Question

All of the following processes occur in the mouth EXCEPT A. moistening of food. B. bolus formation. C. chemical digestion of starch. D. chemical digestion of proteins.

Short answer

D. chemical digestion of proteins.

Step-by-step solution

Understanding the Processes Occurring in the Mouth

The mouth is responsible for several functions in the digestion process. These include moistening food with saliva (A), forming it into a bolus for swallowing (B), and initiating the chemical digestion of starches using enzymes like amylase (C).

Identifying the Outlier

Next, identify which of the options does not fit the typical functions of the mouth. The mouth does not produce enzymes for the chemical digestion of proteins.

Key concepts

Saliva Function

Saliva plays a crucial role during the initial stages of digestion in the mouth. It is produced by the salivary glands and has several important functions. First, saliva moistens food, making it easier to chew and swallow. Moistening is crucial as it ensures that the food can be comfortably moved around in the mouth and prepared for digestion.
Saliva also contains enzymes like amylase that begin the process of chemical digestion. Amylase specifically breaks down starches into simpler sugars, starting the digestive process in the mouth itself. Besides enzymes, saliva contains mucous which helps in the formation of the bolus.
Additionally, saliva has antibacterial properties, which help maintain oral health by killing harmful bacteria in the mouth and preventing infections.

Bolus Formation

Bolus formation is another essential function that takes place in the mouth. When you chew, your teeth break down food into smaller pieces, and saliva helps to further moisten it. This mixture of chewed food and saliva is shaped into a small, easily swallowed mass known as a bolus.
The tongue plays a significant role in this process by pushing the food around as you chew and eventually moving the bolus to the back of the mouth for swallowing. Forming the bolus is essential because it facilitates the efficient passage of food from the mouth to the stomach through the esophagus.
Without this process, swallowing would be difficult, and the digestive process downstream could be less efficient.

Chemical Digestion of Starch

One of the primary roles of saliva in the mouth is to initiate the chemical digestion of starch. Saliva contains an enzyme called amylase, also known as salivary amylase. This enzyme breaks down complex carbohydrates, specifically starches found in foods like bread and potatoes, into simpler sugars like maltose.
The importance of this process cannot be overstated as it kick-starts the digestion of carbohydrates long before the food reaches the stomach. The early breakdown of starches in the mouth allows for a more efficient digestive process overall.
Though the mouth is not the site for the complete breakdown of starches, the initial steps that take place here set the stage for further digestion and absorption in the small intestine.
In summary, chemical digestion of starch in the mouth is a critical part of our digestive system, making the nutrients in our food more accessible and easier to absorb by the time they reach the later stages of digestion.