Digestive System Structure and Function Unit Test

Question 1

Which of the following correctly lists the three main functions of the digestive system in the order they occur?

Accepted Answer

Digestion, absorption, elimination

Question 2

What is the term for the muscular contractions that push food through the digestive system?

Accepted Answer

Peristalsis

Question 3

A student is studying how the stomach contributes to digestion. Which of the following BEST describes the stomach's role in mechanical digestion?

Accepted Answer

It churns food into a thick liquid called chyme, exposing nutrients to enzymes.

Question 4

The table below shows the digestive enzymes produced by the pancreas and the nutrients each one breaks down.

| Enzyme   | Nutrient Broken Down       | Product            |
|----------|----------------------------|--------------------|
| Amylase  | Complex carbohydrates      | Simple sugars      |
| Trypsin  | Proteins                   | Amino acids        |
| Lipase   | Fats                       | Fatty acids & monoglycerides |

A student eats a meal high in protein. Which pancreatic enzyme would be MOST active during digestion of this meal?

Accepted Answer

Trypsin, because it breaks down proteins into amino acids

Question 5

Which organ is responsible for storing bile, which is used to emulsify large fat droplets during digestion?

Accepted Answer

Gallbladder

Question 6

A scientist ran an experiment tracking how fat Calories are absorbed when different organs are present. The results are shown below.

| Setup                          | Fat Calories Absorbed |
|--------------------------------|-----------------------|
| Pancreas only                  | 27 Cal                |
| Pancreas + Gallbladder         | 86 Cal                |
| Gallbladder only               | 3 Cal                 |
| No accessory organs            | 0 Cal                 |

What conclusion is BEST supported by the data?

Accepted Answer

The pancreas and gallbladder work together to maximize fat digestion and absorption.

Question 7

Which cells in the stomach produce hydrochloric acid (HCl), which creates an acidic environment that helps the enzyme pepsin work effectively?

Accepted Answer

Parietal cells, because they produce hydrochloric acid in the stomach

Question 8

[FIGURE: Diagram of the human digestive system showing the mouth, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine, and rectum. Arrows indicate the direction of food movement. The small intestine is highlighted in yellow and labeled 'Site of primary nutrient absorption.']

Based on the diagram, which vessels are responsible for absorbing fatty acids from the small intestine into the body?

Accepted Answer

Lymphatic vessels, because they specifically absorb fatty acids from the small intestine

Question 9

A student eats a baked potato, which is mostly starch (a complex carbohydrate). Which sequence correctly describes how the starch is chemically digested?

Accepted Answer

Starch → simple sugars → absorbed by capillaries in the small intestine

Question 10

The table below shows the percentage of protein Calories converted to amino acids under different stomach conditions.

| Stomach Condition                   | Protein Converted to Amino Acids |
|-------------------------------------|----------------------------------|
| No special cells                    | ~2%                              |
| Chief cells only (pepsin)           | ~40%                             |
| Parietal cells only (HCl)           | ~8%                              |
| Chief cells + Parietal cells        | ~97%                             |

What does the data suggest about protein digestion in the stomach?

Accepted Answer

Pepsin and hydrochloric acid together are required for maximum protein digestion.

Question 11

Which organ absorbs water and vitamin K from digested food, and also contains bacteria that can break down fiber into absorbable sugars?

Accepted Answer

Large intestine, because it absorbs water, vitamin K, and fiber-derived sugars

Question 12

[FIGURE: Flow diagram showing the path of a fat molecule through the digestive system. Boxes labeled in order: 'Mouth (mechanical chewing)' → 'Stomach (churning → chyme)' → 'Small Intestine (bile emulsifies fat droplets)' → 'Small Intestine (lipase breaks fat into fatty acids)' → 'Lymphatic vessels (fatty acids absorbed)' → 'Bloodstream.' Arrows connect each step.]

According to the diagram, what role does bile play in fat digestion?

Accepted Answer

Bile emulsifies large fat droplets into smaller droplets for lipase to act on.

Question 13

A student designs two digestive systems and tests how many Calories each absorbs from the same food.

| System | Organs Included                                      | Calories Absorbed |
|--------|------------------------------------------------------|-------------------|
| A      | Mouth, Esophagus, Small Intestine, Rectum            | 41%               |
| B      | Mouth, Stomach, Small Intestine, Pancreas, Rectum    | 79%               |

Which explanation BEST accounts for why System B absorbed more Calories than System A?

Accepted Answer

System B includes the stomach and pancreas, which improve mechanical and chemical digestion so more nutrients are exposed and broken down for absorption.

Question 14

Mechanical digestion and chemical digestion both play important roles in breaking down food. Which of the following BEST explains how they work together?

Accepted Answer

Mechanical digestion breaks food into smaller pieces, increasing surface area so chemical enzymes can break down nutrients more effectively.

Question 15

[FIGURE: Bar graph titled 'Nutrient Absorption by Vessel Type and Location' with four grouped bars. The x-axis shows four scenarios: 'Capillaries – Small Intestine,' 'Capillaries – Large Intestine,' 'Lymphatic – Small Intestine,' 'Lymphatic – Large Intestine.' The y-axis shows Calories absorbed (0–300). Bars show: Sugars absorbed (blue) highest in 'Capillaries – Small Intestine' (~272 Cal); Fatty acids absorbed (orange) only present in 'Lymphatic – Small Intestine' (~175 Cal); Amino acids absorbed (green) only in 'Capillaries – Small Intestine' (~21 Cal); Water absorbed shown as a separate small bar.]

A nutritionist wants to maximize absorption of ALL macronutrients (sugars, amino acids, and fatty acids) from food. Based on the graph, which combination of vessels and locations would achieve this goal?

Accepted Answer

Capillaries on the small intestine AND lymphatic vessels on the small intestine, because together they absorb sugars, amino acids, and fatty acids

Question 16

Mechanical digestion in the stomach churns food into a thick liquid called chyme, which increases the surface area of nutrients exposed to digestive enzymes.

Accepted Answer

true

Question 17

Fatty acids from digested fats are absorbed directly into the capillaries of the small intestine, following the same pathway as sugars and amino acids.

Accepted Answer

false

Question 18

The large intestine plays no role in nutrient absorption — its only function is to store and compact waste before elimination.

Accepted Answer

false

Question 19

The enzyme pepsin works most effectively when the stomach also contains hydrochloric acid produced by parietal cells, because pepsin functions best in an acidic environment.

Accepted Answer

true

Question 20

[FIGURE: Diagram of the human digestive system showing the path of food from the mouth through the esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine, and rectum, with the pancreas and gallbladder labeled as accessory organs attached near the duodenum.]

Based on the diagram, the pancreas and gallbladder are organs through which food passes directly as part of the main digestive pathway from mouth to rectum.

Accepted Answer

false

Question 21

The digestive system carries out three major processes in order. Name and briefly define each of the three processes, and identify at least one organ involved in each process.

Accepted Answer

The three processes are: (1) Digestion — the breaking down of food into simple nutrients; organs include the mouth, stomach, and small intestine. (2) Absorption — the movement of nutrients into the bloodstream; organs include the small intestine (via capillaries) and lymphatic vessels. (3) Elimination — the removal of leftover waste from the body; organs include the large intestine and rectum.

Question 22

A student ran an experiment testing how well a digestive system broke down a baked potato (mostly complex carbohydrates) with and without a stomach. The results are shown in the table below.

| Digestive System Setup | Complex Carbs Remaining (Cal) | Sugars Produced (Cal) |
|------------------------|-------------------------------|------------------------|
| Without stomach        | 196.68                        | 31.32                  |
| With stomach           | 22.26                         | 205.74                 |

Using the data table, explain why the system WITH a stomach converted significantly more complex carbohydrates into sugars. Include the terms 'mechanical digestion,' 'chyme,' and 'enzyme' in your answer.

Accepted Answer

The system with a stomach converted far more complex carbohydrates into sugars (205.74 Cal vs. 31.32 Cal) because the stomach performs mechanical digestion by churning food into a thick liquid called chyme. This process breaks large food chunks into smaller pieces, exposing more surface area to digestive enzymes such as amylase. When food is in smaller pieces, enzymes can act on more of the nutrients, resulting in greater breakdown of complex carbohydrates into simple sugars.

Question 23

[FIGURE: Diagram of the human digestive system showing the mouth, esophagus, stomach, small intestine (labeled with duodenum, jejunum, and ileum), large intestine, and rectum. Arrows indicate the direction of food movement. The small intestine is shown as a long, coiled tube, and the inner wall of the small intestine is shown in an inset with finger-like projections labeled 'villi.' Capillaries and lymphatic vessels are shown threading through the villi.]

Using the diagram, explain how the structure of the small intestine is specialized for absorption. In your answer, describe the roles of BOTH capillaries and lymphatic vessels in absorbing different types of nutrients.

Accepted Answer

The small intestine is specialized for absorption because its inner walls are lined with villi — finger-like projections that increase surface area. Capillaries inside the villi absorb sugars and amino acids into the bloodstream. Lymphatic vessels absorb fatty acids from fat digestion. Together, these two vessel types ensure that carbohydrates, proteins, and fats are all absorbed efficiently from the digested food (chyme) passing through the small intestine.

Question 24

A student notices that when the gallbladder is added to a digestive system model, fat digestion improves dramatically. The data below shows the results.

| Setup | Fat Calories Converted to Fatty Acids |
|-------|---------------------------------------|
| Pancreas only (no gallbladder) | 27 Cal |
| Pancreas + Gallbladder         | 86.36 Cal |

Using the data and your knowledge of digestion, explain WHY adding the gallbladder caused such a large improvement in fat digestion. What substance does the gallbladder store, and how does that substance help the enzyme lipase do its job?

Accepted Answer

Adding the gallbladder caused fat digestion to improve from 27 Cal to 86.36 Cal — more than three times as much. The gallbladder stores bile, a chemical that emulsifies fat. Emulsification breaks large fat droplets into many tiny droplets, which greatly increases the surface area of fat exposed to the enzyme lipase. Because lipase is water-based and fat does not normally mix with water, the large fat droplets are difficult for lipase to act on. Once bile breaks the fat into tiny droplets, lipase can efficiently break down the fat into fatty acids and monoglycerides, resulting in much greater fat digestion.

Question 25

A biomedical engineer is designing an artificial digestive system for a research study. She wants the system to absorb as many Calories as possible from a meal that contains carbohydrates, proteins, and fats. Using your knowledge of mechanical digestion, chemical digestion, and absorption, recommend which organs and accessory structures she should include and explain the specific role each plays. Your response should address all three nutrient types.

Accepted Answer

To maximize Calorie absorption from all three nutrient types, the engineer should include the following: (1) Mouth — performs mechanical digestion by chewing food into smaller pieces, increasing surface area for enzymes. (2) Stomach — performs further mechanical digestion by churning food into chyme, exposing more nutrients to enzymes; chief cells produce pepsin to begin protein digestion, and parietal cells produce HCl to create an acidic environment that activates pepsin. (3) Pancreas — produces amylase (breaks complex carbohydrates into sugars), trypsin (breaks proteins into amino acids), and lipase (breaks fats into fatty acids and monoglycerides). (4) Gallbladder — stores bile to emulsify fats, allowing lipase to work more effectively on fat digestion. (5) Small intestine — the primary site of absorption; capillaries absorb sugars and amino acids into the bloodstream, and lymphatic vessels absorb fatty acids. Including all of these organs ensures that carbohydrates, proteins, and fats are all broken down and absorbed efficiently.

Digestive System Structure and Function Unit Test

Part A: Multiple Choice

Part B: True / False

Part C: Short Answer

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