Digestion

  • What do animals need to live
    • Animals make energy using food and oxygen
    • Animals build bodies using food for raw materials and ATP energy for synthesis
  • Different diets; different lives
    • All animals eat other organisms
    • Herbivores
    • Eat mainly plants
    • Ex: gorillas, cows, rabbits, snails
    • Carnivores
    • Eat other animals
    • Ex: sharks, hawks, spiders, snakes
    • Omnivores
    • Eat animals and plants
    • Ex: cockroaches, bears, raccoons, humans
      • Humans evolves as hunters, scavengers, and gatherers
  • Getting and Using Food
    • Ingest
    • Taking in food
    • Digest
    • Mechanical digestion
      • Breaking up food into smaller pieces
    • Chemical digestion
      • Breaking down food into molecules small enough to be absorbed into cells
      • Enzymes
    • Absorb
      • Absorb nutrients across cell membranes
      • Diffusion
      • Active transport
    • Eliminate
      • Undigested material passes out of the body
  • Mouth
    • Functions
    • Mechanical digestion
      • Teeth
      • Break up food
    • Chemical digestion
      • Saliva
      • Amylase enzyme
      • Digests starch
      • Mucus
      • Protects soft lining of digestive system
      • Lubricates foods for easier swallowing
      • Buffers
      • Neutralizes acid to prevent tooth decay
      • Antibacterial chemicals
      • Kill bacteria that enter mouth with food
  • Swallowing
    • Epiglottis
    • Flap of cartilage
    • Closes trachea (windpipe) when swallowing
    • Food travels down the esophagus
    • Peristalsis
    • Involuntary muscle contractions to move food along
  • Stomach
    • Functions
    • Disinfect food
      • Hydrochloric acid
      • pH 2
      • Kill bacteria
    • Food storage
      • Can stretch to fit about 2 liters of food
    • Digests protein
      • Pepsin enzyme
  • Ulcers
    • Used to think that ulcers were caused by stress
    • Tried to control with antacids
    • Now know that ulcers are caused by a bacterial infection of the stomach
    • Now cure with antibiotics
  • Small intestine
    • Functions
    • Digestion
      • Digests carbohydrates
      • Amylase from pancreas
      • Digests proteins
      • Trypsin and chymotrypsin from pancreas
      • Digest lipids
      • Bile from liver and lipase from pancreas
    • Absorption
      • Nutrients move into body cells by diffusion and active transport
      • Absorption through villi and microvilli
      • Finger-like projectors
      • Increases surface area for absorption
  • Pancreas
    • Produces digestive enzymes
    • Digests proteins
      • Trypsin, chymotrypsin
    • Digests starch
      • Amylase
    • Digests lipids
      • Lipase
    • Buffers
    • Neutralize acid from stomach
  • Liver and Gall Bladder
    • Produces bile
    • Breaks up fats
    • Gallbladder only stores bile
      • That’s why it can be removed
  • Large intestines (colon)
    • Function
    • Reabsorbs water
      • Uses about 9 liters of water every day in digestive juices
      • If you don’t reabsorb water, would die of dehydration
      • \         > 90% of water is reabsorbed
      • Not enough water reabsorbed

Diarrhea

Can be fatal

  • Too much water reabsorbed

Constipation

  • Reabsorb by diffusion
    • Company
    • Escherichia coli
      • E. coli
      • Digest cellulose

Digests fruits and vegetables

  • Produce vitamins

Vitamin K and B vitamins

  • Generate gases

By product of bacterial metabolism

Methane and hydrogen sulfide

  • Rectum
    • Last section of large intestines
    • Eliminate feces
    • Left over
      • Undigested materials
      • Mainly cellulose from plants
      • Called roughage or fiber
      • Keeps everything moving and cleans out intestines
      • Masses of bacteria
  • Different diets; different bodies
    • Adaptations of herbivores vs. carnivores
    • Teeth
    • Length of digestive system
    • Number and size of stomachs
  • Teeth
    • Carnivore
    • Sharp ripping teeth
    • Canines
    • Herbivore
    • Wide grinding teeth
    • Molars
    • Omnivore
    • Both kinds of teeth
  • Length of digestive system
    • Herbivores and omnivores
    • Long digestive systems
    • Harder to digest cellulose
      • Bacteria in intestines help
    • Carnivores
    • Short digestive systems
    • Protein easier to digest than cellulose
  • Deficiency diseases
    • Scurvy - vitamin C
    • Collagen productions
    • Rickets - vitamin D
    • Calcium absorption
    • Blindness - vitamin A
    • Retinol production
    • Anemia - vitamin B12
    • Energy production
    • Kwashiorkor - protein
  • Vegetarian diets
    • Need to make sure you get enough protein
    • 20 amino acids make protein
      • 12 amino acids humans can produce
      • 8 we have to eat
      • “Essential amino acids”
    • Grains like corn have 6 amino acids
    • Beans have 6 amino acids
      • Mix beans and grains for complete group of amino acids