Lecture 13 Outline (Ch. 41)

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Lecture 13 Outline (Ch. 41)

• I. Animal Nutrition Overview
• II. Essential Parts of Animal Diet
• III. Food Intake
• Digestive Compartments
• Adaptations
• Obesity
• Lecture Concepts

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Overview The Need to Feed

• Food is taken in, taken apart, and taken up in
  the process of animal nutrition
• In general, animals fall into three categories
• Herbivores eat mainly autotrophs (plants, algae)
• Carnivores eat other animals
• Omnivores regularly consume animals as well as
  plants or algal matter

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How does a diet of lean fish help make a bear fat?
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Essential Parts of Diet

• Chemical energy, which is converted into ATP and
  powers processes in the body
• Organic carbon and organic nitrogen
• Essential nutrients must be obtained from dietary
  sources

• Essential amino acids
• Essential fatty acids
• Vitamins
• Minerals

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Essential Parts of Diet

• Meat, eggs, cheese - provide all nine essential
  amino acids ( complete proteins)
• Individuals eating only plant proteins need
  specific plant combinations for all essential
  amino acids

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Essential Fatty Acids

• Animals can synthesize most fatty acids they need
• The essential fatty acids are certain unsaturated
  fatty acids that must be obtained from the diet
• Deficiencies in fatty acids are rare

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Vitamins

• Vitamins organic molecules, small amounts needed
• 13 vitamins essential to humans have been
  identified
• Two categories fat-soluble water-soluble

Table 41-1
Vitamin A Vitamin D Vitamin E Vitamin K
B-complex Biotin Vitamin C (ascorbic acid)
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Minerals

• Minerals simple inorganic nutrients, usually
  required in small amounts

Calcium Phosphorus Potassium Sulfur Chlorine Sodiu
m Magnesium Iron
Table 41-2
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Dietary Deficiencies

• Undernourishment diet consistently low in
  chemical energy
• Malnourishment long-term absence of essential
  nutrients

An undernourished individuals use up stores,
break down own protein and muscle
Malnourishment can cause deformities, disease,
and death
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Food Intake

• Ingestion the act of eating
• Suspension feeders - many aquatic animals, which
  sift small food particles from the water
• Substrate feeders are animals that live in or on
  their food source
• Fluid feeders suck nutrient-rich fluid from a
  living host
• Bulk feeders eat relatively large pieces of food

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• Digestion is the process of breaking food down
  into molecules small enough to absorb
• In chemical digestion, the process of enzymatic
  hydrolysis splits bonds in molecules with the
  addition of water
• Absorption is uptake of nutrients by body cells
• Elimination is the passage of undigested material
  out of the digestive compartment

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Food Intake
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Digestive Compartments

• Most animals process food in specialized
  compartments
• Reduces risk animal digesting
  its own cells/
  tissues

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Digestive Compartments

• More complex animals digestive tube with two
  openings (mouth, anus)
• Tube called a complete digestive tract or an
  alimentary canal
• Can have specialized regions, carry out digestion
  and absorption stepwise

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Digestive Compartments

• Mammalian alimentary canal and accessory glands
  that secrete digestive juices through ducts

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Oral Cavity, Pharynx, Esophagus

• Food shaped into a bolus, lubricated by saliva,
  digestion begins with amylase.
• Pharynx, a junction that opens to both the
  esophagus and the trachea (windpipe)

• The esophagus conducts food from the pharynx down
  to the stomach by peristalsis
• Epiglottis blocks entry to the trachea, and
  larynx.

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Digestion in the Stomach

• The stomach stores food and secretes gastric
  juice, which converts a meal to acid chyme

• Gastric juice - hydrochloric acid and the enzyme
  pepsin
• Mucus protects the stomach lining from gastric
  juice

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Digestion in the Small Intestine

• The small intestine longest section of
  alimentary canal
• Major organ of digestion and absorption

• First is the duodenum - acid chyme from the
  stomach mixes with digestive juices from the
  pancreas, liver, gallbladder, and the small
  intestine itself.

liver/gallbladder bile aids digestion and
absorption of fats
small intestine lining of duodenum (brush border)
produces several digestive enzymes jejunum and
ileum mainly absorb water nutrients
pancreas proteases trypsin chymotrypsin,
protein-digesting enzymes neutralizes the acidic
chyme
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Absorption in the Small Intestine

• small intestine has huge surface area, from villi
  and microvilli exposed to the intestinal lumen
• enormous microvillar surface greatly increases
  rate of nutrient absorption

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Absorption in the Large Intestine

• The colon of the large intestine is connected to
  the small intestine
• The cecum aids in fermentation of plant
  material, connects where the
  small and large
  intestines meet
• Human cecum has extension
  (appendix), plays a minor
  role in immunity

Feces stored in rectum until eliminated
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• The colon houses strains of the bacterium
  Escherichia coli, some of which produce vitamins
• Two sphincters between the rectum and anus
  control bowel movements

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Adaptations

• Herbivores generally have longer alimentary
  canals than carnivores, reflecting the longer
  time needed to digest vegetation

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Mutualistic Adaptations

• Many herbivores have symbiotic microorganisms
  that digest cellulose
• The most elaborate adaptations in ruminants

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Energy Sources and Stores

• Animals store excess calories as glycogen in the
  liver and muscles
• Energy secondarily stored as adipose, or fat,
  cells
• When fewer calories are taken in than are
  expended, fuel is taken from storage and oxidized

• Obesity is due to excessive intake of food
  energy, excess stored as fat
• Obesity contributes to diabetes (type 2), cancer
  of the colon and breasts, heart attacks, and
  strokes

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StimulusBlood glucoselevel risesafter eating.
Homeostasis90 mg glucose/ 100 mL blood
StimulusBlood glucoselevel dropsbelow set
point.
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Energy Sources and Stores

• The complexity of weight control in humans is
  evident from studies of the hormone leptin
• Mice that inherit a defect in the gene for leptin
  become very obese

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Obese mouse with mutant ob gene (left) next to
wild-type sibling mouse.
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Obesity and Evolution

• The problem of maintaining weight partly stems
  from our evolutionary past, when fat hoarding was
  a means of survival
• A species of birds called petrels become obese as
  chicks in order to consume enough protein from
  high-fat food, chicks need to consume more
  calories than they burn

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Figure 41.25 A plump petrel
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Lecture 13 concepts

• - Name the three nutritional needs that must be
  met by diet
• - Describe the four classes of essential
  nutrients
• - Distinguish among undernourishment,
  overnourishment, and malnourishment
• - Describe the four main stages of food
  processing
• - Distinguish between complete digestive tracts
  and gastrovascular cavities
• - Follow a meal through the mammalian digestive
  system
• List important enzymes and describe their roles
• Compare where and how the major types of
  macromolecules are digested and absorbed
• - Explain where and in what form energy-rich
  molecules may be stored in the human body
• Make a list of new vocabulary with definitions.