recap

50.1 recap

As heterotrophs, animals must obtain the energy and molecular building blocks for biosynthesis from their food. Energy can come from the metabolism of carbohydrates, fats, and proteins. Molecular building blocks include carbon skeletons, vitamins, and minerals. Lack of essential nutrients results in deficiency diseases.

learning outcomes

You should be able to:

  • Describe energy storage adaptations in animal species.

  • Discuss challenges related to obtaining all essential amino acids from the diet.

  • Discuss examples of mineral macro- and micronutrients and their functions.

  • Compare water-soluble and fat-soluble vitamins and their effects on an animal’s body.

Question 1

Gray whales migrate each year from their summer range off Alaska to their winter range off Mexico. During their migrations and their stay in Mexican waters, they eat very little, if anything. What is their energy source over this long time, and what are the advantages of this energy source?

When gray whales are migrating and on their wintering grounds, their energy source is their stored fat (blubber). Fat has a high energy content and low water content and therefore is ideal for long-term storage of energy with minimal mass. It also contributes to the buoyancy of the whale body.

Question 2

Inuit peoples do not eat polar bear liver because it contains so much vitamin A that consuming it produces a serious disease called hypervitaminosis A. Why isn’t there a disease called hypervitaminosis C?

Vitamin A is fat-soluble and can accumulate in the body. Vitamin C is water-soluble and rapidly excreted in the urine, so a toxic level of it cannot accumulate.

Question 3

Anemia is lack of the micronutrient iron. The incidence of anemia is greater in premenopausal women than in men. Why?

The micronutrient iron is largely recycled in the body, but due to menstrual blood loss, premenopausal women do lose iron each month.

Question 4

A comatose patient is fed a nutrient mix through a food tube into the stomach, but a person with a nonfunctional gastrointestinal system will receive a nutrient mix via blood vessels. Mixes introduced into the stomach include proteins, but mixes delivered into blood vessels do not. Explain why this is, and what must take the place of proteins in the mix delivered into blood vessels.

If proteins were added to a solution delivered into the blood, it would stimulate an immune response in the patient to foreign proteins. Therefore it is essential to supply all amino acids in such a mix.

We have surveyed the essential elements of nutrition in animals. Next we will look at various methods and adaptations by which animals obtain the food they need, and the mechanisms they use to extract nutrients from their food.