Which two systems are most directly involved in providing molecules needed for the synthesis of fats in human cells?

Correct Answer: A

Rationale: The correct answer is A (digestive and circulatory). The digestive system breaks down food into molecules like fatty acids, which are needed for fat synthesis. The circulatory system then transports these molecules to cells for fat synthesis. The other choices are incorrect because the excretory system is involved in waste removal, the immune system defends against pathogens, the muscular system supports movement, and the reproductive system is responsible for reproduction, none of which are directly related to providing molecules for fat synthesis.

Correct Answer: B

Rationale: The correct answer is B: Kidneys. The kidneys do not manufacture digestive juices. The liver produces bile to aid in digestion, the stomach produces gastric juices, and the pancreas produces digestive enzymes. The kidneys, however, are responsible for filtering blood, regulating fluid balance, and producing urine, not digestive juices. Therefore, option B is the correct answer.

Correct Answer: B

Rationale: The correct answer is B: pepsin. Pepsin is a digestive enzyme that breaks down proteins into smaller peptides. In this demonstration, the decrease in mass of the meat from 10g to 3g suggests protein digestion occurred. Bile (A) emulsifies fats, maltose (C) breaks down carbohydrates, and amylase (D) also breaks down carbohydrates, so they wouldn't cause the observed mass change.

Correct Answer: C

Rationale: The correct answer is C: pepsin. Pepsin is an enzyme produced in the stomach that breaks down proteins into peptides. It functions in an acidic environment, which is characteristic of the stomach. Amylase (A) breaks down carbohydrates, lipase (B) breaks down fats, and trypsin (D) breaks down proteins in the small intestine, not in structure W.

Correct Answer: C

Rationale: Sure. Secretin is the correct answer as it specifically stimulates the release of pancreatic juice. Secretin is released from the duodenum in response to the acidic chyme entering from the stomach. It acts on the pancreas to increase the secretion of bicarbonate-rich pancreatic juice, which helps neutralize the acidic chyme. Insulin (choice A) regulates blood sugar levels, gastrin (choice B) stimulates gastric acid secretion, and glucagon (choice D) increases blood glucose levels. These hormones do not directly stimulate the release of pancreatic juice.