Nutrition and Digestion

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Chapter 21

• Nutrition and Digestion

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Ingestion

• Kind of food
• Carnivore meat eating
• Herbivore plant eating
• Omnivore - eat both plants and animals
• Means of feeding
• Suspension feeders extract food from water
• Substrate feeders - live in or on food
• Fluid feeders suck fluids
• Bulk feeders ingest large particles of food

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Stages of Food Processing

• Ingestion act of taking food in
• Digestion - breakdown food to molecules that can
  be absorbed
• Adsorption uptake of food into cells and
  transfer to blood for distribution
• Elimination removal of undigested material

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Digestion

• Specialized compartments
• Gastrovascular cavity
• Alimentary canal
• Pharynx and esophagus
• Stomach or gizzard
• Intestine
• Anus
• Regions vary with type of food eaten

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Movement

• Food is propelled through alimentary canal by
  peristalsis
• Waves of contraction of smooth muscle
• Controlled flow
• Sphincters control rate of flow
• Circular muscle closes tube
• Before and after stomach anus

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Digestion

• Begins in oral cavity
• Mechanical breakdown of food
• Enzyme chemical breakdown of food
• Amylase
• Starch ? maltose
• Food passes through pharynx and esophagus
• No additional digestion
• Pharynx connects alimentary canal and respiratory
  tract
• Epiglottis controls movement

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Digestion

• Begins in oral cavity
• Mechanical breakdown of food
• Enzyme chemical breakdown of food
• Amylase
• Starch ? maltose
• Food passes through pharynx and esophagus
• No additional digestion
• Pharynx connects alimentary canal and respiratory
  tract
• Epiglottis controls movement

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Stomach

• Stores food and digests protein
• Chemical secretions
• Mucus lubricates and protects
• Pepsinogen converts to pepsin to break peptide
  bonds for digestion of protein
• HCl converts pepsinogen to pepsin
• Gastric glands stimulated by nerves and hormones
  (gastrin)

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• Food mixed with gastric fluid ? acid chyme
• Sphincters keep food in stomach 2-6 hours
• Backflow of acid into esophagus is heart burn

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Gastric ulcers

• Ulcers are open sores
• Gastric ulcers are sores in stomach wall
• Helicobacter pylori survives in stomach and
  damages stomach wall
• May be linked to gastric cancer

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Small Intestine

• Major organ for digestion and adsorption
• Digestion of starch, protein, fat
• Associated organs help with digestion
• Liver makes bile for fat dispersion
• Gall bladder stores bile
• Pancreas produces enzymes and bicarbonate that
  work in small intestine

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Digestion

• Bicarbonate raises pH to neutral level
• Bile emulsifies fat droplets
• Amylase breaks down starch
• Trypsin and chymotrypsin break down proteins
• Lipase acts on fats
• Nucleases act on nucleic acids

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Final Digestion

• Small polypeptides, maltose, nucleotides are
  digested to amino acids, glucose, and other small
  molecules
• Fat is broken down to fatty acids and glycerol
• Some enzymes are produced by small intestine

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Absorption

• Structure of small intestine aids in absorption
  of nutrients
• Folds, villi, and microvilli provide increased
  surface area
• Blood vessels (capillaries) close to cells
• Blood flows to liver then to rest of body
• Liver produces new compounds from nutirents

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Large Intestine

• Cecum and appendix are found at juncture of small
  and large intestine
• Large intestine (colon) absorbs water
• 7 liters fluid/day enter colon
• 90 absorbed back into blood
• Feces is remaining undigested food and bacteria
• Eliminated through rectum and anus

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Chapter 21

• Diet

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Purpose

• Provides fuel for bodys activities (energy)
• Provides nutrients to make body molecules
• Provides specific essential nutrients

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Chemical Energy

• Measured in Calories (kilocalories)
• Basal metabolism kilocalories needed for
  essential processes at rest
• Activity requires additional energy
• Extra energy taken in above requirement is stored
  as fat

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Diets

• Normal levels of body fat necessary for health
• Females 20-25
• Males - 15-19
• Diet should contain essential fatty acids
• Feedback mechanisms regulate fat levels (storage
  vs use)

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Fad Diets

• Low carbohydrate (lt100mg/day)
• Fatigue, headaches, long term muscle loss
• Extremely low fat (lt20 fat)
• Inadequate essential fatty acids, protein,
  fat-soluble vitamins and minerals
• Formula
• Loss of body protein, dry skin, hair loss, salt
  imbalance

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Vegetarian Diet

• Require 8 essential amino acids
• Deficiency of one can inhibit protein synthesis
• Combine grains and legumes to get all amino
  acids

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Vitamins

• Organic compounds required in small amounts
• Used as coenzymes
• Excess may cause harm
• Fat soluble vitamins can be stored
• Water soluble vitamins are not stored
• Required every day

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Water Soluble Vitamins

• Vitamins B, C are water soluble
• B group contains at least 8 compounds
• Most B vitamins are used as co-enzymes in energy
  (ATP) production
• Found in meats, grains, vegetables
• Vitamin C is used in collagen synthesis, is
  antioxidant, aids in detoxification and iron
  absorption

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Fat-Soluble Vitamins

• A- visual pigments, skin maintenance
• Dark green and orange vegetables and fruit
• D aids in absorption of calcium for bones
• dairy products (added), skin
• E antioxidant
• Oils, nuts, seeds
• K - aids blood clotting
• Green vegetables

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Minerals

• Inorganic compounds
• Calcium and phosphorus for bones
• Sulfur amino acids
• Sodium, potassium, chloride electrolytes
• Iron hemoglobin (O2 carrying protein)
• Iodine thyroid hormone (energy levels)
• Others enzyme cofactors

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Diet and Health

• Diet influences cardiovascular disease and cancer
  risk
• High cholesterol, especially LDL, associated with
  risk of heart attack
• High fat and carbohydrate diets associated with
  breast and colon cancer

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