Base your answer to the following question on Which statement best expresses the information represented in the graph shown below?

A. The action of enzymes varies with pH.

B. A pH of 7 provides the optimum environment for digestive enzymes.

C. Gastric juice is active at a pH extending from 0 to 12.

D. Acids have a pH greater than 7.

Answer Explanation:

The action of enzymes vary with pH. Enzymes are proteins that catalyze biochemical reactions, and their activity is influenced by various factors including pH.

The pH level affects the ionization state of amino acid residues within the enzyme's active site. This, in turn, can affect the enzyme's ability to bind substrate molecules and catalyze reactions.

Different enzymes have different optimal pH ranges at which they exhibit maximum activity. This optimal pH range is determined by the specific environment in which the enzyme typically functions. For example, pepsin, which is involved in digesting proteins in the stomach, works optimally at an acidic pH around 2, whereas enzymes in the small intestine function optimally at a slightly alkaline pH around 7 to 8.

Extreme deviations from the optimal pH can denature enzymes, causing them to lose their structure and function. Therefore, maintaining the appropriate pH level is crucial for ensuring the proper functioning of enzymes in biochemical reactions.

Therefore, the Correct Answer is A.

Q #1: In humans, chemical digestion is accomplished

A. by enzyme action that begins in the mouth and ends in the

B. esophagus

C. stomach

D. small intestine

Answer Explanation

C) small intestine

- Correct: Chemical digestion in humans is a complex process involving various enzymes acting on different nutrients. While digestion does begin in the mouth with the action of enzymes like salivary amylase on carbohydrates, the majority of chemical digestion occurs in the small intestine. Enzymes secreted by the pancreas (such as pancreatic amylase, lipase, and proteases) and the small intestine itself (such as maltase, sucrase, lactase, and peptidases) break down carbohydrates, fats, and proteins into smaller molecules. Additionally, bile salts produced by the liver and stored in the gallbladder aid in the emulsification and digestion of fats in the small intestine. Therefore, chemical digestion largely concludes in the small intestine before nutrients are absorbed into the bloodstream.

A) esophagus

- Incorrect: The esophagus is primarily involved in the mechanical process of swallowing, which pushes food down into the stomach. While some minor enzymatic activity may occur due to saliva coating the food during swallowing, significant chemical digestion does not occur in the esophagus.

B) stomach

- Incorrect: While the stomach does play a role in chemical digestion, particularly in the breakdown of proteins by the enzyme pepsin and the denaturation of proteins by hydrochloric acid, the majority of chemical digestion occurs in the small intestine. The stomach mainly serves to mechanically churn food and begin the process of protein digestion.

D) gallbladder

- Incorrect: The gallbladder stores and releases bile produced by the liver, which aids in the emulsification and digestion of fats in the small intestine. However, the gallbladder itself is not directly involved in chemical digestion, and the majority of digestive enzymes are not secreted or stored in the gallbladder.
Q #2: The absorptive surface of the small intestine is greater than that of other human digestive organs because of its length and the presence of

A. alveoli

B. neurons

C. villi

D. nephrons

Answer Explanation

C) villi

- Correct: The absorptive surface of the small intestine is greatly increased due to the presence of villi. Villi are finger-like projections that line the inner surface of the small intestine. These structures greatly increase the surface area available for absorption. Each villus contains capillaries and lacteals (lymphatic vessels) that absorb nutrients from digested food. The large surface area provided by the villi allows for more efficient absorption of nutrients such as carbohydrates, proteins, fats, vitamins, and minerals.

A) alveoli

- Incorrect: Alveoli are tiny air sacs in the lungs where gas exchange occurs during respiration. They are not found in the digestive system and do not contribute to the absorptive surface of the small intestine.

B) neurons

- Incorrect: Neurons are nerve cells that transmit signals throughout the body, including the digestive system. While neurons play a role in regulating digestion and other digestive processes, they do not directly contribute to the absorptive surface of the small intestine.

D) nephrons

- Incorrect: Nephrons are the functional units of the kidneys responsible for filtering blood and producing urine. They are not part of the digestive system and do not contribute to the absorptive surface of the small intestine.
Q #3: In humans, structures that release digestive secretions directly into the small intestine include both the

A. salivary glands and the pancreas

B. gall bladder and the lacteals

C. villi and the salivary glands

D. pancreas and the gall bladder

Answer Explanation

D) pancreas and the gallbladder

- Correct: Both the pancreas and the gallbladder release digestive secretions directly into the small intestine. The pancreas secretes pancreatic enzymes (such as amylase, lipase, and proteases) into the small intestine to aid in the digestion of carbohydrates, fats, and proteins. The gallbladder stores bile produced by the liver, which is released into the small intestine to aid in the emulsification and digestion of fats.

A) salivary glands and the pancreas

- Incorrect: While the pancreas releases digestive secretions directly into the small intestine, the salivary glands secrete saliva into the mouth, which contains enzymes (such as amylase) that begin the digestion of carbohydrates. Salivary glands do not release digestive secretions directly into the small intestine.

B) gall bladder and the lacteals

- Incorrect: The gallbladder stores bile produced by the liver, which is released into the small intestine to aid in fat digestion. Lacteals are lymphatic vessels found in the villi of the small intestine and are involved in the absorption of fats, but they do not release digestive secretions directly into the small intestine.

C) villi and the salivary glands

- Incorrect: Villi are finger-like projections in the small intestine that increase the surface area for absorption of nutrients but do not release digestive secretions directly into the small intestine. Salivary glands secrete saliva into the mouth to initiate the digestion of carbohydrates but do not release digestive secretions directly into the small intestine.

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Base your answer to the following question on Which statement best expresses the information represented in the graph shown below?

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Q #1: In humans, chemical digestion is accomplished

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