Correct Answer: B
Rationale: Hemoglobin is a protein that carries oxygen in the blood, making it the correct answer. Choice A, Saline, is a salt solution and not a protein. Choice C, Cellulose, is a complex carbohydrate found in the cell walls of plants, not a protein. Choice D, Prostaglandins, are lipid compounds with hormone-like effects, not proteins.