Nokea
Two amino acids are chemically joined by a:
- A. double bond.
- B. hydrogen bond.
- C. carboxyl bond.
- D. peptide bond.
Correct Answer: D
Rationale: The correct answer is D, peptide bond. A peptide bond is formed through a dehydration synthesis reaction between the amine group of one amino acid and the carboxyl group of another amino acid. This bond is crucial in protein synthesis. Choices A, B, and C are incorrect. A double bond involves sharing two pairs of electrons, a hydrogen bond is a weak attraction between a hydrogen atom and an electronegative atom, and a carboxyl bond is not a common term in biochemistry.
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Which of the following monosaccharides is considered one of the most important in human nutrition along with glucose and fructose?
- A. Lactose.
- B. Galactose.
- C. Maltose.
- D. Sucrose.
Correct Answer: B
Rationale: The most important monosaccharides in human nutrition are glucose, fructose, and galactose. Galactose is crucial as it is one of the main components of lactose, a disaccharide sugar found in milk. Therefore, choices A, C, and D are incorrect as lactose, maltose, and sucrose are disaccharides composed of two monosaccharide units.
Pepsinogen secreted by the gastric cells is converted into pepsin by:
- A. enterokinase
- B. hydrochloric acid
- C. gastric lipase
- D. pancreatic lipase
Correct Answer: B
Rationale: Pepsinogen is converted into its active form, pepsin, by hydrochloric acid in the stomach. Hydrochloric acid helps in unfolding the pepsinogen molecule to transform it into pepsin, which is crucial for protein digestion. Therefore, the correct answer is hydrochloric acid (choice B). Enterokinase (choice A) is an enzyme produced in the small intestine that activates trypsinogen into trypsin, not pepsinogen. Gastric lipase (choice C) is an enzyme that digests fats, not involved in converting pepsinogen to pepsin. Pancreatic lipase (choice D) is an enzyme produced by the pancreas that aids in breaking down fats in the small intestine, not part of the process of pepsin activation.
What group makes each amino acid unique?
- A. Radical group
- B. Amino group
- C. Carboxyl group
- D. Peptide bond
Correct Answer: A
Rationale: The correct answer is the radical group (R-group) because it is the unique side chain that differentiates each amino acid. The amino group (choice B) and carboxyl group (choice C) are functional groups common to all amino acids but do not make them unique. The peptide bond (choice D) is the bond formed between amino acids in a protein chain, not the group that makes each amino acid unique.
Plasma lipoproteins contain varying amounts of:
- A. ascorbic acid.
- B. triglycerides.
- C. lecithin.
- D. glucose.
Correct Answer: B
Rationale: The correct answer is B: triglycerides. Plasma lipoproteins, such as LDL and HDL, contain triglycerides, cholesterol, and other fats. Ascorbic acid (choice A) is not typically found in plasma lipoproteins; it is a form of vitamin C. Lecithin (choice C) is a phospholipid found in cell membranes but is not a major component of plasma lipoproteins. Glucose (choice D) is a type of sugar and is not a primary component of plasma lipoproteins.
How many amino acids are considered indispensable or essential?
- A. 9
- B. 10
- C. 12
- D. 14
Correct Answer: A
Rationale: The correct answer is A: 9. Nine amino acids are considered essential or indispensable because they cannot be synthesized by the body and must be obtained through the diet. These amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Choices B, C, and D are incorrect as the number of essential amino acids is specifically 9, as they are crucial for various bodily functions.