This chapter explains how digestion breaks down
carbohydrates, proteins, and lipids in food (2.9–2.11).
Nutrient molecules enter the bloodstream by way of
transport mechanisms that include diffusion, osmosis,
and active transport (3.10–3.11).
Food digestion provides the various types of biological
molecules from which many body cells can extract
energy (3.16).Key ConCepts
LinKs to earLier ConCepts
Top: © Cengage Learning; Middle: Peter Hawtin, University of Southampton/
Science Source; Bottom: © Brian Chase/Shutterstock.comThe Digestive System
The digestive system mechanically
and chemically breaks down food,
absorbs nutrients, and eliminates
the residues. S e c t i o n s 11.1–11. 8Roughly two out of three people in North America
are overweight, about half of them heavy enough to be considered
obese. The excess weight is a risk factor for diabetes, heart
disease, osteoarthritis, and some forms of cancer.
Storing fat comes naturally to us. Like other mammals, our
adipose tissues are packed with fat-storing cells. Once these
cells form, they are in the body to stay. When you consume more
calories than you burn, the cells fill with fat droplets.
In this chapter we look at how the digestive system brings nutrients
into the body. We also consider the body’s nutritional needs and
health issues related to maintaining a healthy body weight.11 Digestion and Nutrition
Disorders of the Digestive
System S e c t i o n s 11. 9 –11.10Nutrition and Body Weight
Food should supply the nutrients,
vitamins, and minerals body cells
require. Body weight depends on
the balance between energy from
food and energy used for bodily
functions. S e c t i o n s 11.12 –11.15coNNecTioNS:
The Digestive System in
Homeostasis S e c t i o n 11.11195Homeostasis preview
Except for oxygen, food digestion and the absorption of nutrients
provide all the raw materials cells require to survive.© Aleksandr Kurganov/Shutterstock.comCopyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).