Which of these nutrients is absorbed mainly in the duodenum?
A. glucose
B. iron
C. sodium
D. water
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b) iron
- Correct: Iron is mainly absorbed in the duodenum, particularly in its proximal portion. Iron absorption occurs through active transport mechanisms facilitated by specialized transport proteins in the duodenal epithelial cells. Once absorbed, iron can be transported into the bloodstream and utilized for various physiological functions, including the production of hemoglobin and other iron-containing proteins.
a) glucose
- Incorrect: Glucose is primarily absorbed in the small intestine, but its absorption occurs mainly in the jejunum and ileum rather than the duodenum. Glucose is absorbed through facilitated diffusion and active transport mechanisms in the epithelial cells lining the small intestine.
c) sodium
- Incorrect: Sodium is absorbed throughout the small intestine, including the duodenum, jejunum, and ileum. Its absorption occurs through active transport mechanisms in the epithelial cells lining the intestinal mucosa, primarily in conjunction with glucose and other nutrients.
d) water
- Incorrect: Absorption of water indeed takes place in the large intestine, particularly in the colon.
Therefore, the Correct Answer is B.
More Questions on Digestive System Practice Exam 1
Question 1:
Which foods should be included in a balanced diet as a good source of roughage?
A. red meat and poultry
B. fresh fruits and vegetables
C. eggs and milk products
D. animal fat and plant oil
The Correct Answer is B.B) fresh fruits and vegetables
- Correct: Fresh fruits and vegetables are excellent sources of roughage, also known as dietary fiber. These foods provide insoluble fiber, soluble fiber, or a combination of both, which adds bulk to the stool and promotes healthy digestion. Insoluble fiber, found in foods like leafy greens, celery, and broccoli, helps to move food through the digestive tract, preventing constipation. Soluble fiber, found in foods like apples, oats, and beans, can help lower cholesterol levels and regulate blood sugar levels.
A) red meat and poultry
- Incorrect: While red meat and poultry are good sources of protein and other nutrients, they are not significant sources of dietary fiber or roughage. These foods do not contribute to the fiber content of the diet.
C) eggs and milk products
- Incorrect: Eggs and milk products are valuable sources of protein, vitamins, and minerals, but they are not significant sources of dietary fiber or roughage. These foods do not provide the fiber needed for healthy digestion.
D) animal fat and plant oil
- Incorrect: Animal fat and plant oils are sources of dietary fat, which is important for providing energy and essential fatty acids in the diet. However, they do not contain significant amounts of dietary fiber or roughage. These foods do not contribute to the fiber content of the diet.
Question 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
The Correct Answer is C.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.
Question 3:
Glycogen is best described as a
A. complex carbohydrate that is often stored in red blood cells
B. complete protein necessary for the synthesis of cell membranes
C. polysaccharide that is synthesized and stored within the human liver
D. by-product of sucrose digestion within the pancreas
The Correct Answer is C.C) polysaccharide that is synthesized and stored within the human liver
- Correct: Glycogen is a polysaccharide, which means it is a complex carbohydrate composed of many glucose molecules linked together. It is synthesized and stored primarily in the liver and muscles of humans and other vertebrates. Glycogen serves as a form of energy storage, allowing organisms to store glucose for later use when energy demands are high or when glucose availability is low.
A) complex carbohydrate that is often stored in red blood cells
- Incorrect: While glycogen is a complex carbohydrate, it is not stored in red blood cells. Red blood cells do not contain nuclei or organelles, including glycogen storage structures.
B) complete protein necessary for the synthesis of cell membranes
- Incorrect: Glycogen is not a protein. It is a carbohydrate used for energy storage. Proteins are composed of amino acids and are involved in various cellular functions, including the synthesis of cell membranes, but glycogen does not play a direct role in this process.
D) by-product of sucrose digestion within the pancreas
- Incorrect: Glycogen is not a by-product of sucrose digestion within the pancreas. Sucrose is a disaccharide composed of glucose and fructose, and it is broken down into its component sugars by enzymes in the small intestine, not the pancreas. Glycogen is synthesized and stored in the liver and muscles as a form of energy storage.
Question 4:
In gastric bypass surgery, the stomach is reduced to hold 1 ounce of food, instead of 3 pints. This surgery would drastically impact one's
A. excretory system
B. digestive system
C. circulatory system
D. respiratory system
The Correct Answer is B.B) digestive system
- Correct: Gastric bypass surgery involves the reduction of the stomach's size, typically to hold only about 1 ounce of food instead of its normal capacity of 3 pints or more. This surgery drastically impacts the digestive system because it alters the anatomy and physiology of the gastrointestinal tract. By reducing the stomach's size, gastric bypass surgery restricts the amount of food that can be consumed at one time, leading to reduced calorie intake and aiding in weight loss. Additionally, the rearrangement of the digestive tract may affect the absorption of nutrients, potentially leading to changes in nutrient absorption and metabolism.
A) excretory system
- Incorrect: While changes in diet and weight loss resulting from gastric bypass surgery may indirectly affect the excretory system, the primary impact of this surgery is on the digestive system itself, not the excretory system.
C) circulatory system
- Incorrect: Although obesity and associated health conditions may impact the circulatory system, such as increasing the risk of cardiovascular disease, the direct impact of gastric bypass surgery is on the digestive system, not the circulatory system.
D) respiratory system
- Incorrect: Gastric bypass surgery does not directly impact the respiratory system. While weight loss resulting from the surgery may improve respiratory function in individuals with obesity-related respiratory conditions such as sleep apnea, the surgery primarily affects the digestive system by altering the anatomy and function of the gastrointestinal tract.
Question 5:
The enzyme pepsin is produced in the cells of the stomach but not in the cells of the small intestine. The small intestine produces a different enzyme, trypsin. The reason that the stomach and small intestine produce different enzymes is that the gene that codes for pepsin is
A. in the cells of the stomach, but not in the cells of the small intestine
B. expressed in the stomach but not expressed in the small intestine
C. mutated in the small intestine
D. digested by the trypsin in the small intestine
The Correct Answer is B.Enzymes are proteins that catalyze specific biochemical reactions in living organisms.
The production of enzymes is regulated by gene expression, where specific genes are activated (expressed) to produce particular enzymes in different cells or tissues.
In this case, the gene responsible for coding the enzyme pepsin is expressed in the cells of the stomach, leading to the production of pepsin in the stomach.
Conversely, the gene for trypsin is expressed in the cells of the small intestine, resulting in the production of trypsin in the small intestine.
Therefore, the reason that the stomach and small intestine produce different enzymes is due to the differential gene expression in these respective tissues.
Question 6:
The digestion of food and subsequent absorption into the bloodstream is important because
A. absorbed food is toxic to the body
B. absorbed food stimulates reproduction
C. absorbed food is the raw material for metabolism
D. absorbed food aids in respiration
The Correct Answer is C.C) absorbed food is the raw material for metabolism
- Correct: The digestion of food and subsequent absorption into the bloodstream are essential processes because absorbed food molecules serve as the raw material for metabolism. Once nutrients from food are absorbed into the bloodstream, they are transported to cells throughout the body where they are used for various metabolic processes. Carbohydrates are broken down into glucose, which is used for energy production. Proteins are broken down into amino acids, which are used for building and repairing tissues, as well as for synthesizing enzymes and hormones. Fats are broken down into fatty acids and glycerol, which are used for energy production and for building cell membranes and certain hormones. Overall, absorbed food molecules provide the necessary energy and building blocks for cellular activities, growth, and maintenance of the body.
A) absorbed food is toxic to the body
- Incorrect: Absorbed food is not inherently toxic to the body. In fact, nutrients obtained from food are essential for the body's survival and proper functioning. However, certain substances in food may be harmful if absorbed in excessive amounts, such as certain vitamins or minerals. Generally, the body has mechanisms to regulate nutrient absorption and maintain homeostasis.
B) absorbed food stimulates reproduction
- Incorrect: While proper nutrition is important for overall health and fertility, absorbed food does not directly stimulate reproduction. Reproduction is regulated by various hormones and physiological processes within the body.
D) absorbed food aids in respiration
- Incorrect: While nutrients obtained from food are used by cells for energy production through respiration, absorbed food itself does not directly aid in respiration. Respiration is a complex physiological process that involves the exchange of gases (oxygen and carbon dioxide) in the lungs and cellular respiration within cells to produce energy.
Question 7:
Three days after an organism eats some meat, many of the organic molecules originally contained in the meat would be found in newly formed molecules of
A. glucose
B. protein
C. starch
D. oxygen
The Correct Answer is B.B) protein
- Correct: After an organism consumes meat, the organic molecules present in the meat, such as amino acids and lipids, are broken down through the process of digestion. These molecules are then absorbed into the bloodstream and transported to various cells throughout the body. In the cells, these molecules are used as building blocks for synthesizing new proteins. Proteins are essential macromolecules involved in numerous cellular functions, including structural support, enzymatic activity, and regulation of cellular processes. Therefore, many of the organic molecules originally contained in the meat would be found in newly formed molecules of protein within the organism's cells.
A) glucose
- Incorrect: Glucose is a simple sugar that is primarily derived from the digestion of carbohydrates. While some amino acids obtained from the digestion of protein can be converted into glucose through gluconeogenesis, the majority of amino acids are used for protein synthesis, not glucose production.
C) starch
- Incorrect: Starch is a complex carbohydrate found in plants. It is not typically present in meat, and it is not directly synthesized from the organic molecules obtained from meat consumption.
D) oxygen
- Incorrect: Oxygen is a gas essential for cellular respiration but is not synthesized from the organic molecules obtained from meat consumption. Oxygen is mainly obtained through breathing and is used in cellular respiration to generate ATP, the energy currency of the cell.
Question 8:
Emulsification of fats in the small intestines is due to the action of bile, which is released into the intestine from the
A. stomach
B. gall bladder
C. villi
D. lacteals
The Correct Answer is B.B) gall bladder
- Correct: Bile, which aids in the emulsification of fats in the small intestine, is stored and concentrated in the gall bladder before being released into the small intestine. When fatty foods enter the small intestine, the gall bladder contracts and releases bile into the duodenum (the first part of the small intestine). Bile helps to break down large fat globules into smaller droplets, a process known as emulsification, which increases the surface area for the action of digestive enzymes, such as lipase, facilitating the digestion and absorption of fats.
A) stomach
- Incorrect: Bile is not released from the stomach. The stomach primarily secretes gastric juices containing hydrochloric acid and pepsinogen to aid in the digestion of proteins.
C) villi
- Incorrect: Villi are finger-like projections in the lining of the small intestine that increase its surface area for nutrient absorption but do not release bile.
D) lacteals
- Incorrect: Lacteals are lymphatic vessels found in the villi of the small intestine that absorb dietary fats and fat-soluble vitamins. They do not release bile.
Question 9:
Which process is represented by the diagram below?
A. emulsification
B. excretion
C. absorption
D. peristalsis
The Correct Answer is A.Emulsification is a process by which large fat globules are broken down into smaller droplets. This process is facilitated by substances called emulsifiers, with bile being one of the most common emulsifiers in the human body.
Question 10:
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
The Correct Answer is D.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.