DIGESTION AND NUTRITION

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DIGESTION AND NUTRITION

• Chapter 37

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• Why must certain organisms consume food?
• To obtain energy raw materials required for
  growth, repair, and maintenance of the body.

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• Often classify consumers based on what they eat.
• Carnivore - animals
• Frugivore - fruits berries
• Herbivore - plants
• Insectivore - insects
• Omnivore - plants animals
• Detritivore - nonliving organic matter

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• Consumers process food in stages
• ?Ingestion - intake of food.
• ?Mechanical breakdown - physically cutting food
  into smaller pieces.
• ?Digestion - chemically breaking food particles
  into small molecules (monomers).
• ?Absorption - cellular uptake of monomers.
• ?Elimination - ridding the body of undigested
  material.

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• A. Digestive Diversity
• 1. Types of Digestion
• Intracellular digestion - occurs within a cells
  food vacuoles.
• Extracellular digestion -

occurs outside cells usually within a cavity or
tube connected with the outside world.
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• Why must digestion occur in some type of
  compartment (food vacuole, gastrovascular cavity,
  stomach)?

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• Digestive systems may have one or two openings.

Separate mouth anus food travels in 1
direction.
Opening serves as both mouth anus.
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• 2. Digestive System Adaptations
• Digestive systems are adapted to an animals
  diet.
• Insectivores Carnivores - tend to have short,
  simple digestive tracts cecum is greatly reduced
  or absent.

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• Herbivores - tend to have long, complex digestive
  tracts cecum is prominent.

Exception is giant panda - herbivore with a short
digestive tract.
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• B. Human Digestive System
• Consists of gastrointestinal tract (mouth,
  pharynx, esophagus, stomach, small intestine
  large intestine) and accessory structures
  (salivary glands, pancreas, liver gall bladder).

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• 1. Mouth
• Site of
• ingestion
• mechanical breakdown (teeth)
• digestion (carbohydrates)

salivary amylase
starch polysaccharide
maltose disaccharide
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• 2. Pharynx - passageway for air bolus opens
  into larynx esophagus.
• What structure ensures that bolus enters
  esophagus?
• 3. Esophagus - muscular tube leading to stomach.

Bolus is pushed down esophagus by peristalsis.
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• 4. Stomach - muscular J-shaped sac.

• Structure
• 4 regions (cardia, fundus, body, pylorus)
• lower esophageal sphincter
• pyloric sphincter
• rugae

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• Stomach mucosa (lining) contains gastric glands
  consisting of

• mucus cells - secrete mucus
• parietal cells - secrete HCl
• chief cells - secrete pepsinogen

pepsinogen HCl ? pepsin (active enzyme)
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• Stomach is site of
• storage
• mechanical breakdown (muscle contraction)
• digestion (proteins)

pepsin
protein
polypeptides

• minimal absorption (H2O, salts, some drugs,
  alcohol)
• Why doesnt pepsin digest stomach?
• Mucus
• Stomach converts bolus into acid chyme.

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• 5. Small Intestine - muscular 23-foot tube
  (duodenum, jejunum, ileum).
• Intestinal mucosa

• has a large surface area (circular folds, villi,
  microvilli)

• produces several enzymes
• - carbohydrases - peptidases

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• Liver, gall bladder pancreas empty secretions
  into duodenum.

Liver - produces bile (emulsifies lipids) Gall
bladder - stores bile
Pancreas - produces pancreatic juice (H2O,
bicarbonate ions, pancreatic amylase, trypsin,
chymotrypsin, lipase nuclease)
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• Small intestine is site of
• mechanical breakdown (segmentation)
• digestion (carbohydrates, proteins, lipids
  nucleic acids)

pancreatic amylase
starch
maltose
carbohydrases
disaccharides
monosaccharides
trypsin
polypeptides
peptides
chymotrypsin
peptidases
peptides
amino acids
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fat globules bile ? small fat droplets
lipase
fat droplets
monoglycerides fatty acids
nuclease
RNA DNA
nucleotides

• absorption (monosaccharides, amino acids,
  monoglycerides, fatty acids, nucleotides)
• Absorbed materials enter circulatory system.

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• 6. Large Intestine (colon) - large 5-foot tube
  framing the small intestines.

• Note
• cecum
• appendix
• rectum
• Colon contains large number of vitamin-producing
  bacteria

B1, B2, B6, B12, folic acid biotin
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• Large intestine is site of
• absorption (H2O, salts, minerals vitamins)
• elimination (feces)
• Feces consist of indigestible materials, bacteria
  sloughed off intestinal cells.
• How would antibiotics affect normal colon
  function?

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Fats (3-6 hours) Proteins (?3 hrs) Carbs (1-2 hrs)
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• C. Human Nutrition
• Nutrients are chemical substances in food that
  are required for growth, maintenance repair.
• Essential nutrients - must be ingested body
  cannot synthesize.
• Nonessential nutrients - can be synthesized if
  not ingested.
• Essential nutrients vary among species.

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• Humans cannot synthesize 9 amino acids.

• meats contain all 9
• vegetables contain some, but not all

Strict vegetarians must eat certain vegetables in
combination to obtain all 9 essential amino acids.
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• 1. Macronutrients (energy nutrients)
• Nutrients required in large amounts can be
  broken down by cellular respiration to supply
  energy (ATP).
• Carbohydrates - cells major energy source.
• Proteins - required to make enzymes, hemoglobin,
  antibodies some hormones.
• Lipids - required to make cell membranes some
  hormones needed for insulation absorption of
  fat-soluble vitamins.

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• The amount of energy a macronutrient releases is
  measured in kilocalories (kcal).
• Which macronutrient yields the most energy (ATPs)
  per gram?

Lipids
Lipids ? 9 kcal/gram Carbohydrates Proteins ? 4
kcal/gram
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• 2. Micronutrients
• Nutrients required in small amounts.
• Vitamins
• water-soluble vitamins Bs C
• fat-soluble vitamins A, D, E K
• Minerals
• Bulk minerals calcium, chloride, sodium,
  magnesium, phosphorus, potassium sulfur
• Trace minerals chromium, cobalt, copper,
  fluorine, iodine, iron, manganese, selenium zinc

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• Good Nutrition a balanced diet

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• Poor Nutrition
• Primary nutrient deficiencies - caused by an
  inadequate diet.
• Marasmus - lacking all nutrients.
• Kwashiorkor - lacking protein in diet.
• Anorexia nervosa - self imposed starvation.
• Bulimia - eating followed by purging.
• Secondary nutrient deficiencies - caused by a
  metabolic abnormality.
• Celiac disease - genetic condition in which
  nutrients cannot be absorbed from small intestine.