Question

Chapter 14- Digestive System   

Case Scenario 1: You have just eaten a sausage, egg, with the bread sandwich for breakfast.

a. Explain how a piece of bread as you chew for a few minutes expect to change its taste? Why?

b. Explain the chemical changes that occur in the sandwich that you eat as it passes through the parts of the GI tract with relation to the processes of the digestive system.   

c. Name all enzymes or secretions involved and their source.

d. How many calories are produced when 1gram of carbohydrate is oxidized? 1 gram of protein? 1 gram of fat? If you ate 100 grams of food that were 20% protein, 30% carbohydrate and 10% fat, how many kilocalories did you consume?

Answer 1

Basic information:

Sausage: Sausages are a meat product usually made from ground meat, often pork, beef, or poultry, along with salt, spices and other flavourings. Other ingredients such as grains or breadcrumbs may be included as fillers or extenders. Some sausages include other ingredients for flavour.

Egg- Contains Protein

Bread sandwich(Carbohydrates+protein): Sandwich breads are produced in many varieties, such as white, whole wheat, sourdough, rye, multigrain and others.

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a. Specifically salivary amylase converts starch into glucose which is a sugar. Therefore, rice/bread starts to taste sweet after chewing for few minutes.

b. Before your food passes from the mouth and down your esophagus, salivary amylase, an enzyme in saliva, begins to digest the starch in your bread. That is the start of chemical digestion. The mass of chewed sandwich is called a bolus. In mouth polysaccharides convert into monomers.

Bolus-A bolus (from Latin bolus, "ball") is a ball-like mixture of food and saliva that forms in the mouth during the process of chewing (which is largely an adaptation for plant-eating mammals). ... Under normal circumstances, the bolus is swallowed, and travels down the esophagus to the stomach for digestion.

Chyme-Chyme, a thick semifluid mass of partially digested food and digestive secretions that is formed in the stomach and intestine during digestion. In the stomach, digestive juices are formed by the gastric glands; these secretions include the enzyme pepsin, which breaks down proteins into simple form, and hydrochloric acid.

Here the meat and egg digestion occurs-stomach.

Chyle-Chyle (from the Greek word means , "juice") is a milky bodily fluid consisting of lymph and emulsified fats, or free fatty acids (FFAs). It is formed in the small intestine during digestion of fatty foods, and taken up by lymph vessels specifically known as lacteals.

c.All enzymes secretion:

Mouth- Amylase,ptyline.

Stomach- Pepsin

Intestine- Chemical breakdown begins in the stomach and continues in the small intestine. Proteolytic enzymes, including trypsin and chymotrypsin, are secreted by the pancreas and cleave proteins into smaller peptides. Carboxypeptidase, which is a pancreatic brush border enzyme, splits one amino acid at a time.

d. Carbohydrates provide 4 calories per gram, protein provides 4 calories per gram, and fat provides 9 calories per gram.

100gm food have:

20% means 40gm protein ×4= 160 calories

30% means 60gm carbohydrates×4= 240 calories

10% means 20gm fat ×9 =180 calories