Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 45
Processing Food and
Nutrition
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Heterotrophs
• Organisms that obtain nourishment
from the organic molecules
manufactured by other organisms
• Nutrients used to
• Run the systems of the body
• Make compounds for metabolic
processes
• Grow and repair tissue
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Nutrition
• Process of taking in and using food
• Malnutrition results from dietary
intake that is either below or above
required need
–Undernutrition (particularly protein
deficiency)
–Obesity (common in the US)
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Food processing
• Ingestion
–Taking of food into the digestive cavity
• Digestion
–Process of breaking down food
mechanically and chemically
• Absorption
–Nutrients pass through the lining of
the digestive tract and into the blood
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Food processing, cont.
• Egestion or elimination
–Food that is not digested and
absorbed is discharged from the body
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• In cnidarians and flatworms
• Food is digested in the
gastrovascular cavity
• The gastrovascular cavity serves
as both mouth and anus
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
Simple
invertebrate
digestive
systems
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• In more complex invertebrates
and in all vertebrates
• The digestive tract is a complete
tube with an opening at each end
• Digestion takes place as food
passes through the tube
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
Digestive tract with two openings
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Various parts of the digestive
tract are specialized to perform
specific functions
• Food passes in sequence
through
• The mouth, pharynx, esophagus,
stomach, small intestine, large
intestine, and anus
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
Human
digestive
system
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Mechanical and enzymatic
digestion of carbohydrates begin
in the mouth
• Mammalian teeth include incisors
for biting, canines for tearing, and
premolars and molars for crushing
and grinding
• Three pairs of salivary glands
secrete saliva
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
Teeth
and diet
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
Tooth structure
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• As food is swallowed, it is
propelled through the pharynx
and esophagus
• A bolus of food is moved by
peristalsis
• The mixing and propulsive
movements of the digestive tract
are known as motility
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
Peristalsis
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• In the stomach
• Food is mechanically digested by
vigorous churning
• Proteins are enzymatically digested
by pepsin
• Rugae are stomach folds that
expand with food
• Gastric glands secrete hydrochloric
acid and pepsinogen
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
Structure
of the
stomach
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• After several hours in the
stomach
• Chyme leaves the stomach through
the pylorus and enters the small
intestine
• Most enzymatic digestion takes
place in the duodenum
• The liver produces bile, which
emulsifies fats
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• After several hours in the stomach,
cont.
• The pancreas releases enzymes
that digest protein, lipid, and
carbohydrates, as well as RNA and
DNA
• The large intestine eliminates
undigested waste and incubates
bacteria that produce Vitamin K and
certain B vitamins
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
The liver
and
pancreas
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Digestion of carbohydrate,
protein, and lipid
• Nutrients in chyme are
enzymatically digested as they
move through the digestive tract
• Polysaccarides are digested to the
disaccharide maltose by salivary
and pancreatic amylases
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Digestion of carbohydrate, protein,
and lipid, cont.
• Maltase splits maltose into glucose
• Proteins are split by pepsin and by
proteolytic enzymes into the final
product of amino acids
• Lipids are emulsified by bile salts and
then hydrolyzed by pancreatic lipase
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
Summary of digestion
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
Some hormones that regulate digestion
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Structural adaptations that
increase the surface of the
digestive tract
• The surface area of the small
intestine is greatly expanded by
–Folds in its wall
–Intestinal villi
–Intestinal microvilli
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
Villi and
microvilli
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Lipid absorption
• Nutrients are absorbed through the
thin walls of the intestinal villi
• The hepatic portal vein transports
amino acids and glucose to the
liver
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
How the
body uses
fat
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Absorption of other nutrients
• Fatty acids and monacylglycerols
enter epithelial cells in the intestinal
lining where they are reassembled
into triacyglycerols
• They are packed into chylomicrons
• The lymphatic system transports
chylomicrons to the blood
circulation
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Nutritional requirements for
dietary carbohydrates
• Most carbohydrates are ingested in
the form of complex carbohydrates
• Fiber is a mixture of cellulose and
other indigestible carbohydrates
• Carbohydrates are used mainly as
an energy source
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Lipids are used as
• An energy source
• Components of cell membranes
• To synthesize steroid hormones
and other lipid substances
• Most lipids are ingested in the
form of triacyglycerols
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Proteins
• Serve as enzymes
• Are essential structural
components of cells
• The best distribution of essential
amino acids is found in the
complex proteins of animal foods
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
How the
body uses
protein
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Vitamins
• Organic compounds required in
small amounts for many
biochemical processes
• Many serve as components of
coenzymes
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Vitamins, cont.
• Fat-soluble vitamins include A, D,
E, and K
• Water-soluble vitamins are the B
and C vitamins
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
The
vitamins
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Minerals are inorganic nutrients
ingested as salts dissolved in
food and water
• Trace elements are minerals
required in amounts less than
100 mg per day
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
Some important minerals and their functions
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Basal metabolic rate (BMR)
• The body’s cost of metabolic living
• Total metabolic rate
• BMR plus the energy used to carry
on daily activities
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Energy input and output
• When energy (kilocalories) input
equals energy output, body weight
remains constant
• When energy input exceeds energy
output, body weight increases
• When energy output exceeds
energy input, body weight
decreases
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Biology, Seventh Edition
CHAPTER 45 Processing Food and Nutrition
• Current hypotheses regarding the
regulation of food intake and
energy homeostasis
• Researchers are identifying
signaling molecules
–The hormone leptin
–The neuropeptite Y (NPY), a
neurotransmitter produced in the
hypothalamus
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