Review & Rehearse

Chapter 22: Nutrition and Digestion

Chapter 22. Chapter 22: Nutrition and Digestion

Review & Rehearse

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You must read each slide, and complete any questions on the slide, in sequence.

Instructions

Review the visual summaries and answer the essay questions below.

Make sure to enter a brief response that completely answers each question and explains your reasoning. When you click "Submit," you will be provided instant feedback, allowing you to check if your response is correct.

(This activity contains 16 total essay questions. Each new question will be revealed once you complete the preceding question.)

1.

1. What are the six groups of nutrients? What is their primary role in human health?

The six groups of nutrients are carbohydrates, lipids, proteins, vitamins, minerals, and water. They are needed for energy, raw materials, and maintenance of the body’s systems.

2.

2. Why must herbivores spend a large portion of each day eating?

Herbivores spend much of their time eating because plants provide a lot more fiber and are more difficult to digest, and thus provide fewer kilocalories and nutrients (for the same weight), than the meat consumed by carnivores.

3.

3. What is basal metabolic rate?

Basal metabolic rate is the minimum amount of energy expended by an organism when it is not engaged in any activity, other than resting.

4.

4. Why can it be dangerous to consume too much water?

Drinking too much water can cause an imbalance of electrolytes, particularly a deficit of sodium, in the blood.

5.

5. What is meant by a “complete” protein?

A complete protein contains, among its amino acids, all eight essential amino acids—those that cannot be made by the body and must be supplied by food.

6.

6. Animals, including humans, require 20 different amino acids to make proteins. How many of these can be made in the body? Where do the others come from?

Twelve amino acids are made by the body; the other eight amino acids must come from food.

7.

7. Why does over-consumption of fat-soluble vitamins pose a greater health risk than over-consumption of water-soluble vitamins?

Fat-soluble vitamins are stored in fatty tissue and in the liver and are not excreted in the urine, as are water-soluble vitamins. Over-consumption of fat-soluble vitamins can lead to toxic levels of these vitamins in the body.

8.

8. What are the four distinct phases used by humans to extract nutrients from food? During each phase, what significant activity contributes to nutrient harvesting and absorption?

(a) Ingestion: food is taken into the body. (b) Digestion: food is dismantled by physically breaking it into smaller pieces and chemically breaking it down into smaller molecules. (c) Absorption: molecules are taken up from the intestine into the cells of the body. (d) Elimination: unnecessary materials are swept from the body as waste.

9.

9. Describe the process whereby about 20% of ingested starch is broken down in the mouth.

In the mouth, the enzyme alpha-amylase in saliva breaks the bonds of starch molecules to release small quantities of glucose that can be used for energy. About 20% of the ingested starch is broken down in this way.

10.

10. Besides helping to chemically break down food in your stomach, what other function do stomach acids serve?

Stomach acids kill bacteria.

11.

11. Which structural feature of the small intestine is crucial in helping the body get nutrients from food into the bloodstream?

The small intestine has a huge absorptive surface area. Its surface area is increased by its long length, its folded structure, and an interior lining made of finger-like projections called villi, which are further lined with tiny projections called microvilli.

12.

12. Too much dietary fiber can lead to diarrhea. Why?

Water is attracted to fiber. When an over-abundance of fiber is present in the colon, large amounts of water pass into the colon and this can cause diarrhea.

13.

13. Describe how some mammals, which do not produce enzymes to break down cellulose, are able to extract nutrients from cellulose-containing food.

Some mammals have four-part stomachs that contain symbiotic cellulose-digesting bacteria. Other mammals have bacteria living in an outcropping of the digestive tract called the cecum, and these bacteria also can digest cellulose.

14.

14. Which characteristic of human evolutionary history probably led to the evolution of strong appetites?

Our ancestors lived in an environment where food was often scarce. Powerful, instinctual hunger kept our ancestors going through times of feast and famine. Enthusiastic eaters were more likely to survive and reproduce.

15.

15. Describe the role of insulin in human digestion and absorption.

Following the digestion of carbohydrates, insulin is secreted by the pancreas in response to the increased glucose concentration in the blood. Insulin stimulates the uptake of glucose by cells, such as those of muscle and fat tissue.

16.

16. How does adding spices to food help reduce the risk of infection from pathogenic microbes?

Spices, substances produced by plants, contain toxic compounds with anti-microbial properties. (These compounds also prevent predation by animals or insects.)

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